abundance, area sensitive, field size, grassland birds, habitat fragmentation, Iowa, landscape composition, occurence
Many species of grassland birds have been shown to avoid smaller fields. The avoidance of smaller fields, however, has not been consistently reported; avoidance may occur in one study, but not in another. To examine one possible reason for these inconsistencies, we examined how landscape composition influenced the relations between occurrence or abundance and field size. The study took place during the 1998 breeding season on 44 Conservation Reserve Program (CRP) fields located in Adair, Ringgold, and Union counties. The relations between occurrence, abundance, and field size were not influenced by landscape composition for any species.
Grasshopper Sparrow, Ammodramus savannarum, Bobolink, Dolichonyx oryzivorus, and Eastern Meadowlark, Sturnella magna, were more likely to occur or were more abundant in larger fields. Field Sparrow, Spize!la pusilla, Western Meadowlark, Sturnella neglecta, Brown-headed Cowbird, Molothrus ater, and American Goldfinch, Carduelis tristis, were less likely to occur or were less abundant in larger fields. Field size is an important factor influencing the occurrence and/or abundance of grassland songbirds in fields. Future studies that investigate the effects of landscape composition on area sensitivity should use landscapes that have similar habitat compositions other than the habitat being varied, and use similar sized fields in each landscape.
Journal of the Iowa Academy of Science
© Copyright 2002 by the Iowa Academy of Science, Inc.
Horn, David Joseph; Koford, Rolf R.; and Braland, Malinda L.
"Effects of Field Size and Landscape Composition on Grassland Birds in South-Central Iowa,"
The Journal of the Iowa Academy of Science: JIAS: Vol. 109:
, Article 3.
Available at: http://scholarworks.uni.edu/jias/vol109/iss1/3