Aerial photos and colony counts of nesting colonial waterbirds in the Columbia River Basin, 2023

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), and American white pelicans (Pelecanus erythrorhynchos) nesting in the Columbia River Basin, during the 2023 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 and DotDotGoose. Colony size was reported as the number of birds on colony, and, in the case of terns and cormorants, the number of active breedin..., Three fixed-winged aerial surveys were conducted in 2023, on the 13th–15th May, 3rd–5th June, and 15th–16th June, to help identify all active nesting colonies of piscivorous waterbirds in the region. To estimate the size of waterbird colonies, aerial photos were taken at oblique angles using a Canon EOS 7D digital SLR camera with one of two image stabilizing lenses, Canon EF 70 - 200mm or Canon EF 100 - 400mm. The lens and camera settings used is included within the image metadata. Photos were taken through the open window of the plane during low altitude flyovers, ~800 – 1,200 feet above the colonies. Aerial images were reviewed and select images were imported to ArcGIS (ESRI 2020. ArcGIS Desktop: Release 10.8.1. Redlands, CA) or DotDotGoose (Ersts, P.J. Version 1.7.0. American Museum of Natural History, Center for Biodiversity and Conservation) to be used for manual colony photo counts. Using ArcGIS, point shape files were created for each image or series of images depending on colony..., , # Aerial photos and colony counts of nesting colonial waterbirds in the Columbia River Basin, 2023

Evans, A.F., K. Collis, N. Banet, Q. Payton, R. Kobernuss, N. Windels, A. Peck-Richardson, W. Kennerley, A.R. Piggott, R.A. Orben. 2023. Avian predation in the Columbia River Basin: 2023 Final Annual Report: Submitted to the Bonneville Power Administration, Portland, Oregon and the Grant County Public Utility District/Priest Rapids Coordinating Committee, Ephrata, Washington.

This README file describes the data package for the nesting distribution and colony size of colonial waterbirds in the Columbia River Basin, 2023, which accompanies the above technical report.

Description:

This dataset consists of high resolution aerial images and corresponding individual species or nest counts of colonial waterbirds breeding in the Columbia River Basin in 2023. Date were collected during three aerial surveys conducted on the 13th–15th May, 3rd–5th June, and 15th–16th June, 2023. These three surve...