Repost from the old site.
For the last few weeks here in Coarsegold, California (elevation 2000′ in the Sierra Nevada Mountains), I have been hearing strange “Screech! Screech!” noises at night, often very late at night. I’m hearing them right now, as a matter of fact. I’m an experienced bird watcher, and I assumed they were birds, so I grabbed a strong flashlight (you need a strong flashlight to look at any night birds) and went outside.
Most birds are simply not active at nighttime. Day-active birds will usually just go up into a tree and sleep there at night. I had a rare bird on my property in 1990 in Southern California and I had bird-watchers coming every day to come see it.
It was a Brown Thrasher, common in the Eastern US but very rare in the West. The bird stayed on my property for about three days. At nighttime, I went out looking for it and found it in a bunch of trees on the side of the house. We think that they just go up into a tree and probably sleep up there. I guess they need to sleep too, like everything else.
The only birds active at nighttime are generally owls. There are also some birds like nightjars and whippoorwills that become active at dusk. I’m not sure if they stay active at night or not. So if you hear a bird at night, it’s an owl.
Well, I went outside and the strange screeches kept coming from a huge tree nearby. I shone my light up there and there were some good-sized owls up there. I couldn’t figure out what kind they were because it was night and they weren’t fitting into any known categories. One flew away and I noticed how huge it was in flight. I went back in and did some research on the Net.
At first I was thinking “Screech owl” because we do have Western Screech Owls here. But they are quite small and have a distinctive call. They make this call on hot summer nights, often very late at night, but it’s not a screech, in spite of the name. It’s more of a “bouncing ball” call. It’s hard to describe unless you have heard it.
On the Net I learned that baby Great Horned Owls do make a “Screech!” call. That fit in with my perceptions about the birds’ size. A horned owl is a very large bird. They are so large that they are known to prey on house cats. They are also very common in the foothills of the Sierra Nevada.
So these were baby Great Horned Owls. I guess they fledge here in July and August. What was interesting was there were around 5-10 of them in a small area, all calling to each other. The size also ruled out Screech Owls , because they are quite small.
You need to understand that “baby birds”, once fledged, are about the size of adult birds and are often indistinguishable from them. Some smaller birds have juvenile plumage, but among larger birds, it’s not common.
In Orange County in the late 1980′s, I saw two crows of about the same size, one feeding the other one with its beak. This is how birds feed each other. I did some research and learned that that is a baby crow. Baby crows are about the same size as adults. Adults will feed them for a while after they fledge and leave the nest, but then they need to take off.
I also had some acorn woodpeckers living in a huge oak tree on my property in the mountains. They live in communal units of multiple adults and even raise the young communally. They may raise more than one clutch in a good year. I noticed that after the young were fledged, they stuck around for a while, and the adults continued to feed them. Then I guess they took off.
This myth, so beloved by American parents with adult kids still at home long past the time to leave, about adult birds “throwing the young out of the nest” as soon as they fledge, is just not true.
First of all, baby birds can’t fly very well as soon as they fledge. Sometimes if you are lucky in Spring you can see baby birds scuttling along the ground trying to fly. I’ve seen this in House Sparrows in Fresno, California. I think they scuttle along the ground and half-fly for a few days or so, then they get it. They fly for a short distance, then they land. They must be extremely vulnerable to predation in this stage.
Keeping baby birds around after they fledge is a positive adaptation in evolutionary terms. Larger birds such as woodpeckers and surely crows are thought to be more evolved, so they seem to keep the young at home for a while after fledging. Tossing the babies out of the nest is evolutionarily stupid, since if they can’t fly well, they will be very vulnerable to predation.
Trust me, they are vulnerable enough in the nesting phase! I had an Ash-Throated Flycatcher nesting on my Oakhurst property one year. My cats figured out the story after a while, and kept trying to climb up to the nest. I’m sure predators like raccoons are even worse. I even understand that snakes can climb trees and raid nests.
I’ve never seen so many owls as I’ve seen up here in the mountains.
Twice I saw Northern Saw-Whet Owls on the road in Oakhurst, once at dusk and once at 9:30 PM on a sleety night in winter – this one had a mouse in its talons! Saw-Whet Owls descend to the Oakhurst area in winter.
Another time, also in Oakhurst at dusk, I saw small birds “mobbing” something just before dusk. When you see that, it’s generally a predatory bird like a hawk or an owl. It was dusk. I ran inside, got my binoculars, and went back. After a while, I saw that they were mobbing a Northern Pygmy-Owl .
It’s a pretty cool little bird, with fake eyes in the back of it’s head! Nice evolutionary trick to fool you into thinking it’s looking at you when it’s not. I think that this trick evolved to help this small owl avoid predators, because there I’m not sure there is an advantage for a predator to seem like it has eyes in the back of its head.
A couple of years ago, in Oakhurst near some apartments at dusk, I saw a huge bird swoop down on some bare ground in front of some apartments, grab something and take off back up to a Ponderosa Pine tree, where it was promptly mobbed by a bunch of small birds. I stopped and looked long enough to see that it was a Great Horned Owl with a mouse (probably a deer mouse) in its talons.
Mobbing is an interesting tactic. Small birds with fly in large numbers at a hawk or an owl. Often these hawks or owls are the same ones that kill and eat these same small birds. Accipter hawks such as Goshawks are mobbed, but I have never seen a Buteo such as a Red-tailed Hawk mobbed.
Buteos typically subsist solely on small mammals and reptiles and seldom if ever eat other birds. But accipters are bird hawks. They prey on other birds. I once saw a Goshawk being mobbed by small birds, fly out of some underbrush, and over to a post where it sat for a bit while the others continued to mob it.
The idea of mobbing is strength in numbers. Although they attack predators known to prey on them, if you have enough small birds, it will confuse and upset the predator enough to so it won’t attack them. It’s also an early warning system for any other small birds in the area that a predator is in the area. In addition, by mobbing, the small birds try to drive the predator away from them and off to somewhere else.