Monday, July 7, 2014

Bobolink

Gene Bauer, Gerry Hoekstra and I checked out a prairie being restored by the Nerstrand Big Woods State Park in Rice County. Bobolinks bred in the grassland. Bobolinks are relatively common nesting birds in our part of Minnesota, yet these first two photos are my first for the female of the species. Perhaps their relative drabness compared to the striking black and white males diverted my attention. Both sexes gave curious wing quivering behaviors (shown in all but the first photo), flapping their wings without flying.  I am not sure if this action is aggressive or territorial, or if it was directed at other bobolinks or at me. I have seen similar displays by other grassland birds like Henslow’s and Grasshopper sparrows.
Bobolinks are polygynous, with males breeding with multiple females. Males defend their territories until they begin feeding nestlings. At this time, males without territories establish territories of their own and often attract females that have been unsuccessful at breeding. Female Bobolinks almost never defend areas against other females within their male’s territory (Martin and Gavin 1995). Thus my photo of the female giving a wing display may well be intended to distract me from the nesting area.
Bobolinks are long-distance migrants, wintering in southern South America, a round-trip distance of about 12,500 miles. A banded female Bobolink was recaptured after nine years, thus “presumably made this trip annually, a total distance equal to traveling 4.5 times around the earth at the equator” (Martin and Gavin 1995). Studies indicate that Bobolinks orient using magnetic clues.

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