DOI: 10.5061/dryad.866t1g229
title: Increased drought drives avian community declines in the warm deserts of the United States

description: The frequencies, intensities, and durations of extreme weather are
 increasing under climate change, furthering biodiversity loss. In the
 Southwestern USA, rising drought frequencies and intensities are
 anticipated to increasingly affect wildlife and their habitat.
 Particularly in highly arid regions, where species live closer to the
 limit of physiological tolerances, increasing drought emerges as a major
 threat to biodiversity. Using North American Breeding Bird Survey data
 (1998–2022) in combination with the Standardized Precipitation-Evaporation
 Index (SPEI), we estimated the effects of short-term (3-month), annual
 (12-month), and prolonged (36-month) drought on avian abundance and
 species richness in the warm deserts of the USA. We assessed
 community-level drought effects using six Bayesian relative abundance and
 species richness models. Our results indicate declines in avian community
 abundance and richness under multiple drought durations, with the
 strongest effects associated with annual droughts. Our models estimated
 that in years where annual drought met the threshold of ‘severe’, 9 out of
 38 species would have 18–34% declines in relative abundance compared to a
 year with long-term average conditions, and species richness would decline
 by 10%. Availability of open water slightly mitigated negative drought
 effects on the avian community. Our results suggest drought will
 increasingly contribute to the collapse of aridland avian communities
 through declines in habitat generalists and obligate aridland species.
 Beyond mitigating future climate change, developing local adaptation
 strategies in arid regions, such as the conservation of water sources,
 appears necessary for biodiversity conservation.
description: # Increased drought drives avian community declines in the warm deserts of
 the United States Dataset DOI:
 [10.5061/dryad.866t1g229](10.5061/dryad.866t1g229) ## Description of the
 data and file structure **Final_Script_BBS.R**: All code required to
 create the models and results visualization, as well as links to the
 open-source data used for the analysis. **birddata_bigger.csv**: CSV file
 with breeding bird survey data used for the analysis. ### Files and
 variables #### File: Final_Script_BBS.R **Description:** All code required
 to create the models and results visualization, as well as links to the
 open-source data used for the analysis. #### File: birddata_bigger.csv
 **Description:** CSV file with breeding bird survey data used for the
 analysis. ##### Variables * Year: Year of survey * English_Common_Name:
 Common name of bird * Sroute: Route number attached to a state number  *
 ObsN: Unique observation number * TotalSpp: Total species observed during
 the particular survey * count: count of the species in question *
 Route_year: Combination of the route number and survey year * Julian_day:
 Julian day at which the survey took place * water: Percentage of open
 water during this year at this location * wetland: Percentage of wetland
 during this year at this location * shrub: Percentage of shrubland during
 this year at this location * barren: Percentage of barren land during this
 year at this location * crop: Percentage of cropland during this year at
 this location * developed: Percentage of developed land during this year
 at this location * spei_03: SPEI-3 values during this year at this
 location * spei_12: SPEI-12 values during this year at this location *
 spei_36: SPEI-36 values during this year at this location ## Code/software
 We used R version 4.4.3 for analysis. All necessary software packages are
 listed within the .R file. ## Access information Data was derived from the
 following publicly available sources: * SPEI-gamma data were downloaded
 from the nClimGrid monthly:
 [https://www.ncei.noaa.gov/pub/data/nidis/indices/nclimgrid-monthly/](https://www.ncei.noaa.gov/pub/data/nidis/indices/nclimgrid-monthly/) * Annual NLCD data were obtained from: [https://www.mrlc.gov/data](https://www.mrlc.gov/data) * North American Breeding Bird Survey data were obtained from: [https://www.sciencebase.gov/catalog/item/52b1dfa8e4b0d9b325230cd9](https://www.sciencebase.gov/catalog/item/52b1dfa8e4b0d9b325230cd9)