A strong contender for Creepiest Nature Video has just emerged, and it’s equal parts upsetting and amazing.

The video depicts a moth surreptitiously sipping tears from the eye of a snoozing bird. At one point, the avian—a black-chinned antbird—opens its peeper as the erebid moth feels around with its proboscis, or sucking apparatus.

The astounding footage was captured by ecologist Leandro Moraes last year in central Amazonia. At the time, Moraes was working with the National Institute of Amazonian Research in Manaus, Brazil. Moraes described the phenomenon in a paper published this month to Ecology, and shared last week by Science Magazine.

According to the paper, moths may drink the tears of sleeping birds “as a supplementary method to obtain nutrients, mainly sodium and proteins.” Few have witnessed this exact type of event—the only other documentations of moth-on-bird “tear-feeding” are from Madagascar in 2007, and Colombia in 2015.

Sodium is an important nutritional element to some moths, and other strange rituals. ”Mud-puddling” for example, wherein males extract sodium from wet soil and deliver it to female mates, revolves around it.

While it may seem weird, tear-drinking isn’t uncommon among several moth and butterfly species. A Julia butterfly, for instance, was photographed in 2013 drinking from a spectacled caiman crocodile. Other animals, such as turtles, elephants, and even people have fallen prey to the thirsty insects.

Researchers don’t fully understand how hosts are chosen, however—whether the chemical makeup of tears varies among animals, or something else. But feeding can require the insects to probe beneath their host’s eyelid. In which case, a docile donor may be preferred.