Swarming on a different level

Last week I began seeing Tree Swallows. They were returning after spending the winter in the warmer zones of Florida and down through Mexico. Yesterday, I witnessed something I hadn’t seen before. My mind immediately asked the question, “Is Tree Swallow swarming a thing?”

I looked it up, and learned that there is definitely something called Tree Swallow swarming, but it was nothing like what I saw. When Tree Swallows “officially” swarm it doesn’t happen where they breed. Rather, AllAboutBirds website states; “Migrating and wintering Tree Swallows can form enormous flocks numbering in the hundreds of thousands. They gather about an hour before sunset and form a dense cloud above a roost site (such as a cattail marsh or grove of small trees), swirling around like a living tornado. With each pass, more birds drop down until they are all settled on the roost.”

Although, it would be splendid to see such an event, it is not what I observed. Perhaps there’s a different name for the behavior I saw, which was still quite interesting in its own right.

First, I noticed a dozen or perhaps a few more Tree Swallows sitting on a utility wire on the west side of our west hay field. Below that wire, sits a nest box (#22) which, last year, was used by a pair of Tree Swallows that fledged two broods from that location.

I saw a pair of birds landing on the nest box, much like a pair of Tree Swallows does when they are considering it for the breeding season.

Soon, the birds from the wire above began to fly close to the couple on box #22 until, in my mind, I felt as if they were swarming the pair. Most of the remaining images don’t require additional words.

This next few photos shows what I believe to be the ‘primary’ female (clutching the hole opening) and chasing off another, approaching bird.

I suspect it’s the same ‘primary female’ that returns to the hole (it’s under a minute later when this next series was recorded.)

I posted a few weeks ago about a Mouse in the House issue we are having in the boxes on the east side of our property, two of which had been used by Tree Swallows last year. Yesterday, I checked again and the dang mice have rebuilt nests in three of the boxes on the east side. I have a plan to remove the boxes that the mice can access (they sit atop fence posts that the mice can climb), put up boxes that are mouse proof (off the fence and baffled) in the east. That will provide additional Tree Swallow housing there. And, I’ve designed some new boxes which will also accommodate Tree Swallows and Bluebirds that we can add to the western side and central part of the property.

If the seemingly territorial “swarm” I observed was due to limited nest sites, we can rectify that in the nest few days. I will say, that I did a box check yesterday and they are not nearly all occupied, but like all real estate experts will tell you is most critical to getting folks in the house: LOCATION LOCATION LOCATION!

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