By, Darlene Betat
Strings of geese heading north in loosely shaped Vs are often our first clue that spring migration is underway. Migration is all about moving from areas with decreasing resources to areas with increasing resources. For birds, those resources are primarily about food and nesting sites. It is no wonder, then, that migratory songbirds who nest with us arrive in time to take advantage of the increasing abundance of hidden nesting sites, insects, blooms, fruits, seeds and longer daylight hours. Migration can be split according to how far a bird travels during migration.
Short-distance migrants are mostly species we see year round. Why call them migrants? In late fall, our resident birds are joined by others of their kind—birds who nest a relatively short distance from here but whose breeding grounds become too harsh to survive in winter. These movements can be latitudinal, longitudinal, or altitudinal or a mix thereof. Examples of birds we enjoy as both residents and short-distance migrants include Spotted Towhees, Steller’s Jays, and Anna’s Hummingbirds. Varied Thrushes and Townsend’s Warblers are not resident but migrate short distances seasonally. These birds travel down from the mountains in winter to lower elevations, only to return to their high-elevation breeding grounds in spring.
Medium-distance migrants cover distances spanning from one to several states. Our wintering flocks of Golden-crowned Sparrows are a good example. Their entire population migrates south from Alaska and Canada for winter only to return north in spring. Some species fall into both short- and medium-distance migrants. Again, these include species we see year round such as American Robins, Northern Flickers, White-crowned Sparrows and Dark-eyed Juncos.
Long-distance migrants are our neo-tropical birds—those that travel from Central or South America to breed in North America. We begin to see our first long-distance migrants in the Portland area in early February. Already we have welcomed back Tree and Violet-green Swallows, Rufous Hummingbirds, Turkey Vultures, Osprey and more. Spring arrival dates are fairly reliable for a given species from year to year. Birds still to arrive and watch for in late April through early May include Western Tanager, Black-headed Grosbeak, and Swainson’s Thrush.
Knowing that feeders and birdbaths can help birds refresh and refuel during migration gives a sense of fulfillment in addition to the simple joy of watching them.