The Auk 127(1):108 118, 2010 The Amerin Ornithologists Union, 2010. Printe in USA. Ptterns of Fuel Use n Storge in Migrting Psserines in Reltion to Fruit Resoures t Autumn Stopover Sites Su s n B. Sm i t h 1 n S o t t R. MWilli ms Deprtment of Nturl Resoures Siene, University of Rhoe Isln, Kingston, Rhoe Isln 02881, USA Astrt. Fuel eposition rtes of migrting irs my inite the qulity of hitt t stopover sites, yet little is known out how iet hits n foo vilility ffet ft n protein metolism in free-living songirs t stopover sites. We ompre plsm initors of ft eposition (triglyerie), ft tolism (B-hyroxyutyrte), n protein tolism (uri i) mong psserine speies tht re frugivorous to vrile egree uring utumn stopover on Blok Isln, Rhoe Isln. We lso ompre plsm lipi metolites from 3 of these speies tht were pture t 2 stopover sites with ifferent fruit unne. The more frugivorous Hermit Thrushes (Cthrus gutttus) h the highest plsm triglyerie, n uri i ws highest in the lest frugivorous speies smple on Blok Isln, ut other ifferenes mong speies were not lerly relte to iet. B-hyroxyutyrte ws more vrile mong the speies smple on Blok Isln. Plsm triglyerie ws signifintly higher in Hermit Thrushes pture on Blok Isln, where fruit resoures were unnt, thn in Hermit Thrushes pture t minln site in southern Rhoe Isln, where less fruit ws ville. Our results suggest tht iet hits my influene ft n protein metolism in migrting psserines, ut reful stuy esign n sttistil nlyses re neessry to ontrol for or minimize the effets of the mny influentil ftors tht ffet plsm metolites so they n e use to ssess fuel eposition in free-living irs n to ompre the qulity of migrtion stopover sites. Reeive 6 June 2008, epte 27 My 2009. Key wors: migrtion, plsm metolites, sesonl frugivory, songirs, stopover. Ptrones e Uso y Almenmiento e Comustile en Pseriformes Migrtorios on Relión Reursos e Frut en Sitios e Prs Migrtoris e Otoño Resumen. L ts e umulión e reursos energétios por prte e ls ves que se enuentrn en migrión puee inir l li el háitt en los sitios e prs migrtoris. Sin emrgo, se se poo sore er e ómo los háitos e limentión y l isponiili e limentos fetn el metolismo e ls grss y proteíns e ves silvestres en los sitios e pr. Comprmos iniores plsmátios e l umulión e grss (trigliérios), el tolismo e ls grss (B-hiroxiutirto) y el tolismo e proteíns (áio úrio) entre espeies e ves pseriformes on epeneni vrile e un iet frugívor urnte ls prs migrtoris e otoño en Blok Isln, Rhoe Isln. Tmién omprmos metolitos lipíios plsmátios e otrs tres espeies que fueron pturs en os sitios e pr migrtori que iferín en l unni e frutos. L espeie más frugívor, Cthrus gutttus, tuvo l myor nti e trigliérios plsmátios, y el áio úrio fue más lto en l espeie menos frugívor que fue muestre en Blok Isln. Sin emrgo, otrs iferenis entre espeies no se relionron lrmente on l iet. El B-hiroxiutirto fue el inior plsmátio más vrile entre ls ves muestres en Blok Isln. Los trigliérios plsmátios fueron signifitivmente más ltos en iniviuos e C. gutttus pturos en Blok Isln, one los frutos ern un reurso unnte, que en los iniviuos e l mism espeie pturos en un sitio ontinentl en el sur e Rhoe Isln, one hí menos frutos isponiles. Nuestros resultos sugieren que los háitos limentiios pueen influenir el metolismo e ls grss y proteíns en pseriformes migrtorios. Sin emrgo, es neesrio eliner iseños experimentles uiosos y nálisis e tos euos pr ontrolr o minimizr los efetos e otros ftores que tmién influenin los metolitos plsmátios, e moo e que éstos puen ser usos pr eterminr l umulión e energí en ves silvestres y pr omprr l li e los iferentes sitios e prs migrtoris. Annul migrtions of irs etween reeing n wintering grouns involve energetilly emning noturnl flights fuele primrily y store ft (Blem 1980). Smll songirs must regulrly stop etween flights to umulte energy stores to ontinue migrtion. Foo unne is importnt for effiient refueling n n influene the time spent t stopover sites (Biy n Green 1981; Shu n Jenni 2000, 2001). In ition, the qulity of foo resoures n ffet the rte t whih energy stores 1 Present ress: Deprtment of Biology, Villnov University, Villnov, Pennsylvni 19085, USA. E-mil: susn.smith@villnov.eu The Auk, Vol. 127, Numer 1, pges 108 118. ISSN 0004-8038, eletroni ISSN 1938-4254. 2010 y The Amerin Ornithologists Union. All rights reserve. Plese iret ll requests for permission to photoopy or reproue rtile ontent through the University of Cliforni Press s Rights n Permissions wesite, http://www.upressjournls. om/reprintinfo.sp. DOI: 10.1525/uk.2009.09139 108
J n u ry 2010 Fu e l Use n St o r g e in Mi g r t i n g P s s e r i n e s 109 re reple (Birlein n Gwinner 1994, Birlein 2002). Thus, migrtion suess epens on the vilility of high-qulity hitts tht provie equte foo resoures, prtiulrly in res long migrtion orriors tht support lrge numers of irs uring migrtions. Beuse mny migrnts use stopover sites to inrese their energy stores, mesuring fuel eposition rtes of irs uring stopovers n provie informtion out the qulity n use of speifi sites. Fuel eposition rtes re typilly ssesse y mesuring mss hnge of irs repture uring stopovers or y ompring oy mss of irs pture t ifferent times of y to infer rte of mss gin s ily forging progresses (Winker et l. 1992; Winker 1995; Dunn 2000, 2002). The first pproh is limite y smll smple sizes euse few irs re repture uring short stopovers, wheres the seon pproh ssumes tht rrivl times n rtes of mss gin re similr mong ll iniviuls (Dunn 2000, 2002), n the results of these two types of nlyses re sometimes inonsistent (Winker et l. 1992, Bonter et l. 2007). Plsm metolite profiling vois these limittions n provies informtion out fuel use n eposition over the pst severl hours in iniviul irs pture one. For exmple, plsm onentrtions of lipi metolites inrese uring ft eposition (triglyerie) n tolism (B-hyroxyutyrte, nonesterifie ftty is, glyerol), n plsm uri i inreses uring protein tolism (Stevens 1996). Aoringly, plsm triglyeries n B-hyroxyutyrte were iretly relte to mss hnges of ptive irs over perio of severl hours (Jenni-Eiermnn n Jenni 1994, Jenni n Shwilh 2001) to severl ys (Willims et l. 1999, Semn et l. 2005). Plsm metolite profiling hs een use to etet ifferenes in fuel eposition rtes of migrting irs n hitt qulity t stopover sites (Shu n Jenni 2001; Guglielmo et l. 2002, 2005; Yenerg et l. 2002; Aeveo Semn et l. 2006; Willims et l. 2007). Here, we use plsm metolite profiling to ompre fuel eposition rtes mong vriety of songirs throughout utumn migrtion t stopover site n mong selete songirs with ifferent forging strtegies t 2 stopover sites with ifferent fruit unne. Mny psserine speies in estern North Ameri swith from primrily insetivorous iet on their reeing grouns to primrily frugivorous iet uring utumn migrtion (Prrish 1997). This ietry plstiity llows irs to utilize fruit resoures tht re often superunnt uring utumn n tht re presumly less energetilly expensive to fin n et thn inset prey (Prrish 2000). In ition, mny temperte fruits re high in ft or sugr (Thompson n Willson 1979, White 1989, Smith et l. 2007), whih my filitte migrtory fttening (Birlein n Simons 1995, Stevens 1996). We hypothesize tht higher fruit onsumption n enhne fuel eposition rtes of irs uring migrtory stopovers. We teste this hypothesis in two wys: (1) we ompre plsm metolites from vriety of songirs tht iffere in egree of frugivory while they inhite stopover site with unnt fruit, n (2) we ompre fuel eposition rtes of 3 songir speies with ifferent forging strtegies while they inhite 2 stopover sites tht iffere in fruit unne. Beuse we re involve in long-term (>40 yers) ir-ning progrms t oth the southern New Engln stopover sites use in the present stuy, our ojetives lso inlue etermining the reltive importne of environmentl n methoologil vriles tht my influene plsm lipi n protein metolite onentrtions n their interprettion s initors of physiologil n nutritionl stte of migrting songirs. Met h o s Stuy res. We onute our stuy t 2 lotions in southern Rhoe Isln. Blok Isln, whih is lote ~19 km off the southern ost of Rhoe Isln (41 12 N, 71 35 W), is ielly lote to reeive lrge numers of migrting irs tht frequently rift offshore when they enounter the strong northwesterly wins typil uring utumn in southern New Engln s ostl res. These migrnts reorient themselves n onentrte t the north en of the isln efore flying k to the minln to ontinue migrtion (Ale 1977). The Cly He Preserve omprises lrge re of mritime shruln hitt t the north en of the isln (~77 h) tht serves s stopover site for mny of these psserine speies uring utumn migrtions (Bir n Niset 1960, Reinert et l. 2002). This re is hrterize uring utumn y superunnt wil fruits tht provie foo resoure for psserine migrnts uring utumn stopover (Prrish 1997, Smith et l. 2007). The shruln ommunity is ominte y wooy fruit-ering shrus, suh s Arrowwoo Viurnum (Viurnum enttum), Northern Byerry (Myri pensylvni), Blk Chokeerry (Aroni melnorp), n Common Wintererry (Ilex vertiillt). The ense unerstory lso ontins fruiting plnt speies suh s Amerin Pokewee (Phytol merin), Virgini Creeper (Prthenoissus quinquefoli), n Northern Dewerry (Ruus flgellris). Highly invsive speies, nmely Orientl Bittersweet (Celstrus oriultus), Multiflor Rose (Ros multiflor), n Autumn Olive (Elegnus umellt) re lso present within Cly He Preserve. The Kingston Willife Reserh Sttion (KWRS) is lote in southern Rhoe Isln in South Kingstown (41 27 N, 71 31 W). The lnspe of this re is primrily eiuous forest pthes frgmente y evelope ln n griulturl fiels. Bning of songirs hs ourre eh fll sine 1956 long set of estlishe net lnes within eiuous wooln n erlysuessionl hitts in the nopy openings. The forest nopy is ominte y White Ash (Frxinus merin), Re Mple (Aer rurum), n oks (Querus spp.). Dominnt fruiting speies in the unerstory n nopy openings inlue Common Greenrier (Smilx rotunifoli), Orientl Bittersweet, Europen Privet (Ligustrum vulgre), n Fox Grpe (Vitis lrus). Arrowwoo Viurnum, Amerin Pokewee, Virgini Creeper, n Common Wintererry re rre n our in isolte pthes in the unerstory n nopy openings. Within-site omprisons. We smple loo from 8 speies of migrtory psserines tht ommonly our on Blok Isln. These speies were selete euse they were pture in suffiient numers (n 10) n iffer in level of frugivory while on Blok Isln uring utumn migrtion. Hermit Thrush (Cthrus gutttus), Yellow-rumpe Wrler (Denroi oront), Gry Ctir (Dumetell rolinensis), n Re-eye Vireo (Vireo oliveus) re highly frugivorous uring utumn migrtion on Blok Isln ( 74% fruit in fel smples; Prrish 1997). White-throte Sprrow (Zonotrihi liollis), Drk-eye Juno (Juno hyemlis), n Blue-hee Vireo (V. solitrius) onsume onsierly
110 Sm i t h n MWilli m s Au k, Vo l. 127 less fruit n more insets thn these other speies uring utumn migrtion ( 62% fruit in fel smples; Prrish 1997). Bloo smples from 2 White-rowne Sprrows (Z. leuophrys) were omine with those from the ongeneri White-throte Sprrow (herefter Zonotrihi ) for the nlyses. We esigne our loo-smpling protool so tht it oul fit within the typil ily sheule t ir-ning sttions. We pture irs using 30-mm nylon mist nets situte long estlishe trils within the shruln hitt in Cly He Preserve uring utumn 2005. Nets were opene t sunrise on eh morning of opertion, n irs were inlue in susequent nlyses if they were pture 1 6 h fter sunrise. This ensure tht irs h egun forging in the morning efore they were pture. Birs were extrte from nets t intervls of 20 30 min n then rought to entrl lotion where they were hel in loth holing-gs until morphologil mesurements n loo smples were otine. We rew ~50 μl of loo from the rhil vein fter punture with 27-guge neele n ollete it in heprinize pillry tues. After loo ws rwn, we mesure wing hor n oy mss n then relese the irs. We reore the time of y s net hek time when irs were extrte from nets n then onverte the time of y to numer of full hours plus frtions of hours fter sunrise (herefter hours fter sunrise ). This ontrolle for hnges in time of sunrise s the seson progresse. Blee time ws reore s the time elpse etween the net hek n loo smpling. Only irs for whih lee time ws 30 min were inlue in susequent nlyses. Bloo smples were entrifuge t 8,000 rpm for 10 min to seprte plsm from re loo ells, n plsm ws then store t 80 C until nlysis. Between-site omprisons. We pture n le Hermit Thrushes, Yellow-rumpe Wrlers, n White-throte Sprrows t KWRS n on Blok Isln. We selete these speies euse they re ommonly pture t oth sites n re sesonlly frugivorous uring utumn migrtion (Prrish 1997). We onute loo smpling, proesse loo, n mesure irs using the sme proeures esrie ove. Birs were then ne with serilly numere feerl luminum leg ns n relese. Nets were operte t oth sites on 4 ys in 2004 (21, 23, 26, n 28 Otoer) n 4 ys in 2005 (16, 18, 20, n 27 Otoer). The simultneous pture of irs t oth sites minimizes ifferenes in wether or migrtion ptterns mong smpling ys t the 2 sites. We lso minimize temporl vrition in ily forging y inluing only irs pture within the sme 2.5-h perio in the morning t eh site on eh smpling y. We ssesse frequeny of ourrene of 10 plnt speies tht proue fruits n the presene of ripe fruit t eh site in 2005 to ompre the vilility of fruit resoures etween sites for the following speies: Arrowwoo Viurnum, Northern Byerry, Amerin Pokewee, Virgini Creeper, Blk Chokeerry, Ros spp., Orientl Bittersweet, Common Wintererry, Common Greenrier, n Europen Privet. Smpling ws onute within twenty-four 4-m 2 plots lote 1 m into the vegettion long the estlishe net lnes or trils. We reore the presene of plnt speies tht proue fruits n the presene of ripe fruit on these plnts in eh plot on Blok Isln n t KWRS on 6 n 7 Otoer 2005, respetively. We reognize tht there my e nnul vrition in fruit proution n tht fruit vilility my hve een ifferent in 2004 n 2005. However, suh vrition is likely to ffet these 2 sites similrly eh yer given their reltive proximity. Mesurement of plsm metolites. We mesure onentrtions of triglyerie (TRIG), B-hyroxyutyrte (BUTY), n uri i in plsm ollete for within-site omprisons mong speies pture on Blok Isln, n we mesure TRIG n BUTY in plsm ollete for etween-site omprisons (Blok Isln vs. KWRS). We mesure TRIG y sequentil enpoint ssy (Sigm, St. Louis, Missouri; 5 μl plsm, 240 μl regent A, 60 μl regent B) y first mesuring free glyerol n then sutrting free glyerol onentrtion from mesure totl triglyerie onentrtion. We mesure BUTY y kineti ssy (R-Biophrm, Mrshll, Mihign; 5 μl smple, 150 μl working solution, 3 μl BUTY ehyrogense, re kinetilly for 30 min) using metho similr to tht of Guglielmo et l. (2005). We mesure uri i y enpoint ssy (TECO Dignostis, Anheim, Cliforni; 5 μl smple, 300 μl regent). Smples with smll plsm volumes were ilute 2-fol to 3-fol with 0.9% NCl efore ll ssys, n we repete mesurements until the oeffiient of vrition etween replites ws <10%. Sttistil nlyses. The ir speies tht we use vry onsierly in overll oy size, n these struturl ifferenes in oy size will influene oy mss (Connell et l. 1960). Thus, we juste oy mss for mesure of oy size y using the resiuls from liner regression of oy mss n wing length in ll susequent nlyses. We use n informtion-theoreti pproh to investigte the importne of 5 vriles for explining vrition in TRIG, BUTY, n uri i onentrtions of irs uring utumn stopover on Blok Isln. We evlute moel set ontining ll possile omintions of speies, hours fter sunrise, te, size-orrete oy mss, n lee time. We lulte Akike s informtion riterion juste for smll smple sizes (AIC ) n use ifferenes in AIC (Δ i = AIC i AIC min ) to rnk nite moels (Burnhm n Anerson 2002). We onsiere nite moels with Δ i < 2 sustntilly supporte (Burnhm n Anerson 2002). We use Akike weights (w i ) to lulte eviene rtios (w 1 /w j ; Burnhm n Anerson 2002) to etermine the reltive likelihoo of eh nite moel (w j ) ompre with the highestrnke moel (w 1 ). We then lulte the reltive importne (w + (j)) of eh explntory vrile y summing the w i ross ll nite moels in whih tht vrile ourre (Burnhm n Anerson 2002). We use Person s orreltion oeffiients to lrify the iretion of the reltionship etween the highest-rnke ontinuous vriles n metolite onentrtions. We then use nlysis of ovrine (ANCOVA) with post ho Tukey s HSD tests to test for expliit ifferenes in metolite onentrtions mong the speies pture on Blok Isln in utumn 2005. We use reltive importne vlues s guie to etermine whih vriles (hours fter sunrise, te, lee time, n oy mss juste for oy size) to inlue s ovrites in ANCOVA. We then eliminte ovrites tht i not ontriute signifintly to the moel. We onute preliminry nlyses to etermine whether metolite onentrtions iffere etween yers in ll irs exept Hermit Thrush euse of smll smple sizes in 2004. Twoftor nlysis of vrine (ANOVA) with yer n speies s fixe vriles revele no ifferenes etween yers; therefore, we omine yers for ll susequent nlyses. Blee time ws not reore for ll irs in 2004 t KWRS; therefore, we etermine
J n u ry 2010 Fu e l Use n St o r g e in Mi g r t i n g P s s e r i n e s 111 whether lee time oul e exlue s n explntory vrile y lulting Person s orreltion oeffiients etween lee time n metolite onentrtions n ompring lee time mong sites n speies with two-wy ANOVA for ll other smples for whih lee time ws reore. Blee time ws not signifintly orrelte with TRIG (P = 0.81) or BUTY (P = 0.10) onentrtions, n verge lee time ws similr etween sites (F = 2.1, f = 1 n 58, P = 0.15) n mong speies (F = 0.1, f = 2 n 58, P = 0.91), presumly euse we limite our site-omprison t set y speies, time of y, n te. Our stuy esign for the etweensite omprison effetively ontrolle for te y limiting smpling to 4 ys eh yer. Thus, we eliminte lee time n te s potentil ovrites. We use n informtion-theoreti pproh (s esrie ove for within-site omprisons) to evlute the importne of site, speies, hours fter sunrise, n size-orrete oy mss for explining vrition in TRIG n BUTY onentrtions in irs pture t the 2 stopover sites. We then use two-wy ANOVA with site n speies s fixe ftors to test for expliit ifferenes in TRIG onentrtions etween sites. Heterogeneity of vrine of BUTY onentrtions etween sites for Hermit Thrush n etween speies t KWRS prelue the use of two-wy ANOVA to test for speifi site ifferenes. Thus, we use one-wy ANOVA to ompre BUTY onentrtions mong speies on BI n the Kruskl-Wllis test to ompre BUTY onentrtions mong speies t KWRS. We then use two-smple t-tests using the Stterthwite pproximtion for egrees of freeom when there ws unequl vrine etween speies or sites. Speies-speifi ifferenes in BUTY onentrtions etween sites were onsiere signifint t P = 0.017, tking into ount Bonferroni orretion for ompring 3 speies. We lulte perent presene (numer of plots present / totl plots 100) of eh fruiting plnt speies n presene of ripe fruit seprtely for eh site n yer for tulr representtion of plnt presene t. We use hi-squre tests (2 2 ontingeny tles) to ompre the frequeny of ourrene for eh fruiting plnt speies or ripe fruit etween sites. The TRIG, BUTY, n uri i onentrtions of irs pture on Blok Isln uring utumn 2005 evite from normlity. Therefore, we log (X + 1) trnsforme TRIG n BUTY, n we trnsforme uri i using the fourth root power trnsformtion, X (0.25), whih normlize the t. These trnsforme metolite onentrtions were use for ll within-site nlyses on Blok Isln. The BUTY onentrtions of irs pture t KWRS n on Blok Isln were log (X + 1) trnsforme n, onsequently, the t were normlly istriute for etween-site omprisons. All sttistil tests were lulte using SAS, version 9.1 (SAS Institute, Cry, North Crolin), with the signifine level set t P < 0.05. Re s u lt s Vrition in plsm metolites of irs pture on Blok Isln. Speies, hours fter sunrise, n size-orrete oy mss were inlue in the highest-rnke moel explining vrition in plsm TRIG (see Tle 1 for rw metolite onentrtions use for within-site nlyses); however, 2 other moels lso h sustntil support, with Δ i < 2 (Tle 2). Reltive importne vlues suggeste tht speies n hours fter sunrise were more importnt thn te, lee time, n size-orrete oy mss for explining vrition in TRIG (Tle 3). Hours fter sunrise ws onsistently positively orrelte with TRIG ross speies (overll: r = 0.36, P < 0.001; Hermit Thrush: r = 0.47, P = 0.001; Yellow-rumpe Wrler: r = 0.43, P = 0.01; Gry Ctir: r = 0.39, P = 0.05; Re-eye Vireo: r = 0.21, P = 0.51; Zonotrihi: r = 0.60, P = 0.01; Drk-eye Juno: r = 0.38, P = 0.15; Blue-hee Vireo: r = 0.47, P = 0.12). The moel explining plsm BUTY onentrtions ws more omplex euse speies, hours fter sunrise, te, n lee time were inlue in the highest-rnke moel (Tle 2). In ition, there were 3 other moels with Δ i < 2, whih were only 1.6 1.9 times less likely to explin more vrition thn the highest-rnke moel (Tle 2). Reltive importne vlues suggest tht speies, te, n lee time were more importnt thn hours fter sunrise n size-orrete oy mss (Tle 3). Dte ws negtively orrelte with BUTY, n orreltion oeffiients were vrile mong speies (overll: r = 0.17, P = 0.04; Hermit Thrush: r = 0.06, P = 0.69; Yellow-rumpe Wrler: r = 0.59, P < 0.001; Gry Ctir: r = 0.14, P = 0.50; Re-eye Vireo: r = 0.88, P < 0.001; Zonotrihi: r = 0.03, P = 0.90; Drk-eye Juno: r = 0.43, P = 0.10; Blue-hee Vireo: r = 0.18, P = 0.58). Blee time ws positively orrelte with BUTY, lthough the strength of this orreltion vrie onsierly mong speies (overll: r = 0.15, Tle 1. Cpture t n metolite onentrtions for migrtory irs smple on Blok Isln, Rhoe Isln, uring utumn 2005. Men (± SE) onentrtions of plsm triglyerie (TRIG), B-hyroxyutyrte (BUTY), n uri i (UA) re provie lthough trnsforme vlues were use in ll sttistil nlyses. Speies n Dte HAS Blee time Mss e TRIG (mm) BUTY (mm) UA (mm) Hermit Thrush 43 289 307 3.02 ± 0.19 16 ± 1 31.4 ± 0.3 2.44 ± 0.12 0.95 ± 0.08 0.36 ± 0.03 Gry Ctir 25 277 301 3.28 ± 0.27 15 ± 1 42.7 ± 0.8 1.53 ± 0.13 1.39 ± 0.13 0.37 ± 0.04 Yellow-rumpe Wrler 34 277 307 3.33 ± 0.23 15 ± 1 13.8 ± 0.3 1.75 ± 0.11 2.53 ± 0.18 0.36 ± 0.04 Re-eye Vireo 12 277 294 2.99 ± 0.28 15 ± 1 18.6 ± 0.5 1.69 ± 0.15 1.56 ± 0.24 0.50 ± 0.06 Zonotrihi 16 289 300 3.01 ± 0.31 16 ± 1 25.8 ± 0.7 1.72 ± 0.22 2.37 ± 0.34 0.79 ± 0.05 Drk-eye Juno 16 290 307 2.96 ± 0.32 18 ± 1 19.9 ± 0.7 1.80 ± 0.17 1.60 ± 0.28 0.71 ± 0.09 Blue-hee Vireo 12 289 307 4.26 ± 0.33 13 ± 1 15.7 ± 0.5 2.01 ± 0.28 1.44 ± 0.12 1.00 ± 0.09 Zonotrihi inlues White-throte Sprrow n White-rowne Sprrow. Rnge of ll pture tes for given speies. Dte = Julin te of pture, where 277 = 4 Otoer 2005. Men (± SE) hours fter sunrise t pture. Men (± SE) minutes etween net extrtion n loo smpling. e Men (± SE) oy mss (g) t loo smpling.
112 Sm i t h n MWilli m s Au k, Vo l. 127 Tle 2. Moel seletion results for the 5 highest-rnke nite moels tht explin vrition in plsm metolite onentrtions of irs smple on Blok Isln, Rhoe Isln, uring utumn 2005. Moels re rnke on the sis of Akike weights (w i ). Metolite n moel n K Mximize log e (L) AIC Δ i w i w 1 /w j Triglyerie Y = speies + HAS + mss 158 10 379.1 736.65 0.00 0.340 Y = speies + HAS 158 9 377.4 735.50 1.16 0.190 1.8 Y = speies + HAS + mss + te 158 11 379.4 734.93 1.72 0.144 2.4 Y = speies + HAS + mss + t 158 11 379.1 734.47 2.19 0.114 3.0 Y = speies + HAS + te 158 10 377.6 733.66 3.00 0.076 4.5 B-hyroxyutyrte Y = speies + HAS + t + te 156 11 328.1 632.40 0.00 0.337 Y = speies + HAS + mss + t + te 156 12 328.8 631.51 0.89 0.216 1.6 Y = speies + t + te 156 10 326.4 631.34 1.06 0.198 1.7 Y = speies + mss + t + te 156 11 327.5 631.08 1.32 0.174 1.9 Y = speies + HAS + te 156 10 324.1 626.63 5.77 0.019 17.9 Uri i Y = speies + te 136 9 341.2 662.90 0.00 0.310 Y = speies + t + te 136 10 341.9 661.99 0.91 0.197 1.6 Y = speies + mss + te 136 10 341.4 661.11 1.78 0.127 2.4 Y = speies + HAS + te 136 10 341.2 660.67 2.23 0.102 3.0 Y = speies + mss + t + te 136 11 342.2 660.23 2.67 0.082 3.8 Prmeters: Y = trnsforme metolite onentrtions (see text), HAS = hours fter sunrise t pture, te = Julin te of pture, mss = resiuls from liner regression of oy mss n wing length, n t = time (min) etween net extrtion n loo smpling. Numer of estimle regression prmeters in moel inluing the interept n vrine. Clulte s: [ 0.5n*log e (RSS/n)], where RSS is the resiul sum of squres. Eviene rtio where w 1 = the highest-rnke moel. P = 0.06: Hermit Thrush: r = 0.29, P = 0.06; Yellow-rumpe Wrler: r = 0.03, P = 0.87; Gry Ctir: r = 0.40, P = 0.05; Re-eye Vireo: r = 0.01, P = 0.97; Zonotrihi: r = 0.55, P = 0.03; Drk-eye Juno: r = 0.12, P = 0.67; Blue-hee Vireo: r = 0.35, P = 0.27). Speies n te were inlue in the highest-rnke moel explining plsm uri i onentrtions (Tle 2). Moels tht inlue lee time or size-orrete oy mss lso h sustntil support. Reltive importne vlues lrifie tht speies n te were the most importnt vriles explining uri i onentrtions (Tle 3). However, we i not etet signifint orreltion etween te n uri i (overll: r = 0.09, P = 0.27; Hermit Thrush: r = 0.25, P = 0.12; Yellow-rumpe Wrler: r = 0.35, P = 0.10; Gry Ctir: r = 0.13, P = 0.59; Re-eye Vireo: r = 0.52, P = 0.08; Zonotrihi: r = 0.21, P = 0.43; Drk-eye Juno: r = 0.11, P = 0.67; Blue-hee Vireo: r = 0.40, P = 0.22). Tle 3. Reltive importne (w + (j)) of preitor vriles tht explin vrition in plsm metolite onentrtions of migrtory irs on Blok Isln, Rhoe Isln, uring utumn 2005. Moel set Speies HAS Dte Mss Blee time e Triglyerie 1.000 1.000 0.293 0.646 0.250 B-hyroxyutyrte 1.000 0.605 0.963 0.417 0.959 Uri i 1.000 0.176 0.859 0.342 0.430 Trnsforme metolite onentrtions were use for nlyses (see text). Hours fter sunrise t pture. Julin te of pture. Resiuls from liner regression of oy mss n wing length. e Time (minutes) etween net extrtion n loo smpling. Hermit Thrush h higher TRIG onentrtions thn ll other speies fter ounting for hours fter sunrise (speies: F = 8.2, f = 6 n 157, P < 0.001; HAS: F = 35.8, f = 1 n 157, P < 0.001; Fig. 1). We etete signifint speies*te intertion for BUTY. If we restrite our t set to Otoer smples only when we pture 90% of iniviuls, this intertion ws no longer signifint. We foun signifint ifferenes in BUTY onentrtions mong speies pture uring Otoer while ontrolling for oth te n lee time (speies: F = 17.2, f = 6 n 140, P < 0.001; te: F = 14.0, f = 1 n 140, P < 0.001; lee time: F = 15.6, f = 1 n 140, P < 0.001). Yellow-rumpe Wrler h higher BUTY onentrtions thn ll other speies exept Zonotrihi spp. (Fig. 1), n Zonotrihi h higher BUTY onentrtions thn Hermit Thrush n Gry Ctir (Fig. 1). Zonotrihi, Drkeye Juno, n Blue-hee Vireo h higher onentrtions of uri i thn the other 4 speies fter orreting for te (speies: F = 25.0, f = 6 n 135, P < 0.001; te: F = 7.9, f = 1 n 135, P = 0.001; Fig. 1). Site ifferenes in plsm metolites. Site n speies were inlue in the highest-rnke moel explining vrition in plsm TRIG onentrtions (see Tle 4 for rw lipi metolite onentrtions use for etween-site nlyses); however, the moel tht inlue site, speies, n hours fter sunrise lso h sustntil support (Tle 5). Speies n site ifferenes were the most importnt vriles, n hours fter sunrise n oy mss were less importnt for explining vrition in TRIG onentrtions of irs pture t the 2 sites (Tle 6). Conentrtions of TRIG were higher in irs pture on Blok Isln thn in those from KWRS, n this ifferene n primrily e ttriute to higher TRIG onentrtions in Hermit Thrushes from Blok
J n u ry 2010 Fu e l Use n St o r g e in Mi g r t i n g P s s e r i n e s 113 Isln thn in those from KWRS (site: F = 6.7, f = 1 n 71, P = 0.01; speies: F = 3.3, f = 2 n 71, P = 0.04; site*speies: F = 3.1, f = 2 n 71, P = 0.05; Fig. 2). Speies n hours fter sunrise were inlue in the highestrnke moel explining vrition in plsm BUTY onentrtions, ut 2 other moels h sustntil support (Tle 5). Interspeifi ifferenes n hours fter sunrise h the highest reltive importne vlues, wheres site n oy mss were less importnt for explining vrition in plsm BUTY onentrtions of irs t the 2 stopover sites (Tle 6). Overll, BUTY onentrtions were similr etween sites (t = 1.0, f = 70, P = 0.33; Fig. 2). Hermit Thrushes h the lowest BUTY onentrtions of the 3 speies on Blok Isln (F = 13.6, f = 2 n 39, P < 0.001), ut there were no interspeifi ifferenes in BUTY onentrtions t KWRS (χ 2 = 0.4, f = 2, P = 0.84; Fig. 2). Site ifferenes in fruit vilility. In 2005, the following plnt speies tht proue fruits were more ommon on Blok Isln thn t KWRS: Arrowwoo Viurnum, Northern Byerry, Virgini Creeper, Blk Chokeerry, n Ros spp. (Tle 7). By ontrst, Common Greenrier n Europen Privet were less ommon on Blok Isln thn t KWRS (Tle 7). The following plnt speies more ommonly h ripe fruit on Blok Isln thn t KWRS: Arrowwoo Viurnum, Virgini Creeper, Blk Chokeerry, n Ros spp. (Tle 7). There were signifintly more fruits present on Common Greenrier n Europen Privet t KWRS thn on Blok Isln (Tle 7). Di s u s s i o n Fig. 1. Lest-squres (LS) mens (± SE) of plsm triglyerie (log [TRIG + 1]), B-hyroxyutyrte (log [BUTY + 1]), n uri i (UA 0.25 ) onentrtions fter orreting for signifint ovrites (see text) for migrtory psserine speies pture on Blok Isln, Rhoe Isln, in utumn 2005. Arevitions: HETH = Hermit Thrush, GRCA = Gry Ctir, YRWA = Yellow-rumpe Wrler, REVI = Re-eye Vireo, DEJU = Drk-eye Juno, n BHVI = Blue-hee Vireo. Zonotrihi inlues White-throte n White-rowne sprrows. Brs with ifferent letters within eh grph re signifintly ifferent. Our results emonstrte tht plsm lipi n protein metolites iffer mong speies of migrting songirs uring utumn migrtion, whih my e ttriutle, in prt, to interspeifi ifferenes in iet hits n fruit vilility t stopover sites. In ition, ftors suh s time of pture, time tken to lee the ir, n te my ffet iniviul plsm lipi n protein metolite onentrtions in ifferent wys. However, stnrize protools tht limit loo smpling to portion of the y or tht restrit smpling to ertin speies or perios of the migrtion seson will further minimize the influene of these potentilly onfouning vriles on plsm metolite onentrtions in free-living irs. Plsm triglyerie s n initor of fttening. Our results suggest tht plsm TRIG is likely the single most useful lipi metolite for ssessing fttening n fuel eposition in free-living migrtory irs. Plsm TRIG ws reltively unffete y most potentilly onfouning ftors ommon in fiel stuies, suh s time lg etween net extrtion n loo smpling or te of pture. Plsm TRIG vlues onsistently inrese with hours fter sunrise when irs were pture, n this positive reltionship etween time of y n TRIG hs een shown in mny speies of free-living psserines (Jenni n Jenni-Eiermnn 1996, Jenni- Eiermnn n Jenni 1997, Guglielmo et l. 2005). Conentrtions of TRIG inrese rpily in response to the onset of feeing fter sunrise n my eventully plteu (Jenni-Eiermnn n Jenni 1996, 1997). We i not etet suh plteu, lthough we only smple irs 6 h fter sunrise. Plsm TRIG onentrtions in our stuy inite tht fttening rtes of migrting songirs iffer mong speies n
114 Sm i t h n MWilli m s Au k, Vo l. 127 Tle 4. Cpture t n plsm metolite onentrtions for 3 migrtory speies pture on Blok Isln (BI) n t Kingston Willife Reserh Sttion (KWRS), Rhoe Isln, uring utumn 2004 n 2005. Speies Site n HAS Mss TRIG BUTY Hermit Thrush KWRS 8 2.06 ± 0.22 29.8 ± 0.5 1.29 ± 0.19 2.18 ± 0.59 BI 15 2.34 ± 0.22 31.9 ± 0.5 2.04 ± 0.08 1.16 ± 0.14 Yellow-rumpe Wrler KWRS 11 2.14 ± 0.17 14.0 ± 0.5 1.22 ± 0.19 2.42 ± 0.29 BI 19 2.50 ± 0.14 13.6 ± 0.4 1.47 ± 0.09 2.47 ± 0.21 White-throte Sprrow KWRS 11 2.27 ± 0.25 25.1 ± 0.6 1.31 ± 0.20 2.25 ± 0.30 BI 9 2.44 ± 0.17 25.4 ± 0.6 1.32 ± 0.17 2.53 ± 0.38 Men (± SE) hours fter sunrise t pture. Men (± SE) oy mss (grms) t loo smpling. Men (± SE) onentrtions (mm) of plsm triglyerie. Men (± SE) onentrtions (mm) of plsm B-hyroxyutyrte. Trnsforme vlues were use in ll nlyses (see text). Tle 5. Moel seletion results for the 5 highest-rnke nite moels tht explin vrition in plsm metolite onentrtions of irs smple on Blok Isln n t Kingston Willife Reserh Sttion, Rhoe Isln, uring utumn 2004 n 2005. Moels re rnke on the sis of Akike weights (w i ). Metolite n moel n K Mximize log e (L) AIC Δ i w i w 1 /w j Triglyerie Y = site + speies 73 5 50.8 90.64 0.00 0.423 Y = site + speies + HAS 73 6 51.2 89.12 1.53 0.197 2.1 Y = site + speies + mss 73 6 50.8 88.31 2.33 0.132 3.2 Y = site + speies + HAS + mss 73 7 51.3 86.83 3.81 0.063 6.7 Y = site 73 3 46.2 86.11 4.53 0.044 9.7 B-hyroxyutyrte Y = speies + HAS 73 5 144.4 277.81 0.00 0.300 Y = speies 73 4 142.8 276.99 0.83 0.199 1.5 Y = site + speies + HAS 73 6 145.0 276.66 1.15 0.168 1.8 Y = speies + HAS + mss 73 6 144.4 275.57 2.24 0.098 3.1 Y = site + speies 73 5 143.0 275.19 2.63 0.081 3.7 Prmeters: Y = metolite onentrtion (log [X + 1] trnsforme vlues were use for B-hyroxyutyrte nlyses), HAS = hours fter sunrise t pture, n mss = resiuls from liner regression of oy mss n wing length. Numer of estimtle regression prmeters in moel inluing the interept n vrine. Clulte s [ 0.5n*log e (RSS/n)], where RSS is the resiul sum of squres. Eviene rtio where w 1 = the highest-rnke moel. stopover sites, n these ifferenes my e relte to iet n qulity of foo resoures t stopover sites in ition to other speiesspeifi trits. For exmple, Hermit Thrush h the highest plsm TRIG onentrtions, n it is lso one the most frugivorous of the speies tht we stuie. However, Hermit Thrush is lso one of the heviest speies smple, n some previous stuies of songirs Tle 6. Reltive importne (w + (j)) of preitor vriles tht explin vrition in plsm metolite onentrtions of migrtory psserines pture on Blok Isln n t Kingston Willife Reserh Sttion, Rhoe Isln, in utumn 2004 n 2005. Moel set Site Speies HAS Mss Triglyerie 0.895 0.916 0.332 0.249 B-hyroxyutyrte 0.327 0.997 0.618 0.250 Hours fter sunrise t pture. Resiuls from liner regression of oy mss n wing length. Log (X + 1) onentrtions were use in nlyses. hve emonstrte positive reltionship etween plsm TRIG n oy mss (Guglielmo et l. 2005, Cersle n Guglielmo 2006) or ft mss (Smith n MWillims 2009). We foun tht oy mss ws only moertely relte to plsm TRIG ross speies even fter orreting for overll oy size, n visul estimtes of suutneous ft revele tht Hermit Thrush h verge ft sores ompre with other speies. Therefore, the higher TRIG onentrtions of Hermit Thrush in the present stuy re not likely ttriutle simply to the lrger overll oy size of this speies ompre with other, smller-oie speies. If the egree of sesonl frugivory is positively relte to plsm TRIG, Hermit Thrush shoul hve the highest TRIG, long with other primrily frugivorous speies (Yellow-rumpe Wrler, Re-eye Vireo, n Gry Ctir). However, these other speies i not hve TRIG levels s high s those in Hermit Thrush, whih suggests tht interspeifi ifferenes within site nnot e fully expline y iet hits. Further support for the importne of iet hits on plsm TRIG onentrtions is provie y our fining tht plsm TRIG ws higher in Hermit
J n u ry 2010 Fu e l Use n St o r g e in Mi g r t i n g P s s e r i n e s 115 Tle 7. Presene of 10 plnt speies (perent ourrene in twenty-four 4-m 2 plots) on Blok Isln (BI) n t Kingston Willife Reserh Sttion (KWRS), Rhoe Isln, n presene of ripe fruits (perent ourrene in the sme plots) of eh plnt speies uring 2005. Plnt presene (%) Fruit presene (%) Speies BI KWRS χ 2 BI KWRS χ 2 Arrowwoo Viurnum 83 38 10.5** 50 8 10.1** Northern Byerry 29 0 8.4** 13 0 3.2 Virgini Creeper 38 0 11.1** 29 0 4.4** Amerin Pokewee 4 0 1.0 4 0 1.0 Blk Chokeerry 17 0 4.4* 17 0 4.4* Common Wintererry 8 8 0.0 4 4 0.0 Orientl Bittersweet 42 54 0.8 29 38 0.4 Common Greenrier 4 75 25.2*** 0 21 5.6* Ros spp. 71 13 16.8*** 58 8 13.5*** Europen Privet 0 71 26.3*** 0 46 14.3*** *P < 0.05, **P < 0.01, ***P < 0.001; f = 0.05 n 1. Fig. 2. Men (± SE) plsm triglyerie (TRIG) n B-hyroxyutyrte (log [BUTY + 1]) onentrtions in Hermit Thrushes (HETH), Yellowrumpe Wrlers (YRWA), n White-throte Sprrows (WTSP) pture t Kingston Willife Reserh Sttion (soli rs) or on Blok Isln (hthe rs), Rhoe Isln, uring utumn migrtion, 2004 n 2005. Thrushes pture on Blok Isln, where high-qulity ntive fruits re unnt, thn in Hermit Thrushes pture t KWRS, where fruit vilility n qulity were muh lower. In ition, Hermit Thrushes pture on Blok Isln h higher plsm TRIG thn Yellow-rumpe Wrlers n White-throte Sprrows, n these interspeifi ifferenes were sent in irs pture t KWRS, where fruit ws less unnt. We reognize tht there re mny other ifferenes etween speies n our stuy sites, in ition to fruit resoures, tht my ontriute to vrition in plsm TRIG onentrtions. For exmple, Hermit Thrushes, White-throte Sprrows, Drk-eye Junos, n Yellow-rumpe Wrlers ll winter on Blok Isln to some extent (S. Comings pers. omm.); however, speies tht re stritly migrnts uring utumn on Blok Isln (Blue-hee Vireo n Re-eye Vireo) showe no extrorinry pttern of ft eposition. Gry Ctir is the only speies smple in our stuy tht is known to ree on Blok Isln (S. Comings pers. omm.), n plsm TRIG ws lowest in this speies, perhps euse some irs were not yet in migrtory stte. It is lso possile tht the fuel eposition rte ws influene y ge or sex (Woorey n Moore 1997, Yong et l. 1998, Jones et l. 2002, Heise n Moore 2003). Age is not likely n importnt ftor explining interspeifi vrition in fuel eposition rtes on Blok Isln, euse nerly ll irs pture were hth-yer. In generl, more oler irs re pture t KWRS thn on Blok Isln, ut this is not likely signifint ftor for Hermit Thrushes, most of whih pture t KWRS were hth-yer. Further, Drk-eye Juno ws the only speies in whih more mles thn femles were pture (mong iniviuls tht oul e relily sexe). Molt is proly irrelevnt to the interspeifi ifferenes in plsm metolites reporte here, euse most of the irs smple were just ompleting their presi molt n so were t reltively similr molt stges. In ition, plsm lipi metolites o not orrelte strongly with intensity of molt throughout the presi molting perio in migrtory songirs (Jenni-Eiermnn n Jenni 1996). Given tht iet n other interspeifi ifferenes my ontriute to vrition in plsm metolite onentrtion, suh interspeifi omprisons shoul e unertken with ution or limite to speies with very similr life histories, iet hits, n migrtion strtegies. Plsm B-hyroxyutyrte s n initor of ft tolism. The most vrile of the 3 metolites mesure in this stuy ws BUTY, n the most plusile explntory AIC moels inlue ovrites suh s lee time. The positive reltionship etween lee time n plsm BUTY onentrtions in irs pture in our stuy hs previously een esrie in free-living irs, though not onsistently ross ll stuies or speies (Jenni- Eiermnn n Jenni 1996; Guglielmo et l. 2002, 2005; Aeveo Semn et l. 2006). Given tht BUTY inreses rpily uring trnsitions etween physiologil sttes n short-term fsts uring the y (Jenni-Eiermnn n Jenni 1991, 1997; Jenni n Jenni- Eiermnn 1992), lee time is n importnt ovrite to mesure in stuies of free-living irs so tht its influene on metolite onentrtions n e resse. Plsm BUTY ws lso negtively relte to te of pture, lthough this reltionship ppere to e importnt in only few speies, like the Yellow-rumpe
116 Sm i t h n MWilli m s Au k, Vo l. 127 Wrler n the Re-eye Vireo. The effet of te on BUTY onentrtions in our stuy is iffiult to interpret euse smpling of given ir speies vrie through time. Our results suggest tht te will likely lwys e n importnt onfouning ftor in suh nlyses, euse mny ifferent speies migrte t ifferent times within given seson. Plsm BUTY ws ifferent mong ir speies pture on Blok Isln, even fter ontrolling for te n lee time, whih suggests tht itionl ftors influene BUTY onentrtions. Hermit Thrush n Gry Ctir re highly frugivorous, n they h the lowest BUTY onentrtions uring utumn migrtion on Blok Isln, where fruit ws unnt. However, other ifferenes etween speies were not lerly relte to iet. If BUTY is negtively ffete y fruit vilility, we woul expet plsm onentrtions to e higher t KWRS, where vilility of highenergy fruits, suh s Arrowwoo Viurnum, is lower thn on Blok Isln. However, site ws of reltively low importne for explining BUTY onentrtions, n the interspeifi ifferenes in BUTY mong irs pture on Blok Isln were not pprent t KWRS. We onlue tht BUTY is less onsistent initor of fuel eposition rtes thn TRIG in migrtory psserines euse of the mny itionl potentil soures of vrition. Plsm uri i s n initor of protein tolism. Plsm uri i onentrtions iffere sustntilly etween ir speies pture on Blok Isln. In generl, less frugivorous speies h higher onentrtions thn more frugivorous speies. Given tht plsm uri i ws positively relte to protein intke in previous stuies of ptive irs (Golstein et l. 2001, Smith et l. 2007), the lower onentrtions in free-living frugivorous irs my our euse most fruits hve less protein thn other ville foos (Smith et l. 2007). Plsm uri i ws lso influene, to lesser egree, y te of pture, lthough the ft tht there ws not signifint orreltion etween uri i n te of pture for ny of the speies suggests tht the reltionship etween these 2 vriles my e nonliner. If plsm uri i is relte to onsumption of high-protein inset resoures, this oul explin the eline in plsm uri i s utumn progresse n inset resoures eline. The effet of te is not strightforwr, euse most of our irs were pture lter in the seson, primrily euse of verse wether tht prelue mist netting on erlier tes. Uri i my e useful for stuies of free-living irs, euse it seems to relily inite ietry protein intke in ptive stuies n euse it ws less sensitive to other ftors like lee time, time of y, n oy mss. Implitions for hitt qulity n migrtion monitoring t stopover sites. Fruit vilility n influene the unne of frugivorous lnir speies n their use of speifi hitts uring utumn migrtion (Blke n Hoppes 1986, Mrtin n Krr 1986, Prrish 2000, Suthers et l. 2000, Roewl n Brittinghm 2004). Our t suggest tht highly frugivorous migrtory speies n refuel t fster rte when fruit iversity, qulity, n vilility re high, s emonstrte y higher plsm TRIG in irs pture on Blok Isln. The fruit resoures present t KWRS re ominte y few speies tht hve low energy ensity (e.g., Orientl Bittersweet) or tht re voie y migrting irs n persist into the winter (e.g., Europen Privet) more thn the ommon high-energy fruits (e.g., Arrowwoo Viurnum) foun in the mritime shruln hitt on Blok Isln. Therefore, these high-qulity fruit resoures my e useful initor of hitt qulity t stopover sites. However, stopover hitts must provie suffiient mounts of other foos, suh s insets, tht n e utilize y less frugivorous speies tht re unle to rely primrily on fruits uring utumn stopover. Plsm metolites n provie useful informtion out fuel eposition n resoure use of irs t migrtion stopover sites, provie tht severl importnt vriles re onsiere. Although plsm TRIG n BUTY n urtely inite ifferenes in mss hnge etween sites in fiel-pture irs (Guglielmo et l. 2005), we suggest tht plsm TRIG n uri i, ut not BUTY, re the est nites for use t ning n monitoring sttions. Within given stopover site, plsm TRIG n provie informtion out short-term fuel eposition in iniviuls, n uri i my provie informtion out reltive mounts of ietry protein in irs pture one. Further, we foun tht plsm TRIG n uri i were less sensitive to vrition in lee time thn BUTY. This is prtiulrly importnt when it is unfesile to ontinuously monitor nets to reor the ext time of pture. However, we stress tht minimizing the time etween net pture n lee time is ritil to ensuring tht plsm TRIG represents the feeing stte of iniviul irs. Plsm lipi metolites my relily inite fttening rtes of irs, lthough omprisons mong speies shoul e limite to speies with similr iet hits n to sesons when irs et similr foos, euse lrge ifferenes in ietry mronutrient omposition, prtiulrly sugr n protein ontent, my influene lipi metolite onentrtions (Smith et l. 2007, Smith n MWillims 2009). Given these potentil iet effets, plsm lipi metolites re likely to e most useful for proviing qulittive estimtes of the trjetory of ft eposition in iniviul free-living irs. Using suh metolites to quntittively estimte mount of ft eposition in free-living irs will require itionl stuies tht iretly mesure oth metolite onentrtions n tul ft eposition rtes in onjuntion with mesurements of ietry mronutrient intke. A k n o w l e g m e n t s We thnk S. Comings n the Nture Conservny for fiel support on Blok Isln. We re grteful to P. Pton, L. Du, D. Cooper, M. MEnroe, n A. Alreht for oopertion n ssistne with loo smpling n ning t Kingston Willife Reserh Sttion. 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