We have barn swallows in our barn and based on circumstantial evidence, we think that a red squirrel killed a nest full of very young swallows.  The squirrel had a nest in the second story of the barn and there were several hatchlings on the floor under the swallow nest.  For years we had a platform under the roof of our front door entrance, but had to take it down because  “something” kept killing whoever was using it (swallows or phoebes). 
Janet Warren, Cornwall
> On May 16, 2019, at 10:18 PM, David J. Hoag <[log in to unmask]> wrote:
> 
> Arriving home at 12:30 Thursday I noticed that both Phoebes were off the nest — one phoebe perched — one flying back and forth; and I thought it would be an opportune time to check on the eggs.
> 
> I found two Red Squirrel tails hanging off one corner of the nest; one tail was inert — one was frequently twitching, although with no reaction when tapped with my nest mirror. I pushed the mirror over the nest. One squirrel jumped to the ground. I raised the mirror again. The second squirrel jumped to my arm and to the ground.
> 
> All six eggs were still intact. I doubt the eggs lost any heat with two young(?) squirrels jammed into the nest as surrogates/incubators!  A phoebe was back on the nest within a minute and was still incubating at nighttime.
> 
> 7 PM: Continuing .... Two small squirrels were entangled on the deck on the other side of the house; one carrying the other beneath it across the lawn, back to the deck, up the wall and jammed between the downspout and the wall. At 6 AM the two also had been hyperactively chasing each other.
> 
> Dave Hoag, Grand Isle