Purple Martins: The Largest North American Swallow

June 17th, 2024

As we approach summer, the Willits Bypass Mitigation Lands are a sight to behold. The lush green grass and thriving plants are a testament to the sufficient winter rain and balanced temperatures keeping the groundwater at a healthy level. This is a stark contrast to the drought years we’ve experienced in the past, instilling a sense of hope for the future.

The success of the eighth annual spring breeding bird survey demonstrates the strong spirit of our local community. We were fortunate to have a dedicated group of volunteers from Peregrine Audubon, making the survey a smooth and efficient process. While the final tallies have yet to be completed, initial findings indicate good bird diversity, albeit with a slight decline in the overall numbers. In line with national findings, this trend is something we need to monitor closely as we finalize the bird count.

Some exciting news is that Purple Martins have been nesting in the viaduct cavities for the past three years. It started with a couple of pairs, and this year, we may have up to ten pairs. The Purple Martin (Progne subis) is designated as a Species of Special Concern by the California Department of Fish and Wildlife because of substantial declines in its numbers and geographic range (Shuford and Gardali 2008; Airola and Williams 2008). This decline began in the 1980s due in part to the increase in the European Starling population. Starlings are also cavity nesters and arrive here in the early spring, since they don’t migrate to faraway places like the Purple Martins that travel to South America for the winter. So, the starlings take many available cavities before the swallows arrive back from their homelands for nesting.

Luckily, these native swallows have chosen the viaduct outside of the MCRCD office on East Commercial to nest in. These drainage vents are not easy for most birds to fly in and out of. Observing the swallows, it takes a strong acrobatic flier to swoop straight up into the holes. It is fun to watch them do this repeatedly throughout the day. Every morning, the sweet sounds of these large swallows surround the parking lot, and they are easily seen from the road.

The western Purple Martin subspecies has a few habits that differ from the eastern subspecies. One major distinction important to note is that western populations do not prefer to nest in the traditional martin birdhouses and instead choose cavities in trees or bridges instead. The highway viaduct also harbors another species of cavity-nesting swallow that is doing quite well, the Northern Rough-winged Swallow. Since I have been observing birds on the mitigation lands, the Northern Rough-winged has had a robust population.

There is always something outstanding to observe and admire in the natural world if one takes the time to slow down and take it in.