THE EFFECTS OF FUELWOOD CUTTING ON HOLE-NESTING BIRD POPULATIONS IN THE OAK-JUNIPER WOODLAND by Paul Edward Peterson A Thesis Submitted to the Faculty o f the DEPARTMENT OF RENEWABLE NATURAL RESOURCES In P a rtia l F u lfillm e n t o f the Requirements For the Degree of MASTER OF SCIENCE WITH A MAJOR IN WILDLIFE ECOLOGY In the Graduate College THE UNIVERSITY OF ARIZONA 1 9 8 1
STATEMENT BY AUTHOR This thesis has been submitted in p a rtia l f u lf illm e n t o f re quirements fo r an advanced degree at The U n ive rsity o f Arizona and is deposited in the U n iv e rs ity L ib ra ry to be made a va ila b le to borrowers under rules o f the L ib ra ry. B rie f quotations from th is thesis are allow able w ith o u t special permission, provided th a t accurate acknowledgment o f source is made. Requests fo r permission fo r extended quotation from or reproduction o f th is manuscript in whole or in part may be granted by the head o f the major department or the Dean o f the Graduate College when in his judgment the proposed use o f the m aterial is in the in te re s ts o f scholarship. In a ll other instances, however, permission must be obtained from the author. APPROVAL BY.THESIS DIRECTOR This thesis has been approved on the date shown below: LYLE K. SOWLS Professor o f W ild life Date
ACKNOWLEDGMENTS I would lik e to thank the W ild life Management I n s titu te, the Rocky Mountain Forest and Range Experimental S ta tio n, and the Arizona Cooperative W ild life Research U nit fo r fin a n cin g th is study. Lyle K. Sowls aided in planning the p ro je c t and provided valuable advice throughout it s research and w ritin g. Dr. Sowls also took the photographs fo r the th e s is. Thanks also to Ron Thompson and Steve Loe o f the Forest Service fo r th e ir encouragement, and to Charles R. Hungerford and Peter F. F f o ll io t t fo r reading the manus c r ip t and making suggestions fo r improvement. i i i
TABLE OF CONTENTS Page LIST OF TABLES...'... LIST OF ILLUSTRATIONS... ABSTRACT... v vi v ii 1. INTRODUCTION... 1 2. THE FOREST SERVICE FUELWOOD PLAN (1978)... 3 3. THE STUDY AREAS... 6 4. METHODS.... 12 5. RESULTS... 16 6. DISCUSSION....... 30 7. LITERATURE CITED... 48 iv
LIST OF TABLES Table. Page 1. Dominant Tree Species in the Oak-Juniper Areas... 19 2. Nest Holes Used by Birds During Spring 1979... 20 3. Estimated Bird Populations (#/Hectare) a t Each 21/22 o f the Study Areas... 4. Tree Species in Which Holes Were F o u n d... 23 5. Nest-Hole Types Found, and Those Selected by 24 H o le -N e s te rs... 6. Mean Diameter Breast Height o f Trees (With and 25 W ithout H o le s )... 7. Aspect o f Nest H o le s...'. 26 8. Condition o f Nest Trees... 27 9. Entrance Diameter o f Nest C a v it ie s... 28 10. D ire ctio n o f Face o f Nest C a v it ie s... 29 v
LIST OF ILLUSTRATIONS Figure Page 1. The Area Surrounding the Oak-Juniper Study Areas.... 8 2. The Oak-Juniper Study Areas w ith TV Repeater in 9 Background......... 3. The Access Road as i t Runs Through the Control Area... 10 4. Slash P iles L e ft by Woodcutters on the Western Oak-Juniper Area................ 33 5. A Dying A llig a to r Juniper W ithout Nesting C avities... 36 6. Nest Hole Made by an Arizona Woodpecker in an Emory Oak....... 37 7. A Hole R esulting from Branch Stub Rot in an Arizona White Oak... 38 v i
ABSTRACT To evaluate the e ffe c t o f fuel wood harvest on hole-nesting b ird populations in southern Arizona, two study areas were located in the oa k-ju n ip e r woodland. One study area included an area which the Forest Service had designated fo r p u b lic fuelwood c u ttin g s, the other was uncut. A th ir d study area was located a t Madera Canyon to provide comparison w ith a rip a ria n area o f s im ila r e le va tio n. A llig a to r Juniper (Juniperus deppeana) dominated both the cut and control areas. More nests were found on the cut area than the control area. B ird populations were nearly equal over the two oak- ju n ip e r study areas, but were higher a t Madera Canyon. Quercus arizonicus was most fre q u e n tly used as a nest tree by a c tiv e nesters and by woodpeckers (past and present). Old woodpecker holes were chosen most o fte n by hole-nesters. Trees w ith a t le a s t h a lf th e ir branches a liv e were chosen more ofte n than those w ith less than h a lf. The importance o f the o a k-ju n ip e r woodland is in d ica te d by the data; it s com position may be changed in the fu tu re. A fuelwood p ro je ct lik e th is one w ill not be detrim ental as long as a small percentage o f the trees are cut and care is taken to preserve trees w ith nest holes. v i i
INTRODUCTION W ith.the cu rre n t fuel c r is is, p u b lic pressure has been applied to government and p riv a te landowners to make trees a v a ila b le fo r fu e l- wood harvest. In southern Arizona, where the w in te r heating energy requirement is not as great as in northern la titu d e s, fuel wood could supply a substantia l fra c tio n o f th a t need. The U.S. Forest Service has designated areas where fuel wood may be harvested by the p u b lic. Depending upon the extent and method o f harvest, b ird populations in these areas may be a ffe c te d. One im portant avian requirement a ffe cte d by fuel wood harvest is nesting h a b ita t, s p e c ific a lly c a v ity - nesting tre e s. According to S cott and Patton (1975), twelve species o f c a v ity -n e s tin g birds use the oak-ju n ip e r type, prevalent in southern Arizona. In the past, dead trees (c a v ity -n e s tin g trees may be dead) were ro u tin e ly removed as f ir e hazards, fo re s t health hazards (sources o f disease inoculum) and as a p a rt o f logging o p e ra tio n s. Problems may re s u lt as hole-nesters disappear from an area. An increase in d e s tru c tiv e in sect populations may fo llo w (Michael and Thornburgh 1971). According to J. Verner (Smith 1975), the type o f nest s ite u tiliz e d is a c r it ic a l fa c to r in h a b ita t se le c tio n fo r many species. This is p a r tic u la r ly tru e fo r those species o f hole-nesting birds which do not excavate t h e ir own c a v itie s. In th is study, only three o f e ig h t hole-nesting birds are prim ary hole-nesters. The c r it ic a l importance o f management fo r 1
re te n tio n o f snags in a natural fo re s t has been re a lize d and subs ta n tia te d by various authors (Baida 1969; Conner 1975; McClelland 1976).
THE FOREST SERVICE FUELWOOD PLAN (1978) 1 In response to pu b lic demand, the Forest Service O ffices o f the Sierra V ista and Nogales D is tr ic ts have made permits a v a ila b le fo r the c u ttin g o f fuelwood. In southern Arizona, there are two types o f harvest areas: mesquite sale areas, and oak-ju n ip e r sale areas. This re p o rt pertain s to one o f the oa k-ju n ip e r areas. The o b je ctive s o f the Nogales D is tr ic t plan are: 1. Increase food resources fo r liv e s to c k and w i ld lif e ; 2. Provide fo r perennial water sources fo r w i ld lif e and liv e s to c k ; 3. Reduce erosion and r e s t r ic t o ff-ro a d ve h icle tra v e l where needed; 4. Increase h a b ita t d iv e rs ity and edge e ffe c t; 5. Increase cover a v a ila b ilit y fo r w ild lif e ; and, 6. Provide fo r the sustained y ie ld o f harvested fuelwood. Further, the Forest Service claims th a t because o f extensive f ir e suppression and h is to r ic overgrazing over the e n tir e ty o f a ll small sale areas, tre e and shrub invasions re sulted in a general degradation o f land resources and a m onotyptic homogeneous vegetative type (Johnston 1978). An example o f th is is the invading A llig a to r Juniper ( Juniperus deppeana) (Kearney and Peebles 1951), which now dominates areas fo rm e rly pine-oak (Baida 1969). More re c e n tly there has been a sharp increase in fuelwood demands by the p u b lic, m ostly as the re s u lt o f higher energy costs and the fa s t growth o f communities 3
4 surrounding the Nogales Ranger D is tr ic t. Providing fuelwood to meet th is pub lic demand was recognized as a means o f accomplishing land management o b jectives s im ila r to those stated fo r th is plan. However, p ub lic harvesting o f fuelwood has re su lte d in increased o ff-ro a d vehicle tra v e l, accelerated s o il lo ss, f ir e hazards in the form o f slash, and harvesting o f s im ila r age-class trees (due to p re fe re n tia l removal o f la rg e r diameter tre e s ). S p e c ific a lly, in the study area designated fo r fuelwood c u ttin g by the Forest Service, only those. trees marked are to be cut. A llig a to r Juniper and Emory Oak (Quercus emoryi) are s e le c tiv e ly marked, leaving a ll Arizona Oaks ( Quercus a riz o n ic u s ) unmarked. According to the plan, c u ttin g u n its should be sm all, p re fe ra b ly less than twenty acres. Uncut s trip s o f vegetation need to be l e f t between u n its fo r tra v e l routes and escape cover. S elective marking should be used along zone edges cre a tin g b u ffe r areas and fo r leaving ca vity -b e a rin g tre e s. Leaving two to three slash p ile s per acre w i l l provide re s tin g, escape and nesting cover fo r Mearn's Quail (Cyrtonyx montezumae m e rria m i), turkey (Meleagris gallopavo), brown towhee ( P ip ilo fuscus), Mexican junco (Junco phaeonotus), chipping sparrow ( S p iz e lla passe rina), and c o tto n ta il (S ylvilagus auduboni). Permit cost to the public was $2.50 per cord in 1979 (two-cord minimum, green wood or dead and down), lim ite d to two cords per household per woodcutting year. These p o lic ie s are as y e t untested as fa r as w i ld lif e is concerned. The ob je ctive s o f my study were: 1. To evaluate the e ffe c ts o f the Forest S e rvice 's fuelwood p o lic y on avian c a v ity -n e s te rs ;
5 2. To determine the nest c a v ity preferences o f hole-nesting b ird s ; fo r instance, tre e species, aspect o f hole, size o f hole, e t c. ; 3. To id e n tify those snags which are-unused by c a v ity - nesters; those th a t could be removed w ith out nesting e ffe c t; 4. To id e n tify key b ird species th a t may in d ic a te e ffe c ts o f c u ttin g to fo re s te rs ; 5. To compare the r e la tiv e b ird numbers and species o f the study areas to those o f Madera Canyon, a sycamore canyon w ith high b ird d e n sity, thereby evaluating the re la tiv e importance o f the oa k-ju n ip e r type; and, 6. To provide fo re s t managers w ith data upon which to base management decisions concerning fuel wood c u ttin g in o a k-ju n ip e r woodlands.
THE STUDY AREAS In February 1979, I located two adjacent study areas in the northeastern f o o t h ills o f the Santa R ita Mountains (Pima County) f i f t y m iles southeast o f Tucson, Arizona (Fig. 1 and 2) in the Santa Rita D is tr ic t o f the Coronado National Forest. Adjacent canyons. were Gardner and Fish to the south and Enzenberg and Box to the north. Sonoita, Arizona is 16 kilom eters (KM) to the southeast o f the study areas. Each area was roughly oval and contained 200 hectares. The two areas were divided by washes running north to south toward Gardner Canyon. The access road ran through the control area and encircled the cut area (F ig. 3). The topography sloped upward to a western ridge and to a northeastern h illt o p. On the western rid g e there was a te le v is io n repeater (F ig. 1). Presumably, the access road was o r ig in a lly b u ilt to service the repeater. According to Johnston (1978), s o ils in the area are o f the Bakervi11 e-gaddis complex, g ra n itic in o rig in and h ig h ly erosive. The area's e le v a tio n ranged from 1,675 to 1,700 meters (M), map coordinates are N 31 4 7 ', W 110 4 8 '; temperature was approxim ately 6 degrees Celcius cooler than Tucson. The clo se st weather s ta tio n which approximates the study area's clim a te is CaneTo, A rizona, to the south. s ta tio n, the average y e a rly p re c ip ita tio n is 44.4 CM. A t th is There are 120 days per year in which the temperature is below fre e z in g. The average la te s t fre e zin g n ig h t occurs May 11. The weather was cool 6
and w etter than normal over the study period. fo r March 1979 was.2 Celcius below normal. The mean temperature During th a t same time period 3.5 CM o f ra in and snow f e l l which was 1.4 inches above normal (N.O.A.A. 1978). The temperature was below free zing before dawn in February and March. The access road remained impassable to non fo u r- wheel -d riv e vehicles u n til m id -A p ril, due to heavy spring ra in and snow. Consequently, woodcutting a c t iv ity was not heavy over the period. As described by Lowe (1964), the study areas are ty p ic a l o f oak woodland areas o f southeastern Arizona. Included in the two, 200 hectare areas were 1) open oak-grass savanna (open e n c in a l), and 2) oak-wood!and (dense e n c in a l). The woodland canopy was comprised o f A llig a to r Juniper, Arizona White Oak, and Emory Oak. These trees were 2 to 15 M t a l l. The t a lle s t in d iv id u a ls were Arizona White Oaks near g u llie s and a few old ju n ip e rs. The canopy was most continuous near washes, le a s t on ridgetops where A llig a to r Juniper was dominant. Beneath the canopy were, a few shrubby species, although grasses comprised most o f the understory. Some o f these shrubs were velvet-pod mimosa (Mimosa dysocarpa), skunkbush ( Rhus t r ilo b a t a ), buckbrush ( Ceanothus fe n d le r i), Mt. Mahogany ( Cercocarpus montanus), s il ktassel (Garrya w riq h ti i ), pincushion icactus (MamiH a ria v iv ip a ra ), and hedgehog cactus (Enchinocereus t r o g lic h id ia t u s ). Rare species in the areas included c h o lla (Opuntia sp.) and Mexican Pinyon ( Pinus cembroides). The savanna p o rtio n s o f the area were m ainly near ridges. In these
Bowman bpring Box.Canyon \ T19S Melendrez Pass / / / @ \ o ' LEGEND * TV Repeater - - Access Road 1 Cut Area (v - Ophir Gulch k r e a te rv il1e 2 Control Area z 1.6 KM 1 Mile To Madera Canyon /To Gardner and Fish Canyon l RISE FIG. 1. THE AREA SURROUNDING THE OAK-JUNIPER STUDY AREA oo
FIG. 2. THE OAK-JUNIPER STUDY AREAS WITH TV REPEATER IN BACKGROUND
FIG. 3. THE ACCESS ROAD AS IT RUNS THROUGH THE CONTROL AREA
n areas, grasses dominated. Presumably grassy areas would be increased according to the.f orest Service plan. Some common species were bul 1 - grass (Muhlenbergia em ersleyi), blue grama (Bouteloua g r a c ilis ), bluestem (Andropogon scoparius), and plain s lovegrass (E ragrostis interm edia). W ild life in the area included many b ird species, to be mentioned la te r (Table 3), as w ell as w h ite -ta ile d deer (Odocoileus virginanus cousei), gray fox (Urocyon cinereoargenteus), coyote ( Cam's la tra n s ), deer mouse ( Peromyscus m aniculatus), c o tto n ta il (S ylvila g u s flo rid a n u s ), s trip e d skunk (M ephitis m e p h itis ), rock s q u irre l i. (C ite llu s v.ariegatus), and Arizona gray s q u irre l ( Sciurus a rizo n e n sis). A th ir d study area was located a t Madera Canyon to the west, also in the Santa Rita Mountains. This canyon drains the two t a lle s t peaks o f the Santa R itas: Mt. Wrightson and Mt. Hopkins. I chose the area to provide co n tra s t w ith the b ird populations o f the previous areas which were r e la tiv e ly dry. Madera Canyon has a year-round water supply and is lo c a lly famous fo r it s abundance o f b ird l i f e. Map coordinates fo r Madera are N 31 43", W 111 521. The elevation o f the study area was 1,460 M. Vegetation near the creek was ty p ic a l o f a rip a ria n woodland in southeastern Arizona. The rip a ria n area was dominated by large (up to 15M) tre e s, m ainly Arizona Sycamore (Platanus w r iq h t i i). Walnut (Juglans m ajor), Alder (Alnus o b lo n g ifo lia ), and Cottonwood (Populus fre m o n tii). The a d jo in in g h ills id e s contained vegetation s im ila r to th a t o f the o a k-ju n ip e r study areas. Oaks (Quercus sp.) dominated.
METHODS The o a k-ju n ip e r study s ite s were v is ite d three to fo u r times weekly, from January 1979 through June 1979. I began by lo c a tin g and tagging a ll trees (dead or a liv e ) in each area w ith any s o rt o f c a v ity Large ye llo w tags were attached to a low lim b o f each tre e w ith a c a v ity to f a c il it a t e lo c a tio n a t a la te r date. I found th a t the hours o f 7:00 to 11:00 a.m. were best fo r f ie ld work because avian a c t iv it y was greatest a t sunrise and nesting a c t iv it y was g reatest in the mid- morning. To lo cate p o te n tia l nest tre e s, I thoroughly searched the area ra th e r than use a tran sect or sampling method. This was necessary because snags were not e a s ily found in e ith e r area. Searching was most e a s ily done because a ll hole trees were found near dry washes which traversed the area. On my tre e den sity tra n s e c ts, in which 80 trees were cataloged in each area, only two p o te n tia l nest- hole trees were encountered (1%). to fin d a ll the holes in each area. I t would have taken many transects The ninety-one holes discovered in each area must be considered nearly a ll those a v a ila b le to the b ird s. To avoid bias in th is survey, I ignored only those holes th a t provided easy access to predators, due to large hole diameter or softness o f wood-. I ignored trees w ith c a v ity diameter greater than 15 CM. An equal number o f holes (91) had been located and tagged in each area by the end o f the breeding season. I stopped searching a t 91 holes because i t was becoming in c re a s in g ly d i f f i c u l t to locate 12
new hole tre e s, and I needed to recheck the ones I had located e a r lie r. I t was intended th a t by choosing adjacent study areas, h a b ita t 13 c o n tin u ity between control and cut areas would be achieved. A technique designed by Baida (1969) was used to q u a n tify th is c o n tin u ity (Table 1). The p o in t-q u a rte r method by Cottam and C u rtis (1956) was used to determine re la tiv e d e n sity, r e la tiv e frequency, re la tiv e dominance, and importance value (an average o f the former three) fo r the three dominant tre e species on the study area. These were calcu- la te d over twenty points (80 tree s) per area. At each p o te n tia l nest hole the fo llo w in g data were recorded: - 1. Tree species; 2. Diameter breast height (DBH) o f nest tre e ; 3. Hole exposure (fa c in g u p /d o w n /h o rizo n ta lly); 4. Status 1. Dead 2. At le a s t h a lf branches dead 3. At le a s t h a lf branches a liv e 4. A liv e 5. Hole aspect (d ire c tio n o f hole face: N to E; E to S; S to W; W to N ), hole diameter (to nearest h a lf CM); and type o f hole (woodpecker caused, crack, branch stub, e tc.) I chose to evaluate liv e trees as well as dead snags because I found c a v itie s in many o f them. The Forest Service p o lic y fo r Region I I I (1980) regarding snags considers only DBH and amount o f bark remaining when evaluating snag q u a lity. I found th a t tree species and nest hole data were also im portant. I estimated b ird populations a t each o a k-ju n ip e r area and a t Madera Canyon in May and June 1979. Means calculated from th is data
14 were compared using the stu d e n t's t te s t a t the one percent level o f s ig n ific a n c e. Three d iffe r e n t c ir c u la r p lo ts were set up at each o f the three study areas. C irc u la r p lo t center points were chosen fo r th e ir v i s i b i l i t y c h a ra c te ris tic s. Those w ith a wide range were prefe rre d. This was necessary due to the h illin e s s o f the te rra in. Avian d e n sitie s were calcula ted using the V ariable C irc u la r P lot Method (Reynolds, et al 1978). Each p lo t was censused fiv e times and means were calcula ted fo r each species (Table 3). This census technique has two advantages over the popular tra n se ct method described by Emlen (1971). F ir s t, more time is spent searching fo r birds and less watching the tra n se ct path when the observer is s ta tio n a ry. Second, a standing observer should have a lesser e ffe c t on the a c t iv it y o f the avifauna. The advantages seem e s p e c ia lly re le va n t fo r the h i l l y te rra in o f the oak-ju nip er study areas. Censusing took place a t or s h o rtly a fte r sunrise. At each census p o in t, a ll birds were counted during a fifte e n -m in u te period and th e ir distances from the observer noted using a range fin d e r. No d is tin c tio n was made between visual and a ud itory sensing. Birds up to 200 M d is ta n t were recorded. Increments o f 5 M were used from 0 to 50 M, and 10 M increments from 50 to 200 M. Population densitie s were then ca lcu la te d fo r each o f the r a d ii from 5 to 200 M. These numbers are converted to in d iv id u a ls per hectare and placed in a histogram. The p o in t o f in fle c tio n o f th is curve is assumed to be the distance (X) in which a ll in d iv id u a ls are seen or heard. Density
15 is then determined by summing the number o f in d iv id u a ls recorded in the c ir c le o f radius (X), d iv id in g by the area and converting density to a standard area. For example: i f the distance from the observer a t which detections o f the b rid le d titm ouse begin to decrease is 70 M, and the number o f detections were 10, the calculated d en sity fo r th a t b ird would be 10,000 M2/hectare f 4900 M2 X 3.14 X 10 birds = 6.5 b ird s /h e c ta re. A ll d e n s itie s, converted to a per hectare basis, are presented in Table 3. Also, a ll b ird species observed w hile searching fo r hole-nests on the study areas were recorded, as w ell as those noted in less than h a lf the den sity t r i a ls. However, no d e n sitie s were ca lcu la te d fo r these species. Only a was used in Table 3 to in d ic a te th e ir presence.
RESULTS Vegetation data fo r tree species are summarized in Table 1. I intended th a t these data evaluate diffe re n ce s in tre e d e n sitie s over the two o a k -ju n ip e r areas. I used a technique introduced by Baida (T969) to compute these d e n s itie s. I measured, three parameters: 1) re la tiv e d e n s ity, 2) re la tiv e dominance, and 3) re la tiv e frequency. (Baida 1969). The importance value is the average o f the former three. I c o lle c te d these data a fte r the breeding season had ended. In each o f the o a k -ju n ip e r study areas, A llig a to r Juniper was the dominant tre e (importance value), although Emory Oak dominated according to two o f three c a lc u la tio n s in the uncut area ( re la tiv e dominance and re la tiv e frequency) (Table 1). Data p e rta in in g to a ctive hole-nesting species are shown in Table 2. These data also appear in Tables 5 through 10. Twenty-one o f twenty-two nests were found in Arizona White Oaks. A ll nests faced e ith e r h o riz o n ta lly or downward, and the m a jo rity o f the a c tiv e nest holes were d r ille d by woodpeckers. B ird population estimates appear in Table 3. These are den sity fig u re s (b ird s /h e c ta re ) fo r each o f the two o a k-ju n ip e r areas, as well as fo r Madera Canyon. I intended th a t these numbers provide a r e la tiv e comparison between the three areas. I used a technique o u tlin e d by Reynolds et al (1978 unpublished) to c a lc u la te d e n sitie s. I recorded more species a t Madera Canyon and populations were s ig n ific a n tly higher ( t te s t 1%). 16
Eight o f tw enty-nine species were noted only a t the oa k-ju n ip e r areas, seventeen o f th irty -s e v e n at Madera only. 17 Nesting data appear in Table 2. These data represent the a ctive nests found on e ith e r o f the oak-ju nip er areas during the breeding season. To fin d these hole nests I used the thorough search method, and I consider these birds nearly a ll o f the hole-nesting species in the areas. Although these data seem the most re le va n t, the r e la tiv e ly small number o f nests found on e ith e r area makes i t suspect. To draw conclusions concerning nest-hole c h a ra c te ris tic s I used data concerning a ctive and non-active woodpecker holes. Table 4 gives the tre e species preference o f avian hole- nesters. Arizona White Oak is by fa r the hole-nesting tre e most o fte n used. Table 5 catalogs a ll holes found, used and unused, as well as those selected by a c tiv e nesters. Woodpecker holes were most commonly used fo r nests, w hile branch stub holes were most prevalent among unused holes. Table 6 shows the mean DBH o f trees w ith c a v itie s as compared w ith those w ith o u t. On each study area, the Arizona Oaks w ith c a v itie s were la rg e r than those w ith o u t.. Aspect, or d ire c tio n o f face, is shown in Table 7. In each case, N to E was used most o fte n. However, the data were divided regarding the second most used aspect. Table 8 describes the cond itio n o f the trees w ith nest holes. Trees w ith less than o ne -h alf th e ir branches dead were preferred by woodpeckers and a c tiv e hole- nesters. Table 9 shows the mean diameter o f the nest hole. The mean c a v ity diameter fo r woodpecker holes and a ctive nests was less than
fo r a ll c a v itie s found. A ctive nest hole diameter ranged from 3 to 9 CM. F in a lly, the angle o f the nest hole to the v e rtic a l is cataloged in Table 10. In each area the m a jo rity o f woodpecker holes and a ctive nests faced downward or h o riz o n ta lly. Unused holes tended to face upward. These data are shown fo r the control and cut areas to provide a comparison (see Tables 1-10).
19 TABLE 1. DOMINANT TREE SPECIES IN THE OAK-JUNIPER AREAS (%) CONTROL AREA R elative Density _ Juniperus deppeana 36 Quercus emoryi 40 Quercus arizon icus 24 100 R elative R elative Importance Dominance^ Frequencyc Value^ 57 34 42 31 36 36 12 30 22 100 100 100 CUT AREA Juniperus deppeana 51 Quercus emoryi 17 Quercus arizonicus 32 100 60 44 52 10 20. 15 30 36 33 100 100 100 Number o f In d iv id u a ls o f the Species» nn Number o f In d iv id u a ls o f a ll Species Basal Area o f the Species y 1nn Basal Area o f a ll Species Number o f Points o f Occurrence o f /the Species» ^qq Number o f Points o f Occurrence o f a ll Species d: Average o f R elative Dominance, D ensity, Frequency
TABLE 2. NEST HOLES USED BY BIRDS DURING SPRING 1979 CONTROL AREA (NO WOODCUTTING) Bird Species Status^ DBH (CM) Diameter o f Hole (CM) Type o f Hole Aspect Exposure Tree Species Ash-throated Flycatcher 2 56 3.8 Woodpecker NE Down Q. arizonicus Bridled Titmouse 4 41 5.1 Woodpecker SW Down Q. arizonicus Arizona woodpecker 1 67 5.1 Woodpecker N Horiz. Q. arizonicus F licke r * 4 36 7.7 Branch Stub NE Horiz. Q. arizonicus Bridled Titmouse * 1 67 5.1 Woodpecker N Horiz. Q. arizonicus F Iicker 3 82 5.1 Branch Stub N Horiz. Q. arizonicus Wb. Nuthatch 2 26 2.6 Woodpecker E Horiz. Q. arizonicus Bewicks Wren * 3 108 6.4 Branch Stub S Down Q. arizonicus Arizona Woodpecker 3 56 3.8 Woodpecker W Down Q. arizonicus Bird Species Status^ DBH (CM) LEGAL WOOD- CUTTING AREA Diameter o f Hole (CM) Type o f Hole Aspect Exposure Tree Species Eastern Bluebird 3 31 5.1 Woodpecker N Down Q. arizonicus Birdled Titmouse 4 26 3.8 Woodpecker E Down Q. arizonicus Ash-throated Flycatcher 4 36 5.1 Woodpecker NW Down Q. arizonicus Wb. Nuthatch 2 31 5.1 Woodpecker N Down Q. arizonicus Bewicks Wren 4 46 5.1 Woodpecker W Horiz. Q. arizonicus Bridled Titmouse 3 67 2.6 Woodpecker N Down Q. arizonicus Bewicks Wren * 4 41 3.8 Woodpecker W Down Q. arizonicus Arizona Woodpecker 2 46 9.0 Woodpecker NE Horiz. Q. emoryi (See Fig. 6) Q. arizonicus Wb. Nuthatch * 1 62 6.4 Branch Stub NE Horiz. F Iicker 4 62 6.4 Woodpecker N Down Q. arizonicus Bridled Titmouse 2 31 2.6 Branch Stub SW Down Q. arizonicus Bridled Titmouse * 4 41 3.8 Woodpecker N Down Q. arizonicus ^1 = dead; 2 = a t le ast h a lf branches dead; 3 = at le ast h a lf branches a liv e ; 4 = a liv e * unsuccessful (no birds fledged)
21 TABLE 3. ESTIMATED BIRD POPULATIONS (#/HECTARE) AT EACH OF THE STUDY AREAS N = 37 Madera N = 27 Control N = 29. Cut Area Turkey v u ltu re + 1 + +2 Cooper's hawk + - Sharp-shinned hawk - 4- + R ed-tailed hawk + + + Kestrel - + + Mearn's quail - + + 3 Mourning dove - 6.3T 3.8 W.w. dove 5:1 + + Great horned owl -. + +. Screech owl + + + Pygmy owl + - Flammulated owl + - - Whiskered owl - + + W hip-poor-w ill + - - W h ite -th r. s w ift + - Hummingbird sp. + - - Red-shafted f lic k e r + 1.3 1.9 Acorn woodpecker 12.0 + 4 - Arizona woodpecker +. 1.6 1.6 S u lp h u r-b e llie d fly c a tc h e r 2.5 - - Ash-throated fly c a tc h e r + 1.9 1.3 Cassin's kin g b ird 7.6 - - Coues1 fly c a tc h e r + - - W. wood pewee 12.6 - - Mexican ja y + 3.2 4.8 S te lla r 's ja y + - - Common raven + + 4 - B rid led titm ouse + 5.0 6.3 Common b u s h tit + - - W hite-breasted nuthatch. 5.1 5.4 5.0 ^Species was found in the area, but not in de n sitie s great enough to be ca lcu la te d. 2 Species was not recorded in the area. 3 Density as determined by "v a ria b le c ir c u la r p lo t method" by Reynolds e t al (unpublished).
22 TABLE 3. ESTIMATED BIRD POPULATIONS (#/HECTARE) AT EACH OF THE STUDY AREAS Cont'd N = 37 Madera N = 27 Control N = 29 Cut Area Bewick's wren + 6.0 6.3 C u rve -b ille d thrasher - + + Robin 5.0 + + E. bluebird + 1.3 1.3 S o lita ry v ire o 2.5 -. - B1. Thr. gray w arbler + 3.1 2.5 Painted re d s ta rt + - - O live w arbler + - - Grace's w arbler + + + B u llo ck's o rio le + - - Western tanager + + + B1. headed grosbeak 1.3 - - House fin c h - + + Rufous-sided towhee 3.8 + Brown towhee - + + Mex. junco + - Chipping sparrow + +
TABLE 4. TREE SPECIES IN WHICH HOLES WERE FOUND (%) Control Area Cut Area Arizona Oak 99 91 Emory Oak 1 5 A llig a to r Juniper 0 4
24 TABLE 5. NEST-HOLE TYPES FOUND AND THOSE SELECTED BY HOLE-NESTERS {%) ' Cut Control Area Area X ALL HOLES: Woodpecker Holes 37 25 31 Branch Stubs 56 70 63 Natural C avities 7 5 6 (cracks, e tc.) ACTIVE NEST Woodpecker Holes 85 67 76 HOLES: Branch Stubs 15 33 ' 24
TABLE 6. MEAN DIAMETER BREAST HEIGHT OF TREES (WITH AND WITHOUT HOLES) Control Area Cut Area Mean DBH A ll Arizona Oaks N = 26, 19 33 CM 24 CM Mean DBH A ll Hole Trees N = 76, 78 50 CM 47 CM Mean DBH Woodpecker Trees N = 22, 27 45 CM 45 CM Mean DBH A ctive Nest Trees N = 9, 13 60 CM 43 CM
26. TABLE 7. ASPECT OF NEST HOLES (%) C o n tro l Cut Area Area ' X A l l Holes Facing N to E 31 34 32 A l l Holes Facing W to N 22 19 20 A l l Holes Facing S to w 29 32 30 A l l Hoi es Facing E to s 19 15 17 Woodpecker Holes F acing N to E 26 55 40 Woodpecker Holes F acing W to N 43 15 29 Woodpecker Hoi es F acing S to W 17 18 18 Woodpecker Holes F a cin g E to S 14 12 13 A c tiv e Nest Holes Facing N to E A c tiv e Nest Holes Facing W to N A c tiv e Nest Holes F acing S to W A c tiv e Nest Holes Facing E to S 56 54 55 11 30 20 22 8 15 11 8 10
27 TABLE 8. CONDITION OF NEST TREES (%) C o n tro l Cut Area Area X Dead^ Trees D r il le d by Woodpeckers 43 39 41 2 L iv e Trees D r ille d by Woodpeckers 57 61 59 Dead Trees Used by A c tiv e N e ste rs 44 31 38 L iv e Trees Used by A c tiv e N esters 56. 69 62 1 A t le a s t h a lf branches dead 2 A t le a s t h a lf branches a liv e
28 TABLE 9. ENTRANCE DIAMETERS OF NEST CAVITIES {%) C o n tro l Area Cut Area X Mean Diam eter o f A ll C a v itie s 6.7 5.6 6.2 Mean D iam eter C a v itie s o f A ll Woodpecker 4.9 4.9 4.9 Mean D iam eter o f A ll A c tiv e Trees 4.9 4.6 4.8
29 TABLE 10. DIRECTION OF FACE OF NEST CAVITIES (%) C o n tro l Cut Area Area X H oles F acing Upward 44 42 43 Holes F a cin g Downward 25 36 30 Holes Facing H o r iz o n ta lly 31 22 26 Woodpecker H oles F acing Upward 9 0 4 Woodpecker H oles F acing Downward. 65 82 74 Woodpecker H oles F acing 26 18 22 H o r iz o n ta lly A c tiv e N ests F acing Upward 0 0 0 A c tiv e N ests F acing Downward 44 69 56 A c tiv e Nests Facing H o r iz o n ta lly 56 31 44
DISCUSSION B efore b ir d p o p u la tio n s and n e s tin g success can be compared, one must analyze th e v e g e ta tio n in each s tu d y area. My hope was th a t th e two o a k -ju n ip e r areas would be id e n tic a l in tr e e species and d e n s ity. Data p e rta in in g to th e s tu d y areas appear in Table 1. I used a te ch n iq u e in tro d u c e d by Baida (1971) to measure th e r e la t iv e abundance o f tre e s on each stu d y area (T a b le 1 ). C o n sid e rin g the im portance v a lu e, Junip e ru s deppeana is th e dom inant tre e on each a re a. In each case ( r e la t iv e d e n s ity, r e la t iv e dom inance, and r e la t iv e fre q u e n c y ), Quercus em oryi is more abundant than Quercus a riz o n ic u s on th e c o n tro l a re a, b u t le s s abundant on th e c u t area. T h is c o n tra s t o f dominance c o u ld be a t tr ib u te d to s e le c tiv e c u ttin g o f Quercus emoryi by th e p u b lic, s in c e A rizo n a W hite Oaks cannot be le g a lly c u t on th e w o o d c u ttin g a re a. However, th e e x te n t o f c u ttin g in th e c u t area was n o t g re a t enough to e x p la in such a wide d iffe r e n c e. I encountered few Emory Oak stumps in my d e n s ity tra n s e c ts thro ugh th e c u t a re a. I must h y p o th e s iz e, th e r e fo r e, th a t th e h ig h e r e le v a tio n, g re a te r steepness o f s lo p e, and general d ry ness o f th e c o n tro l area has le d to a h ig h e r d e n s ity o f Quercus em oryi in th e c o n tro l a re a.. C o nversely, th e c u t area may be a w e tte r and more s u ita b le h a b ita t f o r A rizo n a Oaks. Quercus a r iz o n ic u s was c lu s te re d near washes in both a re a s. The c u t area had ru n n in g w a te r in i t s washes la t e in th e d ry season (m id M ay); th e c o n tr o l area had 30
31 none. I concluded th a t, a lth o u g h Junip e ru s deppeana dom inates each a re a, th e second most dom inant tre e is Quercus a riz o n ic u s in the c u t a re a, th e Quercus emoryi in th e c o n tro l area. More nests were found (13) in the c u t area than in th e cont r o l area ( 9 ). Ten o f th ir te e n n e s tin g a tte m p ts were s u cce ssfu l (a t le a s t one b ir d fle d g e d ) in th e c u t a re a ; s ix o f n in e in th e c o n tro l area (T a b le 2 ). In e s tim a tin g b ir d p o p u la tio n s o ve r th e two a re a s, I found o n ly two species (A s h -th ro a te d F ly c a tc h e r, B la c k -th ro a te d Gray W a rb le r) in g re a te r abundance in th e c o n tro l a re a. I found one species in th e c u t area th a t was. n o t counted in th e c o n tr o l area (hum m ingbird s p. ), and p o p u la tio n s were n o t s t a t i s t i c a l l y d if f e r e n t over th e two areas ( t t e s t IX ) (T able 3 ). These d ata seem to in d i cate th a t w o o d c u ttin g has n o t a ffe c te d b ir d p o p u la tio n s o r n e s tin g success. However, th e areas may n o t be e q u a lly a b le to s u p p o rt b ird p o p u la tio n s. The g re a te r d e n s ity o f A rizo n a Oaks in th e c u t area (Table 1) may a llo w i t to s u p p o rt a g re a te r d e n s ity o f b ir d s. Thus, th e d a ta 's in te r p r e t a tio n is u n c le a r. One may argue th a t th e e ffe c ts o f w o o d c u ttin g are n o t lim ite d to th e c u t a re a, th a t b ir d p o p u la tio n s are a ffe c te d on e ith e r a re a. The access road tra v e rs e d th e c o n tro l area (F ig. 3) b u t i t s e ffe c ts are d i f f i c u l t to q u a n t if y.. I saw no evidence o f ille g a l c u ttin g on th e c o n tro l a re a, b u t th e re was some evidence in th e c u t area. Lower lim b s were o fte n removed from la rg e unmarked tr e e s, e s p e c ia lly ju n ip e r s. Noise from c h a in saws was o fte n heard on th e c o n tro l a re a, b u t i t s e f f e c t may be m in im a l. In my e s t i m a tio n, th e v e g e ta tio n a l c o n tra s t between th e two areas is due in a
32 sm all p a rt to w o o d c u ttin g ; more im p o r ta n tly, i t is due to e le v a tio n, s lo p e, w a te r, e xp e rim e n ta l e r r o r, e tc. T h is v e g e ta tio n d iffe r e n c e may e x p la in th e n e s tin g success on th e c u t area. / One must c o n s id e r th e p o s itiv e e ffe c ts o f w o o d cu ttin g - - c re a t io n o f s la s h being an im p o rta n t one (F ig. 4 ). A cco rding to th e F o re st S e rv ic e manual (Johnston 1978), s la s h must be p ile d in d ra in a g e s, where a v a ila b le, to be used as e ro s io n c o n tr o l, w i l d l i f e h a b ita t, o r to be burned a t a la t e r d ate by F o re st S e rv ic e p e rsonnel. Slash p ile s were commonly found on th e c u t a re a, e s p e c ia lly near th e access ro a d. I noted a g re a te r p o p u la tio n o f c o t to n ta ils ( S y lv ila g u s f lo r id a n u s ) in th e c u t area than in th e c o n tro l a re a. Many were flu s h e d from sla sh p i l e s. l e f t by w o o d c u tte rs. In h is stu d y o f h o le -n e s tin g b ir d s, M cc le lla n d (1976) m entions th a t w o o d cu ttin g may be d e trim e n ta l when fe e d in g s ite s are covered w ith c u t tre e s and branches. In my study a re a, these p ile s were used to a lim ite d e x te n t by in s e c tiv o ro u s b ird s. However, I do n o t c o n s id e r sla sh p ile s a n e g a tiv e e f f e c t o f w o o d cu ttin g T h is is p a r t ly because th e re was o n ly one common ground fe e d e r found in th e stu d y a re a s : th e ru fo u s -s id e d towhee. Increased food resources f o r liv e s to c k is a p o s itiv e e f fe c t o f w o o d c u ttin g noted by th e F o re st S e rv ic e. The F o re s t S e rv ic e plans to prune e x is tin g tre e s and c le a rc u t t o accom plish t h is. E xte n sive p ru n in g has been done, b u t o n ly hear th e access road (F ig. 3 ). This, p r a c tic e may in c re a s e th e growth o f g ra s s, b u t seems o f f s e t by poor a e s th e tic s. C le a r - c u ttin g would b e n e fit th e M earn's Q u a il, among o th e rs, w hich has been reduced w ith th e decrease o f grass in southern
FIG. 4. SLASH PILES LEFT BY WOODCUTTERS ON THE WESTERN OAK-JUNIPER AREA GO GO
34 A riz o n a. I t p re fe rs grassy woods (M a rsh a ll 1957). However, fo r e s t species o f b ird s would s u re ly s u f f e r. F u rth e r goals n o t y e t com pleted a re : 1. P ro v is io n f o r p e re n n ia l w a te r sources f o r w i l d l i f e and liv e s to c k.; 2. Increased cover a v a i l a b i l i t y f o r w i l d l i f e ; and, 3. P ro v is io n f o r th e s u s ta in e d y ie ld of. h a rv e s ta b le tim b e r. F in a lly, some e ro s io n has been prevented on th e w o o d c u ttin g area by c re a tio n o f s la s h p ile s and blockage o f a u x ilia r y roads th ro u g h th e a re a. However, e ro s io n has been c o n s id e ra b le along th e access ro a d, making i t im passable f o r th e w in te r season and most o f th e s p rin g. I f th e f u l l b e n e fits o f th e fuelw ood program are to be r e a liz e d, the F o re s t S e rvice must make an e f f o r t to keep th e access road p a ssa b le, e s p e c ia lly f o r n o n.fo u r-w h e e l-d riv e v e h ic le s. I t became apparent e a r ly in th e stu d y th a t Quercus a riz o n ic u s was th e p re fe rre d h o le -n e s tin g tr e e to Quercus emoryi and Ju n ip e ru s deppeana. The abundance o f Quercus em oryi (16% c u t, 35% c o n tr o l, im portance v a lu e ) is f a r above th e p ro p o rtio n o f Emory Oak h o le tre e s found d u rin g search f o r hole nests (3 c u t a re a, 1 uncut a re a ) to th e t o ta l number o f h o le tre e s found (76 c u t a re a, 78 uncut a rea) (T able 1 ). On the o th e r hand, 91% o f hole tre e s were A rizo na Oak on th e c u t area and 99% on th e c o n tro l area (T able 4 ). Im portance va lu e s f o r A rizo n a Oak were 22% ( c o n tr o l) and 33% ( c u t a r e a ). I would h yp o th e size th a t Quercus a riz o n ic u s is s e le c te d over Quercus emoryi by h o le -n e s te rs because o f i t s decay c h a r a c te r is tic s. Thus, woodpeckers are a b le to
excavate s u ita b le c a v itie s. O ther a u th o rs have noted h o le -n e s te rs ' p re fe re n c e f o r s o f t wooded tre e s ; f o r in s ta n c e. Aspen was p re fe rre d by f lic k e r s (Dennis 1969). Junip e ru s deppeana was c o m p le te ly ig nored by h o le - d r ille r s d e s p ite a g re a t number o f la rg e dead ju n ip e rs w ith s u ita b le lim b s (F ig. 5 ). A p p a re n tly woodpeckers cannot break the o u te r hardwood o f Ju n ip e ru s deppeana and have a c o m p a ra tiv e ly d i f f i c u l t tim e w ith Quercus e m o ry i. S e v e r a l'c la s s ific a tio n s o f hole typ e s were used in the s tu d y : 1. Those d r i l l e d by. woodpeckers (F ig. 6) ; 2. Those r e s u ltin g from branch stu b decay ( F ig. 7 ) ; and, 3. O ther n a tu ra l c a v itie s (c ra c k s, e t c. ). The most common type o f h o le t h a t I found was th e branch stu b typ e (56% c u t a re a, 70% c o n tro l a rea) (T a b le 5 ). The abundance o f b ra n c h -s tu b caused holes in the p o p u la tio n may be due to la c k o f s e le c t i v it y in procedure. I was n o t s e le c tiv e in ta g g in g p o te n tia l n e s t holes and tagged many th a t may have been u n s u ita b le f o r one * reason o r a n o th e r. Pinkow ski. (1976) c la im s th a t o f th e unused c a v i-. t ie s he fo u n d, most 1) had a la r g e r c a v ity d ia m e te r, and 2) had a g re a te r number o f dead branches than those tre e s which were used by h o le -n e s te rs. Holes d r ille d by woodpeckers were second most p re v a le n t (37% c u t a re a, 25% c o n tro l a re a ). p re fe rre d woodpecker h o le s. However, secondary h o le -n e s tin g b ird s On th e c o n tro l a re a, 67% o f a c tiv e nest hole s were d r ille d by woodpeckers; on th e c u t area 85% o f th e a c tiv e n e s t holes were woodpecker-caused. Woodpecker holes are p re fe rre d by
36 FIG. 5. A DYING ALLIGATOR JUNIPER WITHOUT NESTING CAVITIES
37 FIG. 6. NEST HOLE MADE BY AN ARIZONA WOODPECKER IN AN EMORY OAK
38 FIG. 7. A HOLE RESULTING FROM BRANCH STUB ROT IN AN ARIZONA WHITE OAK
39 secondary h o le -n e s tin g b ird s because t h e ir d ia m e te r is sm all enough to keep p re d a to rs o u t and la rg e enough to p e rm it e n tra n ce by th e b ir d. T his p re fe re n c e f o r woodpecker holes p o in ts o u t th e e c o lo g ic a l im portance o f p rim a ry h o le -n e s te rs in the o a k -ju n ip e r woodland. W ith o u t these b ir d s, secondary h o le -n e s te rs would have to move elsew here. In t h is case, th e h o le - d r ille r s are A rizo n a woodpeckers and f lic k e r s. To th e fo r e s te r, p o s s ib ly th e most im p o rta n t measure o f a l l is th e average DBH o f th e n e s t tre e s (T able 6 ). Trunk d ia m e te r may a f f e c t avia n p re fe re n c e s in c e many A rizo na Oaks w ith holes were la r g e r (g re a te r than 77 CM DBH) than th e la r g e s t Emory Oak (67 CM). However, some e x tre m e ly sm all A rizo n a Oaks (DBH: 26 CM) were found w ith a woodpecker h o le, so DBH is p ro b a b ly n o t a lim i t i n g fa c to r. The average DBH f o r a l l hole tre e s on th e two areas was n e a rly equal (50 CM c u t a re a, 47 CM uncu t a r e a ), and th e average DBH o f tre e s w ith woodpecker holes was id e n tic a l (45 CM). However, woodpecker holes were found in la r g e r A riz o n a Oaks than average: 45 CM to 24 CM on th e c u t a re a, 45 CM to 33 CM on th e uncu t area (T a b le 6 ). T h is may be because A rizo n a Oak tre e s le s s than 26 CM were in s u f f ic i e n t ly la rg e to p ro v id e tru n k space f o r a n e s t. M cc le lland (1976) noted th a t few nests were found in s ite s where p o le (DBH le s s than 23 CM) o r where s m a lle r s iz e tre e s predom inated. S ix ty p e rc e n t o f th e h o le tre e s were le s s than o r equal to 46 CM DBH; 40% were g re a te r than 46 CM DBH. A p p a re n tly th e p refe rre d oaks were le s s than 46 CM DBH. G re a te r DBH than average tre e s are s e le c te d f o r tru n k c a v ity space. The a sp e ct o f th e n e st h o le was a ls o recorded (T a b le 7 ). T h is re fe rs to th e d ir e c tio n, th e entra n ce h o le fa c e s. I d iv id e d th e compass
40 in to fo u r 90 s e c to rs : N to E ( 0-9 0 ); E to S (9 0-1 8 0 ); S to W (1 8 0-2 7 0 ); and W to N (.270-360 ) f o r h o le -n e s t c la s s if ic a t io n. I in c lu d e d each n e st in one o f these s e c to rs. For a l l holes found (woodpecker, s tu b, e t c. ), N-E and S-W were th e most used a sp e cts. However, as we have seen, many o f these holes may never have been used, so a b e tte r measure o f a sp e ct p re fe re n ce is woodpecker h o le s. In t h is sam ple, N to E and W to N are th e most commonly fo u n d, b u t th e re is disagreem ent in th e two stu d y areas. An average o f the two areas shows N to E th e p re fe rre d d ir e c tio n (40% N-E, 29% W-N). N to E was the overw helm ing ch o ice a c co rd in g to th e n e s tin g data (56% cont r o l a re a, 54% c u t a re a ). There may be s e v e ra l e x p la n a tio n s : 1. Avoidance o f th e summer a fte rn o o n sun; 2. Avoidance o f summer thunderstorm s (u s u a lly a s s o c ia te d w ith s o u th e rly w in d s) and w in te r f r o n ta l ra in s (u s u a lly a s s o c ia te d w ith w e s te rly w in d s ), th u s keeping ra in w a ter o u t o f th e n e s t h o le. In a d d itio n, S to W (18%) and E to S (13%) seem to be s e le c te d a g a in s t, presum ably f o r th e same reasons. The a sp e ct o f n e s t lo c a tio n has been discussed by many a u th o rs, and th e re seems to be c o n s id e ra b le disagreem ent re g a rd in g i t. From c e n tra l O n ta rio, Lawrence (1967) re p o rts th a t s o u th e a st fa c in g is th e p re fe rre d d ir e c t io n. In.M a s s a c h u s e tts, Dennis (1969) found south and east fa c in g holes most abundant. In M ichig a n, Pinkow ski (1976) re p o rte d th a t so u th e a s t is th e most commonly found d ir e c tio n th a t n e st holes fa c e. O nly Conner e t a l (1975) found more nests fa c in g n o rth e a s t ( in V ir g in ia ), b u t he s a id th a t i t was due to the slo pe o f th e la n d. Slope in th e area was such t h a t, to excavate a hole on th e d o w n -fa cin g
41 sid e o f th e tru n k, th e hole must fa ce n o rth e a s t. E v id e n tly, warmth from th e m orning sun plays a p a rt in th e n e s t-h o le s e le c tio n from these s tu d ie s in n o rth e rn la titu d e s. On th e o a k -ju n ip e r stu d y a re a s, slo p e was v a r ia b le in and around the d ry washes, and d i f f i c u l t to e v a lu a te. Avoidance o f a fte rn o o n sun seems to be a f a c to r in choosing an A rizo n a n e s t h o le. F in a lly, these a u th o rs have fu r t h e r e x p la n a tio n s f o r h o le n e s t s e le c t iv it y w hich may a ls o a p p ly to A riz o n a. Blume (1961) suggests th a t fo ld s and o th e r typ e s o f grow th o f the wood caused by s c a rs, branches, f u n g i, o r th e w eather may a ffo r d c o n d itio n s f o r e a s ie r excav a tio n o f c a v itie s. These grow ths are most p re v a le n t on a tr e e 's n o rth s id e. Lawrence (1967) p o in ts o u t th e im portance o f th e roughness o f b a rk, r e s u ltin g in a good fo o th o ld. A p p a re n tly bark is rougher on th e n o rth s id e o f th e tr e e. A n oth er v a r ia b le measured in t h is stu d y was th e r e la t iv e h e a lth o f th e n e st tr e e (T a b le 8 ). I used fo u r c a te g o rie s ra n g in g from dead to a liv e, depending upon th e amount o f liv e fo lia g e. Woodpecker h o le s seem to p ro v id e th e most c o n s is te n t data because th e se holes were used a t one tim e. The m a jo r ity (59). o f th e tre e s w ith woodpecker holes had more than o n e -h a lf liv e branches. T h is may be because many dead tre e s w hich are e a s ily excavated by woodpeckers are a lso e a s ily d estroyed by p re d a to rs. Gray fo xe s and coyotes fre q u e n te d th e s tu d y area. Due to th e r e la t iv e ly sm all s iz e o f th e n e s t tre e s, these p re d a to rs are p ro b a b ly a b le to reach lo w e r bra n ch e s. A ls o, n e a rly dead tre e s may blow over in summer thunderstorm s w hich are o fte n accompanied by s tro n g w inds. I d e a lly, a woodpecker may search f o r a tre e ju s t s o ft enough to excavate b u t n o t s o f t enough to be e n te re d by a p re d a to r. P inkow ski
42 (1976) found th a t o f th e unused c a v itie s he fo u n d, most were found in tre e s w ith more dead branches than those w hich were used by h o le - n e s te rs. F o re ste rs should be c a re fu l to le a ve la rg e liv e A rizo na Oaks and those w ith a few dead branches. Because o f p re d a tio n, h o le d ia m e te r is im p o rta n t to h o le - n e ste rs (T a b le 9 ). Many branch stu b holes were p ro b a b ly unused because t h e ir d ia m e te rs were to o la rg e. Mexican ja y s in th e area may r a id c a v ity nests W ith d iam e te rs la rg e enough to p e rm it e n try. Small b ird s are a b le to e n te r am azingly m inute holes so i t is no s u rp ris e th a t th e average woodpecker h ole was 4.9 CM in d ia m e te r. The average d ia m e te r o f a l l holes was la r g e r (6.2 CM) because many la rg e d ia m e te r unused nests were tagged. Exposure o f th e n e st hole is an im p o rta n t s e le c tiv e fa c to r. Exposure r e fe rs to th e angle w ith th e v e r t ic a l th a t th e h ole faces (T able TO). I used th re e c a te g o rie s : 1. Facing up ( F ig. 6 ) ; 2. F acing down; and, 3. Facing h o r iz o n ta lly (F ig. 5 ). I c o n s id e r th e woodpecker holes to be the b e st measure o f h o le p re fe re n c e. Only 9% o f a l l woodpecker hole s faced upward on the cont r o l a re a ; none on th e c u t a rea. The rem ainder o f th e holes on each area was d iv id e d between dow n -fa cin g and h o r iz o n t a lly - f a c in g, w ith more fa c in g down in each case. None o f th e a c tiv e nests faced upward in e ith e r a re a. In Southern A riz o n a, r a i n f a l l as w e ll as d ir e c t s u n lig h t
may d isco u ra g e b ird s from choosing holes w ith an upward fa c in g exposure. R ainw ater may d r ip in to an upward fa c in g hole o r a h o r iz o n ta lly fa c in g 43 one, b u t is le s s l i k e l y to f i l l a dow n -fa cin g one. As high as the summer sun reaches in June (9 south o f d ir e c t ly overhead a t m id -d a y ), i t would be d i f f i c u l t to keep an upward fa c in g n e s t c o o l. B ird s in both stu d y areas s e le c te d h o r iz o n ta lly o r d ow n-fa cing h o le s. O ther a u th o rs found t h is to be th e case. Lawrence (1967) found th a t most holes faced downward; she claim ed t h is was because downward-?facing holes are le s s v is ib le to p re d a to rs. Conner (1975) b e lie v e s th a t th e u nderside o f th e tre e tru n k is a b e tte r m icro e n viro n m e n t f o r f u n g i, th u s, p e r m ittin g e a s ie r e x ca va tio n o f the h o le. He a ls o m entioned th a t a dow nw ard-facing h o le is e a s ie r to defend than an upward o r h o r i z o n ta l ly fa c in g one. S e venty-tw o p e rce n t o f th e Ponderosa Pines ( Pinus ponderosa) and 60% o f th e Quaking Aspens ( Populus tre m u lo id e s ) in th e nearby Santa C a ta lin a M ountains had more than one h o le per h o le -n e s tin g tr e e. The fo llo w in g data shows th a t most h o le -n e s tin g tre e s On th e oakju n ip e r stu d y areas had o n ly one h ole per tre e. O nly fo u r o f tw e n ty - seven (15%) w o o d p e c k e r-d rille d n e st tre e s had more than' one hole in th e c u t a re a. In th e c o n tro l a re a, one o f tw e n ty -tw o (4%) had more than one n e s t h o le. M cc lelland (1976) found th a t 70% o f w estern la rc h n e st tre e s had th re e o r more n e st h o le s, in d ic a tin g reuse from y e a r to y e a r. A p p a re n tly th e re are n o t as many p o s s ib le n e st hole s ite s on th e A rizo n a W hite Oak because o f i t s r e la t iv e ly sm all s iz e. These data seem to emphasize th e im portance o f r e ta in in g a la rg e number o f p o te n tia l A rizo n a W hite Oak n e st tre e s in an a re a, sin ce no
one n e st tre e can accommodate a la rg e number o f h o le -n e s te rs. As I m entioned e a r lie r, b ird p o p u la tio n s o f th e c o n tro l area and th e c u t area a re n o t s ig n if ic a n t ly d if f e r e n t (T able.3) ( t te s t; 1%). T h e re fo re, I w i l l c o n s id e r th e d iffe re n c e s between Madera Canyon counts and o a k -ju n ip e r stu d y area counts ( e le v a tio n o f each a p p ro x im a te ly 1,524 M). The most n o ta b le d iffe r e n c e is th e number and abundance o f species a t Madera Canyon. Speaking o f the r ip a r ia n w oodland, M a rsh a ll (1957) notes i t s h e ig h t, d iv e r s it y, r ic h u n d e rs to ry o f h e rb s, sh ru b s, and flo w e rs, and i t s extended edge p e rm it a g re a te r c o n c e n tra t io n o f b ir d s, c o n s id e rin g i t s narrow ness. The a u th o r m entions th a t eleven sp e cie s from h is p in e -o a k woodland l i s t would n o t o ccu r on th e consensus (p in e -o a k woodland) w ith o u t r ip a r ia n woodland: C ooper's Hawk, Mexican B la ck Hawk, B lu e -th ro a te d Hummingbird, B lack-c hinned Hum m ingbird, e tc. T h is tre n d seems to f i t my data s in c e seventeen species observed a t Madera Canyon were n o t noted a t th e s tu d y a re a s. E ig h t species were observed on th e o a k -ju n ip e r stu d y a re a s, b u t n o t. a t Madera Canyon. I t should a ls o be m entioned th a t r ip a r ia n f lo r a o f Madera Canyon, e s p e c ia lly o ld A rizo n a Sycamores, p ro v id e s an abundance o f h o le -n e s tin g space. Some o f th e la r g e r tre e s co n ta in e d as many as f iv e c a v it ie s, presum ably d r ille d by Acorn Woodpeckers, b u t used a ls o by secondary h o le - n e s te rs. As M a rsh a ll (1957) p o in ts o u t, th e re is a- g re a te r v a r ie t y o f species (16) in th e r ip a r ia n woodland (such as Madera Canyon) than th e re is in o a k -ju n ip e r areas (1 4 ). However, he found t h ir te e n p a irs ( b ir d s ) per m ile in th e r ip a r ia n w oodland, tw e n ty -n in e p a irs per m ile in th e o a k - ju n ip e r. B a ile y (1923) recorded
45 f i f t y - t h r e e species a t G ardner Canyon (n ear th e o a k -ju n ip e r study a re a s ), s ix t y - f i v e species a t Madera. A lth ough most b ird s recorded on th e stu d y areas are found in v e g e ta tio n types o th e r than th e o a k -ju n ip e r ty p e, some are more o r le s s dependent upon i t. One example o f a b ird th a t can e x is t in a v a r ie ty o f v e g e ta tio n a l types is th e S potted Screech Owl, w hich was found on th e e a s te rn stu d y areas and a t Madera Canyon. M a rsh a ll (1957) cla im s th a t th e S potted Screech Owl is a t home in any kin d o f woodland. The A rizo n a Woodpecker, however, is r e s t r ic t e d to woods in w hich oaks are p le n t if u l (M a rshall 1957).. Because i t is a p rim a ry h o le -n e s te r, i t s disappearance would r e s u lt in th e exodus o f secondary h o le -n e s te rs such as those in t h is s tu d y. T h is evidence seems to p o in t o u t the im portance o f r e ta in in g th e o a k -ju n ip e r woodland as w e ll as th e r ip a r ia n w oodland. H o p e fu lly, r e te n tio n o f th e o a k -ju n ip e r woodland is n o t th e issu e here. The q u e stio n should be: How much s h a ll i t be changed? Some species w i l l b e n e fit by i t s change; o th e rs w i l l n o t. As m entioned e a r lie r, a g re a te r abundance o f grassy a re a s, cre a te d by fu e l wood c u ttin g o f oaks, may r e s u lt in a g re a te r number o f M earn's Q u a il, as w e ll as E astern B lu e b ird s, w hich p r e fe r s a v a n n a h -lik e woods o r fre q u e n t c le a rin g s (M a rs h a ll 1957). A cco rd in g to Baida (1 9 6 9 ), th e B la ck- th ro a te d Gray W a rb le r, C hipping Sparrow, B rid le d T itm ouse, B la c k - Chinned Hummingbird are a b le to u t i l i z e s u c c e s s fu lly th e high f o lia g e - d e n s ity p ro vid e d by A llig a t o r J u n ip e r. These b ir d s ' p o p u la tio n s w ould p ro b a b ly be reduced w ith th e removal o f th a t s p e c ie s. A s h -th ro a te d F ly c a tc h e rs p r e fe r ro cky o r brushy e n c in a l slopes (M a rs h a ll 1957), so
46 t h is species would b e n e fit from a re d u c tio n in tre e d e n s ity. The R u fous-sided Towhee is fa v o re d by lo g g in g, c le a r in g, and fuelw ood c u ttin g w hich r e s u lts in th e growth o f oak scru b. The Brown Towhee as w e ll p re fe rs open woods and p re va le n ce o f meadows. I t s g re a te s t numbers are reached in grassy woods. C ontinuous chapparal and scrubby oak and ju n ip e r-c h o k e d woods o f Southern A rizo n a M ountains a re o f course unacceptable ( f o r th e Brown Towhee) (M a rs h a ll 1957). F in a lly, a key sp e cie s whose disappearance would in d ic a te change o f th e e n v iro n m e n t's co m p o sitio n may be th e A rizo n a Woodpecker. As I have m entioned, t h is b ird r e lie s on th e oak typ e and w i l l disappear i f th e re is too much c u t tin g. F o re ste rs should m o n ito r t h is b ir d 's p o p u la tio n as fuelw ood c u ttin g programs p ro g re ss. The im portance o f th e o a k -ju n ip e r woodland to a via n as w e ll as o th e r w i l d l i f e species cannot be doubted. A lthough t h is stu d y f a i l s to q u a n tify t h is b e lie f as Baida d id (1 9 7 1 ), a l l tre e s in th e e n v iro n ment are used to some e x te n t by b ir d s. A lth o u g h Ju n ip e ru s deppeana is an in v a d e r and p ro v id e s no h o le -n e s tin g space, i t is e x te n s iv e ly used by se ve ra l species f o r r o o s tin g, fo ra g in g, n e s tin g, e tc. Morse (1967) and M ca rthur and L evins (1964) found th a t th e volume o f fo lia g e may be an im p o rta n t fa c to r in lim it in g d e n s ity o f some species o f b ird s. Thus, th e im pact o f e x te n s iv e c u ttin g as p ra c tic e d in th e S ie rra V is ta F o re s t S e rv ic e D i s t r i c t (a d ja c e n t to th e e a s t) may be s ig n if ic a n t. S ix ty to e ig h ty p e rc e n t removal o f tre e s in th a t area may have a ffe c te d b ir d p o p u la tio n s. I t seems f a r b e tte r to remove a sm all percentage o f s e le c te d tre e s from many areas (as in th e Nogales d i s t r i c t ), than a
la rg e percentage from a new a re a. Since th e re is no sh o rta g e o f n e s t- hole tre e s on th e stu d y a re a s, 20 to 30% o f a l l tre e s co u ld be removed 47 w ith o u t a f fe c tin g h o le -n e s tin g b ir d s. S p e cia l care should be taken to le a ve a l l A riz o n a Oak tre e s, o f 40 CM o r g re a te r DBH near g u l lie s, as w e ll as a l l tre e s w ith woodpecker h o le s. Due to th e r e la t iv e ly sm all s iz e o f th e tre e s in th e o a k -ju n ip e r w oodland, fo r e s te r s can id e n t if y tre e s w ith holes e a s ily and in s u re th a t th e y are n o t c u t. These g u id e lin e s should be fo llo w e d in fu tu r e o a k -ju n ip e r fu e l wood program s. T. Several designated areas per fo r e s t s e rv ic e d i s t r i c t should be a v a ila b le to th e p u b lic to a v o id overuse o f a few a re a s ; 2. O nly s p e c if ic a lly marked tre e s should be c u t; 3. Oaks should be c u t to a lim ite d e x te n t, ju n ip e rs o r o th e r in v a d in g specie s to a g re a te r e x te n t; 4. No tre e s should be c u t in o r near d ry o r flo w in g washes; 5. P e rio d ic avia n censuses should be taken to e v a lu a te the e ffe c ts o f tre e re m o va l, w ith s p e c ia l a tte n tio n paid to A rizo n a woodpeckers. I f these g u id e lin e s are c o n s id e re d, th e in t e g r i t y o f the oak- ju n ip e r woodland may be preserved and fuelw ood needs s a t is f ie d.
\ LITERATURE CITED B a ile y, F lo re n ce A ugusta. 1923. B ird s Recorded From th e Santa R ita M ountains in Southern A riz o n a. 60 p. B aida, Russel P. 1969. F o lia g e Used bv B ird s o f th e O ak-ju nip er Woodland and Ponderosa Pine F o re st in S o uth eastern A riz o n a. Condor 7 1 (4 ): 399-412. _ Blume, D. 1961. Uber d ie Lebenweise e in ig e r S p e c h ta rte n. Jo u rn. O rn ith o lo g y 102: 1-115. Conner, R ichard. 1975. O rie n ta tio n o f E ntrances to Woodpecker Nest C a v itie s. Auk 92(2) :371-374. ~ ~ ~ ~ Conner, R ich a rd ; Hopper, R obert G.; C raw ford, H e w le tte S. and Mosby, Henry S. 1975. Woodpecker N e stin g H a b ita t in Cut and Uncut Woodlands in V irg in T a. J. o f W ild l. Manage. 3 9 (1 ):1 4 4-1 5 0. Cottam, G. and C u r tis, J. T. 1956. The Use o f D istance Measures in P h y to s o c io lo g ic a l S a m plin g. Ecology 37:451-460. D ennis, John. 1969. The Y e llo w -s h a fte d F lic k e r (C olaptes a u ra tu s ) on N antucket Is la n d T "M a s s a c h u s e tts. B ird Banding 4 0 (4 ):2 9 0-3 0 8. Emlen, J. T. 1971. P o p u la tio n D e n s itie s o f B ird s D erived From T ra n s e c t Counts. Auk 8 8 (2 ) =323-342.' E rs k in e, A., and M cclaren, W. 1972. Sapsucker Nest Holes and T h e ir Use by O ther S pecies. Canad. F id. N at. 8 6 (4 ):3 5 7-3 6 1. ^ ~ F o re s t S e rv ic e U.S. 1980. Region Three Sang Management P o lic y on N a tio n a l Tim ber Sales F.S.M. 3/7 8 R-3. Supp. 130. 4 p. Johnston, A. L. 1978. E n vironm ental A n a ly s is Report-: Fuelwood Sale P r o je c t, U.S. F o re s t S e rv ic e, Nogales D i s t r i c t, A riz o n a. 5 p. 48
49 Kearney, Thomas H. and P eebles, R obert H. 1951. A rizo n a F lo ra, U. o f C a lif. P ress, 1081 p. Lawrence, L o u is e. 1967. A Com parative L ife H is to ry Study o f Four Species o f W oodpeckers. O rn ith o lo g ic a l Monographs No. 5. 156 p. Lowe, C harles H. 1964. A riz o n a 's N a tu ra l E n viro n m e n t; Landscape H a b ita t. U. o f A r iz. P ress, Tucson, A riz o n a. 136 p. M a rs h a ll, Joe T. 1957. B ird s o f Pine-Oak Woodland in Southern A rizo n a and A d ja ce n t M exico. P a c ific Coast A vifa una 32. 125 p. M ca rthur, R. H., and L e v in s, R. 1964. C o m p e titio n, H a b ita t S e le c tio n, and C h ara cte r D isplacem ent in a Patchy E n viro n m e n t. P ro c. N a tl. Acad. S c i. 51:1207-1210. M cc le lla n d, R. 1976. R e la tio n s h ip s Between F o re s t Snags and B ird s in the N o rth e rn Rocky M o u n ta in s. Ph.D. D is s e rta tio n (Summary). U. o f Mont. 7 p. M ic h a e l,, Edwin, and T hornburgh, P. 1971. Im m ediate E ffe c ts o f Hardwood Removal and P re scrib e d B urning on B ird P o p u la tio n s. S.W. Nat. 1 5 (3 ):3 5 9-3 7 0. Morse, D. H. 1967. C o m p e titiv e R e la tio n s h ip s Between Parula W arblers and O ther Species D uring th e B reeding Season. Auk 84:480-502. N a tio n a l Oceanic and Atm ospheric A d m in is tra tio n 1978. C lim a to lo g ic a l D a ta. V o l. 83, No. 3. P in kow ski, B e n e d ic t. 1976. Use o f Tree C a v itie s by N e stin g E astern B lu e b ird s. J. o f W ild!. Manage. 4 0 (3 ):5 5 6-5 6 3. Reynolds, R. T., S c o tt, J. M., and Nussbaum, R. A. 1978. A V a ria b le C ir c u la r P lo t Method f o r Censusing B ir d s. U n published. S c o tt, V i r g i l, and P a tto n, D avid. 1975. C a v ity -n e s tin g B ird s o f A rizo n a and New M exico F o re s ts. USDA F o re st S e rv ic e, General T e ch n ica l R e port, RM-10, 51 p. V e rner, J. (T e c h n ic a l C o o rd in a to r) 1975. Proceedings o f th e Symposium on Management o f F o re st and Range H a b ita ts f o r Nongame B ir d s. USDA F o re st S e rv ic e, General T e ch n ica l R e p o rt, W0-1, 343 p.