[cobirds] Gulls? Bird ID help

These gull looking birds have been swooping around in a flock of 20+, circling (eating bugs?) early dusk for the past two nights in my neighborhood. Terrible photo quality, but does anyone know what they are, and why they're suddenly here? Thanks!

-Natalie

--
You received this message because you are subscribed to the Google Groups "Colorado Birds" group.
To unsubscribe from this group and stop receiving emails from it, send an email to cobirds+unsubscribe@googlegroups.com.
To post to this group, send email to cobirds@googlegroups.com.
To view this discussion on the web visit https://groups.google.com/d/msgid/cobirds/df496a25-5673-464e-a7de-02dbb1c10f77%40googlegroups.com.
For more options, visit https://groups.google.com/d/optout.