Saw a sparrowhawk trying to break into the house martin nest under the eves of the house opposite to me the other day. I did not see it fly up to the house, so do not know if it chased an adult martin up to the nest or whether it has just found an easy way of making a living. This time it was unsuccessful as it came out from the eaves and sat on the roof, Looked like a juvenile male from the comfort of my armchair (bird watching made comfortable)
I have seen sparrowhawks take many prey over the years, one crashed into a larch tree containing crossbills just 10 feet above my head once, and seen several blackbirds taken, once saw a femail hit a wood pigeon but never trying to gain access to a house martin nest.
I would not expect a martin on the wing to be easy prey for a sparrowhawk.
Any thoughts
I wouldn't be surprised if it's seen them coming and going whilst it's perched up and figured it would try for an easy meal. I've heard of them occasionally catching Swifts flying close to the ground so they may go for a House Martin if the opportunity arises. I've only seen them take perched birds myself - maybe it's seen a young House Martin poke it's head out of the nest?
The nest in question is well hiden under the eves of the house opposite so I would doubt if a young Martin would be spotted, The House martins on on My side of the road (south facing) tend to favour nesting on top of the Burgler alarms and the youngsters are quite visable and noisey for that matter.I agree that the only times I have seen a successful "Catch" has been from birds perched on the ground. I once saw one chase a song thrush over Guisborough Cricket field for about 50 yards before admitting defeat.
You usually hear the hit rather that see it, then the Hawk just seams to stand on the prey and look around with a smug expression as if to to say "look at what I have just done"