Site Fidelity and Annual Survival of the Western Yellow-breasted Chat (Icteria virens auricollis) at the Northern Edge of its Range

We studied return rates, site fidelity, dispersal, and survivorship of an endangered population of the Western Yellow-breasted Chat (Icteria virens auricollis) in the southern Okanagan River valley, British Columbia, between 2001 and 2007. Between 2001 and 2006, we banded a total of 75 adults and 385 nestlings. Apparent survival for male Western Yellow-breasted Chats banded as adults was 65%, and survival and recapture were constant across time. Other results were as follows: 44% of males and 13% of females banded as adults were re-sighted during the period 2002–2007; 33% of males and 10% of females were re-sighted the year after they were banded; 31% of males and 10% of females had fidelity to the study site where they were banded as adults; 10% of Western Yellow-breasted Chats banded as nestlings returned and, of these, 62% of males and 54% of females returned to their natal study site to breed. The dispersal distance for males banded as adults (n = 5) that did not return to their sites ranged from 6.4 km to 42.9 km. Natal dispersal ranged from 2.5 km to 15.6 km for males (n = 7) and 2.3 km to 2.6 km for females (n = 2); 16 males and 7 females banded as nestlings did not disperse. These findings contrast with predictions that species at the northern limit of their range will have low site fidelity and return rates and higher dispersal distances than passerine populations at the core of their range.

Size of Territories and Home Ranges of Male Western Yellow-breasted Chats (Icteria virens auricollis) in British Columbia

During 2005 and 2006, radio-transmitters were fitted to a total of 11 male Western Yellow-breasted Chats, Icteria virens auricollis, in the southern Okanagan River valley, British Columbia, to compare the area used, as detected by radio-telemetry and as defined by mapped observations of breeding males singing and perching. Data were only collected for 5 males. For 2005 and 2006, the 95% kernel density estimation (KDE) revealed that mean area used by male Western Yellow-breasted Chats, as determined by radio-tracking (n = 5), was 1.16 ha, whereas the mean area as defined by observations of breeding males singing and perching was 0.62 ha (no statistical difference). Our hypothesis that the area determined by radio-tracking would be significantly larger than the area defined by observations of males singing and perching was rejected, but the area determined by radio-tracking was almost twice the area defined by observations of breeding males singing and perching.

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

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.