Genetic mating system and population history of the endangered Western Yellow-breasted Chat (Icteria virens auricollis) in British Columbia, Canada

Abstract

The Western Yellow-breasted Chat ( Icteria virens auricollis (Deppe, 1830)) is a Neotropical migrant, with a Canadian distribution restricted to breeding populations in southern British Columbia. Given its small population size and diminishing breeding habitat, Yellow-breasted Chats are federally endangered in Canada. We used genotypic data at eight microsatellite loci to assess genetic diversity, reconstruct population structure and demographic history, and characterize genetic mating system of Yellow-breasted Chats sampled across 60 nesting sites at five locations in the Okanagan Valley (n = 148). Microsatellite-based analyses indicated lack of significant genetic differentiation among breeding sites and no genetic evidence of population decline. Parentage assignments indicated moderate levels of extra-pair paternity, with 30.7% offspring not sired by attending males. Patterns of sibship among nestlings revealed 49.1% of the clutches were composed entirely of full-siblings, with half-siblings and unrelated nestlings present in some broods. These findings suggest that extra-pair paternity is common in Yellow-breasted Chats, similar to other avian species, and present the first evidence of conspecific brood parasitism in warblers. Our findings add to a growing body of research informing the need to establish a national park in the south Okanagan to preserve critical habitat and connect populations of species at risk.