Aleutian Tern Surveys Begin

2024 Aleutian tern surveys in southern Alaska begin today.

Aleutian terns

Trent McDonald


June 4, 2024

The U.S. Fish and Wildlife Service, the U.S. Forest Service, and I are happy to announce initiation of the 2024 Aleutian tern surveys.


The Aleutian tern, a lesser-known cousin of the Arctic tern, nests exclusively in Alaska and eastern Russia. While no systematic surveys of Aleutian terns have been conducted, their numbers are know to have plummeted since the 1960s.

McDonald Data Sciences has been assisting the U.S. Fish and Wildlife Service (Alaska region) and the U.S. Forest Service (Alaska region) for the past 4 years to design scientifically defensible surveys of Aleutian terns. The goal of these surveys is to estimate the total number of nesting individuals in the entire state of Alaska.

2024 Surveys

Partnavia aircraft used for portions of the aerial surveys

Aerial surveys for Aleutian tern nesting colonies began today in two regions: Cook Inlet and the Alaskan Peninsula. Aerial surveys entail flying the coastline and randomly selected blocks of habitat farther inland in fixed-wing aircraft. Survey aircraft are crewed by 2 to 3 observers and a pilot. The aerial portion of the surveys employ a double-observer line-transect sampling methodology. For the interested reader, there are YouTube video introductions (search ‘distance sampling’ and ‘line transect sampling’) and a nice description on Wikipedia.

When a nesting colony is discovered, biologists go to the site to count terns. Biologists conduct ground-based counts because the number of terns at a colony cannot be determined from the fixed-wing aircraft when it is discovered.

Biologists hard at work counting Aleutian terns.

From aerial surveys, we estimate the number of nesting colonies. From ground-based counts of nesting colonies, we estimate the average number of terns per colony. From both, we estimate total abundance ((number of colonies)\(\times\)(average terns per colony)).

Bigger Picture

The 2024 surveys are the second year of a planned 3-year effort to survey for terns over the entire coastline of Alaska. 2023 surveys focused on southeast Alaska, from Gustavus to Cordova. 2025 surveys are planned for the Aleutian Islands and the west coast of Alaska to Point Hope.

More Information

More information about Aleutian terns, the surveys, and progress, can be found on the U.S. Fish and Wildlife Services’ Aleutian tern survey page and related X and Facebook posts.