1. A mud source: Since Cliff Swallows construct their nests out of mud, a mud source is an important habitat feature. Farming activities and livestock create readily available mud, but with the decline in small farms and agriculture in general in the northeast, there is less mud available at nesting sites. Cliff Swallows are attracted to mud, and the bigger the puddle, the better.
2. Artificial clay nests: Cliff Swallows are very attracted to previous years’ nests, which save time and energy that otherwise would be in the construction of a new nest. We have developed nests made of fired stoneware clay; the nests are durable, breathable, and realistic. They are made to varying degrees of completion, which also mimics natural conditions.
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, which describes the effect of House Sparrows on nesting Cliff Swallows in Massachusetts here.)
4. Social attraction: Cliff Swallows are extremely social, they nest in groups and nesting activity tends to be synchronized. Thus the sounds of breeding calls are very attractive to a passing Cliff Swallow.
There are other factors in addition habitat loss that are negatively impacting Cliff Swallows. In spite of these factors, we have found that by improving habitat at the nesting site, breeding success can increase at a given site. (Data from Shelburne, MA).
We have attracted Cliff Swallows to a previously-unused site only at our pilot study site and note that Cliff Swallows abandoned our site after 2018. At other sites that previously did not have Cliff Swallows we saw similar results; at one, Cliff Swallows visited the site but did not nest. At the others Cliff Swallows were not successfully attracted, even as visitors. There may be habitat factors that are important or adverse to swallows that we can't detect at these sites. We have had the most success attracting Cliff Swallows to existing active sites and to recently-abandoned sites, and it is at these types of locations that we focus our efforts.
Pittsburg, NH, 2016. Project in collaboration with New Hampshire Fish and Game. Left: five artificial clay nests were installed at colony where house was going to be repainted; right: Cliff Swallow adding mud to one of the artificial nests installed at the site.
Rowe Town Hall, MA, 2017-2021. Project in collaboration with Town of Rowe. Left: Cliff Swallows were building nests with sandy mud and nests kept falling. Right: After installation of 15 artificial clay nests, Cliff Swallows nested successfully. Shown are two nestlings almost ready to fledge from artificial nest. This colony has increased in size annually. In 2021, 45 artificial nests were installed and all 35 pairs that nested at the site used artificial nests.
Artificial nests were installed under two bridges in Berkshire County, MA in 2020 at active Cliff Swallow colonies. At these sites, because there was no substrate to which attach nests, we first attached nests to wooden planks, created a roof overhang, and strapped the boards to the metal rebar of the bridge. Cliff Swallows readily use these nests.