What’s Happening This Week During the Nesting Season: July 6

By Dan van den Broek, Educator & Naturalist-in-Residence

As we spend more time at home and in our gardens, neighborhoods, local parks, and green spaces, we want to highlight seasonal bird activity you can expect to see during the breeding season. Join us each week as we show which birds to look out for in your neighborhood and highlight other nature events throughout the year. 

In July many resident and migratory birds are tending young, mostly fledglings out of the nest. This week, we will look at two cavity nesting swallows. They are just finishing up the breeding season and fall migration is just weeks away.

Species to Watch for This Week

Violet-green Swallow

The Violet-green Swallow is a familiar sight over fields, open spaces, along water-ways and wetlands. They stay close to water early in the spring then move into mountain clearings and other open areas as the weather warms in May. Only found in Western North America, the Violet-green Swallow is an acrobatic flier, and an amazing hunter of flies, gnats, mosquitos, beetles, flying ants, and even bees and wasps. Pairs choose a tree cavity or artificial nest box in April or May, and fill it with grasses as well as a thick top layer of feathers that they find while foraging, often from ducks and geese. Pairs incubate four to six eggs for about 15 days. Once hatched, females bring more than 80% of the food to the young. At about 24 days old, chicks venture out of the nest. If started early enough, Violet-green Swallows occasionally have a second brood.

Beginning in July and lasting through September hundreds and sometimes thousands of young and adult Violet-green Swallows congregate along power lines and fences, initiating fall migration.

Violet-green Swallow, photo by Scott Carpenter

Tree Swallow

The twittering bubbly call of the ubiquitous Tree Swallow is a common sound by rivers and wetlands across North America. Nests are constructed in tree hollows such as old woodpecker cavities and nest boxes put up in many public areas and backyard gardens. Mostly insectivores, Tree Swallows will eat a variety of fruits, especially if insects are hard to find, such as in fall and winter. Tree Swallows begin nesting In April when they bring grasses and assorted vegetation into a cavity.  They line the cup of the nest with soft fibers, fur, and feathers.   

Pairs incubate between 5-7 eggs for about 14 days, but that timeline can increase during inclement weather. The young fledge anywhere from 18-22 days after hatching and parents continue feeding for 3 or more days after they leave the nest. Tree Swallows that nest in the Willamette Valley will often have a second clutch.

Local breeders begin heading south between late July through mid-August. Most Tree Swallows from north of our area pass through in August and early September.

Tree Swallow, photo by Keith Williams