Contributed by Mark LaBarr, Conservation Program Manager, Audubon Vermont
Header photo by Jacob Crawford/Audubon Vermont
The 2022 Common Tern (Sterna hirundo) breeding population in Vermont rebounded moderately in 2022 from low numbers and low reproductive success in 2021. Breeding population numbers were up slightly from 2021, and more than 100 chicks survived to fledging. This was still lower than the 2020 breeding population of 230 pairs with more than 250 chicks fledging.
We estimated 190 pairs breeding on 3 islands in 2022. The majority of nesting attempts occurred on Poppasquash Island, with a smaller number of nests being initiated on Rock Island and Grammas Island. Peak adult and nest counts were estimated at 230 adults and 173 nests. Tern chicks fledged from all islands.
Great Horned Owls (Bubo virginianus), regular predators of terns and gulls on all islands in past years, impacted terns in 2022. Black-crowned Night Herons (Nycticorax nycticorax), which were observed regularly on Lazy Lady Island and suspected of breeding there, were also thought to have caused some nest failures on Rock Island. Peak Ring-billed Gull nest numbers were 39 on Poppasquash Island, with 74 gull nests observed on Rock Island, and 44 gull nests on Grammas. An unknown number of gull chicks fledged from all 3 islands. The wire grid system erected on Poppasquash Island reduced the number of nesting gulls in 2022 and may have resulted in the observed higher nesting numbers on the other 2 islands. The wire grid system on Poppasquash and Rock islands effectively limited roosting and nesting of Double-crested Cormorants (Phalacrocorax auritus). Chick shelters, warning sign buoys, and an ant bait system were used to reduce predation and human disturbance. Solar powered walkway lighting was deployed in tern nesting areas on both islands just prior to hatching to limit nocturnal predation. All 105 known fledglings were banded.