Food Color Preferences of Molting House Finches (Carpodacusmexicanus) in Relation to Sex and Plumage ColorationAna L. Bascun˜a´n1, Elizabeth A. Tourville1, Matthew B. Toomey & Kevin J. McGrawSchool of Life Sciences, Arizona State University, Tempe, AZ, USAIntroductionThe dietary choices of animals are generally consid-ered adaptive, being shaped by the availability offood items in the environment and the nutritionalneeds of the consumer (Stephens & Krebs 1986).Animals are known to discriminate among fooditems based upon a wide variety of cues, includingcaloric content (Sprenkle & Blem 1984), nutrientcomposition (Schaefer et al. 2003), antioxidant con-tent (Schaefer et al. 2008a), and coloration (Willsonet al. 1990). Responses to these cues can be innateor learned through social transmission and ⁄ orassociation with post-ingestive consequences (Years-ley et al. 2006). Extensive research has focused onthe food color preferences of birds because they arehighly visual animals and play an important role inthe seed dispersal of fruiting plants (Willson &Whelan 1990). Red is a particularly common colorfor bird-dispersed fruits and is thought to attractavian frugivores by enhancing the conspicuousnessof fruits against background foliage (Schaefer &Schmidt 2004), as well as signaling palatability.Recently it has been suggested that birds may usefood color as an indicator of antioxidant content(Schaefer et al. 2008a). This is a particularlyCorrespondenceAna L. Bascun˜a´n, School of Life Sciences,Arizona State University, Tempe, AZ 85287,USA. E-mail: [email protected] authors contributed equally to thiswork.Received: April 16, 2009Initial acceptance: June 14, 2009Final acceptance: July 29, 2009(S. A. Foster)doi: 10.1111/j.1439-0310.2009.01697.xAbstractFood color can be indicative of specific nutrients, and thus discrimina-tion based on color can be a valuable foraging behavior. Several birdand fish species with carotenoid-based body ornamentation show colorpreferences for presumably carotenoid-rich red and orange foods. How-ever, little is known within species about whether or not individualswith (or growing) more colorful ornaments show stronger food-colorpreferences than those with drabber coloration. Here, we examine foodcolor preferences in house finches (Carpodacus mexicanus) – a specieswith sexually dichromatic and selected carotenoid coloration – as afunction of sex and plumage coloration during molt. We captured wild,molting juvenile house finches over 4 wk in late summer ⁄ early fall,quantified the color and size of plumage ornaments being developed inmales, and determined food color preference in captivity by presentingindividuals with dyed sunflower chips (red, orange, yellow, and green).On average, finches showed an aversion to yellow-dyed chips and apreference for red- and green-colored chips. We found no significant dif-ference between male and female preferences for specific food colors,and food color preference was not significantly related to male plumageornamentation. However, we did find that redder birds demonstrated ahigher degree of food selectivity, measured as the proportion of theirpreferred food color consumed. These results suggest that food color isnot a major factor determining food choice in molting house finches,but that there still may be aspects of foraging behavior that are linked tothe development of colorful plumage.Ethology1066 Ethology 115 (2009) 1066–1073 ª 2009 Blackwell Verlag GmbHethologyinternational journal of behavioural biologyintriguing idea because the expression of sexuallyselected carotenoid-based coloration in birds andfishes is affected by dietary intake of carotenoids(McGraw 2006) and other antioxidants (Bertrandet al. 2006; Pike et al. 2007; but see Karu et al.2008).A link between dietary and mate-choice prefer-ences is a key assumption of the sensory biashypothesis, which proposes that male ornamentalsignaling evolved as a result of female color prefer-ence in the foraging context (e.g. Grether 2000;Rodd et al. 2002). This hypothesis suggests that foodcolor preferences would exist in both sexes, as bothmales and females could be attracted to the samefood types for their nutritive value. Experiments onguppies (Poecilia reticulata), which display carotenoid-containing and sexually selected orange spots, showthat both sexes have a strong preference for orangefood (Rodd et al. 2002). Selective foraging for orangefoods may allow guppies to obtain the carotenoidsnecessary to produce their bright spots (Rodd et al.2002). Three-spined sticklebacks (Gasterosteus aculea-tus), which display sexually selected carotenoid-based red throat coloration, have also demonstratedselective foraging by biting at strips of red plasticmore than any other color presented (Smith et al.2004). Olson (2002) found food color preferences inbreeding female zebra finches (Taeniopygia guttata),which strongly preferred red food over yellow. Thispreference may be driven by the physiological needfor carotenoids during reproduction. Despite theseintriguing observations, comparatively little is knownwithin species about inter-individual variation infood color preferences, i.e. whether individuals ofdifferent sex, coloration, age, or at different times ofyear show varying degrees of food choice. For exam-ple, degree of male coloration could be positivelylinked to food color preference because theconsumption of specific foods might enhance anindividual’s coloration.Male house finches (Carpodacus mexicanus) displaycarotenoid-based plumage coloration ranging contin-uously from pale yellow to bright red, and it hasbeen shown that males with high carotenoid dietsdevelop redder, more saturated plumage and arepreferred as mates by female house finches (Hill2002). Size of colorful plumage patches also variesamong males and is positively correlated with plum-age coloration (Hill 2002). Stockton-Shields (1997)tested preferences for red foods in captive moltingand non-molting male and female house finches andfound that both male and female house finches pre-ferred red food (dyed apple slices) over yellow andblue, but that there was no seasonal effect on thispreference. Redder wild male house finches con-sume more carotenoids than yellower males (Hillet al. 2002), but we do not yet know if or howmales select carotenoid-rich foods. The works ofStockton-Shields (1997) and Rodd et al. (2002) sug-gest that males may use food color to select caroten-oid-enriched