Cliff swallows are a type of small migratory bird found across North America. They are known for building mud nests on vertical surfaces like cliffs, bridges, and buildings. Their populations have declined in recent decades, leading some to wonder if they are endangered.
What are Cliff Swallows?
Cliff swallows (Petrochelidon pyrrhonota) are passerine birds in the swallow family. They are found across most of North America. Cliff swallows get their name from their habit of building cone-shaped mud nests on vertical surfaces like cliffs, caves, bridges, and buildings.
These social birds gather in large colonies numbering in the thousands. Colonies form at nesting sites and provide protection from predators. Cliff swallows migrate long distances, wintering in southern South America and returning to North America every spring to breed.
Cliff swallows have blue-black feathers on the head, wings, and tail, with a pale orange forehead and rump. They feed exclusively on flying insects like flies, bees, wasps, and beetles, which they catch in flight. Their wide mouth and small beak is well-adapted for catching insects.
Are Cliff Swallow populations declining?
Many sources indicate that Cliff Swallow populations have been in decline, especially since the 1980s. The species is not considered globally threatened, but some local populations are shrinking or have disappeared entirely.
According to the North American Breeding Bird Survey, Cliff Swallows declined at a rate of 1.27% per year between 1966 and 2015. Their total population loss during this period was estimated at 31%. Other surveys have also noted steep declines in Cliff Swallow numbers.
A variety of factors may be contributing to the reduction in Cliff Swallow populations, including:
- Reduction in suitable nesting habitats
- Declines in insect prey populations
- Increasing severe weather events
- Pesticide use reducing insect numbers
- Negative impacts from invasive species like House Sparrows competing for nest sites
While more research is needed, it appears that habitat loss and diminished food supplies due to human activities are the primary drivers of Cliff Swallow declines. Their reliance on vertical nesting surfaces and aerial insects makes them especially vulnerable.
Cliff Swallow conservation status
The Cliff Swallow has been categorized as a species of Least Concern on the IUCN Red List of Threatened Species. This indicates it does not qualify as globally threatened with extinction at this time.
However, the Cliff Swallow has been designated as endangered, threatened, or a species of special concern in several U.S. states including:
- California – Species of Special Concern
- Connecticut – Endangered
- New York – Threatened
- South Dakota – Threatened
At the federal level, the Cliff Swallow is protected under the Migratory Bird Treaty Act which prohibits harming or killing the birds, their nests, or eggs. But there are currently no special nationwide protections or conservation plans.
Why are Cliff Swallows declining in some areas?
The specific reasons for Cliff Swallow declines are not fully understood, but likely involve multiple interacting factors including:
Habitat loss
Cliff Swallows rely on vertical nesting surfaces, and human activities have reduced suitable sites. Destruction of cliffs, changes in bridge designs, and sealing or closing openings in buildings removes potential colony locations. Increased urbanization also plays a role.
Reduced food supply
Cliff Swallows feed entirely on aerial insects. Pesticide use, loss of wetlands, and other habitat changes have diminished flying insect populations in many areas leading to less food for swallows.
Extreme weather
Severe storms, flooding, and drought can destroy nests and kill many Cliff Swallows at once. Climate change may be increasing extreme weather events.
Invasive species
House Sparrows and European Starlings compete with Cliff Swallows for nest sites. These aggressive invasive species take over nesting colonies and reduce swallow reproductive success.
Mortality during migration
Cliff Swallows migrate thousands of miles between North America and South America. Hazards during migration like storms, lack of habitat, or collisions with structures may be increasing mortality.
Can Cliff Swallows recover?
It is possible that Cliff Swallow numbers could recover if some key actions are taken for conservation:
- Protecting and creating nesting habitats
- Controlling invasive species
- Reducing pesticide use
- Maintaining adequate insect populations
- Educating the public to appreciate swallows
Government agencies, conservation groups, and property owners may all be able to assist with Cliff Swallow conservation. While globally secure, targeted efforts are needed to reverse declines before subspecies or local populations become extinct.
Conclusion
Cliff Swallows have experienced concerning population declines since the 1980s, according to data from surveys that monitor bird numbers. Habitat loss, lack of insect food sources, severe weather, invasive species, and mortality during migration are likely contributors to the reduction in Cliff Swallow numbers.
While not currently considered a globally threatened species, Cliff Swallows are endangered or of special concern in several U.S. states. Targeted conservation action is recommended to protect nesting habitats, control predators, maintain insect prey populations, and mitigate climate change impacts. With appropriate effort, it may be possible to reverse declines and recover Cliff Swallow numbers.