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

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.