Fall Shorebird Migration

American Avocet by Bill Powell

At summer's end, each week in Jack Chiles'  bird census for Hagerman National Wildlife Refuge you will find various species of shorebirds  being reported. These birds are arriving in increasing numbers on the fall migration.The following is a reprint of an article by Wayne Meyer, PhD, that appeared in the September, 2009, issue of the Featherless Flyer.

Most people know that there are thousands of geese at Hagerman NWR each winter, but not many know that shorebird migrations bring at least twice that many birds through our refuge. North American shorebirds breed in the northern tier of states, Canada or the high Arctic. Most of them spend the winter in the tropics, although some species will travel into South America.This means that they must fly thousands of miles, a feat requiring a great deal of fuel. Wetlands located along the migration routes, therefore, are important places for the birds to stop and refuel. Since Hagerman NWR is on the southern end of the Central Flyway and close to the end of the Mississippi Flyway, it gets lots of traffic each spring and fall.

Solitary Sandpiper by Bill Powell

The spring migration is rushed. Birds travel quickly to get to their breeding grounds and claim the best territories. A few early migrants arrive in late March and the big rush is over by the second or third week of May. Within that period the individual species tend to occur in waves, each species having its own peak period of just one or two weeks within the 6-8 weeks of spring migration.

In fall, however, the situation is quite different. A few birds appear in late July but the last ones don’t arrive until November. For any particular species there may be two or even three waves in one season.

Breeding success helps explain the reason for these multiple waves. The first migrants are failed breeders and nonbreeders. Injured birds, young birds that didn’t collect sufficient resources to breed, and birds whose young were lost to predators head south early. We see them in July and August. Advantages to coming south early include fewer predators and less competition for food.

The adults who raised young will remain on the breeding grounds until their young are able to care for themselves. They take advantage of the long hours of summer sunlight to collect energy for molting and to store fat prior to their long flights.These birds usually begin showing up at Hagerman NWR in late August or September and peak prior to October. This is an interesting time to observe the birds as some wear breeding plumages that we rarely see.

The third wave is usually made up of juveniles who hatched during the summer and are making their first migrations. Since they used food energy for growth, they need more food than their parents did before they can store enough fat. They begin to arrive in mid-September and peak in mid-October, although a few slow-pokes will not pass through until November. Some overwinter at Hagerman NWR.

Take a few visits to the refuge this fall and watch the shorebirds moving through. Each visit is sure to show you different things and you’ll get all the challenge you could ask for in identifying the many birds that use our favorite fueling station.