Counting Swallows

By Terry Rich, GEAS Guest Blogger

Two years ago, the Idaho Bird Conservation Partnership launched the Swallows and Bridges community science project. The goal of this project is to inform residents of the Treasure Valley about declining populations of aerial insectivores and provide suggestions for how people can help reverse the trend. These bird species live by catching insects on the wing and include swallows, swifts, and nightjars.

Because two species of swallows – the Barn Swallow and Cliff Swallow – routinely nest under bridges in southwest Idaho, we saw an opportunity to engage even the most casual birders in collecting data. Volunteers could visit bridges in their neighborhoods and count the swallows. The Ada County Highway Department graciously provided a GIS map of the 831 bridges and large culverts in Ada County, each of which might be a nesting location.  

Heidi Ware-Carlisle at the Intermountain Bird Observatory quickly designed a phone-based Google Form for volunteers to use when checking any bridge for the presence of swallows. GEAS volunteers and others registered for the project and went to work checking bridges and reporting what they found. Valuable data was reported for months while the swallows were in town.

Barn Swallows by Terry Rich

What Happened in 2023?

Volunteers across Ada County gathered data during the 2023 breeding season. Each volunteer selected which bridge(s) they would visit and set their own visit schedule. The first-year participation was fantastic with the following data reported.

207 – visits to bridges in Ada County

  20 – different observers provided input

180 – different bridges inventoried (22% of total of 831)

            89 – bridges with swallows

            91 – bridges without swallows

            87 – bridges with Barn Swallows (maximum count = 24)

            37 – bridges with Cliff Swallows (maximum count = 100)

            26 – bridges with both species

  27 – visits with unidentified swallows

Barn Swallows are clearly the most common species while Cliff Swallows tend to occur in higher numbers when they are found. Note that reporting unidentified swallows is also very useful because we are just trying to figure out which bridges are useful to some species.

Next Steps Include Education

There are several next steps needed to begin the important education and action component of the project.

1) It will be useful to look more closely at the characteristics of the various bridges – length, width, height over water, type of material, canal vs river, and many other attributes – to see if there is a pattern in occupancy. We can also look at the surrounding land use, soil types, and other factors that we can get from GIS layers.

2) We will design educational signs, like those in Boise City Parks, to place on bridges where swallows occur and there is high human foot and bicycle traffic. The objective will be to inform visitors about swallows and how reducing pesticide use, planting native vegetation in yards, and maintaining natural vegetation elsewhere can help these birds.

3) We will recruit volunteers again and visit more bridges during the 2024 breeding season. Even a very casual birder can quickly learn to identify swallows, and the particular species doesn’t really matter right now. We just want to find the “good” bridges. Watch for a “heads up” alert next spring!

Contact Terry Rich at swallowsandbridges@gmail.com for more information or to submit ideas and ask questions!