Blue-billed black tyrant (male)

The blue-billed black tyrant (Knipolegus cyanirostris) is a species of bird in the Tyrannidae family (tyrant flycatchers, they feed on insects). In Uruguay the bird is valled "Viudita negra común", meaning "Common black widow". Like all "viuditas", they tend to be observed alone. Although I have yet to find an official source confirming my suspicion, I am pretty much sure that's what's been earning them their Spanish names. The female is completely different. See here for some pictures some friends took where you can see the female.