SEXUAL DIMORPHISM IN ACHROMATIC PLUMAGE REFLECTANCE OF WHITERUMPED SWALLOWS, Tachycineta leucorrhoa

CAROLINA ISABEL MIÑO; VIVIANA MASSONI; MARÍA JULIANA BENITEZ SALDIVAR

Puerto Iguazu

Congreso; I Ornithological Congress of the Americas; 2017

Association of Field Ornithologists-Aves Argentinas-Sociedade Brasileira de Ornitologia

Achromatic plumage (white, grey or black) is a good candidate signal for visualcommunication, yet it is relatively less studied than melanin and carotenoid based, orstructural plumage. Here, we sought to determine whether the white plumage ofthe White-rumped Swallow, Tachycineta leucorrhoa, exhibits variation within andbetween sexes. Previous recent research in the congeneric Tree Swallows, found thatwhite plumage brightness is related to the bactericidal capacity of individuals´ plasmathus revealing its potential as a signal of individual quality. We removed five to sevenfeathers from the breast, belly and rump of eight males and 15 females breedinginChascomús, Argentina (35°34?S, 58°01?W), measured their reflectance in the lab usingan Ocean Optics USB2000 spectrophotometer, and applied an avian visual model toestimate chromatic and achromatic contrasts among body regions. We comparedcolorimetric variables (hue, UV-chroma and brightness) with t-tests and calculated unitsof ?Just Noticeable Differences? for each body region, sex and between sexes. Inaddition, we performed a multi-response permutation procedure to generate a ?null?distribution of expected values against which we compared the observed values. Wefound evidence of significant sexual dichromatism in the belly, breast and rump ofbreeding White-rumped Swallows. Females showed more brightness in belly, whereasmales showed more brightness and greater reflectance in the 300-400 nm interval in thebreast; sexes were also different in the rump.These variable traits could, therefore, besubjected to sexual selection in this socially monogamous yet sexually promiscuousspecies with high rates of extra-pair paternity