Timing of activity can reveal an organism’s efforts to optimize foraging either by minimizing energy loss through passive movement or by maximizing energetic gain through foraging. Here, we assess whether signals of either of these strategies are detectable in the timing of activity of daily, local movements by birds. We compare the similarities of timing of movement activity among species using six temporal variables: start of activity relative to sunrise, end of activity relative to sunset, relative speed at midday, number of movement bouts, bout duration, and proportion of active daytime hours. We test for the influence of flight mode and foraging habitat on the timing of movement activity across avian guilds. We used 64570 days of GPS movement data collected between 2002 and 2019 for local (non-migratory) movements of 991 birds from 49 species, representing 14 orders. Dissimilarity among daily activity patterns was best explained by flight mode. Terrestrial soaring birds began activity later and stopped activity earlier than pelagic soaring or flapping birds. Broad-scale foraging habitat explained less of the clustering patterns because of divergent timing of active periods of pelagic surface and diving foragers. Among pelagic birds, surface foragers were active throughout the day while diving foragers matched their active hours more closely to daylight hours. Pelagic surface foragers also had the greatest daily foraging distances, which was consistent with their daytime activity patterns. This study demonstrates that flight mode and foraging habitat influence temporal patterns of daily movement activity of birds.

Data were compiled from previously collected GPS movement datasets. We include days with 8+ h of data, and exclude migrations > 500 km long. For colonial nesting pelagic birds, we compare only days with known foraging trips.

Dataset here includes the six temporal variables used in our study, measured at the hourly and daily scale.

Mallon et al. 2020. Diurnal timing of nonmigratory movement by birds: the importance of foraging spatial scales. Journal of Avian Biology

The dryad repository contents include the following data:
1. Final dataset used in analysis: mallon2020_trait_data.csv
2. Original hourly data measures of several temporal variables: mallon2020_hr_data.csv
3. Original daily data measures of several temporal variables: mallon2020_day_data.csv
4. Final morphological data used in analysis: mallon2020_morpho_data.csv

Data columns of note:
active.hr = if individual is active or inactive, based on threshold defined in Mallon et al. 2020
mspeed = mean speed during active hours
n.hrs = number of location hours per day
dsunrise.min = first activity, relative to sunrise
dsunset.max = last activity, relative to sunset
midday.speed = hourly speed nearest to solar noon
prop.diel = proportion of active hours between sunrise and sunset
n.periods.activity = number of movement bouts
activity.dur = mean duration of movement bouts
r2n = maximum net squared displacement from the beginning of the day (m)
mean.r2n = mean net squared displacement from the beginning of the day (m)
median.r2n = median net squared displacement from the beginning of the day (m)

The dryad repository contents include the following scripts, for use with R 4.0.2:
1. Code necessary to create mallon2020_trait_data.csv from mallon2020_hr_data.csv and mallon2020_day_data.csv: mallon2020_trait_database.R
2. Code necessary to recreate analyses: mallon2020_results.R
2. Custom functions necessary for mallon2020_results.R: mallon2020_functions.R

Diurnal timing of nonmigratory movement by birds: the importance of foraging spatial scales

Data files

Abstract

Methods

Usage notes