Wednesday, March 11, 2009

Covering Eaglets with Grass? More Sharp-shin photos, a Red-tail Drinks, and a Sleeping Saw-whet

From R. of Illinois concerning the Blackwater Eaglets--

The adult covered the chicks with grasses. To keep them warmer? To camouflage them from predators above?

In chilly weather, if the sitting bird must leave the nest, some raptors, including Red-tails and Eagles, will cover their eggs with light materials such as grass. It has always been thought that it was done to conserve the heat of the eggs as the birds don't tend to do it in warm weather.

I would say that covering the eggs and covering the eaglets, has the same impetus, keeping them warm. These eaglets are so young that they can't regulate their body temperature yet, and not having much in the way of feathers means they can't retain what heat they do have. These are the big reasons that the parents continue to sit on them. When the nest is threatened whether there are eggs in it or young, the formel will cover them by sitting on them.

Even when people rented helicopters in order to see into Pale Male's nest to check for eggs, it was all in vain. Why? Because even for an urban hawk a helicopter hovering near the nest registers as a danger, so once the craft got into a position to be able to see into the nest, Lola had already plumped herself down on the contents.

On the other hand if things become so threatening that the larger bird, the female, must either take on the threat or spell the tiring tiercel, the tiercel bombs over to the nest but ordinarily doesn't sit on the young or eggs, he stands in the bowl and looks as scary as possible.

Why? Good question.

I've never even seen the behavior mentioned in the literature so it's doubtful anyone has attempted any hypothesis testing to find out.

Perhaps by the time the tiercel takes over the nest, it is clear to anyone in the area just where the nest is, having seen the female come off and the male go on that there is no reason to be unobtrusive and hunker down.

The male is shorter so standing puts him into a better defensive position? Seems doubtful.

Or perhaps he is just so het up, and testosteroned out he just can't sit down no matter what. Pale Male has been known to, when in a particularly intense nest protection skirmish, where several switches between Lola and he have taken place to spell each other, to stand in the bowl and literally rake his talons across the nest materials. The motion is very much in the style of an infuriated rooster. Though steaming, Pale Male as yet seems never to have done any damage to eggs.

Another New York Botanical Garden adventure with Pat Gonzalez--
While at the garden, I headed on down to the river bank (Bronx River) hoping to catch a glimpse of the elusive hooded merganser. The last time I got a clear shot was three days after the snow storm, but because there was so much snow on the way down to the bank, I didn't want to risk injury, so I settled for a long shot.

I'm not even there one minute when my buddy red-tail shows up. He gracefully glided over the water then touched down. (Note that the Red-tail is having a drink. For many years, the literature agreed it was likely that Red-tails didn't drink water but rather got their necessary liquid from their prey. Hawkwatchers in Central Park have watched Red-tails drink and bath for many years as there are many eyes number one and two they had the opportunity to see it because the resident birds are habituated to humans. D.B.) I creeped in very slooooooow. He stayed long enough for me to get the shot before taking off. As I walked away, quite happy with myself…

I barely noticed the two mergansers quietly going up river. I took several shots before they swam off.

More photos from Pat Gonzalez of Yesterday's Mystery Hawk the New York Botanical Garden, which I thought was a Sharp-shinned Hawk.
Pat then delved into the field guides and she agreed--Sharpie


I, too, think the accipiter in question is a Sharpie. It's hard to see the bug-eyed eyes, but the distance from the smallish beak to the chest is rather small. The head doesn't have a neck. It just sits on the bird's shoulders.

--John Blakeman


Photograph by Pat Gonzalez
And here is a great photograph in which we can check out the field marks of a Sharpie tail.

From Peterson's Field Guide, Birds of Eastern and Central North America--"...folded tail is slightly notched or straight and narrowly tipped with white".
And in the above photograph there it is, the slightly notched tail narrowly tipped with white of a Sharp-shinned Hawk. TA DA!

Did you notice the amazingly long center toes of this bird?

Photograph by Pat Gonzalez
After her wonderful display of the important physical details we needed to identify her species, off she goes refreshed from her bath.
Northern Saw-whet Owl at the New York Botanical Garden

The sleepy little fur ball in the attached photo is a Northern saw-whet owl. I found him (or her) about 1/4 mile from where I left his neighbor, the much larger great horned owl. At one point he opened his eyes for a whole two seconds, then went back to snoozing. Here's a link to my you tube page.

As you can see he only does one thing on camera. zzzzzzzzzzz....


No comments: