Wednesday, August 02, 2006

Grassland Birds and Strip Mines

In this article, the Ohio DNR reports that about 250,000 acres of former strip mines reclaimed as grasslands are attracting large numbers of grassland birds such as Savannah, Grasshopper, and Henslow’s Sparrows and Bobolinks. The question I have, “Are they reproducing?” Extensive studies of reclaimed strip mines in West Virginia have shown that these habitats are ecological “sinks” that readily attract birds but do not provide the resources necessary for the successful production of young. Here, for example, is my summary of the results of a study by Wray et al. (1982):
Detailed analysis of productivity of 4 species (Vesper, Grasshopper, Savannah, and Field sparrows) on a 41.5-ha site in Preston County, 1978-1980, suggests that "adults are not replacing themselves and immigration is necessary to maintain a stable population" and that "these manmade grasslands may not be of benefit to the sparrow populations in this area." Predation was the major cause of egg and nestlings losses in all 3 yrs of the study; of 185 nests located, 43% were lost to predators.

Source: Wray, T., II, K. A. Strait, and R. C. Whitmore. 1982. Reproductive success of grassland sparrows on a reclaimed surface mine in West Virginia. Auk 99:157-164. (Available here as a PDF file from SORA, but may not load properly.)


Anonymous Anonymous said...

why is the predation rate greater in this circumstance?

August 03, 2006 10:50 AM  
Blogger John L. Trapp said...

Thanks for the question, Paul. The 41.5-ha study site was surrounded by woodlots and pasturelands, a situated that the authors thought concentrated predators, the major ones being black racers and American Crows.

August 03, 2006 1:45 PM  
Anonymous Anonymous said...

I would never have thought black racers.

August 03, 2006 1:50 PM  
Blogger John L. Trapp said...

According to the literature, black racers inhabit pastures and overgrown fields and feed on a variety of prey items, including small birds.

August 03, 2006 2:14 PM  

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