Former landfills have long been recognized as a potential source of early successional habitat for wildlife, but their use by migrating grassland and shrubland songbirds has yet to be studied. We estimated mass change rates of 5 grassland and shrubland songbird species during autumn stopovers at a reclaimed landfill in New Jersey, to assess the quality of a former landfill as a stopover habitat. We also examined minimum length of stay, age ratios, and age differences in body mass and fat scores. Regressions of capture time and body mass were statistically significant and indicated gains of 0.8–1.2% of average body mass per hour in Savannah Sparrows (Passerculus sandwichensis), Lincoln's Sparrows (Melospiza lincolnii), and Palm Warblers (Setophaga palmarum), but coefficients of determination were weak (<0.06). White-crowned Sparrows (Zonotrichia leucophrys leucophrys) and Indigo Buntings (Passerina cyanea) did not gain significant mass. Minimum length of stay based on recaptures ranged from an average of 4.7 d in Savannah Sparrows to 10.1 d in Indigo Buntings. Adults did not have higher mass gain rates, body mass, or fat scores than immature birds in any species, with the exception of adult Savannah Sparrows being heavier than immatures in 1 year. The age ratio was significantly skewed toward immatures in all species except the Indigo Bunting, in which the opposite pattern occurred. Food availability at our site may have been poor, limiting the ability of birds to gain mass, or possibly time is not as important to these species at this stage of their migration as energy minimization and predator avoidance are. Considering the low temporal pressure and slow pace of autumn migration relative to spring, these autumn migrants might be using the landfill for rest, energy maintenance, and predator avoidance more so than rapid and substantial fuel deposition. The independence of mass change rate and energetic condition from age suggests that any potential age differences in dominance or foraging ability in these species do not affect their ability to refuel during stopover.

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