Meeting Abstract

P1.6  Sunday, Jan. 4  Variation in the first prebasic molt among House Finches, Red Crossbills, and other Cardueline Finches that differ in reproductive schedule BRAZEAL, K.R.*; CORNELIUS, J.M.; HAHN, T.P.; Univ. of California, Davis; Univ. of California, Davis; Univ. of California, Davis krbrazeal@ucdavis.edu

The annual replacement of feathers is a vital process for all birds. A successful molt is important for insulation, flight capability and efficiency, camouflage, sexually selected ornamentations and courtship displays. In addition, growing new feathers is energetically demanding. Therefore, the timing and pattern of molt can greatly affect reproductive success. The timing and progression of molt was examined in adult and juvenile House Finches (Carpodacus mexicanus) captured in Davis, California, with comparisons being made between the sex and age classes. Furthermore, the first prebasic molt pattern of juvenile birds was compared between seasonally-breeding House Finches and opportunistic Red Crossbills (Loxia curvirostra). Typically in the first prebasic molt, juvenile passerines replace the body feathers but retain their original flight and tail feathers. However, some species deviate from this pattern. Within the 16 North American Cardueline Finch species (subfamily Carduelinae, family Fringillidae), House Finches are unique in that many juveniles replace some of the flight feathers; even the congeneric Purple and Cassins Finches do not do this. Four other Cardueline species (including Red Crossbills) have been reported to occasionally replace some of the flight feathers during the first prebasic molt. Several years of field data from Red Crossbill juveniles captured throughout the Pacific Northwest show this to be surprisingly rare, given how early Crossbills often nest (winter). Potential explanations for these species juvenile molt patterns are discussed, particularly in reference to differences in flexibility of the annual reproductive cycle.