Data from: Migratory routing and departure decisions of Porzana carolina (Sora): New insights from the Motus Wildlife Tracking System
Data files
Jan 30, 2026 version files 494.72 MB
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motus-sex-predict.csv
20.77 KB
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README.md
6.65 KB
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sora-departures.csv
924.69 KB
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SORA-tag-detections-raw-rm-dep.rds
493.77 MB
Abstract
During migration, birds make a variety of decisions that may impact their overall survival and fitness. These decisions include, but are not limited to, their overall migration route as well as their departure timing, considering variable weather conditions. Understanding how birds make these decisions can provide insight into not only their general migration strategy but also the constraints they face on migration. Unfortunately, the migratory ecology of many members of the Rallidae family remains poorly documented, leaving a critical gap in the migration literature. From 2017 to 2022, we fitted 202 Soras (Porzana carolina) with transmitters at Jug Bay, a critical stopover site along the Patuxent River, Maryland, USA, and tracked their migratory movements and decisions using the Motus Wildlife Tracking System. Tracking data revealed a tendency to follow the Atlantic coast in the fall. Spring migrants took variable paths, with routes primarily to the Great Lakes region, but also had shorter stopovers. We also determined the atmospheric conditions under which Soras initiated migration. Rising atmospheric pressure 24 hours before departure increased departure likelihood, as did wind profit (favorable tailwinds), while increased cloud cover had reduced departure probability, possibly due to disrupted nighttime navigation. It also emphasizes the importance of continued research with advanced tracking technologies to better understand the dynamics of extended stopovers.
Dataset DOI: 10.5061/dryad.msbcc2g9k
Description of the data and file structure
This dataset investigates the departure routes and decisions of Sora (Porzana carolina) during their fall and spring migrations. Birds were trapped using modified Seth-Lowe Clover Leaf traps along the Patuxent River in Maryland from 2017-2022. Sora were fitted with Lotek nano tags and tracked via the Motus Wildlife Tracking System. We examine the atmospheric conditions that inform the departure decisions of these birds, as well as detail some of the most commonly used migratory pathways.
Files and variables
File: SORA-tag-detections-raw-rm-dep.rds
Description: Raw, uncleaned detection data across the Motus Network of Soras tagged at Patuxent River Park. Further documentation of variables can be found at motus.org.
File: motus-sex-predict.csv
Description: Dataset of Sora captured and fitted with a transmitter at Patuxent between 2017 and 2022. This data includes morphometric and age data completed at the time of banding. NAs may be present in the data if that particular variable was not measured at the time of banding.
Variables
- FID: Row ID
- tagID: Tag Number
- mfgID: Manufacturer's ID.
- tagDeployID: Tag deployment ID.
- speciesID: Species numerical code from Motus Data)
- speciesName: Latin name of the species tagged
- bandNumber: Aluminum Band Number. Band provided by USGS Bird Banding Laboratory.
- markerNumber: Number of any other identifying markers (e.g. tag number).
- sex: Initial sex assignment in the field upon capture
- age: Adult (ad) or Juvenile (juv, imm). Assigned based on plumage characteristics.
- weight: Weight at capture (g)
- wing: Wing Cord Measurement (mm)
- Tar: Tarsus measurement (mm). Variable used to help determine sex
- Cul: Measurement of exposed Culmen (mm). Variable used to help determine sex.
- bill: length of the bill in mm (if measured).
- head: head and bill length in mm (if measured)
- fatScore: Amount of fat bird accumulated (if measured)
- predict.sex: score from 0-1 based on morphometric model detailed in Dami et al. 2024.
- sex2: Sex assignment based on morphometric models.
- agree.field: Does the initial field assignment match the sex assignment based on morphometric model
File: sora-departures.csv
**Description: **
Variables
- motusTagDepID: Unique identifier for each individual bird. Combination of the Motus Tag ID and the Motus Deployment ID.
- migration: Migration in which detection occurs (spring vs. fall)
- season: Season in which the detection occurs. Combination of a migration and a year (i.e. Fall 2018).
- tagDeployStart: Date/Time motus Tag was deployed
- location.lat: Latitude of location (degrees)
- location.long: Longitude of location (degrees)
- start.date: Time monitoring started/ tag deployment time.
- depart.date: Eventual departure date of bird tagged on stopover
- Date: Date of monitoring for departure.
- depart.event: Indicates departure event. Binomial variable (0 or 1). 1 indicates that the departure occurred while 0 means that the bird did not depart.
- depart.time: Departure date and time as timestamp in UTC.
- start: The beginning of the time interval. The first interval starts at 0 for each subject and indicates the day of capture for most individuals.
- end: The end of the time interval.
- depart.day.of.year: Day of year in which eventual departure occurred
- sex2: Sex assigned based on morphometric model from Dami et al. 2024. Binomial outcome. Male (M) or Female (F).
- Age: Age class of birds. Juvenile (Hatch-Year) or Adult (After-Hatch Year)
- u10_component: U component of wind (m/s). This data was acquired via the European Centre for Medium-Range Weather Forecast's ERA5 Single-Level Dataset.
- v10_component: V component of wind (m/s). Data acquired via ERA5 Single-Level Dataset.
- s.pressure: measure of weight of air contained in vertical column above the Earth's surface (Pa)** **Downloaded from ERA5-Single Level.
- cloud.cover: Proportion of sky hidden by visible clouds (0-1). Downloaded from ERA5-Single Level Datasets.
- total.precip: Accumulate liquid and frozen water (mm) that falls onto the earth’s surface in a one-hour period. Downloaded from ERA5-Single Level Datasets.
- wind.speed: Wind speed (m/s) derived from u and v component of wind.
- tailwind: The wind profit (m/s) experienced by birds based on an individual birds target direction. Calculated using the u and v wind components as well as the departure bearing of the bird.
- pressure.diff: Overall net change in s.pressure.
- pressure.trend: Hourly pressure change (Pa/hour) over 24 hours. Defined as pressure.diff divided by 24.
Code/software
RDS files can be read into Program R, a free software for statistical computing (R Core Team 2024; https://www.r-project.org). Motus data can be downloaded directly from R using the motus package (https://motuswts.github.io/motus/articles/02-installing-packages.html). Departure decisions analysis were implemented using the "survival" package in R.
Other packages for analysis and data manipulation include:
DBI # connecting with SQLite databases
RSQLite # for working with SQLite databases
tidyverse # for data manipulation
lubridate # for working with dates
sf # mapping.
rnaturalearth # mapping
ggplot2
tidyverse
suncalc # calculating sunrise and sunset times.
Access information
This study utilizes environmental and movement data sourced from public repositories and collaborative networks. Atmospheric data (ERA5) was obtained from the Copernicus Climate Data Store (CDS) under Creative Commons Attribution 4.0 International (CC-BY 4.0). Movement data was retrieved from Movebank (Study ID: 1457748657) and the Motus Wildlife Tracking System (Project ID: Project 172). Data from Movebank is used in accordance with the license as specified by the data owners. Motus data access was granted under the Motus Data Use Policy and through collaboration with the respective project investigators.
Other publicly accessible locations of the data:
Motus Project #172 (https://motus.org/data/project?id=172)
Movebank ID: 1457748657
Data was derived from the following sources:
ERA-5 Single Levels (https://cds.climate.copernicus.eu)