Cliff Swallows and Pest Management
Some people consider Cliff Swallows (Petrochelidon pyrrhonota) pests! I know it sounds strange, especially when the folks at Mission San Juan Capistrano are trying to coax them back by playing recordings of the bird’s mating calls.
Because I am a local Audubon board member, I was recently contacted by a bird lover who witnessed Cliff Swallow nests being destroyed at the marina where they dock their boat. He and his wife had enjoyed the swallows for several years and they were appalled that the marina management were destroying them.
Cliff Swallows migrate to North America from their wintering grounds in South America to nest in large colonies, sometimes numbering in the thousands. They build enclosed gourd-shaped nests made of mud pellets which are attached to vertical cliff faces, entrances to caves, under eaves of buildings, under bridges, in highway culverts, and under overhangs on dams.
Cliff Swallows arrive at nest colonies in successive waves led by birds that previously nested at that site, followed by adults who bred at other colonies in previous years and by young birds who have not yet bred. In addition to their homing tendency, breeding swallows are attracted to old nests. Under suitable conditions, a nest is quite durable and can be used in successive years. Old nests are usually claimed on the first day of arrival, although probably not by the original makers. Dilapidated nests are quickly occupied and repaired1.
Herein lies the problem. All swallows are included under the Migratory Bird Treaty Act of 1918 as migratory insectivorous birds and as such are protected by state and federal regulations. It is illegal for any person to take, possess, transport, sell, or purchase them or their parts, such as feathers, nests, or eggs, without a permit. As a result, certain activities affecting swallows are subject to legal restrictions1.
The term “take” is defined as killing a listed species but also includes “harm,” which is defined in regulation as including “significant habitat modification or degradation where it actually kills or injures wildlife by significantly impairing essential behavioral patterns, including breeding, feeding, or sheltering2.
In California, the Cliff Swallows usually arrive in February so the agency in charge of enforcing these laws, the California Department of Fish and Game (CDFG), considers February 15th to September 1st the swallow nesting season. Completed nests during this breeding season cannot be touched without a permit from the U.S. Fish and Wildlife Service. Outside of these dates, the nests can be removed without a permit1.
Ok. This seems pretty straight forward to any thinking individual. If you don’t want Cliff Swallows nesting on your property, remove their mud nests after the birds leave in September or before they arrive in February. Because IT IS ILLEGAL TO INTERFERE WITH NESTING BIRDS!!
You can download the information on controlling Cliff Swallows in PDF format from the University of California here. In the meantime, if you are like me and you enjoy watching Cliff Swallows, here is a video I shot of a colony nesting under a bridge over Cow Creek in Shasta County.
Near the end of the video, watch closely and you will see the swallow at the top, in the middle of the frame, grabbed by the beak and pulled right out of the nest! I wonder what that’s all about?
References: 1University of California Agriculture and Natural Resources, Statewide Integrated Pest Management Program, June 2005. Authors: T. P. Salmon, UC Cooperative Extension, San Diego Co.; and W. P. Gorenzel, Wildlife, Fisheries, and Conservation Biology, UC Davis
Produced by IPM Education and Publications, University of California Statewide IPM Program
2Migratory Bird Treaty Act of 1918