The setting was romantic enough. Sunny spring day. A cherry tree blossoming a vivid pink. One party, the suitor, was dark, fetching and amorous. But the other party lay there like a corpse. It was, in fact, a corpse.

So began the first documented human observation of a crow copulating with a deceased member of its own species.

In April 2015, Kaeli Swift, a doctoral candidate at the University of Washington who studies crows, was demonstrating one of her experiments for a film crew when she left an expired crow, stuffed by a taxidermist, unattended on the ground. A nearby crow soon swooped down upon the stuffed crow, crouching low, its wings spread wide and attempted intercourse. The move astonished Ms. Swift enough that she spent the next three springs and summers recreating these conditions and documenting the behavior.

Ms. Swift and her co-author, Dr. John Marzluff, detail that field work in a study published Monday in the journal Philosophical Transactions of the Royal Society B. Exposed to their dead, crows may touch, attack and attempt to have sex with the body, the authors explain. The study adds a new twist to previous observations that the birds primarily respond to crow cadavers as signs of danger. The conduct, the researchers speculate, may be the result of hormonal fluctuations that cause some crows to become confused about how to respond to stimuli.