Why do Corvid Birds Gather Around Their Dead?

Session Date: 
Mar 3, 2017

The discovery of a dead member of one’s own species is a profound, potentially emotional, and certainly informative experience.  Social species, from insects to humans, seem especially intrigued by their dead.  While mammals often attend to their dead for periods lasting from hours to days, most insect and bird responses are of much shorter duration.  The responses of birds, which typically include large and conspicuous gatherings and displays, appear to be motivated by a need to displace or learn about a potential danger.  I illustrate this with a combination of field and laboratory studies, conducted in collaboration with colleagues and students.  We demonstrate that American crows (Corvus brachyrhynchos) respond immediately and strongly to the discovery of a dead crow.  Upon discovery, they give scolding vocalizations, typically reserved for newly discovered predators, which quickly assemble a mob.  Their response is nuanced by season and age of the dead.  During the breeding season, the discovery of a dead adult crow summons a mob more frequently than does the discovery of a dead juvenile crow. Using PET neuroimaging, we demonstrate that the sight of a dead crow being held by a person activates the hippocampus of adult crows.  When crows encounter people that were associated with a dead crow they scold the person and avoid the place where that person was encountered.  Neuroimaging reveals that the sight of a dangerous person activates the crow’s amygdala. Together, these results suggest that crows gather around their dead in part to learn about dangerous settings and possibly novel predators.  However, crows occasionally respond to their dead by bringing sticks, touching the victim, or even copulating with the corpse.  Therefore, learning about dangers may just be one of many reasons why crows gather around their dead.

File 2017_03_03_04_Marzluff-Web.mp493.91 MB