Reproductive Success of Grassland Birds at East-central Illinois Airports

Abstract

-We determined the densities and reproductive success of birds on seven airport grasslands in east-central Illinois between 10 April and 15 August 1994. One hundred and forty-seven nests of six species were found. Eastern meadowlark (Sturnella magna) was the most abundant nesting species (71% of 147 nests). 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 nest success at individual airports ranged from 0.02% to 29%. Most known nest failure was attributed to mowing (44% of all nests). Thus airport grasslands appear to be population sinks for most grassland birds. Although the overall nest density was only 0.79 nests/ha; eastern meadowlark nest density was 0.56 nests/ha. This is a relatively high value compared to other studies. The relatively high nest densities and low nest success suggest that airport grasslands may be ecological traps for eastern meadowlarks and may be contributing to regional declines of other grassland species.