DOI: 10.5061/dryad.w9ghx3fp2
title: Body temperature and heart rate of free living blackbirds

description: In a seasonal world, organisms are continuously adjusting physiological
 processes relative to local environmental conditions. Due to their limited
 heat and fat storage capacities, small animals, such as songbirds, must
 rapidly modulate their metabolism in response to weather extremes and
 changing seasons to ensure survival. As a consequence of previous
 technical limitations, most of our existing knowledge about how animals
 respond to changing environmental conditions comes from laboratory studies
 or field studies over short temporal scales. Here, we expanded beyond
 previous studies by outfitting 71 free-ranging Eurasian blackbirds (Turdus
 merula) with novel heart rate and body temperature loggers coupled with
 radio transmitters and followed individuals in the wild from fall to
 spring. Across seasons, blackbirds thermoconformed at night, i.e., their
 body temperature decreased with decreasing ambient temperature, but not so
 during daytime. In contrast, during all seasons blackbirds increased their
 heart rate when ambient temperatures became colder. However, the
 temperature setpoint at which heart rate was increased differed between
 seasons and between day and night. In our study, blackbirds showed an
 overall seasonal reduction in mean heart rate of 108 beats/min (21%) as
 well as a 1.2°C decrease in night time body temperature. Episodes of
 hypometabolism during cold periods likely allow the birds to save
 energy and, thus, help offset the increased energetic costs during the
 winter when also confronted with lower resource availability. Our data
 highlight that, similar to larger non-hibernating mammals and birds, small
 Passerine birds such as Eurasian blackbirds not only adjust their heart
 rate and body temperature on daily timescales, but also exhibit pronounced
 seasonal changes in both that are modulated by local environmental
 conditions such as temperature.
description: The data was collected via implanted heart rate and body
 temperature loggers.
description: # Body temperature and heart rate of free living blackbirds
 [https://doi.org/10.5061/dryad.w9ghx3fp2](https://doi.org/10.5061/dryad.w9ghx3fp2) ## Description of the data and file structure ### Files and variables #### File: blackbird.physiology.xlsx ### Description: This dataset includes physiological data of individual blackbirds, specifically focusing on heart rate and body temperature. Additional attributes like sex and tarsus length are also included for each bird. ### File Contents: The dataset contains the following columns: * **timestamp**: Unix timestamp indicating when the data was recorded. * **scaled.tb**: Scaled body temperature of blackbirds in degrees Celsius [°C] * **scaled.fh**: Scaled heart rate of blackbirds in beats per minute [bpm] * **scaled.tarsus**: Scaled tarsus length (a measurement of the bird's leg) in millimetres [mm] * **id**: Unique identifier for each blackbird. * **sex**: Sex of the blackbird (as factor female/male). ### Notes: * Missing values are present in the `scaled.fh` column, which may represent instances where heart rate was not recorded. * All numerical variables are scaled for easier comparison across individuals. ### Usage: This dataset can be used for analyzing the relationship between the physiological variables (heart rate, body temperature) and morphological traits (tarsus length, sex) of blackbirds over time. ## Code/software All statistical analyses were carried out with the R statistical software V.3.3.2. but the data can be viewed in any spreadsheet Microsoft Excel software.