On Sept. 29, Rhonda Little-Aifa posted photographs of an unfamiliar hawk on the Maine birds Facebook page. The bird was at the Millinocket Airport on Medway Road, first seen a few days earlier.

Doug Hitchcox, the naturalist at the Maine Audubon Society, recognized the bird as a Swainson’s hawk. Swainson’s hawks nest on cliffs near grasslands in western North America and spend the winter in South America, as far south as Argentina.

Clearly this was a bird out of place. The Maine Birds Checklist Committee recognizes only two prior sightings for the state, one seen on May 3, 2009 in Pownal, and another on Sept. 23, 2013 in Harpswell. Eight other claims, from 1883 to 2005, lack sufficient documentation.

A major migration of birders to Millinocket began Sept. 30. Dozens of birders got to see this cooperative bird, particularly over the weekend. The hawk was last soon on the morning of Oct. 4. You can see pictures at: http://ebird.org/ebird/view/checklist/S31826769.

Swainson’s hawk belongs to the genus buteo, which includes the red-tailed hawk and broad-winged hawk. A Swainson’s has proportionally longer wings and a smaller bill than the similarly sized red-tailed hawk.

The bird also has the colloquial names of locust hawk and grasshopper hawk. They often feed on the ground, chasing grasshoppers, a favored food. The Millinocket bird spent most of its time perched on the fence surrounding the airport or on the ground chasing grasshoppers. Louis Bevier made a video of the hawk capturing a grasshopper; you can view it at: https://vimeo.com/185072912.

Swainson’s hawks also will catch dragonflies and other large insects on the wing.

Normally, Swainson’s hawks migrate south from their western breeding grounds, through Central America and then spread out in South America. Like most buteo hawks, they don’t migrate over water.

Swainson’s hawks are one of the most abundant species migrating through the Isthmus of Panama. Hawk watchers in Panama City counted 900,000 soaring migrants (mostly Swainson’s hawks and turkey vultures) passing overhead on a single day in November 2013. That record was broken on Nov. 2, 2014 when 2.1 million birds passed over. What a spectacle.

This hawk joins a long list of vagrants in Maine from western North America, including the white-winged dove, western flycatcher, calliope hummingbird, hermit warbler, Brewer’s sparrow, black-throated sparrow and western meadowlark.

I think it’s significant that the Swainson’s hawk in Millinocket was young, born this summer. Many birds that appear in unexpected places during migrations are naive and inexperienced. Young birds are much more likely to make navigational errors.

Navigation during migration involves two abilities. Most migrants are capable of vector navigation, maintaining a particular compass direction for a specified length of time or distance. True navigation requires that a bird know exactly where it is, even if displaced by a storm or wind.

Experiments demonstrate differences between the navigational abilities of juvenile and adult birds. Imagine yellow-rumped warblers banded on their breeding grounds in Maine that normally would migrate south to North Carolina for the winter. Vector navigation on a south-southwest trajectory will get those birds to their wintering grounds.

Some ornithologists have experimentally captured such birds and displaced them eastward or westward. Let’s fly some warblers from Maine to Minnesota and release them there in the fall.

Adult birds have true navigation – they realize where their displaced position is and will migrate in a southeasterly direction to arrive in North Carolina.

The young warblers are poor at true navigation. Most will use their vector navigation skills and head toward Texas. Vagrant birds tend to be young, and are much more likely to get lost.

Herb Wilson teaches ornithology and other biology courses at Colby College. He welcomes reader comments and questions at

whwilson@colby.edu