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Common Terns Extended Foraging Trips by Up to 87% in Poor Prey and Productivity Years

Common tern holding a fish on Petit Manan Island, Maine
Research · Ecology

Common terns (Sterna hirundo) breeding in the Gulf of Maine, United States changed how far and how long they travelled for food between years with very different prey and reproductive conditions. In years when preferred fish were less common in chick meals and breeding productivity was lower, foraging trips lasted 23–87% longer and foraging ranges expanded by 17–51%.

The study, published on 15 July 2026, combined GPS tracking with observations of food brought to chicks and long-term reproductive monitoring on White and Seavey Islands off New Hampshire. The islands supported around 3,100–3,400 nesting pairs during the four study seasons from 2021 to 2024.

Good and poor years produced different movement patterns

In 2022 and 2024, provisioning of preferred prey such as herrings, hakes and sand lances was similar to or better than the 2011–2020 reference period. Clutch sizes and fledging rates were also comparatively good. During these years, the core feeding areas of breeding birds were concentrated around waters close to the colony and nearby river mouths.

Conditions were different in 2021 and 2023. Preferred prey provisioning declined, one-egg clutches and nests producing no fledglings became more common, and the researchers classified these as poor prey and productivity years. Terns then travelled for longer and used a much broader area. For chick-rearing birds, core and full foraging ranges expanded by roughly threefold, and some feeding areas lay more than 150 kilometres south of the colony.

Extra effort did not fully compensate for poorer feeding conditions

The authors interpret the enlarged feeding ranges as a flexible response to poorer local forage-fish conditions. Although local fish abundance was not measured directly, the study used chick diet and reproductive productivity as indicators supported by previous work from the Gulf of Maine.

Despite the additional travel, chick survival was lower in the poor years. The researchers conclude that greater movement effort can help common terns respond to changing prey conditions, but may not be sufficient to maintain chick diet and survival when preferred food is scarce.

The Gulf of Maine is warming rapidly and its forage-fish communities are changing. The study links those varying feeding conditions with changes in where breeding common terns search for food, how much effort they invest and how successfully their young survive. The authors argue that protecting important feeding areas may become increasingly important as prey distributions continue to shift.

Sources and image credit

  1. Linkages among foraging movements, prey provisioning, and reproduction in a central place foraging seabirdOpen-access peer-reviewed primary study published 15 July 2026. GPS telemetry, chick provisioning and reproductive monitoring were integrated across 2021–2024 at the largest common tern colony in the Gulf of Maine. In poor prey and productivity years, foraging-trip duration increased 23–87% and foraging ranges expanded 17–51%; chick-rearing birds used areas more than 150 km from the colony. The authors note that local forage-fish abundance was not measured directly and was inferred from provisioning and productivity indicators supported by previous regional work.

Image: Amanda Boyd / U.S. Fish and Wildlife Service Northeast Region — common tern (Sterna hirundo) carrying a fish at Petit Manan Island, Maine Coastal Islands National Wildlife Refuge, USA; Wikimedia Commons. Representative foraging image; not identified as one of the birds tracked in the study. · CC BY 2.0 · Source

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