Blue-gray gnatcatchers returned to Pennsylvania in April and set up shop immediately. As one of the earliest nesting insectivores they began courtship and site selection right away.
Nest-building is part of blue-gray courtship. Both the male and female build the nest and they make a lot of noise and exaggerated bows when they begin. Meredith Lombard trained her camera on a nearby nest and filmed this pair's efforts. (Click on the image to watch the video on Meredith's Flickr site.)
As you can see in the video, the nest is slightly expandable because it's built on an elastic skeleton of spider webs and tentworm silk. In the early stages of construction I've seen gnatcatchers chatter near decayed fall webworm tents, grab the silk and anchor it to their chosen site. Later they poke the sides of the nest and stick in new bits of lichen and bark. They also drag the silk upward to make the nest cup.
All of this activity makes them easy to find and watch. Cowbirds watch them, too. On Sunday I saw a pair of gnatcatchers harassing a female cowbird. I hope they're able to keep her away from their silky nest.
(video by Meredith Lombard)