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Dryad

Aerial photos and colony counts of nesting colonial waterbirds in the Columbia River Basin, 2024

Data files

Apr 16, 2025 version files 119.17 KB

Abstract

In many situations, colonial waterbird colony size is best evaluated from aerial photographs taken during the breeding season. This is typically the case where colonies are not accessible or when it is not feasible to count all birds or nests from ground locations or by boat. This dataset presents high resolution aerial imagery and corresponding nest counts of Caspian terns (Hydroprogne caspia), double-crested cormorants (Nannopterum auritum), Brandt’s cormorants (Urile penicillatus), California gulls (Larus californicus), ring-billed gulls (Larus delawarensis), American white pelicans (Pelecanus erythrorhynchos), great blue herons (Ardea herodias), great egrets (Ardea alba) nesting in the Columbia River Basin, during the 2024 breeding season. Photos were taken from a fixed-wing aircraft during peak nesting, and colony size was estimated by digitizing photos and enumerating visible birds using ArcGIS. Colony size was reported as the number of birds on colony, and, in the case of terns and cormorants, the number of active breeding pairs. These data are part of a wider project to evaluate the efficacy of management actions to reduce the impacts of predation by piscivorous colonial waterbirds on Endangered Species Act (ESA)- listed juvenile salmonids (smolts; Oncorhynchus spp.) in the Columbia River Basin.