DOI: 10.5061/dryad.h9w0vt4vm
title: Extreme drought increased home range sizes and space use of Aquila chrysaetos (Golden Eagles) in coastal southern California

description: Aquila chrysaetos (Golden Eagles) are long-lived top predators, vulnerable
 to a variety of threats. There is increasing concern about the declining
 population in coastal southern California, which has largely coincided
 with habitat loss due to urbanization of the region. This
 Mediterranean-type ecosystem is also experiencing more prolonged and
 intense droughts, which can reduce the abundance of key prey species, such
 as jackrabbits (Lepus californicus) and ground squirrels (Otospermophilus
 beecheyi). However, the impact of drought on Golden Eagles is poorly
 understood. Here, we used high-resolution GPS tracking data to calculate
 eagle home ranges and hypothesized that home range size would be
 influenced by drought such that home ranges would be larger to meet their
 resource needs with worsening drought severity. Fifty individuals were
 captured over seven breeding seasons, spanning the time both during and
 after a historic drought. We also compared space use for different stages
 of the breeding season throughout each year. Golden Eagle home ranges
 increased by 77% during extreme drought compared to wetter conditions.
 Drought-breaking rainfall corresponded with much smaller home ranges
 compared to home range sizes during drought years. As drought is projected
 to be more prolonged and frequent in this region with climate change, this
 may result in increasingly large home range sizes at the same time as
 eagles are facing ongoing habitat loss and fragmentation from various land
 use changes. Our results suggest that the frequent and severe drought that
 is projected for this region could lead to lowered nesting density and
 increase the risk of further population decline. 
description: # Extreme drought increased home range sizes and space use of Aquila
 chrysaetos (Golden Eagles) in coastal southern California Dataset DOI:
 [10.5061/dryad.h9w0vt4vm](10.5061/dryad.h9w0vt4vm) ## Description of the
 data and file structure Seasonal home range sizes of Golden Eagles in
 southern California 2014-2022 ### Files and variables #### File:
 thomsen\_etal\_06242025\_GOEAdrought\_homerangesizes.csv **Description:** 
 ##### Variables * eagleID: individual eagle ID * sex: sex of eagle * age:
 age category ("adult" or "subadult") * season:
 "winter" (Nov-Jan) "spring" (Feb-Apr)
 "summer" (May-Jul) "fall" (Aug-Oct) * nestyear:
 breeding season year that begins the previous winter in Nov and ends in
 Oct; calendar year during spring season is used to label the nestyear *
 ldistmove: category for individuals that remained in the local study area
 ("local") versus those that moved beyond outside of the local
 study area ("ldist") during that season * floater: category for
 adults with territories "territory" or floaters
 "floater" * PDSI: Palmer Drought Severity Index (PDSI) in
 February for the South Coast climate division in California for the month
 of February during the nestyear * locoh95: home range area as determined
 by the adaptive local convex hull method (*a*-LoCoH) * locoh50: 50% core
 area as determined by the adaptive local convex hull method (*a*-LoCoH) *
 mcp95.sqkm: home range area as determined by the 95% minimum convex
 polygon (MCP) * mcp50.sqkm: core area as determined by the 50% minimum
 convex polygon (MCP) * akde.sqkm: home range area as determined by
 autocorrelated kernel density estimates (AKDE) * akde50.sqkm: 50% core
 area as determined by autocorrelated kernel density estimates (AKDE) *
 locations: total number of GPS locations per season used in the
 calculation of home range sizes