This video shows the amazing Superb lyre bird (yes, that's it's actual name), capable of incredible feats of mimicry. Sure, he's impressive, but it's not until around 1:54 when things start getting strange. At 2:30, they get seriously weird. Watch and hear for yourself:
Here's another lyre bird at a zoo in Adelaide, Australia, that imitates not only the sounds of nearby construction but also human voices with uncanny accuracy: