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It’s in your nature: Eagles’ nesting success and failures

I enjoy following the live video feeds of three different bald eagle nests in Pennsylvania.

Last year the one nest contained two eggs and about five weeks into the incubation time I no longer saw an eagle on the nest.

Something happened to cause them to abandon the nest. Did they know the eggs weren’t viable?

This year, the bald eagle nest at Hays (Pittsburgh) failed as well. The comment’s section of the nest’s progress stated when the first egg was laid, and later, reporting that the egg cracked.

It has been about three weeks since anymore information on that has been updated and that nest failure led me to discuss some bird nesting information.

I was a bluebird trail nut for a while, monitoring many, many boxes for a number of years (I still monitor about 20).

Most of the time I observed as they incubated the eggs, noted when the young pipped through the shells, and watched as they gradually developed and then fledged.

A few times over those years the eggs were laid and well after the normal incubation time of 15 days, they didn’t hatch. Invariably, the pair nested soon after that.

If I didn’t get to clean out the nest box in time, they sometimes built a new nest on top of the unsuccessful one and raised a second brood.

But, why doesn’t that happen with the bald eagles? A bald eagle pair will begin adding new branches, sticks, and limbs to last year’s nest in late fall.

By mid-January most of that nest rebuilding is complete. The pair will remain in the area, guarding their project, and soon may mate on the nest, and egg laying commences.

If you remember, bald eagles, like other raptors, lay an egg and begin “warming and turning” that egg immediately.

Then in another day or two she’ll lay a second, and occasionally, a third a day or two after that.

The female eagle does most of the incubating while her mate brings food to her in the nest. Usually once or twice during the day she leaves and forages on her own. The male eagle also warms the eggs then, but spends less time brooding than her.

Overnight, the female remains on the nest with the mate close by.

Here is the catch. The young that probably should have hatched by early to mid-March, but didn’t due to possible unfertilized eggs, have now taken almost 2 months of the pair’s critical nesting time.

If they mated again, began egg laying by the end of March, they may not have enough time to raise a new brood.

Consider that: 1. The egg incubation begins April 1 and after 35 days of incubation, they hatch about the first week of May.

2. The eaglets usually remain in the nest about 12 weeks until strong enough to fly.

3. That 3- month nesting time would take them until early to mid-September. So that would not “leave” enough time for the adult birds to teach the juveniles to feed, and for them to survive on their own before the challenging winter conditions creep in.

Here, in the northeastern U.S. Bald eagles that have nests fail, will have to wait until the next February to lay eggs again. That is one of the reasons it can take a long time to rebuild the population of raptors that are threatened.

Test Your Outdoor Knowledge: The bare area of a bird’s ----- is called a: A. brood patch; B. sternum; C. “Foreman Grille.”

Last Week’s Trivia Answer: Two oriole species nest in our region, the Baltimore oriole and the orchard oriole.

Email Barry Reed at breed71@gmail.com

The eastern bluebirds in our region generally have two broods per year. They may lay four or five eggs (usually one less in the second brood) and begin incubating after the last egg is laid. Of all the bluebird boxes I've monitored, one pair in my East Penn Township backyard had three broods, with the last young fledging after Labor Day.
I've located several great horned owl nests the past few years. Each nest held one owlet. However, two eggs are the norm for great horned owls. BARRY REED/SPECIAL TO THE TIMES NEWS
Bald eagles lay from one to three eggs with two the norm. This juvenile bald eagle is probably days away from making its first flight. This local nest only had one young though.
Barn owls are an exception in the raptor world. There have been reports of barn owls having two broods per year, but it is very uncommon. However, as in all raptors, they lay eggs a day or two apart. The result, if six or seven eggs are in the nest, the young can differ in ages and obviously size, by almost two weeks. If enough prey can be found, all the young may survive to fledge. If not, the smallest one(s) may fall prey to their bigger, hungry siblings. This size difference is evident in this photo of a Lehighton brood.
Probably the smallest songbird (other than hummingbirds) occasionally nesting in the northern reaches of Carbon and Monroe is the golden-crowned kinglet. However, their two broods usually have six to nine eggs each.