Friday, May 20, 2005
Biodiversity Corner Bobolink
When and where seen: Early on Sunday morning, May 15, while Ken Harte was leading a group of people on the spring bird walk at the Towle Field, six male bobolinks made an appearance. They (the bobolinks) were flying about and singing the bobolink song. Two female bobolinks, more reserved in behavior and less conspicuous in their coloring, were also seen. Bobolinks are migratory birds. They winter over in South America and we don't usually see them in Carlisle until May. These at the Towle Field arrived sometime during the week of May 8 to 14.
Distinguishing characteristics: The male bobolink is most recognizable at this time of year when in its breeding plumage. The face, back, wings and tail are black. The lower back and rump are white and the nape is creamy-buff or straw-colored. By mid- to late-summer, the male more resembles the female which is sparrow-like in plumage.
Food chain: In summer, the bobolink diet is largely insects, and in the fall is largely grain and seeds. The bobolink has a history, from around 100 years ago, of being food for humans. The birds would fatten up on grain in the rice fields of Georgia and South Carolina prior to the next leg of their long migration south. They were pests to the rice farmers and were killed in thousands and sold for food. Bobolinks are still eaten in Jamaica, where they are called butter birds.
Habitat: The bobolink requires open expanses of grasslands or old hayfields that are infrequently cropped for hay. It nests on the ground in dense patches of clover or weeds. It probably likes the Towle Field because there is no plowing or heavy raking and mowing and the woody vegetation is prevented from taking over the field.
Population in Carlisle: The chart, provided by Ken Harte, shows the history of the bobolink count from the annual spring bird walk. The recent uptick could be due to a variety of factors, including the sheep. It could also be thanks in part to all the dog owners who honored the posted requests to keep dogs out of the field during the nesting periods.
References: David Allen Sibley, The Sibley Guide to Birds; Richard M. DeGraaf and Mariko Yamasaki, New England Wildlife; web site of the Smithsonian National Zoological Park which has a Migratory Bird Center, excellent information and a big ugly URL — it is easiest to google it.
© 2005 The Carlisle Mosquito