SOME ASPECTS OF THE BREEDING BIOLOGY OF RED-WINGED BLACKBIRDS IN ALASKA

ABsTRAcr.-Red-winged Blackbirds (Agelaius phoeniceus) reach the northern limits of their breeding range in eastern interior Alaska. Blackbird breeding phenology in Alaska is more synchronous, eggs are larger, nestlings grow more rapidly, and clutch-size and female reproductive success are higher than in populations farther south. The lack of a difference in the rate of tarsometatarsus increase in conjunction with the faster growth rate of nestlings suggests that the differences I found between this and more southerly populations are environmental responses to abundant food resources in the nestling period. Received 16 Jan. 1984, accepted 21 Oct. 1985.