In the Northeastern part of the North America, Cliff Swallow populations reached their peak with the peak of farming, and when farming began to decline, so did the swallows. Farms provide the habitat this species requires: mud for nest-building, open fields for foraging, and barns and other outbuildings to which the swallows attached their mud nests, most commonly under the eaves.
Through many years of observation and experimentation we have found that Cliff Swallow breeding success increases with the implementation of management techniques that mimic habitat lost with the decline of agriculture in the Northeast:
1. A Mud Source: Cliff Swallows are attracted to sticky shiny mud, and the bigger the puddle, the better. Additionally, adding natural clay to the mud improves the consistency, making nests more durable. Note: The addition of clay does not prevent nests from falling, which is a problem at many sites.
2. Artificial clay nests: Cliff Swallows are very attracted to previous years’ nests, which save time and energy that otherwise be used in the building of a new nest. We have developed nests made of potter's clay and fired; the nests are durable, breathable, and most importantly, realistic. They are made to varying degrees of completion, which also mimics natural conditions. Partially-completed nests are often used at established nesting sites, and complete nests are used when attempting to attract swallows to a brand new site.
3. Reduce competition from House Sparrows: Cliff Swallows cannot compete with House Sparrows, which are a non-native, aggressive cavity-nesting species that takes over nests, ejecting adults, eggs, and young. (View our 2021 article on the effect of House Sparrows on nesting Cliff Swallows in Massachusetts here.)
4. Social attraction: Cliff Swallows are very social, nesting in groups, with nests tightly clustered. The sound of breeding calls is very attractive to a passing Cliff Swallow.
Currently there are other factors in addition habitat loss that are affecting Cliff Swallows. However in spite of these factors, we have found that by improving habitat, breeding success can increase at a given site (Data from Shelburne, MA).
Note that there were no active Cliff Swallow nests in 2018. We have had the most success attracting Cliff Swallows to existing active colonies sites and to sites where Cliff Swallows previously nested (but are now abandoned). There may be habitat factors we can't detect that are important or adverse to swallows at these sites. We have attracted Cliff Swallows to a previously-unused site only at our pilot study site in Western MA. We have been taking what we have learned at our pilot study site and applying it at other sites.