Population sampling
Oregon juncos were sampled across their breeding range using mist nets and seed-baited walk-in traps during the breeding season, between the months of April and June, and between the years 2004 and 2014. In addition to samples collected at UCSD in San Diego, California, we included in the study samples from all recognized Oregon junco subspecies, including oreganus from British Columbia,montanus and shufeldti from Oregon, thurberi andpinosus from California, and pontilis and townsendifrom Baja California, Mexico (Fig. 1). At UCSD, birds were sampled both during the breeding season and the non-breeding season, and genetic and isotopic analyses were used to infer whether birds sampled in the non-breeding season were local residents or wintering visitors breeding elsewhere (see below).
Birds were marked with uniquely numbered aluminum bands to avoid resampling, and then released after processing at the site of capture. A blood sample was collected by venipuncture of the brachial vein and stored in Queen’s lysis buffer (Seutin 1991) or absolute ethanol at -80ºC in the laboratory. All sampling activities were conducted in compliance with Animal Care and Use Program regulations at the University of California Los Angeles, University of California San Diego, North Dakota State University and Indiana University, and with State and Federal scientific collecting and bird banding permits in the USA, Canada and Mexico.