Seeking Citizen Scientists for Study

The aerial acrobatics of swallows in flight is a welcome sight in springtime for those concerned about the declining population of barn swallows.

Climate change, the use of pesticides, and even house sparrows are threating the “common” barn swallow, as numbers have steadily declined. The Mass Audubon “State of the Birds” has identified barn swallows as rapidly decreasing in number, and the decline is widespread. Barn swallows have been added to Canada’s list of endangered species.

As part of the “Big Barn Study,” the Mass Audubon Society is seeking the help of Tri-Town residents who would act as citizen scientists in a Barn Swallow counting to find out how many there are, where they are breeding, and which sites they may have abandoned.

All one would have to do is pick a spot and visit it three times before June 30, the end of the mating season, and then enter the data on the Big Barn Study data reporting website.

Barn swallows usually build their nests on manmade structures like barns, bridges, and overpasses, and there are three criteria for choosing a location. The structure must be at least six feet tall, have a large opening that is never sealed such as a barn door or loft, and the bridge or overpass must be large enough to span at least one lane. Empty barns and overpasses where swallows are absent is also valuable information that can be reported to Mass Audubon.

If you encounter a swallow nest and you are not sure if it is inhabited, look for some telltale signs such as bird droppings on the ground (swallows are very clean birds that do not defecate in their nests). There are two swallows to a nest, and a mirror at the end of a retractable pole is a great way to peek inside a nest that is out of reach.

How can you tell if what you spot is indeed a barn swallow? Barn swallow tails are long and forked, and the wings are long and narrow with a distinct point. They are entirely iridescent blue above, and white, buffy, or pale orange underneath.

While tracking the swallows, be on the lookout for house sparrows, an invasive, aggressive species of sparrow not native to North America. These common brown birds often evict other birds, including swallows, from their nests and take them over, sometimes attacking or killing them.

Lauren Miller-Donnelly of Mass Audubon said she once saw a house sparrow nest constructed out of the dead carcass of a blue bird, and she advocates getting rid of the European species whenever possible.

“House sparrows are not protected under the Migratory Bird Treaty Act,” said Miller-Donnelly. “Whenever I can I will ‘eliminate’ them from the population.” One way of repelling house sparrows, added Miller-Donnelly, is to hang strips of Mylar or “anything shiny that could blow in the wind.”

Swallows migrate to South America every fall, making them long-distance migratory insectivores, which means they feed solely on insects, catching their prey in mid-flight.

They generally nest in areas near meadows and ponds where they can be seen catching insects on the wing and swooping low over the water’s surface to drink and bathe while flying. They are agile, swift flyers.

For more information about the Big Barn Study, go to and click the Big Barn Study “report a sighting” link.

The study runs until the end of June.

By Jean Perry


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