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We compiled a >50-year record of morphometrics for semipalmated sandpipers ( Calidris pusilla), a shorebird species with a Nearctic breeding distribution and intercontinental migration to South America. Our data included >57,000 individuals captured 1972-2015 at five breeding locations and three major stopover sites, plus 139 museum specimens collected in earlier decades. Wing length increased by ca. 1.5 mm (>1%) prior to 1980, followed by a decrease of 3.85 mm (nearly 4%) over the subsequent 35 years. This can account for previously reported changes in metrics at a migratory stopover site from 1985 to 2006. Wing length decreased at a rate of 1,098 darwins, or 0.176 haldanes, within the ranges of other field studies of phenotypic change. Bill length, in contrast, showed no consistent change over the full period of our study. Decreased body size as a universal response of animal populations to climate warming, and several other potential mechanisms, are unable to account for the increasing and decreasing wing length pattern observed. We propose that the post- WWII near-extirpation of falcon populations and their post-1973 recovery driven by the widespread use and subsequent limitation on DDT in North America selected initially for greater flight efficiency and latterly for greater agility. This predation danger hypothesis accounts for many features of the morphometric data and deserves further investigation in this and other species. [ABSTRACT FROM AUTHOR]

The objective of this study was to determine the implications of extreme tidal events on duration of stay and behavior of Semipalmated Sandpipers (Calidris pusilla) during migratory stopover in Cobequid Bay, Nova Scotia. This area is part of the Bay of Fundy and experiences the largest tidal range in the world. Radiotelemetry was used to monitor duration of stay of 30 adult and seven juvenile Semipalmated Sandpipers. Adults arriving in Cobequid Bay early in the migration period experienced a greater number of extreme high tides (> 15 m) that submerged preferred roost sites, and stayed on average 8.1 days longer than those that arrived later. Juvenile duration of stay was not significantly different from adults. When tides exceeded 15 m, Semipalmated Sandpipers engaged in over ocean flocking ar high tide; however, this behavior was not observed when high tides were 13.6 morless. These extra flights led to higher energy expenditure by early migrants, requiring an estimated 3.8 to 4.3-day increase in length of stay to reach die same mass as later migrants. In the future, predicted sea level rise could increase the frequency of extreme tidal amplitudes and result in greater energetic costs during Semipalmated Sandpiper stopover. [ABSTRACT FROM AUTHOR]