Gyrfalcon prey abundance and their habitat associations in a changing Arctic

Arctic habitats are changing rapidly and altering trophic webs and ecosystem functioning. Understanding how species’ abundances and distributions differ among Arctic habitats is important in predicting future species shifts and trophic-web consequences. We aimed to determine the habitat-abundance relationships for three small herbivores on the Seward Peninsula of Alaska, USA by fitting data from 983 point counts (collected during 2019, 2021, 2022) with N-mixture models that account for imperfect detection. These herbivore species, Willow Ptarmigan [Lagopus lagopus], Rock Ptarmigan [L. muta], and Arctic ground squirrels [Urocitellus parryii]), are fundamental to tundra food webs, and primary prey for Arctic raptors including Gyrfalcons (Falco rusticolus). Second, we aimed to map herbivore densities within Gyrfalcon breeding territories. Third, we aimed to evaluate whether Gyrfalcons were more likely to occupy territories with higher prey densities using a multi-season occupancy model cou..., The study conducted multi-species point count surveys to detect bird species and Arctic ground squirrels over three years (2019-2022). Surveys began 30 minutes before sunrise and ended when at least ten points were surveyed or by noon. Each point was surveyed once. The surveys followed a time-removal approach, with specific time intervals acting as replicate survey periods. Observations were made for ten minutes, with a two-minute quiet period beforehand. The first detection of each individual within 400 meters was recorded, excluding subsequent detections of the same individual. Data collected included species, time, distance, bearing, group size, and sex. Individuals not actively using the area (e.g., flyovers) were excluded. Observers also measured temperature, wind speed, and direction at each point. Surveys were not conducted in winds over 24 km/h or in heavy rain or fog.
From 2016 to 2022 (excluding 2020 due to Covid-19), the study monitored 97 Gyrfalcon territories on nesting cli..., , # Gyrfalcon prey abundance and their habitat associations in a changing Arctic

[https://doi.org/10.5061/dryad.djh9w0w94](https://doi.org/10.5061/dryad.djh9w0w94)

**Author:** Michaela Gustafson

**Contact:** [[e-mail]](mailto:[e-mail])

**Manuscript DOI:** 10.1002/ECE3.70763

**Study area:** Seward Peninsula, Alaska USA

**Dates:** 2016, 2019-2022

**Species:** Willow Ptarmigan (*Lagopus lagopus*), Rock Ptarmigan (*Lagopus muta*), Arctic Ground Squirrels (*Urocitellus parryii*), Gyrfalcon (*Falco rusticolus*)

**Last updated**: 11 December 2024

## Description of the data and file structure

This study investigates the habitat-abundance relationships of three herbivore species—Willow Ptarmigan, Rock Ptarmigan, and Arctic Ground Squirrels to understand how their distributions may change in response to habitat shifts due to climate change. Data were collected across 983 point count locations during the summers of 2019, 2021, and 2022. These observations were ana...