Why do crows copulate with corpses?

They found that the birds were more likely to caw in alarm when the corpse that they saw belonged to a crow, particularly if the stuffed crow was in a “dead” pose rather than a more lifelike posture. The birds approached dead crows about 25 percent of the time, but only 4 percent initiated sexual activity, hinting that corpse canoodling is not commonly practiced, the study authors reported.

“Clearly, most birds are not engaging in this behavior, and that suggests that there’s probably some cost associated with it that makes it undesirable,” Swift told Live Science.

Furthermore, the crows that mounted dead birds often demonstrated aggressive behaviors in addition to a sexual response.