By Kris Cu, BC Outreach Specialist and Rémi Torrenta, BC Projects Coordinator
The year is 1901 and you are a naturalist hiking along a sea cliff in California. You stumble upon a nest with an unfamiliar egg and send it to an ornithologist for identification. You don’t know it at the time but what you found was the first ever scientific record of a Black Swift nest. This is exactly what happened to A.G. Vrooman and after nearly 120 years, the life cycle of this species is still shrouded in mystery.
Black Swifts are aerial insectivores that build their nests along steep waterfalls and damp canyons. The inaccessible location keeps their chicks safe from predators while providing constant temperature and humidity to the nest. During the day, Black Swifts fly high up in the sky and appear as tiny specs as they feed on winged ants and flies. Their unique life history and behaviour makes them especially difficult to study.
Black Swift on nest. Photo: Kris Cu
Black Swifts are also known as “Cloud Swifts” because they can fly to an altitude of almost 4,000m during full moon cycles. This behaviour is thought to coincide with better foraging opportunities and predator avoidance. During the non-breeding period, these birds have also been documented to stay airborne for up to eight months, a behaviour called aerial roosting. This unique flight adaptation uses a “flap-gliding” technique as opposed to the traditional “continuous flapping” approach used by most birds. This helps Black Swifts conserve energy and remain in the sky for longer periods of time.
One mystery remains: why have Black Swift populations declined by over 90% since the 1970s? The species is listed as Endangered under the federal Species at Risk Act and is blue-listed under the provincial BC Wildlife Act. Canada is home to around 81% of the North American Black Swift population.
To determine new nesting locations in BC, monitor nests, and assess potential causes of decline, our team surveyed over 20 waterfall sites and found a total of 10 nests during the 2022 field season. In 2023, we surveyed 12 waterfall sites and monitored a total of 10 nests, including a few new ones. The work was incredibly challenging and involved hiking through some of BC’s most beautiful, but rugged, terrain.
Rémi Torrenta, BC Projects Coordinator Photo: Kris Cu
Field crew monitoring nest. Photo: Kris Cu
Black Swift Photo: Roger Beardmore
Our video “Of Waterfalls and Wings” provides viewers a first-hand experience of what it’s like to join Birds Canada biologists in the field. We search for nests that are hidden between mossy ledges on the canyon walls. We also shed some light into the mysterious life of the Black Swifts. We hope you enjoy the short film and help us spread the word about these incredible but endangered birds. Our new research paper about a Black Swift colony we monitored in 2022 (the first colony documented in BC’s coastal region!) will be published online this month in the journal British Columbia Birds.