Cliff Swallow

June 29, 2017
Cliff Swallow
Petrochelidon pyrrhonota

by Greg Hanisek, editor of The Connecticut Warbler
Where To Find It: The six species of swallows breeding in eastern North America all occur in Connecticut. Three of them – including Cliff Swallow – have specialized niches and as a result are scattered and uncommon as breeders. (The other two are Purple Martin and Bank Swallow).

Cliff Swallows attach their mud nests to vertical surfaces such as the walls of buildings and the sides of bridge girders, usually beneath some kind of overhang or covering. Most of the nesting occurs in the western part of the state, including on several bridges over the Housatonic River in Litchfield County.

But a well-known one is at Stevenson Dam between Oxford (New Haven County) and Monroe (Fairfield County). There are also scattered small colonies on barns and some commercial buildings at various places west of the Connecticut River.

When To Find It: Northbound migrants arrive in April and the last birds of the season usually depart by mid-September. A few straggle through in early October. Prime southbound migration occurs in late July and August. Nesting sites are most active from May through early July. Cliff Swallows winter in South America.

What It Looks Like: Key field marks include the buffy rump, the pale patch (like a headlight) on the forehead and the dark throat contrasting with otherwise white underparts.

The very similar Cave Swallow, a rare fall and extremely rare spring migrant, is most likely to be seen from late October to early December, when Cliff Swallows have departed our region.

To be sure about an identification, look for the smaller Cave Swallow’s buffy (rather than dark) throat. They also have a darker forehead than eastern Cliff Swallows.

Conservation Status: Cliff Swallow nests are sometimes usurped or destroyed by House Sparrows. Some people ignorantly – and illegally – remove the nests of Cliff Swallows because of concern about droppings or unsightliness, depriving themselves of the insect-eaters’ ability to help control local mosquito populations.Cliff Swallows occupy large colonies on cliffs in parts of the West. They were probably not widespread in the East prior to European colonization, but quickly adapted to nesting on barns and bridges by the mid-1800s.

Their decline to uncommon status in the East began with introduction of House Sparrows in late 1800s. When I lived in rural New Jersey, long-time birders believed that the increased practice of painting wooden barns, along with the use of metal structures, made it harder for the mud nests to adhere to those surfaces. While numbers have declined in the Northeast, a significant range expansion has occurred in the Southeast.

Of Special Interest: Birds of North America Online says: With House Sparrow control, local colony size can increase substantially; annual increases at one North Dakota site averaged 97% when House Sparrows were trapped. Removal of ectoparasites via nest fumigation can also result in colony size increases at some sites. Local increases in the number of birds nesting on barns in Massachusetts have occurred following installation of clay ledges on potential nesting substrates. However, whether any of the conservation measures actually increase total population size over time, instead of causing mostly redistribution of birds among sites, is unknown. Attempts to entice Cliff Swallows to nest in plaster nests at Mission San Juan Capistrano, southern California, have been unsuccessful to date.

Photo: Top, Don DeBold, and Ingrid Taylar, Carolinabrds.org