Spring migrants are moving north. The first blackbirds have crossed the state line, and flocks of common grackles have appeared in the Bangor area.
While we wait for the other migrants to arrive, we can amuse ourselves with the resident local birds that are gearing up for spring. I refer to eagles, crows and ravens.
Bald eagles nest early. Crows and ravens aren’t far behind. They may not be on specific territories yet, but they’re thinking about it. Hence, they’re angry with each other.
Crows and ravens are members of the corvid family. They are clever and resourceful. They will raid the nests of other birds, including those of their fellow corvids, so they generally don’t trust each other.
Eagles just take whatever they want, when they want it. Naturally, crows and ravens don’t want them around as nesting season approaches.
We’ve entered the season when ravens harass eagles, and crows harass both.
It happens more than people realize, and it’s something to watch for.
The crows and ravens get aggressive when their nests contain eggs, and downright ferocious when the eggs have hatched. Nestlings are vulnerable to predation, and their parents won’t put up with much.
There is a dam with a fish passage near my house, installed so that alewives could return to their historic spawning grounds. It works. Alewives return each year by the millions.
Three years ago, crows built a nest in my neighbor’s tree. Eagles occupied their own nest a half mile away. The eagles visited the dam often, feeding on the alewives and carrying them back to their nestlings. Their flight, from nest to dam, took them right past the crows.
For a month, I knew exactly when the eagles were coming. The crows would raise the alarm and fly out to harass the eagles, both coming and going.
The harassment season started for me two weeks ago, in an amusing fashion. Tons of eagles hang out here in winter.
One morning, I witnessed two crows escorting an eagle over my garage. They weren’t nesting yet, and probably didn’t even know where they were going to build a nest. So, their attempt at harassment was mild and unenthusiastic. The eagle didn’t even bother to quicken its pace.
Suddenly, a raven joined the parade. The crows backed off, leaving the raven coasting alongside the eagle. With no nest to defend, the raven was not prepared to attack.
The two birds just glared at each other with apparent dislike.
Occasionally, the raven veered a little closer to the eagle, but mostly they just coasted over the treetops side-by-side, going through the motions.
To observe this territorial drama yourself, it helps to identify the actors properly.
Eagles are easy enough, although there seem to be more young ones around than usual this year. Bald eagles don’t develop their white heads and tails until they’re about 4 years old.
Differentiating crows and ravens is sometimes difficult, but it doesn’t have to be. They give off a lot of clues.
Size matters. Ravens are larger than crows, and twice as heavy. Their bills are much bigger and thicker. That big bill makes a flying raven’s body look as long in front of the wings as it does behind.
Birds flying overhead are particularly easy. The tail of a flying raven is long and diamond-shaped. The middle tail feathers are longer than the outer feathers.
The tail of a crow is shorter and fan-shaped.
The wings of a raven are proportionally much longer, with wingtips that stick out like open fingers.
Because the raven’s wings are so much longer, it flaps more slowly and effortlessly. Crows fly with a faster, choppy rowing motion. Their downbeats churn backwards.
There are significant behavioral differences. Crows form flocks, also called murders. Ravens don’t.
Ravens soar. Crows don’t.
Ravens are downright acrobatic. They can somersault, cartwheel and fly upside down.
One difference makes me laugh. I’ve never seen a scientific explanation, but I swear this is what happens nearly every time. Ravens fly parallel to roadways. Crows fly across them.
If I see a black bird flying down the highway corridor, I know without another look that it’s a raven.
Crows caw. Ravens croak and scream. Ravens sound more guttural, and their voices carry a longer distance. They are particularly noisy right now, because courtship is underway.
I saw my first crow carrying a stick last week. Crows, ravens and eagles all build stick nests, so expect to see lots of stick-carrying too. Use your sighting as a celebration.
Spring is here.
