Tuesday, March 14, 2006

March 13 notes: time for diligence

After only a week of watching incubation, perhaps you can see the strategy of nesting eagles is simple, patient diligence to one duty: keeping eggs warm enough to hatch. The incubation period of approximately 35 days requires steadfast attention. For intervals of only a few minutes, the eggs may be unguarded as one adult takes a break and its partner soon resumes the task. The interval during an incubation exchange was 5 minutes long on March 11, an unusually warm spring morning in coastal Maine. During cold spells and spring rain or snowfall, the incubating eagle must endure the elements to safeguard its egg.

Look for subtle behaviors in this period. An adult may rise up, step around the eggs, and reach down to roll them with its beak. If a prolonged absence is planned, a departing adult may cover its eggs with nest lining before departure. When resuming incubation, the female is likely to almost go face down before settling into a position where its brood patch is pressed snugly against the eggs. This is a thinly feathered area on the upper breast enabling an incubating bird to transfer most of its body heat to the eggs.

Incubation duty is not as easy as it sounds. On March 12, I watched an incubating eagle at a Penobscot County nest sit tightly while a crow perched on the edge of the eagle nest: an apparent attempt to lure the incubating eagle into aggressive pursuit and perhaps allow other crows nearby to predate the eagle egg(s). This eagle did not budge, and its mate appeared after a 10-minute standoff to chase away the crows. Raccoons and fisher may also climb into lofty eagle nests for eggs or nestlings, and biologists may prescribe a predator guard to deter them.

Management comments: Eagles have varying levels of tolerance to intrusions. If you or I get too close to a nest, an incubating bird may abandon its primary mission of egg care to circle the nest vicinity (often with an exaggerated flapping flight: not the typical, effortless soaring) and vocalize in protest. This behavior can be misinterpreted as "the eagles are putting on a show for us" when, in fact, they are imploring you to leave. Please do so! -- Charlie Todd, Maine Dept. of Inland Fisheries and Wildlife

8 Comments:

Anonymous Kelly West said...

Thanks for sharing this with all of us who do not have the opportunity to see it first hand. Our daughter is 8 and recently completed a school report on Bald Eagles and their habitats. This is informative and great enterainment for all of us!

9:36 PM  
Anonymous Paul Hutchins said...

I have posted the web cam site to an Orange County, California bulletin board. The best of louck, and thanks for the web cam opportunity. Here is the site is posted to:
http://talk.ocregister.com/showthread.php?p=336922#post336922

11:18 PM  
Anonymous Anonymous said...

I LOVE this site, as you can imagine.

Our eagle is also incubating ... I think it's very recent.

Last night at supper time the mature male eagle chased one of last year's eaglets away from here and down the river -- several times! The young eaglet hasn't got the message yet that he isn't welcome at the nest any more.

Jane E. (Winslow)
Anon. for the sake of our eagles

12:25 PM  
Anonymous Jane Edwards said...

Could you please tell us about how large the egg is, in comparison to say a hen's egg or a duck's egg?

And what does it look like? Do you have a picture of an eagle's egg?

8:02 AM  
Anonymous Ellie said...

Do you know how many eggs they have?

2:41 PM  
Anonymous jane edwards said...

I saw about the same thing at 6:40 PM tonight as I saw at 6:14 AM. The male flew in, but the female didn't let him take over, and he eventually flew off.

He took a very paternal/maternal interested look down into the nest, first .... and perched there for a while.

Incidentally, earlier I also saw one of them, I think the same one I'm calling the female in the exchange above, nestle down carefully several times with the brood patch to get over the egg correctly, and then look carefully in front of her in the nest and under each wing, as if to be sure the hatched eaglet was okay.

Jane Edwards, Winslow

6:47 PM  
Anonymous Anonymous said...

It was fun to see both of the babies with feathers in their mouths. They must be beginning to play a little and notice their surroundings. It is truly amazing how rapidly they are growing. I saw nicely rounded crops on both of the babies today. It seems like the parents aren't hanging around as much either. Thanks again for this wonderful experience. Jenn
5/4 2:43pst

5:46 PM  
Anonymous Anonymous said...

This is great. What an experience. Hey, tell my little cousin, Barbara Todd, hello for me. She is so lucky to have seen the little head pop out from behind the wing. Patti (Maryland)

12:14 AM  

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