Birds or Bats ?

Chimney Swift stackIf you have chittering in your chimney, it could be birds or bats and the way you can tell is by going outside at dusk and watching whether something comes out of your chimney or goes in. At dusk, bats are just getting ready to exit the chimney to forage for insects, whereas Chimney Swifts are getting ready to roost for the night and so will enter the chimney at dusk. Chimney Swifts look a lot like flying cigars, and are classically described as a “cigar with wings”. They build nests of twigs held together and to the chimney wall by the birds’ own saliva which hardens into a glue-like substance and the birds themselves cling to vertical surfaces like brick or concrete.

Before Europeans arrived on this continent, the virgin forests of eastern North America contained old trees that were hollow and Chimney Swifts nested there. When Europeans arrived they cleared the forests, thus eliminating the swifts’ homes.  However, they unintentionally provided the swifts with a manmade alternative, brick chimneys.Chimney Swift nest Since that time, swifts have almost completely depended on chimneys and structures that look like chimneys for nesting. Unfortunately for the Chimney Swift, brick chimneys are going out of fashion and modern chimneys aren’t useable by swifts. Modern chimneys are lined with metal that the birds cannot cling to or attach their nests to. The decline in Chimney Swift numbers over the last decade is enough to have the species classified as “near threatened” and as a result there is a movement afoot to encourage the erecting of Chimney Swift towers in order to halt the decline the swift populations. Here at the Gulf Coast Bird Observatory we have a curious looking structure that visitors often ask about. It is a square tower about 12 feet tall with an opening at the top. It is, in fact, an artificial chimney built for the nesting of Chimney Swifts. However, unlike Purple Martins which nest in colonies, Chimney Swifts are territorial and the rule is one swift nest per chimney. This makes increasing swift numbers by building artificial chimneys more difficult because unlike a martin house which can house any number of nests, each swift tower accommodates only a single pair. We are pleased that our tower at GCBO has housed a pair of swifts for the past several summers.

Although swifts are most closely related to hummingbirds, they share none of their relatives’ brilliant colors. They are among the least colorful of all land birds. They live their entire lives on the wing with the exception of the nesting cycle. They fly above most of the cities and towns in the eastern half of the United States, including most of Texas. They feed on flying insects and only enter chimneys to sleep at night and to nest. Swifts are so fast and facile, veering and darting along paths that are hard to follow, that they have few predators, except the occasional Sharp-shinned Hawk or other agile bird of prey.

When they are not nesting, Chimney Swifts gather in large chimneys to roost, usually industrial chimneys. In late summer and early fall swift roosts may run into the thousands as the birds mass together prior to their departure for their winter quarters in the Amazon basin. So, if you discover that your chimney provides a temporary roost for staging, you may want to consider building a chimney swift tower to provide alternate housing for these marvelous birds. You can find out more information about this at Get your tower ready for next spring now!


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