Dynamics of Dispersed-Nesting Black Brant on the Yukon-Kuskokwim Delta

The number of black brant Branta bernicla nigricans nests within major breeding colonies on the Yukon-Kuskowkim Delta has declined since 1992. It has been hypothesized that these declines are partially explained by increased numbers of black brant breeding outside of these colonies. To assess this hypothesis, we analyzed spatiotemporal patterns in numbers of black brant nests occurring outside major colonies. Nesting densities of black brant vary among three strata: 1) peripheral to major colonies, 2) other coastal habitats, and 3) inland habitats. We sampled some substrata within each stratum type only between 1986 and 1999 (historical strata), whereas we sampled others over the period 1986–2016 (long-term strata). We fit regression models with number of nests on a plot as a response variable, a log link, and year as the explanatory variable. We allowed each stratum (e.g., historical peripheral) to have its own intercept to account for variation in mean nest density but constrained linear and quadratic regression coefficients to be the same for strata in similar habitats (e.g., historical and long-term peripheral). We used a negative binomial distribution for nests to allow for substantial variation in nests per plot. We fit models using Markov Chain Monte Carlo methods in JAGS. Ninety-five percent credible intervals for both linear and quadratic coefficients for the peripheral and coastal strata, where most nests occurred, broadly overlapped zero, indicating modest trends in numbers of nests in these strata. We estimated there were 6,584 (95% credible interval: 4,221−11,269) dispersed nests in 1986, increasing to 11,051 (95% credible interval: 7,450−17,460) in 2016. Our results indicated that increases in dispersed nests were unable to replace declines in colony nests. Furthermore, quadratic trends indicated that potential earlier annual increases in dispersed nests have declined to zero. We conclude that total numbers of black brant nests on the Yukon-Kuskokwim Delta are likely declining, consistent with the trend in fall age ratios over the same period. Uncertainty about trends in areas not sampled since 1994 adds to the uncertainty about the precise magnitude of the decline. We recommend that the area sampled by the random plot program be expanded to include strata sampled only before 1995.

Trends and Fluctuations in Bird Populations on the Tundra at Cambridge Bay, Nunavut

Bird observations from the Cambridge Bay area on Victoria Island, Nunavut, in the summer of 2011 are presented and compared with those from the 1960s and 1980s. A total of 38 species was observed, compared with 42 in 1983 and 47 in 1986. Abundance of species of the High Arctic, such as Black Brant, Branta bernicla nigricans, Black-bellied Plover, Pluvialis squatarola, and Baird’s Sandpiper, Calidris bairdii, decreased, whereas numbers of the Red-necked Phalarope, Phalaropus lobatus, usually associated with the Low Arctic, increased markedly. Overall, the number of each species observed is rather stable and, for several species, the relative abundance does not seem to have changed significantly.

RECENT RECORDS OF THE BLACK BRANT (Branta bernicla nigricans) IN NAYARIT, MÉXICO

Registros recientes del ganso de collar (Branta bernicla nigricans) en Nayarit, México Presentamos el segundo y tercer registro en 25 años del Ganso de collar (Branta bernicla nigricans) en Nayarit, México. El 24 de enero de 2010 observamos y fotografiamos tres especímenes juveniles del ganso en una granja camaronícola ubicada en la vecindad de San Blás. Uno de ellos (macho) fue marcado el verano anterior en el NW de Alaska. El 14 de diciembre de 2010 se observaron dos juveniles en Laguna Las Garzas, al norte de Nayarit.