Neighborhood Bird Project Report Species Highlight #5: Cliff Swallow

Cliff Swallow | Ryan Leimbach | Audubon Photography Awards

This article is based on our report Fewer and Fewer, which pulls from findings of the Neighborhood Bird Project. 

A common spring migrant to the Seattle area, cliff swallows are the epitome of community-centered living. From migrating to roosting, to feeding, to nesting, these aerial insectivores are rarely seen alone. 

The hyper-social behaviors of cliff swallows come with many advantages. Migrating together allows them to have many eyes on the lookout for predators on their long journeys. Roosting together keeps them warm, and nesting in colonies allows for community parenting. This community-minded behavior goes beyond just sticking together, as they’ve also been observed communicating with other members of their flock when abundant sources of food have been located, ensuring the health and well-being of the whole. 

Their nest colonies can consist of thousands of gourd-shaped mud nests, built along mountain cliffs, or in more urban areas, under bridges and eaves of large buildings. One such colony was a common sight at Magnuson Park, up until 2010. Roughly 100 cliff swallow nests were located under the eaves of Building 27, at the north end of the park. Renovations to welcome the current tenant of the building, Arena Sports, led to the removal of all the nests and installation of screening to prevent future nesting behaviors. 

 This singular, fateful decision is likely the cause of a near wipe-out of cliff swallows at the park. Prior to the nest removal, about two cliff swallows were spotted per survey on average by Neighborhood Bird Project participants. Since the removal of the nests, however, cliff swallow counts at the park decreased by 96%. While cliff swallows are not considered species of concern as a whole, this shows how fragile bird survival can be in urban areas. 

Cliff Swallows aren’t the only birds that commonly use human structures for nesting. Dark-eyed Juncos, American Robins, Bewick’s Wrens, European Starlings, and Barn Owls all regularly nest in, around, or on homes and buildings. 

Modern building design and management practices seek to exclude birds from nesting, which may negatively impact species that nest on human structures. The destruction of mud nests at Building 27 in Magnuson Park and the subsequent crash in Cliff Swallow counts is a poignant example. But coexistence is possible, as demonstrated by Seattle City Light’s support of Osprey nesting on light poles and even building dedicated nesting platforms.  

Recommended actions: Find ways to accommodate nesting while managing genuine human-wildlife conflicts and promote policies and practices that follow the Osprey example. We can also learn to recognize signs of nesting behaviors around our homes, and practice patience during nesting seasons. It’s a temporary nuisance, and we can see it as an opportunity to help future generations of urban birds.