A Summer of Unexpected Terns

Tern Chick

A Summer of Unexpected Terns:  Aleutian and Arctic Tern Research at Kodiak National Wildlife Refuge


By: Jill Tengeres, Biotechnician and Crew Leader
Fall 2017 


Biologists search for tern nestsThe summer of 2017 was an exciting field season for the seabird researchers at Kodiak National Wildlife Refuge! Over the past three decades, the Alaska breeding population of Aleutian terns has dramatically declined by an estimated 92%, creating a high concern for the species. The Kodiak Archipelago is home to multiple Aleutian tern colonies, making it an ideal location to study this elusive, rare seabird. Researchers at Kodiak NWR are part of a state-wide, inter-agency effort to increase our knowledge and improve conservation efforts globally for this species. Despite our increased focus, the number of breeding Aleutian terns in the Kodiak Archipelago this summer was extremely low, highlighting the need for conservation action.

The Aleutian tern is an intriguing bird; it is the only member of its genus to leave the tropics for the far north during the breeding season (the other three species are solidly tropical terns). Recent tagging studies have shown that every year Aleutian terns travel all the way from Alaska in the summer back to Indonesia – some birds fly round trip over 20,000 miles in a single year! On Kodiak they typically nest in mixed-species colonies with Arctic terns and mew gulls. Compared to their Arctic tern neighbors, Aleutian terns are much more cryptic. They do not attack colony intruders with the same vigor as other terns, and their vocalizations are a high-pitched trill which is easy to miss amongst a cacophony of neighboring Arctic tern and mew gull calls. 

Aleutian tern caught on cameraThis season, the seabird field crew at Kodiak NWR set trail cameras at Aleutian tern (and associated nesting species) nests to study nest attendance, causes of nest failure, prey items delivered to chicks, and the overall survival of nests. Unfortunately, both Aleutian and Arctic terns nested in very low numbers this summer throughout the Kodiak Archipelago, making it quite challenging to find nests for camera deployment. We were able to place cameras on 18 active nests (15 Aleutian tern, two Arctic tern, one mew gull). Only two of the nests, both Aleutian tern, hatched chicks. The ultimate fate of these chicks is unknown, but we fortunately observed their behavior at the nest site and documented over 100 prey deliveries to the chicks before they wandered out of camera view into the dense vegetation. We identified kelp greenling, Pacific sand lance, salmonids, gadids, and flatfish among the prey deliveries. 

A red fox predates a tern nest on cameraThe cameras also allowed us to capture images of predators. Four nests were depredated by foxes, three by black-billed magpies, two by Northwestern crows, one by a domestic sheep, one by a mew gull, and one was egged by a human (the mew gull nest). Of the remaining nests three were abandoned and one failed for unknown reasons due to camera malfunction. At one nest, the incubating adult Aleutian tern was killed and eaten by a red fox. It isn’t easy being a tern!

This season we also began collecting tern nesting habitat data. We plan to characterize the difference in nest-site selection and to describe the differences between used and available nesting habitat for Aleutian Terns in the Kodiak Archipelago. We hope to use the results from this project in the future to assess nesting habitat suitability at historical colonies and to aid in selecting sites for possible colony restoration.

The rapid population decline of Aleutian terns in Alaska and the small global population size of this species require fast conservation actions on our part. Even with the challenges of a low nesting year, our data collection provides valuable insight for this little-known species. We will continue this study in 2018, and hopefully implement new methods as well. The more information we have, the more prepared we are to make strides forward in the conservation of this unique and at-risk bird.