Fighting for Treetops

As Numenius said, the Swainson’s hawks have been coming in — over the next few weeks they’ll be nestbuilding all over Northern California. (There were reports yesterday morning of a record-breaking migration over the Anza Borrego desert in Southern California, about 1,300 birds.) As I left the house this morning, there was a gal by the driveway with a clipboard, watching the Swainson’s that was perched in a walnut tree.

The white-tailed kites have been nesting for nearly a month, now, outside my office. I watched them courting; the male then started his solitary courtship flights, toes extended, a barely perceptible hovering glide showing his striking wings to best advantage, around the pine tree where the female was presumably incubating, returning often with rodents; and now, he has taken up attacking any bird larger than a starling that comes near the tree.

Yesterday, it was a Swainson’s. There are fewer and fewer trees in this part of the world that are tall enough and with enough cover for these larger buteos. This one seems taken. The kite, a third of the size but far more agile, went after it again and again until the Swainson’s got so high it was barely visible from the ground. Is it worth expending this much energy? The kite obviously thinks so.

Postscript, Friday, 23 March: I’m adding a photo of the Borrego hawks, taken by Grace Clark. They counted 1365 hawks that all roosted overnight and left between 0900 and 0945 on Wednesday… Paul Jorgensen says in an email “it was one of the greatest natural spectacles I have ever witnessed.”