Data and code from: Long-term drought exposure shapes declines and range shifts in aridland birds
Data files
Jul 10, 2026 version files 9.55 MB
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aridlands.shp.zip
553.67 KB
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Birddata_full.csv
8.51 MB
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Finalscript.R
31.66 KB
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README.md
3.07 KB
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spei12_historical_mean.tif
235.31 KB
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spei12_recent_mean.tif
214.11 KB
Abstract
Climate change increases drought frequencies and intensities, posing risks to biodiversity. Species inhabiting arid regions may be vulnerable to drought because they live near their physiological limits, while species with low historical drought exposure may lack adaptations to cope with unprecedented drought. Using a breeding bird dataset and the Standardized Precipitation-Evaporation Index, we assessed drought vulnerability of 37 bird species across deserts of the western United States. We tested drought effects on community and species-level relative abundance, how species' long-term drought exposure influences these effects, and for drought-induced range shifts. Drought was associated with abundance declines and distributional shifts for over 40% of species, with shift directions reflecting regional drought patterns. Species with lower historical drought exposure declined more strongly, though several highly exposed species were among the most vulnerable. These findings demonstrate that climatic history modulates species’ responses to increasing aridity. Under intensifying drought, incorporating regional drought dynamics and climatic legacies into climate change vulnerability assessments is essential for anticipating conservation issues.
Description of the data and file structure
This repository contains all data and code used to analyze the effects of long-term drought on aridland birds in North America. The files are organized as follows:
- Finalscript.R – R script containing all code to create models and visualizations of results.
- Birddata_full.csv – CSV file with breeding bird survey data used in the analysis.
- aridlands.shp.zip – Zipped shapefile (and associated files) of the study area.
- spei12_historical_mean.tif – Raster (EPSG:4269) of average SPEI-12 values for the first half of the study period, used in result visualizations.
- spei12_recent_mean.tif – Raster (EPSG:4269) of average SPEI-12 values for the second half of the study period, used in result visualizations.
Files and Variables File: birddata_full.csv
Contains breeding bird survey data used for the analysis.
Variables and Description
- RouteDataID Unique ID of the survey conducted
- State State number and Route number, separated by underscore
- AOU Taxon ID as coded by NABBS
- RPID: route protocol ID
- Year Year of the survey
- Count Total count of birds of that species during that survey
- Species Common English name of the species
- Latitude Latitude of the starting point of the survey
- Longitude Longitude of the starting point of the survey
- Month Numerical month during which the survey took place
- Day Numerical day of the survey
- obsN Number of the observer during the survey
- Route_year Combination of State and Year, separated by underscore
- Julian_day Julian day during which the survey took place
- elev Average elevation of the survey location
- spei12 SPEI-12 (annual drought) value of the survey location
Code / Software
Analysis was performed using R version 4.5.0.
All required packages and dependencies are listed within Finalscript. R.
Data Sources / Access Information
The dataset was derived from publicly available sources:
SPEI-gamma data: Monthly nClimGrid indices https ://www.ncei.noaa.gov/pub/data/nidis/indices/nclimgrid-monthly/
Elevation data: USGS GTOPO30 1-km Digital Elevation Model
https://www.usgs.gov/centers/eros/science/usgs-eros-archive-digital-elevation-global-30-arc-second-elevation-gtopo30
North American Breeding Bird Survey data:
https://www.sciencebase.gov/catalog/item/52b1dfa8e4b0d9b325230cd9
Notes
Raster files are in the EPSG:4269 geographic coordinate system.
Missing values in bird counts or raster data are coded as NA.
Note that the coordinates indicate starting points of the breeding bird surveys and not the exact locations where individual birds were observed. See the methodology of the North American Breeding Bird Survey for details.
