|
by Kevin Strauss
While driving up Highway 1 on Sunday, I saw a raven (Corvus corax) fly over with a long stick in its beak. The sight reminded me that while we still have two feet of snow on the ground, some birds are already nesting. Late February and early March is nesting season for the largest of our passerine (perching) birds.
Ravens often build their nests in a protected ledge or cliff crevice, but in this area, nests are much more common on the tops of trees. At 3-5 feet in diameter, raven nests are relatively easy to see.
Ravens build the foundation of their nests out of large sticks, dirt and grass clumps. The birds then line the next with smaller twigs, bark shreds, wool, hair or any other fibers that they can find. The inner nesting cup is about a food in diameter when finished.
It takes a lot of work to build a five-foot wide nest. And ravens, being amongst the most intelligent of birds, are clever enough to keep reusing their nests. An individual nest might be home to ravens for up to 100 years, spanning several generations of individual birds. But that doesn't mean that the nest has young in it every single year. Researchers have found that many raven pairs have two or more nests in their territories and alternate which nest they use. That behavior might reduce the number of feather parasites that build up in an individual nest.
While both male and female ravens build the nest, it appears that usually one member of the pair does most of the work. In one example, the male accompanied the female and perched nearby while the female added nesting material.
Ravens seem to be picky about the sticks that they use in their nests. They don't seem to collect sticks from the ground, preferring instead to break them off of standing trees. The "foundation" sticks can be up to three feet long and an inch in diameter. The stick that I saw that raven carrying was easily three feet long. If a raven drops a stick, it won't pick it up off the ground, preferring to collect a new stick instead. That behavior may be an instinctive defense for the birds. If they were to collect sticks from the ground, ravens would be more vulnerable to ground predators like wolves, foxes and lynx. By only collecting sticks from trees, they reduce this danger. Even if ravens are reusing an old nest, they still add a few new sticks to it every year. So if you see a nest with some new (tan colored) sticks, it is probably an active nest. If it only has old (dull gray) sticks on it, it probably isn't being used this year.
So while you are outdoors this week, look around for ravens building nests in your area.
The Ely Timberjay
|