Crow or Great Black Hawk (GBH)

[h2y]

Crows are easily mistaken for GBHs because they are similar in size and both appear solid black but there is a distinction: the GBH has a white band on it's tail, which is especially noticeable while in flight.

Huge difference: like all raptors, GBHs grab their prey with long, strong legs with talons so they can latch onto a column, etc with one leg & secure any age martin with the other.
Meanwhile, crows grab their prey with their beak. A mere songbird, with relatively short, twig-like legs with "perching" claws, not talons, they are incapable of the above feat. Not completely innocent, opportunistic crows will snatch hatchlings from open top, tree nests of other species and PM hatchlings from shallow, single room housing but with minimal design/safeguards/overhangs that prevent perching, your PMs are relatively crow-safe. So, if 100% black crows are snatching your "pinkies", you have a housing problem.

If a black bird, with any white coloring, carries off a martin while clutching it underbelly, you have a hawk problem.

Great Black Hawk bio: https://biodb.com/species/great-black-hawk/
Crow bio: https://biodb.com/species/carrion-crow/