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Tuesday, January 30 • 4:20pm - 4:40pm
FOREST & GRASSLAND SONGBIRDS: Patch Size Dynamics of Birds in Mixed-Grass Prairies: Why Might the Influence of Patch Size Vary

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AUTHORS. Mike Eichholz, Southern Illinois University Carbondale

ABSTRACT. Patch size dynamics was first used to explain why forest fragmentation has negatively influenced breeding populations of forest nesting birds.  It has evolved into an excepted paradigm for habitat mangers across a range of habitat types including short- and mixed-grass prairies.  Evidence supporting this paradigm for grassland nesting birds in short- or mixed-grass prairies is, however, limited.  I review the potential mechanisms by which patch size dynamics may act and present results of studies conducted in the prairie pothole region of North and South Dakota suggesting area sensitivity and specifically edge effects differ between fragment forests and mixed grass prairies patches ranging in sizes of 60 to 400 ha.  Nest success of upland nesting ducks declined with patch size until patch size reached approximately 200 ha, at which point the relationship became positive.  Furthermore, we found no evidence distance to edge influenced nest success or parasitism rate of passerine nests and edge type had only a marginal impact with wetland edges providing the higher likelihood of nest parasitism. These results indicate that grassland birds have neither adapted the ability to use patch size as a habitat selection characteristic nor receive benefit from choosing larger patches.  Furthermore, consistent with other studies, I found nest success actually declines with increasing patch size for patches ranging in size most frequently preserved and the habitat conservation organizations in this region may be developing prairie patches of sizes that are the least beneficial to grassland birds.

Tuesday January 30, 2018 4:20pm - 4:40pm CST