Long-term Declines of Autumn Fat Scores in Migrating Passerines of Coastal Maine

Jocelyn LaClair¹ and Noah Perlut^1,*

¹School of Marine and Environmental Programs, University of New England, 11 Hills Beach Road, Biddeford, ME 04074. *Corresponding author.

Northeastern Naturalist, Volume 33, Issue 4 (2026): 520–527

First published early online: 11 November 2026

Abstract
Long- and short-distance migratory songbirds acquire fat during migratory flights at stopover sites. With phenological shifts mediated by climate change, alterations in food abundance or peak timing could disrupt historical patterns of this fat storage and therefore migration ecology. Furthermore, these potential disruptions may vary by dietary guild and species, affecting birds that rely on plant matter and animal matter differently. Using data collected at a fall-migration stopover in coastal Maine from 2011 to 2024, we investigated patterns of fat acquisition in omnivorous, insectivorous, and frugivorous migratory songbirds. By guild, fat storage declined significantly in insectivores and omnivores, but not frugivores over the 13-year study. Annually, fat storage declined by 44% and 18% in insectivores and omnivores, respectively, over the study period. The overall decrease in acquired fat over time suggests that some species, particularly insectivores, are less able to accumulate fat for migration at this stopover site in southern Maine.

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