For a family of birds that I like so much, these guys sure have some annoying habits. They are really intelligent, clever birds. Like smart kids who get bored in class, they play - and they also cause trouble.
I spend a lot of time around ravens. Ten or fifteen years ago, that wouldn't have been the case in San Francisco. They've always been around the area in some numbers, but when people appeared they disappeared. In the last decade or so, they've been working their way back into more populated areas, overcoming their wariness in return for a food bonanza. There are now several large raven roosts around town; the largest one that I know of consists of 50+ birds who spend the nights near the Chain of Lakes in Golden Gate Park; many of them seem to spend their days on Ocean Beach. We have a smaller flock across the street from my home (a photo of their roost trees is below). The numbers are down slightly because of construction work in the area, but we still over a dozen (and some new kids as of a few weeks ago).
In an earlier posting, I told of watching adult teach their fledglings how to forage in a dumpster, differentiating between bags likely to hold food vs. those likely to hold dog waste. I also enjoy watching them while I'm banding in the Marin Headlands. They love to play on the air currents; one favorite game that I call "elevator" consists of approaching a ridgeline with a strong updraft. They inch forward in the air until they find the updraft, snap their wings wide open and shoot up 50 or 100 feet, then do a barrel roll and go back to do it again (and again and again).
Yesterday a nature interpreter told me how he teaches kids how to tell ravens from crows by pointing to his beard. This one sure shows that nicely.
If you've ever had a chance to read any of Bernd Heinrich's books about ravens (like Ravens in Winter or Mind of the Raven) , you're familiar with these kind of stories. (and if you haven't read them - do!) One of my favorite examples of their problem solving abilities involved an experiment with a piece of meat hanging from a string, about three feet below a perch - too long to just lift up with a single pull. Ravens studied the situation and came up with two different solutions to get the food. Some of the ravens grabbed the string in their bills and lifted it and held the string with their feet, then repeated the process until they had the food. Others grabbed the string and held it with their feet and slid along the perch until the food was raised to a height where they could grab it. Really some remarkable problem solving ability...
Bernd Heinrich thinks that crows may be even smarter than ravens. They are known to make tools; for a really interesting display of their ability, read about Betty, a New Caledonian crow, who bent a piece of wire into a hook to reach food. (be sure to watch the video!)
As smart as they are, corvids were unable to defend themselves from West Nile Virus. They proved to be extremely vulnerable, with mortality among crows being highest of all - in some studies, it reached 100%. Numbers crashed on the east coast, but some birds have made it through the crisis and numbers are slowly climbing.
I worked late every night this week, and just realized this morning that there was nothing queued up for Dawn Chorus this morning... hence, a repeat from 2007. One happy note is that since that time, corvid numbers seem to be rebounding somewhat from the worst of their West Nile lows, at least here in California. I'd love to hear about the east coast and midwest. The disease also hit Yellow-billed Magpies hard, and for a few years we barely saw any on our trips. The numbers are still low, but we are seeing them more often now.
In the earlier version of this diary, I realized I had no digital photos of American Crows, so these Northwestern Crows had to stand in for them. I thought I'd update the diary a bit now that I'm settling in the morning, but they can stay around for your viewing pleasure.
A few more of our glossy black friends...