Friday, May 21, 2010
Eastern Bluebird 2
As I took the bird from the net, its mate attacked me. I was disappointed that the male was not one of the young banded during the past couple of years. I should not have been surprised, since adult males, after wintering with their young, aggressively chase them away during the next breeding season. (Males will fight over mates or territories, as will females; indeed these fights can result in the death of one of the combatants!)
As is the case with many well-studied species, bluebird breeding behavior can be complicated. Although pairs are often monogamous, males can be polygamous. Females can be in separate cavities in the same territories or the male may have more than one territory, each with a female. Also reported are records of one male with two females in the same nest box! Polyandry is also known, where one female nests with more than one male. About 20% of bluebird houses contain young not fathered by the "owner" of that box. Finally, the young of first broods occasionally help their parents feed the young of second broods.
The source for most of this information is: Gowaty, Patricia Adair and Jonathan H. Plissner. 1998. Eastern Bluebird (Sialia sialis), The Birds of North America Online (A. Poole, Ed.). Ithaca: Cornell Lab of Ornithology; Retrieved from the Birds of North America Online: http://bna.birds.cornell.edu.bnaproxy.birds.cornell.edu/bna/species/381
Posted by Dan Tallman at 3:14 PM