Chimney swifts return in smaller numbers

One of nature’s most dazzling aerobatic displays is shrinking.

The chimney swifts have returned for another season and volunteers throughout Nova Scotia have been anxiously counting, hoping to prove the province wrong. Nationally, numbers have dropped at least 30 per cent in the past 13 years, prompting the Department of Natural Resources to classify them as endangered.

Claire Diggins, of Middleton, said she began monitoring the chimney swifts in 2003. She is one of several people who have been closely watching over these rare birds, helping to compile data for the province.

Other volunteers in Wolfville, Truro, New Glasgow and Oxford gather nightly and note the numbers of swifts, carefully recording details such as time, temperature, weather conditions and cloud cover.

A few weeks ago Diggins counted 317 swifts entering the chimney at Middleton Regional High School- the largest group seen so far this year in the Valley- but these numbers are drastically down. “About three years ago, I counted over 1000 here in one night,” she said. The Middleton colony has survived its share of adversity. A merlin hawk harassed the nest a few years ago, killing swifts as they entered the roost. Inclement weather patterns have also impacted their numbers.

Aside from noticing fewer numbers, the birds’ behavior has also changed over the past few years, according to Diggins. The large flocks always seemed to move in unison, but now they seem to straggle in twos. “They used to funnel inside the chimney during the last five minutes, now it’s more sporadic,” she said. “This is something people should see. I don’t know what signals them, but they gather at the same time. Some go in right away; others veer-off as if to say, ‘well maybe just one more time around.’”

While they remain out of sight and airborne throughout the day, each night they gradually gather around the chimney, circle it and then drop inside like reversing smoke.

Diggins’ observation of the low numbers is consistent with the province’s 2007 decision to include the chimney swifts on its list of endangered species. It’s now estimated that the numbers of chimney swifts have dropped to about 1000 across the province.

The reason for their decline isn’t clear, but biologists believe changes in insect populations, reduced habitat, and climate change all play a factor in the swifts’ low numbers. Historically the birds once roosted in hollowed-out trees, but modern forestry practices cull most of that natural habitat.

In response, the swifts have adapted by switching their roosts to tall, freestanding man-made structures such as chimneys. Chimney swifts don’t perch, instead they use deep shafts to raise their young and roost at night.

Diggins added that Middleton is very fortunate to still have these birds coming in relatively good numbers. There are now only about three known colonies in the Annapolis Valley, this is down from four last year.

The next largest colony is in Wolfville at the Robie Tufts Nature Centre, where between 40 and 90 swifts have been counted this season. Two smaller roosts, one in Falmouth and another in Bear River, are also monitored.

While the numbers in Falmouth seem higher this year, about 100 one evening; the Bear River colony has all been decimated. A new chimney liner was installed at the Oakdene Center and while a few hundred swifts once roosted there, volunteers have only spotted about two so far this year.

Middleton’s chimney was nearly torn down in the early 1990’s as part of a renovation project at the high school. Sylvestor Atkinson, a former teacher and past mayor, was able to stop the renovation and preserve the chimney and the colony. “It could have slipped through our fingers,” Diggins said. One of the marvels about this species is how far these small birds are able to fly. There are more than 70 types of swifts in the world, but only four of them are found in North America.

The chimney swifts spend the winter in Peru and return to North America each May to begin nesting. They travel hundreds of kilometers each day in search of food. It’s estimated they eat more than 1,000 insects per day, caught mid-air.

At around 8:30 p.m. the birds return to the roost for the night. The numbers fluctuate nightly and seem to depend on weather conditions. Shortly before sunset they perform an amazing aerial display of acrobatics and interaction around the chimney.

Diggins said she finds them fascinating to watch and admires how resilient this species is considering all the human activity and hubbub that can happen in the parking lot of the school. The parking lot can be filled with people attending the graduation and still the birds gather for their nightly show. “From about age two, they mate for life,” she said. “And the flock’s relationships are so mysterious. How they all just suddenly decide to funnel inside together. Imagine what the inside of that chimney must be like with 1000 birds inside.”

She added that for all they’re watched, chimney swifts are not well understood. Like other birds, she adds they have a resiliency and a determination she admires. “Birds will die trying to raise their babies,” she said. “It takes two parents and if one parent dies, the other will die of exhaustion trying to make up for the partner.”