Wetter and more forested nonbreeding areas result in later departures but a faster spring migration in Vermivora chrysoptera (Golden-winged Warblers)

Declines in migratory landbird populations require targeted research to identify population-limiting factors acting throughout the annual cycle. Tracking studies provide data on migration timing and speed, which have been used to describe carryover effects of nonbreeding habitat use. To explore how variation in precipitation and forest cover among nonbreeding sites influenced departure dates and migration speed in Vermivora chrysoptera (Golden-winged Warbler), we fitted 69 birds with radio transmitters in Costa Rica and tracked them via the Motus Wildlife Tracking System. Capture sites covered a broad gradient of precipitation and forest cover and were separated by <100 km. The datasets contained herein include departure dates and migration durations for birds tracked via Motus and related data for each individual, including capture location, age, sex, and Motus tag ID. For each capture location in Costa Rica, we extracted precipitation values from Worldclim and estimated forest cove..., Study regions and sites
Five study regions were selected in central Costa Rica that were representative of the gradient of precipitation and forest cover within the nonbreeding range of V. chrysoptera. Within each of the five study regions, one to three discrete study sites were selected for capturing V. chrysoptera.
Captures and deployment of radio transmitters
V. chrysoptera were captured at each of the study sites between February 26 and March 31 in 2022 and February 24 and March 26 in 2023. Birds were captured using 9 or 12 m long mist nets (30 mm mesh) in combination with conspecific playback of V. chrysoptera song and chip calls to lure birds toward nets at ground-level or elevated 1-2 m using net pole extensions. On capture, birds were fitted with a numbered aluminum band (Porzana Ltd, reporting address www.aselva.co) and a unique color band combination for future resightings. Birds were aged and sexed following the criteria in Pyle (1997). For radio tracking, birds were fit..., # Data from: Wetter and more forested nonbreeding areas result in later departures but a faster spring migration in *Vermivora chrysoptera* (Golden-winged Warblers)

Dataset DOI: [10.5061/dryad.qbzkh18w5](10.5061/dryad.qbzkh18w5)

## Description of the data and file structure

The following data were collected to understand how variability in precipitation and forest cover between non-breeding sites occupied by *Vermivora chrysoptera* (Golden-winged Warbler) in Costa Rica influences departure timing on spring (pre-breeding) migration and how subsequent migration speed is related to departure date.

### Files and variables

#### File: Departure\_date.csv

**Description:** Departure dates for individual Vermivora chrysoptera alongside a series of variables expected to influence departure decisions.

##### Variables

* Band_number: Unique identifier for each bird.
* Motus_Tag_ID: Unique identifier for the radiotransmitter installed on each bird.
* Ddate: Departure date for each bird, where...,