Why do ravens, generally understood to be solitary creatures, share food between each other during winter? On the surface, there didnít appear to be any biological or evolutionary imperative behind the ravenís willingness to share. The more Bernd Heinrich observed their habits, the more odd the birdís behavior became. What started as mere curiosity turned into an impassioned research project, and Ravens In Winter, the first research of its kind, explores the fascinating biological puzzle of the ravenís rather unconventional social habits. Paperback. 379 pgs.