Some writers have likened the merlin to a small, sleek, ultra-fast sports car: fast, quick-handling and handsome in appearance.

No, we are not talking about the wizard of King Arthur legend, but the small, sharp-winged falcon. Many of these birds are winging south through Maine, especially coastal Maine, throughout October.

Merlins are small, tiny cousins of the big, bold and better-known peregrine falcon, and just as tough. Like peregrine falcon, merlins prey on other birds, using their speed and agility to surprise and then overtake them.

Given that they are no larger than a blue jay, most of their prey are birds the size of small sandpipers, sparrows, and warblers though they will take small rodents, insects, and in warmer wintering climes, small lizards and snakes.

Amazingly, we have seen them knock a Northern flicker out of the air on Monhegan Island, but such instances are probably rare, since flickers are larger than they are.

The largest part of the merlin’s North American breeding range reaches across the Boreal Forest region of Canada and Alaska, but over the last 10-20 years they have expanded southward, often breeding in cities and towns.

They now nest in many Maine towns where introduced house sparrows and house finches, abundant in most suburban and urban settings, are probably a primary part of the diet they feed their young.

Merlins reuse the nests of other birds, like crows, and perhaps make-use of old squirrel nests as well. They lay 3-4 eggs. When the young are close to fledging (in our area around late June or July) they become very loud, calling constantly for more food, so much so that if you have a sharp ear and eye you may see them. We have enjoyed watching recently fledged and very loud Merlin families among the pines on the Bowdoin College campus the last two summers in late June.

The wintering range of the merlin traditionally has extended in the east from the southern U.S. to northern South America, but with milder winters, more of the birds seem to be wintering farther north.

This may account for the population increases that have led to an expansion of the southern edge of the breeding range into Maine and other parts of the northeastern U.S. Still, large numbers of merlins migrate south (we see them regularly on Aruba, an island off the Venezuelan coast, for example) and the peak of their migration through the Northeast tends to be in October.

This is presumably an adaptation that allows them to be on the move when some of the largest numbers of a favorite food, sparrows, are also on the move. Moving south with their food supply allows merlins to ensure that they can make it to where they need to go.

They prefer to migrate when moderate to strong winds from the Northwest are blowing, usually right after the passage of a cold front, which makes it easier for them to cover more ground while using less energy.

So the next time you see a small falcon zoom by, be prepared to fall under the fascinating spell of the merlin!