montanus Status badge-signalling in male but head:Running Editor : Eivin Roskaft Article type : Original Paper 11-Oct-2016 : Date Accepted :09-Oct-2016 Date Revised :16-Feb-2016 Date Received This article isprotected Allrights bycopyright. reserved. 10.1111/ibi.12425 version andtheVersi this between differences through the copyediting, typesetting, pagination forpublication accepted This articlehasbeen montanus signalling function ofaplumage trait present in both sexes in the conspicuousness of their ornaments is often comparable to those of males. In this study wetested the similar ornaments in females has, however, received much less attention despite the fact that Male ornaments, such asplumage coloration, frequently serve assignals. The signalling function of Email: *Corresponding author. 4 Department of Ecology, University of Szeged, Középfasor 52., 6726 Szeged, Hungary and Institute of 2

AcceptedMTA-DE ‘Lendület’ Behavioural Ecology Resear Article 3 1 Department of Limnology, University of Institute of Biology, University of Nyíregy

[email protected] FERENC MÓNUS, . The black throat patch hasbeenrepeatedly foundtohave asignal function inthe closely Genetics, Biological Research Center, Temesvári krt. 62, 6726Szeged, Hungary Sexdifference in signalling by throat patch in tree sparrow University of Debrecen, Egyetemtér 1.,4032 Debrecen, Hungary

1,2* ANDRÁS ANDRÁS LIKER, Pannonia, P.O. Box158,8201 Veszprém, Hungary háza, Sóstói út2-4., 4400 Nyíregyháza, Hungary not infemale Eurasian Tree Sparrows and undergone full peer review buthasnotbeen review undergone fullpeer and on of Record. Please cite of Record. Please on 3

ZSOLT PÉNZES ZSOLT ch Group,Department of and proofreading process, which may lead to 4 & ZOLTÁN BARTA & ZOLTÁN

this article this as doi: Evolutionary Zoology, 2

Passer Kraaijeveld in ornament expression (e.g. Zebra Poissant females. Although genetic correlation between the sexes may bewidespread (Kraaijeveld independently, sothe selection acting onthe ornaments of males can result in male-like ornaments in genetic correlation hypothesis (Lande1980)argues thatthe traitsnotsexes are inthetwo inherited There are twonot mutually exclusive hypotheses that explain signal design in relation to sex. First, the (Amundsen 2000a). In several , however, both sexes possess conspicuous ornaments. communication have focused onmale ornaments and have frequently disregarded female ornaments and function (Amundsen 2000a, b, Kraaijeveld been intensivelystudied,much less attention has been paidtointer-sexual differencessignal in design Lanyon 2003,Bókony Conspicuously coloured patches of are often found to serve assignals in (e.g. Eaton& Keywords: further experimental studies are necessary tocorroborate these correlative results. findings suggest astatus signalling function ofthroat patch size inmales but not infemales, although morphological traits studied, wing length wasthebe female throat patch size didnotcorrelate with fighting success against either sex.Among the male throat patch size predicted fighting success against both male and female opponents. However, patch size and measurements of body size predicted fighting success in these flocks. We found that aggressive encounters inforaging flocks offree-living Sparrows, Tree and assessed whether throat ornament expression has never, to our knowledge, been considered. We investigated the outcomes of function of theblack throat patch inthe females of related HouseSparrow This article isprotected Allrights bycopyright. reserved. Accepted Article et al. badge-signalling, dominance, feeding competition, melanin, monomorphic ornaments. et al. 2010), it has rarely been shown to prevent 2007). et al. Passer domesticus 2006,Senar 2006). While signalling and communication have Taeniopygia guttata , where onlymales bear theornamental trait. However, the et al. 2007). Most investigations of animal Passer st predictor offighting success in females. Our sexes reaching their own sex-specific optima species that have sexuallymonomorphic bill colour; Price 1996, reviewed in et al. et 2007, Philetairus socius Diamond Firetails al. backed Orioles in American Goldfinches observed to predict dominance status and aggressive behaviour in females of these species. Bill colour querula al. number ofavian studies have investigated its predictions in females (Kraaijeveld ability canbe equally profitable both for males and females, andagainst both sexes –only amoderate (Rohwer 1975, Senar 2006) doesnot assume differences between the sexes –signalling competitive avoid frequent antagonistic interactions with cons hand, may favour female ornamentation if honest si females in various animal taxa (Clutton-Brock 2009, Tobias support of the sexual selection hypothesis, males have been observed to prefer highly ornamented (Price & Birch 1996). Both sexual selection and social The second hypothesis is that female ornaments, like those of males, are maintained by direct selection This article isprotected Allrights bycopyright. reserved. 2008, Clutton-Brock 2009).This kind of evolutionary transition is assumed to have happened in the ornament may be particularly important (Amundsen 2000b, Kraaijeveld evolutionary transition has occurred between sexually monomorphic and dimorphic states of the Recent reviews have concluded that investigating intersexual signal design intaxa inwhich modulate female aggressiveness toward taxidermymode have also been suggested as acting asstatus signals in females, as these ornaments were observed to (Griggio is assumed tohave beendichromatic, having ablack throat patch in males and having nothroat patch Sparrow 2004), chest spottiness in Common Starlings Accepted Article 2012). For instance, the facial colour patterns in Northern Cardinals Passer (Watt 1986) andGolden-crowned Sparrows Passer montanus, et al. , and resulted in the apparently sexually monochromatic oftheEurasian Tree 2010),Blue andUV/blue crownin Tits Icterus pustulatus ( Stagonopleura guttata Rat Rat et al. Spinus tristis in which both males and females possess a black throat patch. Its ancestor 2015) and multiple plumage traits in Harris's Sparrows (Murphy (Murphy (Murphy (Crowhurst et al. Sturnus vulgaris 2009a) and inRock Sparrows et al. pecifics. Although the status signalling hypothesis gnals of competitive ability allow individuals to Zonotrichia atricapilla et al. 2009b),orangebreast coloration inStreak- selection may favour female ornamentation. In Cyanistes caeruleus ls or conspecifics with manipulated signals. 2012), black bib size in Sociable Weavers et al. (Swaddle & Witter 1995) and in 2012). Social selection, on the other Cardinalis cardinalis et al. et (Midamegbe (Chaine 2007, Hofmann Petronia petronia et al. Zonotrichia et al. 2007, Tobias et al. 2011), were (Jawor (Jawor 2011), et al.

et et et et likely more suitable in acting asasignal (Møller 1991, Delhey & Peters 2008). suggests that the role of the throat patch may differ between the sexes, because a more variable trait is throatpatchgreater is male in thaninfemaleSparrows Tree (Mónus their results. In aprevious morphological study, in the relationship between dominance and throat patch size may contribute to the inconsistencies in the authors did not know the sexof the experimental birds, they concluded that intersexual differences strongly related to the individuals' dominance rank in Sparrows under laboratory conditions but did not find consistent results. Throat patch size was relationship between dominance and badge size. Torda ourTo knowledge, in in ameta-analysis was between badge size and fighting ability (Nakagawa copulations or parental effort), the only relationship that wasstrong androbust across several studies male HouseSparrows and some aspects of reproductive behaviour (e.g. frequency ofextrapair females (Liker & Barta 2001). Although some studie fighting ability (Bókony instance, in male HouseSparrows the size of the badge positively correlates with various aspects of social competition, andhence may beusedas ‘badges of status’ (Tibbetts & Safran 2009). For in both NewWorld andOld World sparrows, supporting theidea that they have evolved asaresult of that the presence of these patches is strongly associated with sociality during the non-breeding season assumed toprimarily act as status signals in bi The size of eumelanin-based black patches, like chest and throat patches in sparrows, are of the throat patch in Tree Sparrows (Torda Sparrow Sparrow of the male’s black badge hasbeen intensively studied in the closely related and dichromatic House and in females, as is the case in the species’ closest extant relatives (e.g. Plain-backed Sparrow This article isprotected Allrights bycopyright. reserved. Accepted Article Passer domesticus P. rutilans Passer Passer et al. (Nakagawa species other than the only one study has investigated the the investigated has study one only Sparrow House the than other species 2006) and predicts dominance toward both males (e.g. Møller 1988) and ; Allende et al. et al. et et al. 2007), we have very little information about the function 2001, Tibbetts & Safran 2009). Although thefunction rds (Hill 2006,Senar 2006). Acomparative study found we found that both mean size and variance of the 2004) or in any other other any in or 2004) s have found correlation between badge size of one flock, butnot in the other two flocks. Since et al. (2004) observed three flocks of Tree et al. et Passer 2011). This finding et al. species. 2007). P. flaveolus

of the Garden, but also readily used feeding stations. Preceding theexperiment, in the autumn of1999, winter in groups of various sizes (ranges 1 to 70; pers. obs.). They usually foraged ingrassy open parts Barta Debrecen, Hungary, during thewinter of 1999-2000. For adetailed description of the study site, see This study wasconducted on TreeSparrows resident in theBotanical Garden of the University of site and speciesStudy METHODS morphological correlates of fighting success in both sexes. (Rohwer 1975; but see Liker & Barta 2001, Hein opponents. This is a frequently overlooked aspect of he correlation between throat patch size and fighting success differs according to the sex of the throat patch size ofmales and of females predicts fighting success towards conspecifics, andwhether results in frequent aggressive encounters over forage in flocks of unstable composition during the winter (Mónus & Barta 2010) whichusually Tree Sparrows. Signalling dominance status may beadvantageous in this species because individuals We investigated the status signalling role of the th This article isprotected Allrights bycopyright. reserved. Accepted results were found in sex identification. next breeding season were sexed on the basis ofmorp identification procedure was repeated in 32 individuals, and3 individuals that were recaptured in the binding protein 1 (CHD1; Griffith &Tiwari 1995) as described in Mónus by of sexed sex-chromosome PCR-based the amplification chromodomainwere DNA linked helicase 112 adult Tree Sparrows (54 males and58 females) were individually marked using colour rings, and Article et al. (2004). In theGarden, approximately 200-300 Tree Sparrows foraged regularly during the food resources (Rohwer 1975). We assessed whether et al. roat patch in free-livingmale and female Eurasian the originally proposed status signal hypothesis hological traits (Svensson 1992). No inconsistent 2003). We also investigated other potential et al. (2011). The sex Morphological measurements were taken whenSparrows werecaptured andmarked. Body weight wasmeasured by a Pesola spring balance to the nearest 0.5g, tarsus length by calliper to the & Barta2002, Barta arrangement ofthe food produced a situation in which birds were forced to search for the (Liker of corn grit into twenty of the holes bored into a 12-by-12grid in the feeding platform. This regularly collected the remaining foodfrom theplatform andsupplied small amounts (one teaspoon) rings could be recognized later from therecord observer tried to locate and zoom thecamera towards individually marked sparrows, sothat colour had familiarized themselves with the activity of the observer in the hide. During recordings, the (between 07:00AM and 11:00AM) from mid-December 1999 to mid-January 2000, well after the birds behaviour of individual SparrowsTree on the platform. Recordings were made on 13 mornings observer (ZB) hid in a camouflaged tent 6m from the feeder and used avideo camera torecord the and then initiated feeding trials in flocks from thisbush (Barta After familiarization with the feeder, Sparrows used A 150×150-cm feeding platform wasinstalled on the ground inan undisturbed corner of the Garden. Data collection This article isprotected Allrights bycopyright. reserved. body weight and tarsus length were0.76, 0.64 and 0.59; respectively (F our throat patch size measurement was0.79 (F Before releasing thebirds, the throat patch was photographed again in 73individuals; repeatability for digitalized photographs usingImage 1.24 for J Linux software (see Fig. 1of Mónus reference. Throat patch size wasdefined by the area covered by black feathers measured from the throat patch (badge) was photographed from thefront view, including aruler as a measurement nearest 0.1mm, wing length by ruler to the nearest 1 mm, eachin astandardised holding position. The Accepted (1987). cases; based on34 recaptures). All repeatability values werecalculated following Lessells and Boag Article et al. 2004). 72,73 ings. Before and during recording, theobserver = 8.33, the closest bush (1.5 m from thefeeder) to gather, P <0.001). Repeatabilities for wing length, et al. et 2004, Mónus & Barta2011). The 33,34 > 3.87, P <0.001 for all et al. 2011). bird was searching (i.e.moving onthefeeder and searching for food patches). The focal was was feeding (i.e. staying in a food patch), and as an attack ifthe encounter occurred whenthe focal unambiguous outcomes were categorized as a defence, if the encounter occurred when the focal bird but no obviously aggressive interaction occurr food-containing hole (independently ofwhether the focal bird arrived before or after its flock mates), Non-aggressive encounters were defined as occasions on which the focal bird met other birds at a charging) fighting, (pecking, interaction aggressive non-aggressive encounters. Aggressive encounters were defined asoccasions onwhich any obviously For each focal bird, we recorded the total number of aggressive encounters and the total number of individuals per recording; 4 individuals onaverage). colour rings, weidentified as many individuals as possible on the analysed recordings (1to12 recordings indetail, each lasting from several seconds in length to about 1 minute. Based on their analysed a maximum of30randomly chosen recordings per day. Altogether, we analysed 378 video camera. Since the detailed analysis ofSparrow be experimenter continuously recorded the behaviour of Sparrows on the feeder without switching off the We collected 14–90 separate video recordings per observation day. During each recording, the This article isprotected Allrights bycopyright. reserved. success, but only encounters categorized as attacks and asdefences were included, respectively. AcceptedAttack success and defence success were calculated and analysed in the same way asthe fighting aggressive encounters, preserves the information deriving from thefrequency values (Crawley 1993). in contrast to the proportion ofencounters woncompared to the total number ofunambiguous series of binomial events); in each of them thefocal bird was either a winner or a loser. This measure, binomial variable (see below) considering the total number ofunambiguous aggressive encounters (a dominance (Rohwer & Ewald 1981, Liker & Barta 2001, 2002). Fighting success wasassessed as a the analyses. Finally, we described competitive ability according to fighting success as a surrogate of of 1085) had anunambiguous outcome, andencounters lose a contest if it was clearly supplanted by its opponent. Of all aggressive encounters, 94% (1021 out consideredunambiguously to contesta ifitclearlywin supplanted unambiguously itsopponent,to or Article ed between them. Aggressive encounters with haviour (see below) wasvery time consuming, we occurred between the focal bird and another bird. withambiguous outcomes were excluded from male and female opponents; Table 2). In thesemodels, we analysed fighting behaviour of males and the opponent was identified either as male or female (i.e. webuilt two separate models for fights with males orwhen fighting against females, we repeated the analyses using only those encounters in which In ordertoanalyse whether thecorrelates of competitive ability were different when fighting against 2002); homoscedasticity and residual normality werechecked visually. Overdispersion was accounted for by setting the 2004), so wedid not exclude any ofthe above mentioned continuous predictors from themodels. length, body weight and throat patch area in these models as predictor variables (Table 1). We checked only once in the analyses. We analysed males and females separately, andfitted tarsus length, wing series of binomial events (instead of asimple arithmetic mean), while each individual was included variable. The binomial error distribution allowed us to represent fighting success in ourmodels with a distribution where the total number ofwins and loss R). In orderto analyse the correlates of competitive ability (fighting success) weused abinomial error Team, 2014).We analysed individual differences by fitting generalized linear models ( We carried out all statistical tests in the R interactive statistical environment (R Development Core Data analysis 20 females).and observations, morphological traits and sex identification, were available for 35 individuals (15 males individuals that were colour ringed during the identification was available for16 males and 23 females (there was no sex identification for observed to be involved in any aggressive encounters with an unambiguous outcome); sex encounters per individuals; median =11) wasavailable for47 individuals (four individuals were not In total,we identified 51 individuals from therecordings; fighting success (based on 1to 63 This article isprotected Allrights bycopyright. reserved. Acceptedwidely considered to potentially affect the results if VIF values are greater than 10 (Kutner in any cases, and variance inflation factors (VIF) were lower than 1.6 for all cases. Multicollinearity is for multicollinearity in these continuous variables. Pairwise Pearson correlations did not reach Article previous years). All data, including behavioural behavioural including data, All years). previous glm es of the individuals were entered as a response to quasibinomial (Venables & Ripley glm function in et al. et r =0.4

quasibinomial appropriate test statistic according to the model family (the which were attacks and509 defences. In thecases of individuals for which both attacks anddefences During this time, weobserved 1021 aggressive encounters with an unambiguous outcome, 512of We analysed 217 minutes of recordings of the 51Sparrows individually identified on the feeder. Aggressive behaviour and dominance relationships RESULTS equation 11 in Nakagawa & Cuthill 2007). throughout. Pearson ± SEs coefficients regression and unstandardized squares of IIIsum type with tables ANOVA report time), the When we analysed log-normally distributed variables (e.g. number ofaggressive encounters per unit separately. considered only once; male-male dyads, female-female dyads andmixed-sex dyads were analysed tarsus lengths, wing lengths andbody weights between the opponents in these models. Each dyad was dyad asaresponse variable. Aspredictor variables, we entered the differences in throat patch sizes, glms withthe number of wins and losses of one member of the dyad toward the other member ofthe encounters, we used the dyads in which both opponents were identified (Table 3). We fitted binomial In ordertoanalyse the effect of morphological differences between opponents on theoutcome of our main interests when evaluating these models. whether there are sex related differences in the correlates of the competitive ability, hence these were its interactionand termscontinuouseach ofthefourwith predictors. These interaction termsshow describedmorphological traits,we included thesex individuals fought with opponents of both sexes, se females together, because sample sizes would have been very small for sex-specific models (not all This article isprotected Allrights bycopyright. reserved. Accepted Article glm family was set to , and the r effect sizes were calculated from from calculated were sizes effect χ 2 -test when it was set to Gamma specifying a binomial e Table 2). Inadditione Table2). previouslyto thefour of focal individuals as an explanatory variable, log t -statistics ofregression coefficients (see link (Venables & Ripley 2002) or or F Gamma -test when ; Venables & Ripley 2002). We glm glm family was set to . We used the F 17.2 ± encounters per unit time during the total observation time ( = 11.277 ± 2.927). Birds with higher fighting success were involved infewer non-aggressive affected by themeasured morphological traits ( deviance = 167.270,deviance = Birds with higher fighting success were involved in more aggressive encounters per unit time ( attacks anddefences: females (males:54.9 ± of attacks compared to the total number of both attacks anddefences) did not differ between males and < 0.001, recorded encounters (712outpossibleof the861dyads). dominance structure among these 42 individuals, because for many possible dyads there were no dyads (83%). Unfortunately, theseobservations consistent in most cases, i.e. the same individual won each of the multiple fights in 39out of the 47 observed to fight more than once (2 to 4). The outcomes of these repeated fights within dyads were 149 dyads of 42 known individuals, i.e. where both fighting birds were identified. Only 47dyads were Out of the aggressive encounters with an unambiguous outcome, werecorded 219 encounters between correlation correlation: were registered, attack success and defence success were positively correlated (Spearman rank This article isprotected Allrights bycopyright. reserved. success did not differ significantly between males and females (males: 36.9 ± independent data (attack success remained significant when calculating fighting success andthe rate of aggressive encounters from encounters per unit time during searching time: deviance = 68.103,deviance = Accepted1,29 Article =1.340, SE β : 4.65 %; after controlling for the measured morphological traits: =-21.707 ± 6.120). The proportion of encounters initiated by the focal bird (i.e. the number P = 0.256). = F F 1,44 n 1,45 =36, SE r =20.251, S = 32.968, = 0.620, : 3.72 %; females:%; : 3.72 50.4± χ 2 1 =1.028, vs. P P P < 0.001, < 0.001, aggressive encounters per unit time during feeding time: < 0.001, P = 0.311, β n β =25.678 ± 7.014; defence success =40). n n are fararefrom sufficient toreconstruct thereal =25.002 = 44, = 42, deviance = 79.494, SE β =-0.137 ± 0.136), and was notsignificantly : 3.95 %; binomial χ 2 1 <0.880, ± n 5.725). This strong positive relationship = 47,deviance = 89.870, P > 0.348,> foralltraits). Fighting glm n F = 35, deviance =8.867, 1,40 SE for the frequencies of = 20.872, : 7.86 %; females: vs. aggressive aggressive F 1,45 P =13.932, < 0.001, n n = 46, =47, P β

interactions, wing length and throat patch area affected fighting success in asex-specific way weight by sexinteraction; Table 2). When fighting against females, in commonwith theanalyses of all wing-length by sexinteraction; Table 2,Fig. 2c) Table 2 andFig. 2a).Fighting success did not significantly correlate with wing length ineither sex (no not in females (i.e. there were significant interactions between throat patch size and sexof focal bird; analyses of all interactions: throat patch size correlated positively with fighting success in males but was found. When fighting against males, the effect of throat patch area remained the same as in the When analysing only those interactions in which the sex ofthe opponent wasknown, asimilar pattern longer wings had greater fighting success (Fig. 1b). success was significantly related only towing length (Table 1), but unlike males, individuals with correlated negatively with wing length (Fig. 1b)and body weight. In females, however, fighting 0.993, ( variables Notably, throat patch size was the only trait that was significant without controlling forthe other success in males was significantly correlated with wing length, body weight and throat patch size. When analysing all interactions – towards conspecifics ofboth known andunknown sex– fighting success fighting of correlates Morphological This article isprotected Allrights bycopyright. reserved. success similarly inboth sexes. Acceptedhowever, that in mixed sex dyads wewould expect significant effects only ifa trait predicts fighting mixed sex dyads, neither of themorphological traits predicted the outcomes ofthe encounters. Note, win more frequently than their smaller winged opponents (a marginally non-significant effect). Within encounters more frequently. In female-female dyads, females with the greater wing length tended to with greater throat patch size andsmaller body weight than their opponents tended to win the two opponents predicted the outcomes ofaggressive encounters (Table 3).In male-male dyads, males Where both members ofthe dyad wereknown, the weight was not a significant predictor of fighting success against females (Table 2). (significant trait by sexof focal bird interaction terms in Table 2;Figs. 2band 2d). However, body Article P > 0.337). Inmales, fighting success correlated positively with throat patch area (Fig. 1a)and F 1,13 =5.518, P = 0.035; for all other traits without controlling forother variables and correlated negatively with body weight (nobody- following morphological differences between the F 1,13 < (Murphy example by controlled experiments in an aviary orby using taxidermymodels with manipulated traits size in female Tree Sparrows may lack astatus sign that throat patch size in male Tree Sparrows may function asa status signal, whereas the throat patch unstable composition (Rohwer & Ewald1981, Liker & Barta2001), our correlative results suggest As fighting success and dominance rank arehighly correlated in species foraging inwinter flocks of longer wings wonmore fights against their opponents. anyof theanalyses.in bestpredictor The of fighti throat patch. In contrast, throat patch size in females was not asignificant predictor of fighting success throat patch won more aggressive encounters against their flock mates than did males with a smaller success of males against both male and female opponents (Table 2): male Sparrows with a larger Among themeasured morphological traits, throat patch size was a consistent predictor of fighting correlates of aggressive interactions among free-living TreeSparrows of known sex. possibility (Mónus Intersexual differences in the mean andvariance of throat patch size also pointed towards this apparently sexuallymonochromatic species may differ between the two sexes (Torda In aprevious behavioural study, itwas suggested that the signalling role of the throat patch in this DISCUSSION This article isprotected Allrights bycopyright. reserved. Acceptedwas more even, oreven female skewed. patch size and fighting success consisted mainly ofmales, while in the two other flocks thesex ratio correlation in the other two. Presumably the flock inwhich there was arelationship between throat found a positive correlation between dominance and throat patch size in one flock, andfound no different experimental flocks. Without taking into why Torda test our conclusions. The suggested intersexual differences in the role of throat patch size may explain Article et al et al. . 2009b, Crowhurst (2004), investigating Tree Sparrows of unknown sex, found different results in et al. et 2011). Here, we tested this idea further by studying the morphological et al . 2012) should be performed inthe future in order to more fully account the sex-composition of the flocks, they ng success in females was wing length: females with alling function. Further experimental testing, for et al. et 2004). Furthermore, both males and females may benefit by looking similar to the other sex at first sight (a signalling function (e.g. Catoni female Tree Sparrows. Asan alternative to size, the blackness of the throat patch may have a However, our results donot support the expected status signalling function of throat patch size in The throat patch in females may beadaptive if it has a function that makes its bearer more successful. sexualdifference inthefunctionof throat patch size intheTreeSparrow (Mónus et al. been observed to function in multiple contexts (dual utility hypothesis; Berglund toward males in order to signal some aspects of their quality during pair formation. Many signals have whether female Tree Sparrows use their throat patch as asignal in adifferent context, for example sexes, while the dominance rank offemales correlated with body weight. We have noinformation on reported that badge size was the only significant predictor of the dominance rank ofmales against both Our results are also in accord with those reported in the HouseSparrow. Liker and Barta (2001) (Møller 1991, Delhey & Peters 2008). greater variance inthe size ofatrait may beexpected when thesize ofthe trait functions asasignal other traits did not differ between the sexes (Mónus Sparrows the variance of throat patch size was greater inmales than in females, while the variance of signal some aspects of male quality (e.g. oxygen transport ability). Previously, wefound that in Tree documented inthe casemales of butnot infemales, suggesting that thethroat patchofmales may comm.), inwhich a positive correlation between throat patch size and haematocrit value was Our findings are inaccord withastudy onaTree Sparrow population in (S.Matsui, pers. This article isprotected Allrights bycopyright. reserved. Seress during mate choice (Daunt Tree Sparrow, both males and females may beselected to be choosy andto exhibit quality signals Acceptedthere is a relationship between sexual behaviour and throat patch size (Heeb 2001, Cordero investigated within-pair and extra-pair sexual behaviour in Tree Sparrows have not reported whether Article 2010). In species with socially monogamous mating systems andbiparental care, such as the et al. 2007). et al. et al. 2003, Griggio 2009), which would beworth testing in future studies. et al. 2010). Unfortunately, recent studies that have et al. 2011). This finding also supports a possible et al. et al. et 1996, Griggio 1996, 2011), since et al. 2002, (e.g. &Jones Hunter 1999, Kraaijeveld Several studies have demonstrated that mutual orna and reliability ofsex recognition in wild Tree Sparrow flocks. only the throat patch size of males butnot of females. Future work isneeded to assess the mechanism sex of the opponent, since foraging sparrows seem todifferentiate among individuals and consider However, it seems more reasonable to assume that individuals are capable of easily recognizing the aggression, or may accruesome othersocial or sexual benefit (Clutton-Brock & Huchard 2013). phenomenon referred as intraspecific sexual mimicry), andmay thereby avoid some unnecessary This article isprotected Allrights bycopyright. reserved. black throat patches, using an androgen controlled signal may betoocostly forthem (butseeEens Acceptedfecundity infemales (Packer et al. (Clutton-Brock 2009).Black feather patches are widely Ornaments in females maybe limited more often by thecosts to fecundity rather than to survival may affect males and females differently (Tibbetts 2014), as also may advantages (Tobias throat patch size asa status signal. Honest signals only suggestive, raise the intriguing question of what prevents female Tree Sparrow from using the (Rohwer 1975), our results, although based on observat Whereas signalling competitive ability seems tobe equally profitable for males and for females ornamental trait may change over time ornaments may supersede the information conveyed by throat patch size, or that the function of the foraging competition, ormay signal status with multiple ornaments simultaneously, thatother reasonable explanations. It may bethat females use their ornaments in signalling contexts unrelated to knowledge onthe cause of these intersexual differences, soone can only speculate inorder to find Articleof sexually monomorphic ornaments (reviewed in Murphy common withourwork, have foundevidence of intersexual differences in status signalling inthe case 2011; reviewed inKraaijeveld 2008; but see McGraw 2008 et al. et al. et ) 1995, Clutton-Brock 2009,Rosvall 2013). Even if females possess ; anelevated level of testosterone, in turn, may negatively affect 2007, Tobias or space (Tarvin & Murphy 2012, Murphy et al. 2004, Alonso-Alvarez et al. are thought to involve costs to their bearer, but costs ments may beusedas status signals by bothsexes 2012).However, there are fewstudies that, in ional rather than experimental data and soare thought tobe testosterone-regulated (Bókony et al. 2014). We have very limited et al. 2004, Midamegbe et al. 2014). et al. et et al. 2012).

et et signallingin females (Ketterson Ketterson 2012), little is known about the physiological mechanisms mediating honest status testosterone was shown to modulate female aggressiveness in birds (e.g. Zysling lack the pathway which links throat patch size expression and competitive ability. Although al. This article isprotected Allrights bycopyright. reserved. ornamental traits. Tree Sparrows may enhance ourunderstanding ornaments, and experimental testing of the function of the black throat patch both in male and female Further work needs to investigate the causes of intersexual differences in the function ofmonomorphic signal in free living flocks, whereas female throat patch size is beunrelated to their fighting behaviour. In summary, ourstudy suggests that male Tree Sparro bodymass regulation has often been observed due to mass-dependent predation (e.g. Krams among birds with similarly sized throat patches maintain lower levels of fat reserves. Such strategic patch size, negative relationship with fighting success may arise if more competitive individuals reflect a biologically meaningful effect. In thecase of body weights controlled for body size and throat variability ofmale wing length inour sample (Fig. 1b), it is possible that the pattern observed does not predictor of fighting success inmale House Sparrows (Liker & Barta 2001). Given theobviously small significance only after controlling for other morphological traits. Note also that body size isnot agood not clear. These relationships, however, were not consistent throughout all analyses, and reached The reason for the negative correlations of male fighting successwith wing length and body mass is more aggressively andmay winmore encounters (e.g. Lendvai with similarly sized throat patches may bemoremotivated to compete for food, and hence may forage 2010). Alternatively, individuals with relatively lo

Accepted Article 2000, Vitousek et al. 2013, Pham et al. et al. 2005, Møller 2014). Alternatively, itmay bethat female Tree Sparrows of the function and evolution of monomorphic wer body weight (i.e. poorer condition) among birds et al. ws may usetheir black throat patch as a status 2005, Pham et al. 2004,Preiszner et al. 2014). et al. et al. et 2006, Cain & 2015). et al.

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residuals throat patch area body weight wing length tarsus length Females residuals throat patch area body weight wing length tarsus length M This article isprotected Allrights bycopyright. reserved. Watt, D. J. 1986. Relationship of plumagevariability, size and sex to social dominance in Harris’ Vitousek, M.N.,Stewart, R.A. & Safran, 2013. R.J. Female plumage colour influences seasonal Venables, W. N.& Ripley, B.D.2002.Modern Applied Statistics with S. NewYork: Springer. Torda, G.,Barta, Z. & Liker, A.2004. andstatus signaling in captive tree shown separately for the two sexes. Results are from binomial generalized linear models. 1. Table Zysling, D.A.,Greives, T. Breuner,J., C. W., Ca

Acceptedales Article sparrows. oxidative damage andtestosterone profiles in a songbird. sparrow ( 367:2274–2293. dark-eyed juncos ( Behavioral and physiological responses to experimentally elevated testosterone in female (n =15; number of encounters =407) (n =20; number of encounters = 468) The effects The of themeasuredmorphological traitson thefighting successSparrows, ofTree Passer montanus

Anim. Behav.

Junco hyemalis carolinensis 34:16-27. ) flocks. ) flocks. 15 10 df 1 1 1 1 1 1 1 1

Acta Zool. Acad. Sci. H. 42.479 86.402 36.925 33.439 19.041 68.353 34.499 deviance 5.421 0.939 0.025

sto, M.,Dernas,J. G.E.& Ketterson, E.D.2006. ). Horm. Behav of P Biol. Lett. -value 0.656 0.942 0.015 0.293 0.001 0.015 0.019 0.060 F 50:35-44. -test -test . 50:200 – 207. 9(5):20130539

-0.830 ± 1.839 -0.025 ± 0.336 -0.627 ± 0.573 -0.925 ± 0.334 -0.881 ± 0.344 0.616 ± 0.278 9.078 ± 2.390 1.025 ± 0.496 B ± SE

size ( Effect -0.12 -0.02 -0.27 -0.66 -0.63 0.50 0.77 0.55

r ) residuals sex sex sex throat patch area body weight wing length tarsus length number of individuals = 30 (11 males,19 females); number of encounters = 172 Against females residuals sex sex throat patch area body weight wing length tarsus length number of individuals = 25 (12 males,13 females); number of encounters = 150 Against males significant interactions term were omitted ( according to the sex of their opponents. Results are from binomial generalized linear models; all non- 2. Table This article isprotected Allrights bycopyright. reserved.

Accepted(female) (female) (female) (female) Article(female) *throat patch area *wing length *throat patch area

The effects ofmorphological traits and sex on the fighting success of Tree Sparrows

22 18 df 1 1 1 1 1 1 1 1 1 1 1 1 1

deviance 54.794 12.047 29.877 26.920 23.071 23.965 9.044 7.960 6.149 8.481 1.939 2.837 8.216 0.101 0.014 P > 0.30 forallomitted > terms).

of P 0.018 0.025 0.045 0.021 0.243 0.162 0.039 0.002 0.003 0.083 0.842 0.006 0.941 -value F

-test -test

-121.11 ± 44.60 -6.929 ± 2.760 -0.803 ± 0.329 -9.095 ± 4.524 -1.286 ± 0.514 -0.050 ± 0.668 6.194 ± 2.617 6.194 ± 4.529 ± 2.226 0.243 ± 0.224 0.793 ± 0.553 1.794 ± 0.637 7.066 ± 4.333 0.072 ± 0.359 B ± SE

size ( -0.51 -0.50 -0.39 -0.50 -0.47 -0.02 Effect Effect 0.13 0.43 0.25 0.32 0.51 0.33 0.04 r )

residuals throat patch area body weight wing length tarsus length number of dyads =29; number of encounters = 40 Female-female dyads residuals throat patch area body weight wing length tarsus length number of dyads =52; number of encounters = 81 dyads sex Mixed residuals throat patch area body weight wing length tarsus length number of dyads =23; number of encounters = 32 Male-male dyads details see of aggressive encounters in Tree Sparrows. Results are from binomial generalized linear models (for 3. Table This article isprotected Allrights bycopyright. reserved. a Accepted –Differences in the trait between fighting opponents Article The effects ofmorphological differences between opponents of known sex onthe outcomes Statistical Analyses a a a a a a

a a a

a a a

). 24 47 18 df 1 1 1 1 1 1 1 1 1 1 1 1 35.912 71.493 17.693 2.199 1.187 5.849 0.472 0.327 2.574 0.071 0.000 7.466 8.902 0.424 2.944 deviance

of P 0.013 0.008 0.520 0.101 0.237 0.382 0.060 0.580 0.645 0.200 0.830 0.994 -value F

-test -test

-1.246 ± 0.518 -2.639 ± 2.270 -0.465 ± 0.833 -0.727 ± 1.572 -0.439 ± 0.349 -0.004 ± 0.515 5.655 ± 2.476 0.269 ± 0.407 1.062 ± 0.659 0.314 ± 0.367 0.535 ± 0.346 0.034 ± 0.160 B ± SE

size ( Effect -0.49 -0.23 -0.11 -0.08 -0.22 -0.00 0.47 0.15 0.35 0.17 0.30 0.04

r ) traits. regression lines from generalized linear models after controlling for the measured morphological in relation to (a, b) the area of their throat patch and (c, d) the wing length. Lines are predicted Fig. 2. linear models after controlling forthe measured morphological traits. a) area of their throat patch and b)wing length. Lines are predicted regression lines fromgeneralized Fig. 1. Figure legends This article isprotected Allrights bycopyright. reserved. Accepted Article Fighting success of free-living Tree Sparrow males ( Fighting success of free-living Tree Sparrows against male (a,c) and female (b, d) opponents n = 15) and females ( n =20) in relation to

This article isprotected Allrights bycopyright. reserved. Accepted Article

This article isprotected Allrights bycopyright. reserved. Accepted Article