Nature Notes
Chimney Swifts on Mackinac Island Pay a Surprise Visit
By Patricia Martin

On Mackinac you never know when you will run into an exciting bit of nature. Sometimes you can't avoid it, even in your own home. Not long ago, I had visitors who came down the chimney (as you may have guessed, I have no screen on the top of the chimney nor a damper down below). Once a day, for three days, a fairly small, dark bird flew down the flue and had to be escorted out of the house. My mom dealt with it the first time, a guest the second, and I finally got to see it on its last visit. I was able to identify the bird as, appropriately enough, a Chimney Swift.

Chimney Swifts are dark brown, or as one book described them, sooty gray birds with slim bodies and long, thin, pointed, crescent-shaped wings. They have a blackish gray bill. Their tails are squared off. In flight, they have rapid wing beats, a boomerangshaped profile, and erratic flight patterns. They fly on rapid bat-like flight on stiff swept-back wings that alternate with long sweeping glides. They dart erratically and like to soar on thermal drafts.

One of the reasons that I like to describe the flight pattern is that flying is what they spend most of their time doing. They're considered the "frequent flyers" of the bird world. They feed, bathe, collect nesting material, and even mate while in flight. Sometimes they're referred to as a cigar with wings because of their flight silhouette.

Swifts, along with the hummingbirds, are in the Order Micropodiformes, which may give you an idea about their feet. The feet of the Chimney Swift are not very large as the order name indicates ("micro" meaning small, "pod" referring to the feet), which makes sense, as they spend a considerable amount of time flying, and they're not perching birds. Though the feet are small, they have strong claws, which they use for clinging to vertical surfaces. Unlike many birds, swifts may have all four toes pointing forward.

It is said that the legs of the Chimney Swift are so weak and small that if one of these birds lands on the ground, it might not be able to gain flight again. In addition to the claws to help them hold on to vertical surfaces, they have bristles that help support the tail. These bristles are not visible in the field, however.

The call of the Chimney Swift is a rapid chattering sound given when in flight, sort of a "chitter-chitter-chitter." They also make a rapid series of "chip" notes. In addition, as part of their aerial courtship display, they make noises with their feathers. By altering the spacing of wing or tail feathers and causing them to vibrate, they create a variety of whistling, rattling, or buzzing sounds.

These birds spend their winters in South America and travel north to nest in the central and eastern half of the United States and southern Canada. Their favorite nesting sites are hollow trees or, as an alternative, chimneys, hence the name.

Their nests are often colonial and found deep (on average, 22 feet from the top) in the interior of a chimney or tree cavity or in the attics of abandoned buildings. The mated pair uses saliva to attach a halfsaucer nest of short dead twigs to a vertical wall. It usually takes the pair 18 to 30 days to build a nest, and they often lay eggs before the nest is completed.

Both parents feed the young birds, and occasionally other swifts help in the feeding. Their main diet is flying insects, which they swallow whole during flight. The young birds leave the nests after three weeks and they use their strong claws to cling and crawl up the inside of the hollow tree or chimney.

The advent of European settlement in the Americas supplied great new habitat for these birds, who had over time lost some of the large old hollow trees which they liked, and now these birds are found in most cities and towns near large brick chimneys. After the young are away from the parents, these birds often form large flocks of several thousand birds that all hang out together in chimneys and forage in the evening for insects. In the fall, during migration, they often form huge flocks, joining up with Common Nighthawks for their journey south.

Now, I haven't had any more of these swifts in my house in the last few days. Maybe they didn't like my chimney and decided to go to someone else's. Maybe I should put a screen over the top of the chimney, but then I wouldn't have fun with these types of visitors.

Trish Martin is a yeararound resident of Mackinac Island, has earned a master's degree in botany from Central Michigan University, and owns Bogan Lane Inn.