Buff-breasted Sandpiper (Calidris subruficollis) Measurement Data from Brazil, Texas, and Alaska

Three populations of Buff-breasted Sandpipers were sampled for external morphological measures, including birds caught during the boreal winter (October – March) in southern Brazil (31°15’S, 50°58’W; and 32°32’S, 52°33’W), the migration periods (northbound in late April/early May and southbound in August) in Texas (28°48’N, 96°6’W; 29°19’N, 95°45’W; 28°51’N, 95°58’W), and the breeding season (late May – July) in northern Alaska (70°12’N, 148°15’W). In Brazil, birds were caught at nocturnal roosts using spotlights and dip nets in 2001 and from 2003–2005. In Texas, 52 birds were caught at feeding / bathing areas on turf farms using whoosh nets and cannon nets from 2016–2017, and in Alaska, 78 birds were caught at leks with mist nets or at nearby nests using walk-in traps in 1994.

We collected blood from birds from Brazil and Texas with EDTA capillary tubes or filter paper, respectively, after puncturing the brachial vein with a 27.5–gauge needle. Blood from capillary tubes was placed in Eppendorf tubes filled with Longmire buffer (Longmire et al. 1988) and kept at room temperature until analyzed. Filter paper samples were allowed to dry and then placed in envelopes for transport to the laboratory.

Birds were classified into one of two typical age classes (hatch year [HY, hatched in preceding Arctic summer] and after-hatch year [AHY, hatched > 1 year ago, includes second year and after-second year birds]), based on size and color of the spots on the ventral surface of the outer primaries. Because we could not distinguish between HY and AHY once they completed their outer primary molt in late January, we classified all birds as AHY if captured on the wintering grounds after 1 February or captured during spring migration in Texas although some were not quite a year old. All birds captured in Alaska were classified as AHY by default because they had completed a full migration cycle prior to capture on the breeding grounds. Observers failed to record age on 23 birds captured at the Taim site in Brazil in December 2001; these birds were excluded from analyses involving age but are included in this data set (marked as "U" for age).

Genomic DNA was extracted from blood taken from birds sampled in Brazil and Texas using the protocol described in Khatib & Gruenbaum (1996) and Handel et al. (2006), respectively. All blood samples had fragments of genes CHD-Z and CHD-W located on the avian sex chromosomes amplified using the primers P2/ P8 (Griffiths et al. 1998), whereas samples from Texas were also amplified using primers 2602F/2669R (van der Velde et al. 2017). Methods for polymerase chain reaction (PCR) and electrophoresis of PCR products followed standard procedures. PCR amplifications usually produce electrophoresis gels with a single band in males (derived from the Z chromosome) and two bands in females (Z and W fragments) and this is what we relied on to sex birds.