A Re-evaluation of Age Composition of Irrupting Populations of Black-capped Chickadee (Poecile atricapillus)
Robert P. Yunick
Abstract- Bagg (1969, repeated in Smith 1991 and Foote et al. 2010) characterized fall irruptions of Black-capped Chickadees (Poecile atricapillus) as consisting of mostly immature birds. He based his conclusion on 1968 fall banding data from numerous banding stations where skull examination was used to determine age. Since skull pneumatization in immature chickadees undergoes complete in Oct-Dec (Yunick 1980), the method is not applicable in separating age classes over the entire period of an irruption. Meigs et al. (1983) described a method based on rectrix shape to reliably age chickadees on a year-round basis thus allowing a more complete assessment of year-to-year variation in chickadee age composition during these irruptions. Here I present data over a 43-year period (1970-2013) from a banding station in the Adirondack Mountains of New York illustrating irruptive migration of Black-capped Chickadees, and more particularly age composition through the entire irruptions using Meigs et al.’s rectrix method for the 30-year period, 1983-2013. Contrary to earlier findings, these data indicate that not all irruptions are heavily populated by immature birds. In 13 of the 30 years, adults made up over 50 percent of the birds captured, the highest being 88.5 percent in 1999-2000 when 260 chickadees were captured. In only six years was the adult percentage 30 percent or less; the average over the 30-year period was 52.0 percent adult based on the banding of 3144 chickadees and processing of 1260 return captures of birds banded in previous years.
North American Longevity Records for Nine Landbird Species Monitored at Yosemite National Park’s MAPS Stations
Erin Rowan, Rodney B. Siegel, Danielle R. Kaschube and Sarah Stock
Abstract- Information on longevity of birds may provide insight into ecological pressures faced by particular species and populations and may also be useful in developing conservation approaches. However, longevity can be difficult to study in wild birds, and efforts to determine the ecological, evolutionary, behavioral and physiological factors that govern longevity of landbirds have been constrained by the quantity and quality of long-term monitoring data available. The Monitoring Avian Productivity and Survivorship (MAPS) program provides a framework that encourages the long-term operation of mark-recapture monitoring stations in North America, with more than 300 stations that have been operated for at least ten consecutive years since the program was established. Analysis of mark-recapture data from MAPS stations operated at Yosemite National park between 1990-2013 yielded new North American longevity records for nine species: Red-breasted Sapsucker (Sphyrapicus ruber), Williamson Sapsucker (Sphyrapicus thyroideus), White-headed Woodpecker (Picoides albolavatus), Western Wood-Pewee (Contopus sordidulus), Cassin’s Vireo (Vireo cassinii), Mountain Chickadee (Poecile gambeli), Brown Creeper (Certhia americana), Lincoln’s Sparrow (Melospiza lincolnii) and Cassin’s Finch (Haemorhous cassinii). We suggest that the larger, continent-wide MAPS dataset likely contains a wealth of information for revealing patterns in avian longevity and the ecological factors, evolutionary constraints, and life history characteristics that may drive those patterns.