Hello, saw a bird this morning, it was either a swallow or a martin but I couldn’t figure it out. Was starling-ish size, long triangular wings and had a section of bright white on underneath but dark overall. Flew in a fluttery manner, changing direction a lot. Any ideas? Thanks, Ellis
Without a photo (which can be incredibly hard to get with some birds in flight), its hard to say.
If you can get a look at the tail, Martins tend to have a short forked tail with wider span while swallows are longer forked tails.
Using photos available from a good bird book, that's probably the easiest way to ID the bird in flight.