Posted on: May 29, 2015
Author: Brad Winn
When we arrived on the Yukon River Delta in mid-May, some of the shorebirds were just arriving too. We would find areas on our survey plots that had small flocks of feeding shorebirds instead of one or two defending pairs. We saw flocks of Pectoral Sandpipers, Long-billed Dowitchers, and Red-necked Phalarope at particularly good feeding sites. Many of these birds would be moving on to other Alaskan breeding sites, like the Arctic National Wildlife Refuge, or Seward Peninsula, while others seemed to be establishing themselves as residents, and were testing vocal capacity and partial flight displays as growing signs of territorial aggression.
These new arrivals had come from winter sites on both sides of the Pacific, the western Atlantic, Caribbean, and throughout the Gulf of Mexico. As an example, Red-necked Phalarope likely spent the winter at sea in tropical ocean waters off of the Pacific coast of South America. As the days have passed, we have the sense that migrants have moved on and the residents are now getting down to business.
The shorebirds we are counting are no longer using their wings to propel them on hemispheric journeys, but are using them to secure a territory, a mate, and to produce a four-egg nest. The strong outer flight feathers on their wings that cut through the air on night-and-day flights, flapping millions of strokes during migration to get them here, now come into play during a very intense period of courtship, territorial battles, defense, and fleeing. This is the period of great activity. The shorebirds are in motion in somewhat of a tundra dance—all in the very serious game of reproduction. This is the brief period when we, as observers, can try to understand how many of each species we have on our randomly selected 40 acre plots. Once the birds have a full clutch of eggs, the tundra starts to get quiet again, as incubation begins and embryos develop.
Ironically, the outermost ten feathers known as “primary flight” feathers that are so important during migration and now the breeding season, were grown on migration stopover periods the preceding year. The nutrients of these feathers came from foods that these birds ate on the mudflats thousands of miles from the breeding grounds. To grow these strong feathers takes a tremendous amount of food, usually in the form of invertebrate animals, pulled from soft mud or intertidal sands of a low tide beach.
The fact that the flight capability of these shorebirds is dependent upon finding available, reliable, high quality and abundant food sources in distant places emphasizes the need for cooperative international conservation efforts. The Yukon Delta shorebirds are carrying proteins in their feathers from coastal beaches, freshwater wetlands, and interior grasslands in places as diverse and distant as South Carolina, Hawaii, Australia, China, Ecuador, Brazil, and Argentina.
These wing feathers, grown from nutrients in distant wetlands, have not only transported the shorebird thousands of miles and been critical in securing a nesting site and territory, but they will also aid in incubating the eggs and forming a hard outer surface to protect the soft downy feathering under the incubating adult birds from rain. Once the eggs hatch, the young chicks rely on the adults for periodic warmth as they begin to forage on the abundant insects hatching from the tundra pools. The adult’s wing feathers act as shelter and containment for the chicks as they regain lost heat and ready themselves for another bout of insect hunting.
Almost constantly in motion and exposed to strong sunlight radiation during this period of intense activity, flight feathers will wear down during the breeding season, becoming visibly frayed and pale in color as the weeks go by. When the shorebirds depart again in late July and August to begin their southbound journey, the feather cycle will begin again at strategic staging sites where the birds will seek and find the nutrients they need to molt the old, and grow new flight feathers that will last a year.
Our survey team is privileged to witness this shorebird scene on the immense wetlands of the Yukon, one of North America’s largest rivers, and the complex delta system between the Yukon and Kuskokwim rivers. We will continue to work at full capacity to ensure the conservation mechanisms are in place to provide the habitats these birds need throughout their migration cycles.