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The Greener Side: Chimney swifts in trouble

September 24, 2018   ·   0 Comments

By Mark Whitcombe

Watching the Chimney Swifts in downtown Orangeville, as part of a project with the Upper Credit Field Naturalists Club, it is clear they are in trouble.

The birds breed from the Maritimes to Saskatchewan and winter in the upper Amazon River basin in South America, migrating back and forth annually. Approximately one-quarter of the species’ world breeding range is in Canada. Sadly, they are a threatened species and now listed on Schedule 1 of the Species at Risk Act. Their numbers have fallen 96 percent in the last few decades, making them uncommon to rare, and decreasing further. The main problems are a lack of suitable habitat and nesting sites, as well as food scarcity of their main source – insects.

We are lucky to continue having some Chimney Swifts nesting in downtown Orangeville, though also in decreasing numbers. They nest in old hollow trees or old uncapped chimneys with large diameter flues. Only one pair nests in a chimney at a time. Since old hollow trees are not common anymore, nor are uncapped chimneys with large flues, the birds have few nesting sites.

There is now Ontario protection for known roosting sites of Chimney Swifts (www.ontario.ca/page/chimney-swift-general-habitat-description).

Not only their local nesting sites have diminished, but their South American overwintering habitats are undergoing serious destruction from deforestation. Their migration route takes them across heavily farmed southern and central regions of the US, where the large-scale agriculture also offers little bird habitat, providing limited resting opportunities and insects for them to feed on during their journey.

Chimney Swifts spend their entire day flying fast and acrobatically, catching flying insects. They play a significant role in controlling insect populations, as a single bird can eat 1,000-plus insects in one day. Superficially, they look like swallows but are larger and much faster. One way to describe them is that they look like a flying cigar!

We have had them in downtown Orangeville for decades, though recently in much smaller numbers and down from the highest observed number of 15, seen as recently as three years ago. Until some chimney roosts were discoverae in downtown Orangeville a few years ago, nobody knew where they were nesting here. But they are not doing well.

From June until July, only five birds could be seen flying at any one time – the lowest number observed since beginning to census the birds in town. Sporadically observed flocks of 12 to 14 might have been only migrating birds starting their trip south early. Usually, Chimney Swifts begin their southward migration in August.

About eight birds, often seen flying in close formation, seem to represent our local population. This is some good news, as it indicates three successful fledglings this year. That means three new birds making it to the flying stage, possibly from three separate nests and quite possibly nesting in the chimneys of the old century homes south of Broadway.

A very worrying observation is how few insects seem to be around anymore for the Swifts to feed on. Remember the days when you couldn’t drive anywhere in the countryside in summer without hundreds of insects splattering on the car windshields, and many car lovers automatically installing bug shields on the front of their vehicles every May? These days, there aren’t many flying insects around. No beer bugs pestering us as we eat out on the deck. Only a few small house flies. Even the ant population seems reduced, as well as wasps and spiders.

It was no better at Island Lake, where only some larger dragonflies and only a few Monarch and other butterflies made an appearance. But little else. This means that all the aerial insectivorous birds are affected, and have populated only in very small numbers, and none of the four possible species of swallows, for example.

This is especially disturbing. Why are there so few insects around the lake? The actual drainage basin into the lake is small and includes little farmland, so agricultural runoff can probably be discounted, as can the effects of neonicotinoids (agricultural insecticide) which cause known problems in aquatic ecosystems.

Where have all the insects gone? Bet the Chimney Swifts are wondering, too.

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