Capture histories for radio-tagged Western Sandpipers at four stopover sites on the Pacific Flyway, 1992 to 2022

Shorebirds typically spend more time fueling and refueling during migration than they spend in actual flight, and consequently their stopover ecology has important implications for fitness and conservation. We examined spatial variation and long-term changes in stopover duration of radio-tagged western sandpipers Calidris mauri over three decades on the Pacific Coast of North America. Birds were monitored during 10 periods of northward migration at four key stopover regions including: San Francisco Bay, CA; Willapa Bay/Grays Harbor, WA; Vancouver Island/Fraser River Delta, BC; and Copper River Delta, AK. We used Cormack–Jolly–Seber models to estimate the daily probability of staying at a stopover site (φ) corrected for daily detection rates (p) in relation to annual and seasonal variation. Daily probabilities of staying were then used to calculate length of stay (LOS) in days. Mean LOS decreased at stopover sites as birds progressed northward and varied from 23.1 days at San Francisco B..., Birds were captured and tagged at 10 different locations (latitude – longitude): Playa Ceuta, Mexico (23.94 -106.98), Bahia Santa Maria, Mexico (25.11 -108.22); Punta Banda, Mexico (31.74 -116.63); Point Mugu, California (34.10 -119.12); three areas of San Francisco Bay, California (37.53 -122.07 , 37.62 -122.12, and 37.49 -121.96), including 10 birds in 1992 at nearby Bolinas Lagoon (37.93, -122.69); Honey Lake, California (40.16 -120.23); Grays Harbor, Washington (46.97 -123.95 and 46.89 -124.05); four coastal sites on Vancouver Island, British Columbia (49.05 -125.71, 49.11 -125.88, 49.07 -125.75, and 49.03 -125.69), and two areas of the Fraser River Estuary, British Columbia (49.22 -123.22, and 49.05 -125.69).
All birds were captured with mist nets, banded with an individually numbered metal band, weighed for body mass (± 0.5 g), and measured for three standard morphometric variables (± 1 mm), including exposed culmen, wing (both natural and flattened), and tarsus. Western Sandpiper..., # Capture histories for radio-tagged Western Sandpipers at four stopover sites on the Pacific Flyway, 1992 to 2022

Dataset DOI: [10.5061/dryad.bg79cnpqn](https://doi.org/10.5061/dryad.bg79cnpqn)

## Description of the data and file structure

This dataset provides the underlying basis for the scientific paper entitled 'Three Decades of Western Sandpiper Stopover Dynamics during Northward Migration on the Pacific Coast of North America, 1992 to 2022', written by Nils Warnock, Sarah Warnock, Brett Sandercock, Mary Anne Bishop, John Takekawa, Sydney Bliss, Scott Flemming, and Mark Drever.

These data provide locations and dates for captured Western Sandpipers that were subsequently detected at four stopover sites on the Pacific Flyway, 1992 to 2022. Data also include capture histories used in CJS (Cormack-Jolly-Seber) modelling as well as morphometric data.

### Files and variables

#### File: Warnock_2026_Birds_w_covariates_(April2026).xlsx

##### Variables

* stopover_ch_row: unique row..., ,