Reproductive Success of Grassland Birds at East-central Illinois Airports

Abstract

We determined the densities and reproductive success of birds on airport grasslands in east-central Illinois. Seven airports were sampled between 10 April and 15 August 1994 in Clark, Coles, Crawford, Douglas, Edgar, Macon and Richland counties. Nineteen species were detected on the airport grasslands and 147 nests were found representing six different species. Eastern meadowlarks (Sturnella magna) were the most abundant nesting species found; 105 out of the 147 nests (71%). Other nesting species included: grasshopper sparrow (Ammodramus savannarum), savannah sparrow (Passerculus sandwichensis), red-winged blackbird (Agelaius phoeniceus), song sparrow (Melospiza melodia) and horned lark (Eremophilia alpestris). Overall nest success was 14%, and ranged from 6% for red-winged blackbirds to 100% for horned larks. Individual airport nest success ranged from 0.02% at Robinson to 29% at Decatur. The overall nest density of 0.79 nests/ha is relatively low compared to other studies. However, eastern meadowlark nest density was 0.56 nests/ha, which is a relatively high value compared to other studies. Nearly all nest failure was attributed to mowing (44% of all nests) or nest predation (23% of all nests) and mowing practices may indirectly increase nest predation rates. Management recommendations for these airports include mowing the grass lower and more often to discourage nesting by grassland birds, because grasslands associated with airports appear to be "ecological traps" for eastern meadowlarks and may be contributing to regional declines of other grassland bird species.