I had a similar experience with swallows a number of years ago up in Shoreline. I had been watering the lawn over a dry Memorial Day weekend (we have those occasionally) and noticed that as soon as a puddle formed at the end of the property a pair of Barn Swallows started gathering mud. I remembered that there was a bag of feathers in the basement for an as-yet-started pillow project of my mother's and I decided to donate some to the swallow's cause.

Within about 10 minutes I had 2 pairs of Barn Swallows and 2 pairs of Violet-green Swallows collecting feathers for their nests. About 20 minutes later I noticed a pair of Northern Rough-winged Swallows perched on the wire above all the activity. What's interesting is that rough-wings don't even line their nests with feathers! I think they were attracted to all the swallow activity, assuming it was a feeding flock that they could join.

Mike Donahue
Beacon Hill, Seattle