By Staff
Spring must surely be here for real as last Saturday I saw my first rose-breasted grosbeak of the year. That means I'd better get some oranges up for the orioles, too. I'm tickled to see the tree swallows are more than holding their own against the bluebirds in the battle over my nest boxes. Not that I have anything against bluebirds, they're okay, but I just love to watch the aerial shows of the graceful swallows. Bluebirds already have plenty of press and supporters so I'll be a swallow guy.
I also like the swallows for mosquito control. When living out west our house was on a tiny lake high in the mountains. Violet-green and barn swallows nested on and around the house by the dozens. At times the mosquitoes were horrendous but the swallows unfailingly kept a bug free zone all around the house and yard. As long as we stayed within the zone we never gave a thought to mosquitoes. Tree swallows are the ones hanging around our place here in Michigan. While they often nest in loose colonies, they are fiercely territorial near their nest site so we never have enough around to completely squelch the mosquitoes but every bit helps.
Tree swallows are the most gorgeous, iridescent blue-green above strikingly contrasted by a white underbelly. The females are just slightly duller than the males and often a bit more greenish. The juveniles are a dull gray-brown above and white below. An interesting bit of trivia, tree swallows are the only North American passerine (perching) birds where the young females retain their juvenile plumage for up to two years. This allows them to hang around breeding adults and their nests without being chased away. Therefore, they are readily at hand to replace any adult female that dies during the nesting season. Doesn't Ma Nature have some amazing stuff in her repertoire?
Tree swallows are the last to leave in the fall and first to return in the spring. Often they are coming back right along with the receding snow. Like all swallows, they catch their bugs on the wing. Where they find the insects to sustain them when it's barely above freezing and there’s snow on the ground I have no idea but they must. Often I see a few swallows on an unseasonably warm, early spring day but then a cold snap follows and they disappear. I suspect they are making scouting forays on the warmer days and quickly retreat back south some distance when it turns cold again.
They are one of the widest ranging of our swallows. Their breeding and summer range extends all across the northern half of the U.S. with some going clear up into northern Canada and Alaska to the Arctic coast line. Their winter range is the far southern U.S. extending down into Mexico and Central America with a few choosing to lounge in the Trade Winds of the Caribbean Islands.
Their natural nesting sites are in tree cavities but modern land use practices leave far fewer dead trees and snags for woodpeckers and other cavity makers to ply their craft. For this and other reasons many cavity making species are declining and nesting cavities available for other species such as tree swallows are in short supply. Despite this, the overall tree swallow population remains healthy. I suspect they are thriving on the coat tails of bluebirds as maintaining bluebird nest boxes is practically a national pastime. Despite the bluebird’s superior brawn, the tenacious tree swallows muscle their way into their share of bluebird boxes. Likewise, the decline of purple martins has left vacant martin houses standing all across the country and tree swallows find these high rise apartments just peachy as well. Because of their territorial nature they don't colonize martin houses like the martins do. They just consider it a single family, multi-room mansion. Since the stupid martins haven't even given my two-year-old martin house a glance the swallows are welcome to it. Carpe diem.