Patterns of Nestling Feeding in Harris's Sparrows, Zonotrichia querula and White-crowned Sparrows, Z. leucophrys, in the Northwest Territories, Canada

Résumé

Patterns of nestling feeding by males and females were compared in sympatric populations of Harris’s Sparrows (Zonotrichia querula) and Gambel’s White-crowned Sparrows (Z. leucophrys gambelii) in the Northwest Territories, Canada. In both species, only the female brooded young. Total feeding rate (both parents), and male and female feeding rates, increased with nestling age in both species; total feeding rates did not differ significantly between species. Nestlings of both species were fed most frequently by females during the early part of the nestling period (day 0-5), and feeding rates did not approach parity until nestlings were 6-8 d old. Patterns of nestling feeding, including initially low male provisioning, in Harris’s Sparrows and White-crowned Sparrows at my low arctic study site were similar to those in other populations of Zonotrichia. Low levels of male nestling care, relative to females, appears to be relatively uncommon among socially monogamous passerines. Reduced male care may be adaptive in temperate environments, as it would allow males to pursue other mating opportunities. However, reasons for persistence of the trait in the low arctic, where breeding is highly synchronous, remain unclear.