2024 Pacific flyway region Caspian tern (Hydroprogne caspia) colony surveys – aerial photos and colony count data

The 2024 Caspian tern (Hydroprogne caspia) minimum breeding population in the Pacific Flyway region was estimated by census of known active and historical colony sites. We collected survey data for 155 colony sites (c.a., 98%, 88%, and 93% of known active, historical, and potential colony sites, respectively), including 37 colonies that were confirmed to be active in 2024. This is the fourth population survey conducted under a monitoring strategy developed by the U.S. Fish and Wildlife Service in 2015 and undertaken every third year. As part of this effort, Oregon State University flew aerial surveys from fixed-wing aircraft to locate and photograph Caspian tern colonies in Washington, Oregon, California, Alaska, Nevada, and Utah. Oblique aerial photos were analyzed to estimate the number of nests at active colonies. Here we provide aerial photographs and count summaries for active colonies surveyed by Oregon State University in 2024. Additional colonies in the Columbia River Basin are ..., In 2024, we attempted to collect colony size estimates from all known active, historical, and potential colony locations in the Pacific Flyway region, and for any new colony sites identified during our census effort. Surveys of all colony sites were targeted to capture the peak colony attendance, based on regional and site-specific nesting chronologies from previous years. Numbers of attended nests were quantified using different methods depending on colony location, accessibility, collaborator availability, and independent ongoing research or monitoring efforts. These methods included fixed-wing aerial surveys, UAV surveys, boat surveys, and ground visits. Aerial photography of active colonies was obtained whenever possible, which allowed researchers to efficiently observe colonies across large geographic regions during a short window during peak nesting. Aerial surveys provided high resolution oblique photography (Canon DSLR and mirrorless cameras with 100-600 mm equivalent zoom lense..., , # 2024 Pacific flyway region Caspian tern (Hydroprogne caspia) colony surveys – aerial photos and colony count data

[https://doi.org/10.5061/dryad.kprr4xhgh](https://doi.org/10.5061/dryad.kprr4xhgh)

## Description of the data and file structure

This README file describes the data package for 2024 Pacific Flyway Region Caspian tern (Hydroprogne caspia) colony surveys – Aerial photos and colony count data

Description:

This dataset consists of high-resolution aerial images and corresponding nest counts of Caspian Terns (*Hydroprogne caspia*) colonies surveyed during the 2024 Pacific flyway population census.  Methods used to collect colony images included fixed-wing aerial surveys, UAV surveys, boat surveys, and ground visits.

### Files and variables

#### File: 2024\_CATE\_Aerial\_Survey\_Counts\_Archive.xlsx

Files:

Data folder -Contains an Excel spreadsheet (2024_CATE_Aerial_Survey_Counts_Archive.xlsx) The spread sheet contains colony names, location, including latitude and longi...,