Moonlight drives nocturnal vertical flight dynamics in black swifts
Description
Activity_and_barometric data.txt: Data file in plain text containing time stamped accelerometer, pressure and temperature data for different individuals of black swifts. The first column indicates individual and the second column is date and time. Act0 means number of sequences that scored 0 during the preceding hour (12 measurements per sequence), and the next five columns, Act1-Act5 follow the same pattern, where Act 5 is the number of sequences that scored 5. The column “SUM” is the sum of all activity counts and should be 12 if sampling worked as intended. The column “Pressure” is barometric pressure in hPa and the column “Temp” is temperature in Celsius. X0nn_light data.txt: Seven files in plain text containing light data for seven different individuals of black swift used to determine their geographical positions (geolocation) in the manuscript. The first column is date, the second column is time and the third column is light level in lux.
Files
Steps to reproduce
The activity and barometric data are derived from multisenosr data loggers deployed on Northern black swifts (Cypseloides niger). Light data files are light data (1..254) used for geolocation of the birds. Detailed analysis procedures are given in the published paper. The light-level data obtained from our data logger mainly serve as a control function to provide approximate locations of the swifts at key time periods of the year. When light measurements were activated, the device measured light intensity every minute and stored the maximum value recorded every 5-minutes. Transitions between night and day were distinguished by using a threshold level of 2 (on scale 1-256) in the software IntiProc v 1.03 (Migrate Technology Ltd.). A sun angle of -6 was selected for all loggers by matching the derived positions with the known positions at the breeding site and approximate locations during the winter. Acceleration in the Z-axis was sampled every 5 minutes with runs of 10 measurements at 5 time points, each separated by 5s. Each measurement is a sample during 100 ms at 100 Hz in the range ±4g. For each run, the mean of the values was subtracted from each of the 10 measurements to compensate for static gravity, and the recorded acceleration was considered as indicative of flight if at least 3 of the 10 values were greater than |g/3|, where g is acceleration due to gravity. Each 5-minute sample was assigned the number of runs that indicate flight behavior, i.e. (0, .., 5). Every hour a summary of results from all 12 runs were stored according to the distribution of the samples across the different activity categories (0,.., 5). If the bird is perched and motionless the data stored will be (12, 0, 0, 0, 0, 0), and if it is flying with continuous wing beats the data are (0, 0, 0, 0, 0, 12). To illustrate flight activity in graphical actograms the hourly recordings are coded as ‘white’ to represent continuous flapping flight (0, 0, 0, 0, 0, 12), and ‘black’ to represent no flight (12, 0, 0, 0, 0, 0), with shades of grey representing intermediate activity levels. Please note that a bird in continuous gliding flight could in principle generate a signature indistinguishable from a bird resting on the ground, but when such periods are short and surrounded with activity recordings they most likely refer to gliding/soaring flight with no or few wing beats. The device had the auxiliary function of measuring ambient air pressure once per hour. In addition to measuring altitude the pressure data were useful to corroborate flight behavior as recorded by accelerometry. The device also recorded temperature and because the sensor was positioned on the side of the logger facing the bird body, the recorded values represent the combined effect of the ambient temperature and that of the bird’s body. Hence, the temperature values cannot be used as measure of ambient air temperature, but rather used as a control function of changed flight altitude.