DOI: 10.5061/dryad.7wm37pw06
title: Birds are better at regulating heat loss through their legs than their bills: Implications for body shape evolution in response to climate

description: Endotherms use their appendages – such as legs, tails, ears and bills –
 for thermoregulation by controlling blood flow to near-surface blood
 vessels, conserving heat when it is cold, and dissipating heat in hot
 conditions. Larger appendages allow greater heat dissipation, and
 appendage sizes vary latitudinally according to Allen’s Rule. However,
 little is known about the relative importance of different appendages for
 thermoregulation. We investigate physiological control of heat loss via
 bird bills and legs using infra-red thermography of wild birds. Our
 results demonstrate that birds are less able to regulate heat loss via
 their bills than their legs. In cold conditions, birds lower their leg
 surface temperature to below that of their plumage surface, retaining heat
 at their core. In warm conditions, birds increase their leg surface
 temperature to above that of their plumage surface, expelling heat. In
 contrast, bill surface temperature remains ~2˚C warmer than the plumage
 surface, indicating consistent heat loss under almost all conditions.
 Poorer physiological control of heat loss via bird bills likely entails
 stronger selection for shorter bills in cold climates. This could explain
 why bird bills show stronger latitudinal size clines than bird legs, with
 implications for predicting shape-shifting responses to climate change.
description: Dataset includes surface temperature estimates of bird bills,
 legs, eyes regions and plumage taken from infra-red thermographs of wild
 birds, as well as microclimate data collected in the field. Please see our
 paper for full details.  
description: # Birds are better at regulating heat loss through their legs than their
 bills: implications for body shape evolution in response to climate
 [https://doi.org/10.5061/dryad.7wm37pw06](https://doi.org/10.5061/dryad.7wm37pw06) The dataset includes surface temperature estimates of different surfaces of wild birds taken from infrared thermographs of wild birds in the field, as well as microclimate information collected at the same time and at a similar location. Microclimate measurements were taken using a portable weather station and solar power meter. ## Description of the data and file structure The file includes the data described in the table below. Cells containing 'NA' are present were data are not available (for example where the tarsus surface temperature was not captured on the thermograph). For further details on how the data was collected, please see the published paper. | **Column Name** | **Description** | | ----------- | ----------- | | Date | Sample date | | Observer | Initials of person who took the thermograph | | HourofDay | Sample time | | Location.Name | Name of broad area thermograph was taken | | Species | Species common name | | ScientificName | Genus and species name | | Family | Taxonomic family | | Sex | M = male; F = female; Unk = unknown (determined by plumage or bare part characteristics in the field) | | Age | Adult or Juvenile (determined by plumage or bare part characteristics, as well as behaviours such as begging/being fed by adult birds; birds without obvious juvenile characteristics were presumed to be adults) | | Mass | Body mass for the species, extracted from Avonet data set; used to predict critical body diameter dimensions for heat transfer calculations | | Water.Nearby | Whether there was a water source close to the thermographed bird | | Wet | Does bird appear wet in the thermograph? (cold patches or splashes) | | Distance.Est | Estimated distance (in m) between thermographer and bird | | Air.Temp | Air temperature in degrees C | | Apparent.Temp | Calculated based on the Australian Bureau of Meteorology formula | | GroundMean | Mean ground temperature taken from thermograph region of interest drawn on ground near the bird | | Wind | Wind speed (m/s) | | SE | Solar radiation (W/m2) | | WVP | Saturation water vapour pressure (kPa) | | Humidity | Relative humidity (%) | | Session.Group | Sample session (ID assigned to thermographs taken under similar conditions at a similar time, on the same day) | | FileName | Thermograph ID | | Surface.ID | Surface ID | | Surface.Temp | Surface temperature of body region (surface ID) taken from thermograph | ## Sharing/Access information ## Code/Software