Purple Martin Bird Monitoring

This July, the Land Trust stewardship team, led by Monitoring Scientist Cindy McCormack, completed their annual Purple martin nestling count at a conserved wetland along the Elochoman River.

Each year, we install gourds in April or early May when the migratory Purple martins (Progne subis) return from South America. There are two towers with 33 total gourds, which are made of a thick white plastic, to reflect sunlight and prevent overheating in summer. These human-constructed gourds provide nesting cavities in places where large, natural tree cavities are scarce. The martins prefer riparian, coastal, or burned areas with open space nearby and plenty of flying insects. They often feed on dragonflies, wasps, beetles, flying ants, and butterflies. Because of development, industrial forestry, and other habitat loss, this type of landscape is increasingly rare.

The martins fill the bottom of the nesting cavity with grasses, straw, and small twigs and build a mud dam between the entry and the nest bowl. In the final stages of nest building, they will line the bowl with fresh cut leaves. The female will lay one egg a day, but won’t start incubating until she lays the penultimate egg, so these eggs feel cool to the touch. Once incubation starts, the eggs feel warm and it takes a little over two weeks for them to hatch.

With 33 available gourds, we collected data from 23 occupied nests, which is about a 70% occupancy rate!
• 12 gourds with cold eggs, which indicates that laying is likely still in progress
• 3 gourds with eggs being incubated
• 8 gourds with nestlings

In total there were 36 nestlings, and the oldest nestling at the time of our visit we estimated to be about 11 days old.

“Not all Purple martins are purple—just the adult males—but they are beautiful birds. Their vocalizations are my favorite. It’s a rich mix of chortles, gurgles, and whistles and you can’t help but smile when you hear them,” said Cindy.

This work was performed under a permit issued by Washington Department of Fish and Wildlife (WDFW) as part of an effort to evaluate the status of Western Purple martin in Washington.