DOI: 10.5061/dryad.9zw3r22m1
title: Spatial variation in avian bill size is associated with temperature extremes in a major radiation of Australian passerines

description: Morphology is integral to body temperature regulation. Recent advances in
 understanding of thermal physiology suggest a role of the avian bill in
 thermoregulation. To explore the adaptive significance of bill size for
 thermoregulation we characterized relationships between bill size and
 climate extremes. Most previous studies have focussed on climate means,
 ignoring extremes, and do not reflect thermoregulatory costs experienced
 over shorter time scales. Using 79 species (9,847 museum specimens), we
 explore how bill size variation is associated with temperature extremes in
 a large and diverse radiation of Australasian birds, Meliphagides.
 Overall, across the continent, bill size variation was associated with
 both climate extremes and means and was most strongly associated with
 winter temperatures; associations at the level of climate zones differed
 from continent-wide associations, were complex and non-linear, yet
 consistent with physiology and a thermoregulatory role for avian bills. We
 provide strong evidence that climate extremes have contributed to the
 evolution of bill morphology in relation to thermoregulation and
 demonstrate the importance of including extremes to understand fine-scale
 trait variation across space. Increasing frequency and intensity of
 climate extremes, a signature of climate change, may lead to changes in
 bill size, but this is yet to be tested.
description: We used 79 species from the infraorder Meliphagides, the largest
 radiation of Australian passerines (formerly Meliphagoidea), to assess
 bill size patterns across geographic space and to test for associations
 between bill size and climate across the Australian continent.
description: # Spatial variation in avian bill size is associated with temperature
 extremes in a major radiation of Australian passerines Kalya Subasinghe,
 Matthew R.E. Symonds, Suzanne M. Prober, Timothée Bonnet, Kristen J.
 Williams, Chris Ware, Janet L. Gardner The data file contains variables in
 the analysis. | Variable | Description | | :------------------- |
 :------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | | SpeciesName | Species to which the individual belongs. | | SpeciesNameTree | Species names used in phylogenetic trees downloaded. | | YearCapture | Year in which the individual was captured. This variable is used as a continuous fixed effect and categorical random effect in the model.  | | Latitude | Latitude of the capture location (continuous; fixed effect). | | IBRA\_REG\_CODE\_7 | The IBRA region (the classification of Australian ecoregions) to which the capture location belongs (categorical; random effect). | | Elevation | Elevation at capture location in meters (continuous; fixed effect). | | DistanceToCoast | Minimum distance to the coast from the capture location in meters (continuous; fixed effect). | | Sex | Sex of the individual (categorical; fixed effect). | | Season | Season (spring/summer/autumn/winter) in which the individual has been captured (categorical; fixed effect). | | Season\_tropic | Season (wet season/dry season) in which the individual has been captured (categorical; fixed effect). This applies only to individuals captured from the tropical zone. | | Guild | Feeding guild of species (categorical; fixed effect). | | WL\_Mean | Mean wing length (flattened wing chord) of the individual in millimeters (continuous; fixed effect). | | Bill\_SA | Mean bill surface area of the individual in mm2 (continuous; fixed effect). | | MeanTXsummer0\_5 | Mean maximum summer temperature in degrees Celsius; estimated by averaging the monthly mean maximum temperatures of five summers preceding the capture date (continuous; fixed effect). | | MeanPrecsummer0\_5 | Mean total rainfall of summer in millimeters; estimated by averaging the monthly total rainfalls of five summers preceding the capture date (continuous; fixed effect). | | MeanVapoursummer0\_5 | Mean vapour pressure of summer in hPa; estimated by averaging the monthly mean vapour pressures of five summers preceding the capture date (continuous; fixed effect). | | MeanTNwinter0\_5 | Mean minimum winter temperature in degrees Celsius; estimated by averaging the monthly mean minimum temperatures of the five winter seasons preceding the capture date (continuous; fixed effect). | | MeanPrecwinter0\_5 | Mean total rainfall of the winter season in millimeters; estimated by averaging the monthly total rainfalls of five winter seasons preceding the capture date (continuous; fixed effect). | | Sumgte35summer0\_5 | Days ≥35°C in summer; estimated by averaging the total number of days with maxima ³35°C of five summers preceding the capture date (continuous; fixed effect). | | Sumgte40summer0\_5 | Days ≥40°C in summer; estimated by averaging the total number of days with maxima ³40°C of five summers preceding the capture date (continuous; fixed effect). | | Sumlt5winter0\_5 | Days &lt;5°C in winter; estimated by averaging the total number of days with minima &lt;5°C of five winters preceding the capture date (continuous; fixed effect). | | Sumlt0winter0\_5 | Days &lt;0°C in winter; estimated by averaging the total number of days with minima &lt;0°C of five winters preceding the capture date (continuous; fixed effect). | | MeanTXwet0\_5 | Mean maximum wet season temperature in degrees Celsius; estimated by averaging the monthly mean maximum temperatures of five wet seasons preceding the capture date (continuous; fixed effect). This has been estimated only for the locations of individuals captured from the tropical zone. NA has been assigned to other cells in the column.  | | MeanPrecwet0\_5 | Mean total rainfall of wet season in millimeters; estimated by averaging monthly total rainfalls of five wet seasons preceding the capture date (continuous; fixed effect). This has been estimated only for the locations of individuals captured from the tropical zone. NA has been assigned to other cells in the column.   | | MeanVapourwet0\_5 | Mean vapour pressure of wet season in hPa; estimated by averaging monthly mean vapour pressures of five wet seasons preceding the capture date (continuous; fixed effect). This has been estimated only for the locations of individuals captured from the tropical zone. NA has been assigned to other cells in the column.  | | MeanTNdry0\_5 | Mean minimum dry season temperature in degrees Celsius; estimated by averaging the monthly mean minimum temperatures of five dry seasons preceding the capture date (continuous; fixed effect). This has been estimated only for the locations of individuals captured from the tropical zone. NA has been assigned to other cells in the column.  | | MeanPrecdry0\_5 | Mean total rainfall of the dry season in millimeters; estimated by averaging the monthly total rainfalls of five dry seasons preceding the capture date (continuous; fixed effect). This has been estimated only for the locations of individuals captured from the tropical zone. NA has been assigned to other cells in the column.  | | Sumgte35wet0\_5 | Days ≥35°C in wet season; estimated by averaging the total number of days with maxima ³35°C of five wet seasons preceding the capture date (continuous; fixed effect). This has been estimated only for the locations of individuals captured from the tropical zone. NA has been assigned to other cells in the column.  | | Sumgte40wet0\_5 | Days ≥40°C in wet season; estimated by averaging the total number of days with maxima ³40°C of five wet seasons preceding the capture date (continuous; fixed effect). This has been estimated only for the locations of individuals captured from the tropical zone. NA has been assigned to other cells in the column.  | | ClimZon\_WC05 | Climate zone which described the capture location according to Koppen-Geiger climate classification. This was used to categorize individuals into different climate zones based on their capture location. |