Genetic and morphometric variation across a chickadee hybrid zone in southeastern Pennsylvania Robert L. Curry, Sean P. Mullen, Kerri L. Cornell, Dept. New York Abstract. Parental and hybrid individuals could be identified through RFLP analysis of mtDNA haplotypes and nuclear loci. Using discriminant function analysis on wing, tail, tarsus, and bill measurements, we were able to separate genetically distinct Black-capped and Carolina Chickadees. However, external morphology of hybrid birds was intermediate and variable, so measurements could be used to distinguish hybrids from parental forms within localities.
Ongoing work focuses on breeding patterns in a mixed population within the contact zone.
New York Abstract. We used data on weather patterns and population structure over 30 years, and estimates of food availability from the last 12 years, to explain variation in timing of breeding. Neither nor weather conditions nor arthropod availability in the weeks just prior to clutch initiation accounted for variation in timing. Available evidence suggests that onset of breeding in Florida Scrub-Jays is determined by a combination of demographic and resource influences acting several months prior to clutch initiation. Territories are stable througout and occupy an area of 1-2 ha.