Moved from Louse Flies.

From the pronounced conical projections on "shoulders" of thorax (best seen in last image of series), overall gestalt, and bird-banding context...this is in subfamily Ornithomyinae. It keys in MND(1) to Icosta...some salient key characters are:

  Inner vertical bristle not arising from a nipple-like tubercle; and no ocelli (...eliminating Ornithoica);
  Antennae distinctly shorter than palpi (= visible mouthparts here);
  Scutellum with a pair of strong preapical bristles (...eliminating Olfersia);
  Wing with crossveins r-m and dm-cu present (latter best see here).

Moved from ID Request.

for sure. Knowing the host species would help in narrowing down the possible IDs. Probably liked your hand for warmth and maybe you recently handled it's preferred host. When banding, try spreading the wing and tail feathers to get the flies moving and guide them towards the feather tips and then into a suitable container.