Received a call about a bird issue at a church/school. Sort of like the movie "The Birds", the site was suddenly overrun with birds. They told me the birds were "hanging" on the bricks, so I had them send me a picture. My original thought was maybe Chimney Swifts were fledging, but the picture seems to show a bunch of swallows. Has anyone seem this behavior (sudden appearance), and will it quickly diminish, or what's going on here? I've done a lot of bird work over the years, but have never seen this before.

Ron, we had something similar ( but not quite that many ) on a large house with similar construction, many years ago. If I remember correctly, they were swallows and built mud nests. I think my son put up those angles that took away the corner and the problem was solved. Sorry I can't be more help but it wasn't my job.

Years ago I saw something similar at an apartment complex. Turned out to be an insect infestation that was attracting the birds.

Cliff swallows? I recently saw a photo on the web, west coast iirc, where they had lined an entire home with mud nests at that junction. The solution was the angle boards.

Just did a job today where lady customer said there were at least 18 birds hanging on stone wall of her house. Also had a nest (probably barn swallows) on inside top of stone arch.

I've seen MANY structures with 25 to 75 nests under the soffit overhangs. There are NO nests here. The birds showed up within a matter of an hour or two. This is not a nesting problem. I've dealt with plenty of situations with nesting issues. This one is just plain weird. Possibly an attraction due to insects of some type, or maybe a nearby demolition job going on. Building or bridge work? I'm 120 miles away, so not able to "go look" very easy.

Ron, I'd bet a pretty large wad of cash that this is tied to a colony displacement at a major site. If they are cliff swallows en masse they need to go somewhere when displaced and a typical bridge even a small one has as you know hundreds of them if not thousands on a larger structure.

Though the feds require the activities of exclusion on bridges and other structures to only be done with the nesting season in mind and so forth to net the structure off, etc... there are going to structures that slip through the cracks...

Our swallows are well into the nesting here, both barn and cliff, if they were displaced during this, though you'd think they'd move and mud a new place, it might be too late so they are just moving to a location to "decide" what to do next.

I could see how an insect infestation could cause a flocking since they do communicate food sources to the rest of the flock, but much of their food is aerial hawking type prey, so on the building would they be as likely to find the food as a woodpecker or other bird used to this type of foraging would?

SGS, what kind of infestation did the folks have in your case years ago, just curious, swallows are amazing builders and the tenacity to build that nest is admirable, though causes folks lots of grief in dealing with the messes and of course permits and delays in the construction world.

Interesting topic...

Ants. These were winged ants of some sort. There was a fair amount of damage to the rafters so it was probably carpenter ants.

Thanks SGS, interesting case!

Termites?