Inspite of almost daily rain here most of the female Tree Swallows possessing boxes continue to gather nest material. Box 3, above, has reached what I call the 1/2 cup stage, with a substantial ring of grasses around the outside of the box bottom but quite a bit of bare floor still showing. Boxes 1 and 2 females are adding to their 1/4 cup nests, but at a rather slow rate. Box 4 seems to have stalled temporarily, but the Box 8 female has finally begun. Reading this, I wouldn’t blame you if you wondered if all the responsibilities seems to be falling on the females right now. Don’t the males share in the work?
Although they’re not doing the building, male Tree Swallows do have a role during the nest building. It’s pretty much the same one they’ve been playing since they first claimed their boxes – using calls, physical displays, and chases to defend their box against intruders – and here at Salmon Creek there certainly is an abundance of intruding floaters this spring.
A male that successfully prevents floaters from interrupting makes it easier for a female to devote her time and energy to gathering nest material. I think it’s no coincidence that at the Salmon Creek grid this year the boxes where nest building has lagged, Boxes 5, 6, and 7, are the same boxes where floaters are concentrating their takeover efforts. Along the east row, box defense, and nest building, have both been more effective.
Males also act as though they are genuinely “interested” in the females’ nest building activities. Males frequently peek in the entrances as if to monitor progress, sometimes getting in the way.
Males often give a soft, gurgling “Contact Call” as the female returns with vegetation, and may peek in the entrance and gurgle to her as she arranges things inside. It’s been suggested that this helps cement the “pair bond” between the two, and may “encourage” the female to keep up the good work, or at least to keep working. Sounds reasonable. To hear a YouTube video of this call click here: Contact Call or Gurgle.
And lest you think male Tree Swallows never contribute anything to the nest building effort, we should mention that males are the primary gatherers of one important nest component, feathers. And the first nest feathers at the grid appeared way back on 4/28, most likely brought in by the Box 1 male. We’ll have much more to say about feathering Tree Swallow nests in days to come.