Low migratory flight altitudes may explain increased collision risk for Scolopax minor (American Woodcock)

Understanding bird migration at low altitudes is critical to evaluating risk of collision with obstacles. Recent advances in satellite tracking technologies allow quantifying use of low altitudes by small migrating birds with a high level of precision, allowing species-level inference into potential collision risk based on flight altitude. The American Woodcock (Scolopax minor) is suspected to be a low altitude migrant due to its frequent collisions with buildings, and subsequent mortality during migration may be contributing to population declines. We investigated migratory flight altitudes using satellite transmitters deployed on woodcock in 2020–2024 and examined how flight altitudes compare to the heights of common airspace obstacles. Each transmitter recorded a nocturnal GPS location with an altitude reading every 1–3 days during fall and spring migrations. We implemented a Bayesian hierarchical mixture model to identify whether locations were recorded on the ground or during fligh..., Data Collection and Preprocessing
We collected woodcock locations with altitude readings from 2020 to 2024 using GPS transmitters as a part of a larger collaborative effort by the Eastern Woodcock Migration Research Cooperative (Blomberg et al. 2023, Clements et al. 2024, Fish et al. 2024). We captured woodcock at 100 sites across the eastern portion of their range, including Alabama, Florida, Georgia, Louisiana, Maine, Maryland, New Jersey, New York, North Carolina, Nova Scotia, Ontario, Pennsylvania, Québec, Rhode Island, South Carolina, Vermont, Virginia, West Virginia, and Wisconsin. We caught woodcock using a combination of spotlighting and mist netting (McAuley et al. 1993). We aged and sexed birds upon capture, where we classified birds undertaking their first fall and spring migrations as juveniles, and all other birds as adults. We then attached 4–7 g PinPoint transmitters (Lotek Wireless Inc., Newmarket, Ontario, CA) using a rump-mounted leg loop harness (Fish et al. 2024).
We..., , # Flight altitudes of American Woodcock

### Description of the data and file structure

We collected GPS locations and GPS-derived altitude data using PinPoint GPS transmitters attached to American Woodcock (*Scolopax minor*) throughout the eastern portion of their range from 2020 to 2024. This dataset includes both ground locations (i.e., locations recorded when the bird was not undergoing migratory flight) and flight locations; the procedure for differentiating between these locations is outlined in the accompanying paper in *Ornithological Applications*.

#### Files and variables

##### File: amwo\_flight\_altitudes.csv

**Description**: This csv file contains GPS locations and altitude data collected from American Woodcock, as well as additional covariates recorded on capture or imported from other sources. The data has 16020 rows of 13 variables.

1. ID: Unique ID for each woodcock.
2. time: Time at which the GPS location/altitude were recorded in Coordinated Universal Time.
3. lo...