Spring Migration Ecology of Snow Buntings in Southwest Yukon Territory, 2014-2023.

From 2014-2023 we studied the spring migration of Snow Buntings (Plectrophenax nivalis) through southwest Yukon, collecting data on wing length and body mass, age-sex class composition, and stopover mass gain for birds banded and recaptured during the study. We used walk-in ground traps, baited with cracked corn and millet, to capture birds in agricultural fields near Haines Junction. We banded 10,058 Snow Buntings, 78.5% of which were male (After Second Year or ASY=51.0%, Second year or SY=27.5%), while 21.5% were females (ASY=15.1%, SY=6.4%). The first arrivals were males, 75% which were ASY, and as the season progressed ASY females, then SY females, began to arrive, and males started to move on. Wing length and mass were significantly greater for males than for females among all age classes, and significantly greater for ASY than for SY in congregate and within the same sex class. Body condition index (BCI; mass:wing length) varied among age-sex classes across years: in most years ASY males had the highest BCI, followed by SY males, ASY females, and SY females. During our study, SY male BCI declined significantly and ASY male BCI also declined, while SY female BCI was stable, and ASY female BCI increased significantly. We had 2,630 recaptures (excluding same day recaptures). The majority of the same year recaptures (54.4%) were in the first two days after banding; the longest period from first banding to last recapture was 21 days. The difference in mean BCI was generally positive for the duration of stopover time, but some ASY birds lost mass in the longest stopover duration. Sixty-eight individuals (70 events; two individuals were each recaptured in two different years) were year-to-year recaptures (2.7% of total recaptures), up to five years after banding. Three Snow Buntings that we banded have been recovered elsewhere. Our study of migration phenology contributes to the body of knowledge needed to conserve and manage Snow Buntings in Canada. [ABSTRACT FROM AUTHOR]