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New Jersey Endangered and Threatened Species Field Guide
Species Group: Bird
State: Special Concern
The semipalmated sandpiper is a small shorebird with short webbing between its toes. Considered to be one of the most abundant shorebird species, the semipalmated sandpiper has a short neck and a slightly drooping bill. During breeding season, they have gray-brown upperparts with a slight hint of russet and dark streaking along the sides of the breast. The chest is generally lightly marked. During the non-breeding season, this sandpiper is uniformly gray on the upperparts and white below with a few dark streaks on the breast.
Males and females are similar in plumage, but females are slightly larger especially in bill length. Juveniles have variable plumage with dark upper feathers trimmed with red or buff. Compared to adults, they have less streaking along their sides.
Field identification is typically difficult due to similarities with other sandpiper species. Commonly confused with the western sandpiper, their winter plumages are almost identical. The western sandpiper is typically larger and does not winter in the same location.
DISTRIBUTION AND HABITAT
The semipalmated sandpiper is a migrant visitor to New Jersey’s coastal beaches and bay shores. The Delaware Bay is considered to be their most important spring migratory stopover in the eastern United States. Semipalmated sandpipers, along with millions of other shorebirds, visit the Delaware Bay during migration to feed on millions of horseshoe crab eggs. In late May, the arrival of shorebirds coincides with peak breeding season for horseshoe crabs. As long-distance migrants, semipalmated sandpipers make no other stops from their wintering grounds in South America to their breeding grounds in the Arctic.
After their long journey north, the semipalmated sandpiper reaches its breeding grounds in Arctic & subarctic Canada and coastal Alaska. Here they breed on grassy, dry tundra usually near water. In August and September, post-breeding females depart about 5 days prior to males. Most of the breeding population stages for fall migration at the Bay of Fundy and then fly directly over the ocean making landfall only in northeast South America. During the non-breeding months, they prefer mudflats, sandy beaches, and the shores of lakes & ponds.
Considered to be selective, but opportunistic foragers, the semipalmated sandpiper probes the ground for small arthropods, amphipods, polychaetes and occasionally insects & spiders. Foraging is regulated by the tidal cycle, mostly as the water recedes at low tide.
In late May into June, male semipalmated sandpipers arrive on their breeding grounds first and immediately begin setting up territories. Within the first week of the females arriving, pair bonds are formed. Their courtship begins with the males making numerous depressions in the ground for the female to choose from. Often the pairs return to previous successful nest sites. Pairs are typically monogamous with a high rate of reunion over several years.
In June, semipalmated sandpipers lay a 4 egg clutch, laying 1 egg per day. The eggs are dull white or olive buff with brown markings. Both adults will incubate the nest equally over a 19-21 day period. After the eggs hatch, both adults stay with the brood for 1-2 days. Within hours of hatching, the chicks are out of the nest bowl and foraging for food on their own. The female then leaves by day 6 and the male continues to rear the chicks. The chicks are fledged between 15-17 days old and leave the area where they were born several weeks after both parents have left.
In mid-August, juveniles begin to arrive at the staging area. Most juveniles do not breed as yearlings and stay on their wintering grounds until they are ready to breed in their 2nd year.
CURRENT STATUS, THREATS, AND CONSERVATION
In New Jersey, the semipalmated sandpiper is listed as a species of special concern. Federally, they are considered secure on their breeding grounds in Alaska.
As the most important spring migration stopover in the eastern United States, the Delaware Bay is currently under threat for shorebirds and horseshoe crabs. Overfishing of horseshoe crabs for bait and biomedical research is likely causing the population declines in many shorebird species. As the birds stop here to boost fat reserves, they are finding less and less horseshoe crab eggs to feed on. Regional conservation plans to regulate horseshoe crab fishing in New Jersey have recently gone into effect.
The legal and illegal hunting of semipalmated sandpipers in northern South America still exists and plays a predominant role in their decline. They also face the threat of destruction and manipulation of coastal inland wetlands. Canada and the United States have compiled detailed conservation plans that protect not only the semipalmated sandpiper, but all shorebird species.
Text written by Emily Heiser in 2011.
Species: C. pusilla
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