Interspecific and Local Variation in Tern Chick Diets Across Nesting Colonies in the Gulf of Maine

Authors

Keenan Yakola, University of Massachusetts Amherst, National Audubon Society Seabird Institute
Adrian Jordaan, University of Massachusetts Amherst
Stephen Kress, National Audubon Society Seabird Institute
Paula Shannon, U.S. Geological Survey
Michelle D. Staudinger, U.S. Geological Survey, University of Massachusetts Amherst

Date of this Version

11-11-2021

Citation

Waterbirds 44(4): 397-414, 2021

Comments

U.S. government works are not subject to copyright.

Abstract

The Gulf of Maine, USA is home to four colonial co-nesting tern species: Least Tern (Sternula antillarum), Common Tern (Sterna hirundo), Arctic Tern (Sterna paradisaea), and the federally endangered Roseate Tern (Sterna dougallii). Over three decades of visual observations of chick provisioning were compiled for a comparative dietary study in the region, including the first detailed descriptions of Least and Roseate Tern chick diets. Three prey groups comprised the majority of chick diets among tern species between 1986–2017: hake (Urophycis spp. or Enchelyopus cimbrius) 28–37% frequency of occurrence (FO), sand lance (Ammodytes americanus or A. dubius) 8–22% FO, and herring (Clupea spp. or Alosa spp.) 3–30% FO. Dietary contributions varied across species and islands. At two inshore colonies, Common Tern diets contained higher amounts of sand lance (30–42% FO), while offshore islands contained lesser amounts (5–9% FO). Overall dietary diversity (H′) was similar between Common (H′ = 1.57) and Arctic Terns (H′ = 1.74) and notably lower in Roseate (H′ = 1.24) and Least Terns (H′ = 1.37), whose diets were primarily piscivorous. The degree of dietary plasticity and general feeding ecology provided by baseline dietary information can inform holistic assessments of risk to ongoing and future disturbances from fishing and climate change.