|Location of the incident, redwood and madrone|
Ravens are well established nest predators, and are also know to take adult birds. This was an issue for the heron and egret colony at Audubon Canyon Ranch, where one year a Raven pair decimated the young of the colony (in full view of tourists none-the-less!). There was a detailed study of Raven ecology and predation habits that resulted from that (see references below). I was curious if there was any documentation about how often ravens went after screech owls, but I didn't find anything addressing that specifically.
As I mentioned in the My Side of the Mountain post, this is the first year that I've seen raven's here. Given the frequency that I have seen and heard them this spring, I believe they have a nest just over the ridge. These ravens are not shy around human residences. I've seen one of this pair walking along my fence, eyeing my cat as he rolled in the sun on the deck. It quickly departed when I opened the door, and my neighbors said that it quickly departed when they waved to shoo it, even from a long distance away.
Although Ravens have been relatively rare to the developed areas of eastern Marin in post gold rush days, their population here is increasing as they develop a taste for the food humans inadvertently provide (i.e. garbage). This can be devastating for rare species that are vulnerable to predation by Ravens. The human supplied food can support the Ravens populations at a higher level than the prey species would otherwise. This means that Ravens can completely decimate a prey species, without being regulated by it's decline. This is known as "subsidized predators". Bay Nature did a very nice article on the Ravens in this area, including covering this phenomenon. So it's quite possible that by intervening in this predation, they just helped correct the affects of an anthropogenically enhanced predator.
Keep tuned for updates on Screech's recovery.
References and additional articles: