The Birding Year in the Pacific Northwest
September: Flocks of Birds Moving
Written by Andy McCormick
Andy McCormick, Volunteer and Former Board President of Eastside Audubon
By September, the birding summer has run its course and birds will use the time in late summer and early fall to rebuild their reserves. For most birds, the individualistic drive for the success of their own nest and young dissipates and they join into flocks for mutual support and safety. Birds which began their nesting cycle in April and May have had time to find a mate, build and defend their nest, nurture nestlings, and fledge them into the world.
Many of our resident birds are beginning to move to new locations in search of new food sources. Some higher elevation breeding birds will begin moving downslope to lower elevations in a process called altitudinal migration. The long-distance migrating birds will prepare for their flight back to the neotropical forests and grasslands of the southern United States, Mexico, and Central and South America.
FOLLOWING UP ON BIRDS
The three birds we discussed in June are now in very different stages of their annual cycle.
Killdeer are early breeders, and their chicks have matured. By the end of June, the young Killdeer molted into basic adult plumage and left the nest site. They are now independent and foraging on their own. Most have joined with adults in flocks of up to 300 members for flights to South America.
The juvenile Spotted Towhees are beginning to drop their juvenile feathers and molt new body and tail feathers. This molt takes several weeks and will be completed in October. Towhees in the Pacific Northwest tend to breed at higher elevation, and they will move to the lowlands in fall.
Most Osprey chicks have matured by September and are taking regular foraging flights for fish. Many adults have departed from their nesting areas and any remaining young Ospreys will soon be heading south in their wandering fashion. Ospreys explore a variety of possible wintering areas on a meandering journey over weeks before settling on a place to spend the winter. They will retain their juvenile feathers during migration and molt into their first adult plumage over the winter.
THE BENEFITS OF THE FLOCK
Post-breeding flocking behavior is evident in many bird species. American Robin flocks can reach numbers in the hundreds. Young Steller’s Jays gather in flocks of a dozen to nearly 100 birds. Flocks of Pied-billed Grebes and Common Mergansers are larger now that the young are adult size. Shorebirds are moving south in flocks in the thousands.
During the breeding season, the primary focus of nesting birds is the task of protecting and raising their young. They compete for the most suitable nesting locations and for the best foraging habitat. They do what they need to do to assure the survival of their young and protect them from predators. Birds expend large amounts of energy accomplishing all these tasks, and as the urge to breed dissipates, they take advantage of a less competitive environment to shift their focus to their own survival.
Flocking often begins with family groups joining together. Over thousands of years birds which cooperate during the nonbreeding season have been more successful in living until the next breeding cycle. Birds become less competitive and more cooperative. Some species of waterfowl and seabirds flock all year, but the passerines, the perching birds, flock mostly in fall and winter and during migration.
Research on the benefits of forming flocks indicates that joining a group offers protection for birds. There is safety in numbers. The odds of being captured by a predator decrease as the flock grows larger. For example, a shorebird has a 10-times greater chance of being attacked in a flock of 10 shorebirds than in a flock of 100.
Larger flocks of birds also provide more vigilance against predators. There are simply more eyes available to spot an attacking predator and sound an alarm. This defensive benefit may be enhanced if members of a sentinel species are present in the flock. Shorebirds feeding with their heads down are especially vulnerable to attack by a speeding Peregrine Falcon flying a few feet above the ground in a full stoop. A loud Greater Yellowlegs alternating feeding periods and walking with its head up can warn the flock of an approaching raptor. Shorebirds in mixed feeding flocks demonstrate a willingness to share a tidal flat food source in exchange for the protection that a large flock may provide.
Chickadees are other noisy birds that constantly communicate among themselves. They are responsive to changes in their environment and their alarm calls are loud. In fall and winter, they attract other birds into mixed-species flocks that often include nuthatches, sparrows, warblers, and woodpeckers, all of which benefit from the alertness of chickadees to approaching danger.
ATTENTION ON HAWK FLOCKS
In September, many birders pay special attention to raptor migration. Hawks, eagles, and falcons gather in preferred areas in fall and move in loose flocks during their migration. Unlike smaller birds such as warblers and flycatchers which fly in closer-knit groups and power their flight with constant wingbeats, raptors need more space to soar as their sheer size makes long-distance wing-powered flight very difficult. Hawks and eagles soar on thermals, the rising columns of warm air created as the sun warms the day. These updrafts can also be adjacent to mountains, cliffs, and canyons. A soaring raptor will ride the thermal to a high altitude and then travel on the current until it catches the next thermal. When the tail winds are favorable, raptors can ride these air currents for hundreds of miles in a day.
In the past quarter century, fall hawkwatching sites have become very popular among birders. From mid-August to early October hawk watchers meet at specific locations to count migrating raptors. The Rivers of Raptors count in Veracruz, Mexico began in 1992 and is one of the most successful and most famous hawkwatching sites. The city is located along a narrow strip of land between the mountains and the sea. The geography produces updrafts along the corridor where hawks and eagles following the coastline fly more closely together. Counters tally the totals for each raptor species.
The Hawk Mountain Sanctuary in Pennsylvania is another popular North American location which began hawkwatching in the 1950s. In the Pacific Northwest, Goshute Mountain Watchable Wildlife Area in Nevada sits at 9,000 feet and is reachable by a 2.5-mile uphill hike. The reward for making this climb is the opportunity to see up to 18 species of raptors which over the high migration period can number between 10,000 and 25,000 birds including Bald and Golden Eagles, Sharp-shinned and Cooper’s Hawks, Goshawks, Red-tailed, Rough-legged, and Broad-winged Hawks, Northern Harriers, and the falcons: Peregrine, Prairie, and Merlin. Windy Gap in the Washington Cascades has recently become a more popular hawk-watching area.
MORE FLOCKING BIRD FAMILIES
It is common knowledge that birds of all kinds flock together. This is reflected in the saying, “Birds of a feather, flock together.” From a scientific point of view, taxonomy is the method used to classify living and extinct organisms, including birds. Bird species are grouped by genus and then collected into families. The hawks and eagles described above are in the family Accipitridae, the Latin equivalent for hawks. Many other families of birds are moving as flocks in the fall. I have included the scientific name for each of the following families of birds in parentheses after the common English name.
Flocks of shorebirds (Scolopacidae), many of which set to wing in August, will pass through Washington and Oregon in September. In general, Western and Least Sandpipers, and Greater Yellowlegs follow the coastline, and some Baird’s and Solitary Sandpipers and Lesser Yellowlegs migrate inland following the rivers and through the Malheur National Wildlife Refuge in Southeastern Oregon. The plovers (Charadriidae) represented by Black-bellied and Semi-palmated Plovers will join in the shorebird flocks.
Gulls (Laridae) are also on the move. Heerman’s Gulls begin massing along the coast. The Olympic hybrid of Western and Glaucous-winged Gulls begin moving inland. California Gulls move from inland breeding sites west through the Pacific Northwest then south toward the coast of California.
The Black-footed Albatross (Diomedeidae) and shearwaters (Procellariidae) disperse northward from their breeding zones in the southern oceans. Pink-footed, Flesh-footed, Buller’s, and Sooty Shearwaters, and the Northern Fulmar may all be seen moving during pelagic birding tours in offshore waters.
By the end of the month ducks, geese, and swans ( Anatidae) are gathering into large flocks. American Wigeon, Northern Pintail, and Cackling Geese migrate along the Pacific coast. Snow Geese and Canada Geese will move on the coast and also through inland flyways.
Also on the outer coast, the alcids (Alcidae), the black and white “penguins of the north” such as Common Murre and Rhinoceros Auklet, fly along Cape Flattery and into Puget Sound.
Whether it is a massive flock of thousands of Snow Geese, a murmuration of European Starlings, a family flock of Bushtits, or a mixed flock of forest birds, fall birding provides a different level of excitement in watching birds on the move during fall migration, one of the most exciting and enthralling movement of wildlife each year. I urge you to get out to experience these flocks of birds for yourself.
SUGGESTIONS FOR FURTHER READING
Lovette, Irby J. and John W. Fitzpatrick (2016). The Cornell Lab of Ornithology Handbook of Bird Biology, Third Edition. Cornell University.
Sibley, David Allen (2001). The Sibley guide to bird life & behavior. New York, Knopf.