DOI: 10.5061/dryad.dfn2z3525
title: Presence, precipitation, and temperature data used to estimate eastern forest songbird historical distributions using climatic niche modeling

description: Boundaries between vegetation types, known as ecotones, can be dynamic in
 response to climatic changes. The North American Great Plains includes a
 forest-grassland ecotone in the south-central United States that has
 expanded and contracted in recent decades in response to historical
 periods of drought and pluvial conditions. This dynamic region also marks
 a western distributional limit for many passerine birds that typically
 breed in forests of the eastern United States. To better understand the
 influence that variability can exert on broad-scale biodiversity, we
 explored historical longitudinal shifts in the western extent of breeding
 ranges of eastern forest songbirds in response to the variable climate of
 the southern Great Plains. We used climatic niche modeling to estimate
 current distributional limits of nine species of forest-breeding
 passerines from 30-year average climate conditions from 1980 to 2010.
 During this time the southern Great Plains experienced an unprecedented
 wet period without periodic multi-year droughts that characterized the
 region’s long-term climate from the early 1900s. Species’ climatic niche
 models were then projected onto two historical drought periods: 1952–1958
 and 1966–1972. Threshold models for each of the three time periods
 revealed dramatic breeding range contraction and expansion along the
 forest-grassland ecotone. Precipitation was the most important climate
 variable defining breeding ranges of these nine eastern forest songbirds.
 Range limits extended farther west into southern Great Plains during the
 more recent pluvial conditions of 1980–2010 and contracted during
 historical drought periods. An independent dataset from BBS was used to
 validate 1966–1972 range limit projections. Periods of lower precipitation
 in the forest-grassland ecotone are likely responsible for limiting the
 western extent of eastern forest songbird breeding distributions.
 Projected increases in temperature and drought conditions in the southern
 Great Plains associated with climate change may reverse range expansions
 observed in the past 30 years.
description: 1980-2010 presence data were collected from eBird basic dataset
 and the North American Breeding Bird survey (BBS). BBS presences from the
 first ten stops of BBS routes 1980-2010 were included. eBird presences
 from checklists submitted that were less than 8 km in distance, less than
 one hour in duration, and had fewer than 10 observers from 1980-2010 were
 included. Presence data from eBird and BBS were then spatially rarefied at
 40-km using SDM toolbox in ArcMap. (e.g.,
 merg_acfl_1980_40km_rarefied_points.csv) We also
 include here BBS presence data 1966-1972 from the first ten stops of BBS
 routes. The presence data were filtered to only include unique locations;
 if a species was detected within the first ten stops of a BBS route over
 multiple years, only one record at that location was used to calculate
 omission error and the continuous Boyce index. (e.g.,
 BBS_1966_acfl_OE.txt) Climate data used to train
 climatic niche models for the nine songbird species and project species
 distributions onto historical climate conditions are included here. Data
 include average conditions for the periods 1980-2010, 1966-1972, and
 1952-1958. Variables include summer potential evaporation (e.g.,
 d_es3_1952.asc), spring potential evapotranspiration (e.g.,
 dsp_es3_1952.asc) calculated using the Thornthwaite equation, annual
 precipitation (e.g., p_es3_1952.asc), and average annual temperature
 (e.g., t_es3_1952.asc).