DOI: 10.5061/dryad.9w0vt4bqh
title: Arrival-breeding interval is flexible in a songbird and is not constrained by migration carry-over effects

description: As spring phenology advances with climate change, so too must the timing
 of life cycle events. Breeding at the right time is critical in many
 species as it maximises fitness. For long-distance migratory birds,
 flexibility in the duration of the arrival-breeding interval (pre-breeding
 period) may allow populations to adjust their timing of breeding. However,
 whether first egg-lay dates are flexible to local environmental conditions
 after arrival, and if they are constrained by the time needed to replenish
 energy lost during migration, remains unclear. We investigated the
 regional flexibility of the arrival-breeding interval in an avian migrant,
 the purple martin Progne subis, across their breeding range. We evaluated
 whether the duration of the arrival-breeding interval was flexible to
 temperature and precipitation at breeding sites, and if timing was limited
 by migration rate and stopover duration. We also tested if longer interval
 durations were associated with higher fledging success. To address our
 hypotheses, we used a combination of migration tracking, weather, and
 breeding data collected from four regions across eastern North America
 (26.1ºN to 52.4ºN latitude). We found the arrival-breeding interval to be
 shortest in the north and longest in the south. Across all regions, warmer
 temperatures encountered at breeding grounds were associated with shorter
 intervals, and faster migration rates led to longer intervals. The length
 of the interval was not influenced by precipitation or stopover duration.
 Lastly, longer intervals were not associated with higher fledge success.
 Currently, the longer arrival-breeding intervals in this study system, on
 average 28.3 days, may provide both early- and late-arriving birds with
 ample time for recovery so birds can lay eggs according to temperature.
 Any negative effects of faster migration may have been buffered by longer
 arrival-breeding intervals, as interval length did not determine fledge
 success. With ongoing climate change, further research is needed to
 examine if arrival-breeding intervals become constrained by migration
 timing, which may limit opportunities for migrants to match the timing of
 breeding with key resources. 
description: The data was collected in 2008, 2010-2017 by a large number of
 collaborators across Eastern North America (from Florida to Alberta).
 Migration data (arrival date, migration rate, stopover duration) were
 collected using light-level geolocators, then the information was
 processed in RStudio using BAStag, GeoLight, and FlightR. Nest data (first
 egg-lay date, number of fledged young) were collected by purple martin
 landlords following the Purple Martin Conservation Association guidelines.
 Historical weather data (temperature, precipitation) was collected using
 the packages weathercan (Canada) and GSODR (United States). For further
 details about the dataset please refer to the paper.
description: # Arrival-breeding interval is flexible in a songbird and is not
 constrained by migration carry-over effects
 [https://doi.org/10.5061/dryad.9w0vt4bqh](https://doi.org/10.5061/dryad.9w0vt4bqh) ## Description of the data and file structure We collected data to determine if the arrival-breeding interval, the pre-breeding period, was flexible to environmental conditions (temperature and precipitation) and constrained by carry-over effects from migration (migration rate and stopover duration) in a long-distance migrant, the purple martin (*Progne subis subis*). ### Files and variables #### File: PUMA\_extra\_arrivaldate\_final\_dataset\_LS.csv **Description:** This dataset contains all the Julian arrival dates of purple martins from the PUMA_final_dataset_LS.csv dataset and extra arrival dates from additional geolocator tags. The Julian arrival dates were used to get the mean Julian arrival date within each year and colony which was used to calculate the centred arrival date in the final dataset, see below. ##### Variables * band_number: Federal (silver) band number to identify each individual. * year_deployed: The year the purple martin was fitted with a light-level geolocator using YYYY/MM/DD format. * year_retrieved: The year the light-level geolocator was removed from the purple martin using YYYY/MM/DD format. * region: The region (Northern, Central, Coastal, or Southern) the bird was in. * colony_id: The specific colony where the bird spent its breeding season. Format: province/state-colony name (when more than 1 colony in the same province/state) or province/state only (when only 1 colony studied in the province/state). * arrival_date_julian: The spring arrival date at the breeding colony where January 1 is day 1. #### File: PUMA\_extra\_firsteggdate\_final\_dataset\_LS.csv **Description:** This dataset contains all the Julian first egg-lay dates of purple martins from the PUMA_final_dataset_LS.csv dataset and extra first egg-lay dates from additional nesting data. The Julian first egg-lay dates were used to get the mean Julian first egg-lay date within each year and colony which was used to calculate the centred first egg-lay date in the final dataset, see below. ##### Variables * region: The region (Northern, Central, Coastal, or Southern) the bird was in. * colony_id: The specific colony where the bird spent its breeding season. Format: province/state-colony name (when more than 1 colony in the same province/state) or province/state only (when only 1 colony studied in the province/state). * year: The year the purple martin laid eggs. * first_egg_date: The day the first egg was laid in the nest in YYYY/MM/DD format. * first_egg_date_julian: The day the first egg was laid in Julian days where January 1 is day 1. #### File: PUMA\_final\_dataset\_LS.csv **Description:** The main dataset contains all variables for 131 purple martins used in analyses. Missing values indicated by NA are found in columns: migration_distance, migration_rate_day, stopover_number, stopover_length, number_fledged, stopover_duration, sd_arrival, migration_rate_hour, and sd_first_egg_date. ##### Variables * band_number: Federal (silver) band number to identify each individual. * year_deployed: The year the purple martin was fitted with a light-level geolocator using YYYY/MM/DD format. * year_retrieved: The year the light-level geolocator was removed from the purple martin using YYYY/MM/DD format. * colony_id: The specific colony where the bird spent its breeding season. Format: province/state-colony name (when more than 1 colony in the same province/state) or province/state only (when only 1 colony studied in the province/state). * state_province: Province or state where the colony is located. AB = Alberta, MB = Manitoba, MN = Minnesota, SD = South Dakota, PA = Pennsylvania, VA = Virginia NJ = New Jersey, and FL = Florida, * region: The region (Northern, Central, Coastal, or Southern) the bird was in. * latitude: The latitude where the colony was located using decimal degrees (e.g. 52.39, -113.61) format. * longitude: The longitude where the colony was located using decimal degrees (e.g. 52.39, -113.61) format.. * sex: Sex of purple martin. M = male and F = female. * age: Age of purple martin. TY = third year bird in its second breeding season, ATY = after third year bird in its third or greater breeding season. * spring_arrival_date: The day of arrival at the breeding colony following spring migration using YYYY/MM/DD format. * migration_duration: The total number of days the bird spent on spring migration (unit = days). * migration_distance: The total distance the bird flew during spring migration (unit = km) . * migration_rate_day: The spring migration rate (unit = km/day). * stopover_number: The number of stopovers during spring migration. A stopover was when a bird was stopped consecutively for more than 1.5 days. * stopover_length: The sum of all stopovers during spring migration (unit = days). * first_egg_date: The day the first egg was laid in the nest in YYYY/MM/DD format * clutch_size: The total number of eggs laid in the nest. * number_fledged: The number of successful fledglings from the nest. Juveniles that were at least 26 days old were counted as successfully fledged. * first_egg_date_julian: The day the first egg was laid in Julian days where January 1 is day 1. * arrival_date_julian: The spring arrival date at the breeding colony where January 1 is day 1. * AB_interval: The arrival-breeding interval including the day of arrival at breeding grounds to the day of first egg-lay (unit = day). * stopover_duration: The proportion of spring migration time spent on stopovers, calculated by dividing the stopover_length by migration_duration. * mean_temp: Mean of the average daily temperature during the arrival-breeding interval (unit = °C). * total_precip: Mean of total daily precipitation during the arrival-breeding interval (unit = mm). * mean_arrival: Mean Julian arrival date specific to colony and year, it was used to calculate centred_arrival * n_arrival: Sample size of individuals used to calculate mean_arrival. * sd_arrival: Standard deviation of mean_arrival. * centred_arrival: The centred arrival of each individual, centred within year and colony. Birds arriving earlier than average had negative values whereas birds arriving later on average had positive values (unit = days). * migration_rate_hour: The spring migration rate (unit = km/hour). * mean_first_egg_date: Mean Julian first egg-lay date specific to colony and year, it was used to calculate centred_egglay. * n_first_egg_date: Sample size of individuals used to calculate mean_first_egg_date. * sd_first_egg_date: Standard deviation of mean_first_egg_date. * centred_egglay: The centred egg-lay of each individual, centred within year and colony. Birds laying earlier than average had negative values whereas birds laying later on average had positive values (unit = days). * min_temp_AB_interval: Mean of the minimum daily temperature during the arrival-breeding interval (unit = °C). * max_temp_AB_interval: Mean of the maximum daily temperature during the arrival-breeding interval (unit = °C). ## Code/software To view data Excel or RStudio software, any version, can be used to view the datasets. Statistical analyses were performed using the package 'glmmTMB' (version 1.1.3) in R (version 4.1.3) using RStudio (version 2021.09.2, R Core Team 2022). ## Access information Other publicly accessible locations of the data: * Migration data is available on Movebank, Movebank ID number 1765768285.