Wednesday, July 28, 2010

Sedge Wren

While Erika and I walked by a fairly dense stand of Big Bluestem in the Carleton College Arboretum (see last post), we were startled by a loud bird song only a few feet from our trail.  
I made "spishing" sounds, and up popped a Sedge Wren. Erika continued to "spish" while I took photographs. The wren circled and called back at us.  Click here to hear the call. Often, before I could auto-focus my camera, the wren darted into the grass and out of view.
The Sedge Wren is an odd bird.  This wren is nomadic, breeding in an area during one year but not the next.   Furthermore, Sedge Wrens many breed in the spring, depart the breeding grounds, and, in the same season, breed again elsewhere.  Often they nest in May and June in Minnesota, Wisconsin, North Dakota and Saskatchewan.  A second nesting season occurs in July and September, with birds moving into Nebraska, Kansas, Missouri, Vermont, and Massachusetts.  Our July Sedge Wren definitely appeared to be territorial.  I do not know if it was a local bird making a second breeding attempt or if it was one of those nomads from a foreign breeding area.
Male Sedge Wrens may be polygynous--they may mate with more than one female--and females may be serially polyandrous--they may mate with more than one male.  Females in a Minnesota study, however, had higher reproductive success when they mated with monogamous males.  On the other hand, polygynous males have higher reproductive success than do monogamous males.

Our Monday stroll had one more surprise, which I will share with you in the next blog post.

This information is gleaned from Herkert, James R., Donald E. Kroodsma, and James P. Gibbs. 2001.  Sedge Wren (Cistothrous platensis), 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/582.

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