DOI: 10.5281/zenodo.10416702
title: Skin temperature of Welcome Swallows (Hirundo neoxena)

description: Background

 

We aimed to describe natural patterns of body temperature (Tb) regulation during winter by the welcome swallow (Hirundo neoxena), a small species (~14 g) that relies exclusively on flying insect prey. We studied a population inhabiting a semi-rural landscape in a mild temperate climate in south-eastern Australia. We aimed to ascertain the depth of a nightly reduction in Tb and to test the hypothesis that resting Tb is influenced by environmental conditions that could influence daytime foraging success. We used temperature-sensitive radio telemetry to continuously record skin temperature (Ts) of roosting birds, which we assumed was a close proxy for Tb. Surface skin temperature is regularly used to infer Tb in small free-living birds and mammals (McCafferty et al., 2015).

 

Description of the data and file structure

 

"welcome swallow_raw tskin data_long format.csv": This data is raw skin temperature data of welcome swallows, joined with air temperature and relative humidity at the study site, individual identity (transmitter number), body mass of each individual, and transmitter attachment method. We aligned the air temperature and relative humidity data with the timing of the skin temperature data by the nearest time stamp. 

 

"welcome swallow\_ range in daily tskin.csv": This data is the range in daily skin temperature, using the resting normothermic skin temperature minus minimum recorded skin temperature each restphase. Joined with weather variable from the Australian Bureau of Meteorology. Data also includes individual identity (transmitter number), body mass of each individual, and transmitter attachment method. We calculated a value for the normothermic resting Ts of each individual by averaging the minimum Ts recorded each day between the times of 0800 and 1600 h over the days recorded for that individual

 

Additional information

 

We attached transmitters to the skin of birds in two different ways over the course of the study. Initially, transmitters (LB-2XT, 0.33 g; Holohil Systems, Ltd; Carp, Ontario, Canada) were attached over trimmed feathers by trimming a small patch of feathers close to the skin in the mid-dorsal, interscapular region, and gluing the transmitter to the skin on top of the closely trimmed feathers using a latex-based skin adhesive. However, after preliminary assessment of the data, we suspected that the measurements were not closely representative of Ts and hence Tb because recordings were lower and more variable over a short time period than expected. Subsequently, transmitters were glued to an unfeathered area between the feather tracts (apterium), located slightly lateral to the mid-dorsal in the interscapular region. We refer to Ts data measured by transmitters attached directly to the skin as Ts-apterium, and data measured by transmitters attached over trimmed feathers as Ts-pteryla. 

We measured local external air temperature (Ta) during the study at the roost using data loggers (HOBO U10; Onset Computer Corporation, Bourne, Massachusetts, United States). We sourced data on local weather conditions (e.g., wind speed, relative humidity, cloud cover and rainfall) from the Richmond RAAF weather station (#067105) of the Australian Bureau of Meteorology, located approximately 4 km from the field site. At the roost site we deployed autonomous receiver/logger units to continuously record the pulse interval of each transmitter and hence the Ts of birds at ten minute or shorter intervals when they were at the roost site. Often receiver/logger units recorded the pulse interval multiple times when it cycled through each individual so there is at times up to 3 skin temperature measurements within a single minute, thus have the same timestamp.