The Library calls their collection "the world's largest and oldest scientific archive of biodiversity audio". There are 175,000 audio recordings altogether. That's a lot of chirps and bleats.
As you might expect, given that it's part of an ornithology lab, the archive's most comprehensive area is birds (they've got recordings from 75 per cent of the world's bird species), but there are also thousands of recordings of other species
Some of them are really surprising. Like this recording of what sounds like machine gun fire. See if you can guess what animal's making all the noise (scroll down within the audio window for the animal's name).
For some haunting sounds, check out this recording of coyotes in California.
And this one doesn't sound like it could have been made by an animal: a bird called Montezuma Oropendola makes a sound like some kind of vintage synthesizer.
As for animals that sound a little bit like massive machinery, it's hard to beat the blue whale:
And check out this audio, recorded in 1986 in the Netherlands. It's from a bird with an awesome name: the Great Reed-Warbler.
The Library includes lots of video footage, as well, like this shot of the Indigo-Banded Kingfisher in its natural environment.
Or these penguins running in the rain.
In total, there are over 50,000 video clips in the archive representing 3,500 species.
Basically, if you're not a teacher or a scientist, the archive is just an invitation to spend a whole lot of time listening to and looking at nature without leaving your screen.
But hey, it's better than kitten videos. Although, yeah, they have those too: