January 31, 2006

The Cam Nest

Nest Update: Things are looking good at the nest as the parents dutifully tend to their eggs. We also saw one of the eagles bring a fish to the nest today.

fishdelivery.jpgSome cam watchers have asked about the wind and how it impacts the nest. From what we can tell, our Eagle Cam nest is sturdy and well built, and it has held up well during some very windy days lately. Normally a well-built nest can stand for years. In fact, at least four active bald eagle nest sites in the Chesapeake Bay region are known to have been active for 60 years or more.

But the unfortunate fact is that sometimes eagle nests do fall down. During a storm, a nest may lose its support branches or the entire tree may fall. Or sometimes the nest has just grown too large for the tree branches to support it.

If the nest falls when the eggs are still there or when the chicks are small, then the outcome is not good. If the nest falls when the eaglets are older, there is a chance they'll make it if they survive the fall, because the parents will feed them on the ground until they can fly. The main problem with non-fledgling eaglets being on the ground, however, is that they would be vulnerable to land predators.

The Tulsa Audubon Society has an interesting web page on their site where they describe how they rescued two young eaglets after their nest fell down. Be sure to check out the wonderful photos.

Something that is not visible on our Eagle Cam is how much the nest moves in the wind. Our staff and volunteers at the Refuge have the ability to watch live video from the cam (you can, too, if you go to our Visitor Center) and they report that on windy days, the nest really rocks. Imagine clinging to a branch that is 70 feet up in the air during a 45 mph wind gust. It's truly a tribute to the building skills of eagles that their nests hold up for years, and sometimes decades, at a time.

On a side note, thanks to everyone for their photos. We'll update the Gallery in the next few days.

Until next time,
Lisa - webmaster
(contact)

Posted by Webmaster at 08:03 PM

January 27, 2006

Egg Development

Nest Update: Fortunately our camera seemed to hold up pretty well during the big wind we had this week, and the two eggs look good in the nest. Some cam watchers have asked about what looks like cracks on the eggs. Sometimes pieces of grass fall on the eggs when the parents are moving around, and from our view they look like cracks, but they're not.

Also, one note about the Gallery. If anyone wondered why their photos didn't make it into the last update, my email provider was very slow in getting me the emails that were delayed last week when their server went down. I got some of the Gallery emails a week late, so they didn't get to me in time for the update. The problem seems to be fixed now, so please keep sending your photos. :-)


Now that we have a clutch of two eggs, it's natural to wonder about their care and development. When watching the cam, we sometimes see the parents leave the eggs alone. While it's true that the parents will sometimes step out of the nest for a break, it's not likely that the eggs are completely alone; a parent is probably in a nearby branch. Experienced parents know they shouldn't leave their eggs unattended if they want to keep them.

egg turnIn our Gallery photos we also occasionally see the parents turning the eggs. This is done about once an hour to prevent the membranes and tissues from sticking to the shell wall. Often the parent will roll the egg with a balled-up talon so as not to puncture the eggshell.

When the parents sit back down on their brood, they place the eggs in contact with their brood patch (both female and male eagles have one, although the female's is larger). The brood patch is an area on the eagle's belly where the feathers have dropped out and naked skin is exposed. The skin area has a larger blood supply, so it's like a hot-water bottle resting against the eggs.

If the parents do a good job of keeping the eggs warm, then the cells inside the egg will begin to turn into vital organs, wings, a beak, a tail, etc. Much research has been done on how chickens grow inside their shells, and the results are useful in getting a glimpse into how the eaglets develop. This Embryonic Development Chart shows how a chick develops during the chicken's 21-day incubation period. The chicken's incubation period is about two weeks shorter than the eaglet's, but the general body parts are all there.

In a future log post we'll talk about what's inside the shell, such as the air sac (where the chick gets its first breath of air) and the yolk (which the chick uses for nourishment).

Sometimes eggs will not hatch, and there can be several reasons for this, such as the egg was infertile, the parents had a poor diet or were exposed to pesticides, the eggs were not turned often enough, the eggs were not kept warm enough, or the membranes and tissues inside did not develop properly.

When you consider all the miraculous things that must happen for a small collection of cells to turn into a baby bird, you can understand why many biologists consider the transformation of an egg into a chick as one of the great miracles of nature. And it's even more miraculous when you think about the journey that an eaglet will eventually take from a helpless chick to a powerful, soaring bird of prey. As of today, the eggs are 8 and 10 days old. Their journey is just beginning.

Until next time,
Lisa - webmaster
(contact)

Posted by Webmaster at 08:23 PM

January 23, 2006

Adult Relationships

Nest Update: First, an egg update. At this point we have two eggs, and it's probably best if another is not laid at this late date, as it will put the eaglet at a major disadvantage in the nest, so we kind of hope we hold at two from here.

two eggsThe interesting thing about the second egg was that it was the first one that was not laid in the early morning. Based on the photos we’ve seen, the female laid it sometime in the later morning or early afternoon. All her other eggs have come in the early morning hours, which is typical for a raptor.

For those keeping track, here is where we stand, assuming a 35-day incubation period:

1st egg laid: 1/17
Hatch date: 2/21

2nd egg laid: 1/19
Hatch date: 2/23


Previously in the web log I mentioned that in these early stages -- when there are just eggs in the nest -- the eagle parents share the incubating duties, with the female spending the most time at the nest. This arrangement gets more equitable for the female when the chicks are a few weeks old, and she can get off the nest more and share in the hunting duties along with the male. But in the beginning, the weight of the egg-sitting chores falls to the female.

In the book The Bald Eagle: Haunts and Habits of a Wilderness Monarch, the authors state that since the male eagles are smaller, they are the subordinate sex. And this size difference ultimately affects the dynamics of the couple's relationship, as they go about their duties of incubating the eggs and raising the young.

According to the authors of the book, "If Bald Eagle partners do not exchange roles frequently enough, the bird on the nest may call to its mate for a relief of duties. At one nest I watched in 1976, the female had been caring for the chicks for several hours and had repeatedly called to her mate; she would look in the direction where he was perched not far away. Finally, as if tired of waiting, she took off, circled around, and dived at the male, almost knocking him off the perch; she landed on a tree nearby while he went straight to the nest without a sound."

Female dominance can also be seen at mealtime. The authors relay that "It is common for males to have their prey taken from them by their mates, while on the nest or away from it...A female's response to a male bringing food to the nest is quite variable. Depending on her motivational state, she may either ignore him or be aggressive...Given the female's dominant role, there are times when the male is not allowed to eat on the nest. The male adjusts by feeding immediately after catching prey."

couple

But not all encounters between the couple are ruled by domination. During courtship, the couples stroke each others back and neck, rub beaks, share meals at the nest, and perform aerial displays to cement their bond (click on the thumbnail image above). And this bond continues after the eggs arrive.

An observation of this type was sent in by Alice, one of our cam watchers, who wrote "Two years ago, while watching the eagle pair on the Northeast Utilities eagle cam, I witnessed the female eagle make a call and within a couple minutes her mate arrived. She stepped off the egg she had been sitting on for a couple days and showed him she had laid another egg (I had seen only one a couple hours earlier). Then she sat back down...they didn't change positions. My thought at the time was 'Wow, she called him just to show him they had another eaglet on the way. What a close couple they are!' I felt I had been lucky enough to be in the right place at the right time to witness other species communicating with each other!"

Each of these eagle stories reminds us that humans aren't the only species to have complex relationships; eagles also have their own unique relations that are a mix of genetics and personality. And knowing this just makes it more fun to watch each season unfold.

In our next post we'll talk about the newly laid eggs and the changes that are happening inside the shells as the eaglets slowly develop into baby raptors.

Until next time,
Lisa – webmaster
(contact)

Posted by Webmaster at 02:44 PM

January 20, 2006

Two Eggs and Counting

two eggs
Our egg count is now at two eggs. If we get a third egg, it should come before Sunday evening. Normally there is about 2-3 days between eggs.

Our email is working again. We were down for about a day and a half, so I'm just getting caught up with photos of the second egg. Much thanks to everyone who sent them.

The camera is holding steady for now. Hopefully even if it moves again, we'll still keep sight of the eggs. Someone asked if the camera could fall out of the tree. Not very likely -- the base is screwed into the tree, so something would have to pull very hard for it to come out. Right now it's just moving side to side, but not out.

Over the last couple days we saw some interesting behavior shots. One shot showed the eagle parent preening its feathers by taking oil from the gland at the base of its tail. The bird puts this oil on its feathers to clean and weatherproof them.

Also we saw a great shot of an eagle parent throwing its head back and calling out. The parent might have been calling out for its partner or it might have been calling out in warning to a trespasser flying over the nest. The air space above the nest is prime territory that the eagles will defend, and they don't like it when birds fly too close.

We have a special photo to share showing a close-up of an Alaska eagle calling out. (Click on the photo below for a larger image). This photo is courtesy of one our cam watchers -- Woody Dawson. Woody has been kind enough to share some of his amazing photos from his visits to Alaska, so you'll be seeing more of his eagle shots in the future. Thank you to Woody for his generosity.

wdeaglecall

One other topic: Someone wrote in to ask if we know anything about last year's eaglets. The eaglet that went to Vermont has not been spotted that we know of, but she likely came south for the winter. In fact, there is a chance she returned to the Blackwater area. As for the other two eaglets (which fledged at Blackwater), no one has seen them, but that doesn't mean they aren't around. The bands on their feet were very small and would be hard to spot without a powerful scope. The two Blackwater eaglets might still be in the general area, or they may have begun exploring in nearby states. Immature eagles will often range over long distances while they're maturing and progressing to the age when it's time to settle down (about 4 or 5 years old).

Finally, in case you missed it, be sure to download our Eagle Watchers' Guide (2.5 MB PDF file), which provides eagle facts and highlights from last year's nesting season.

Until next time,
Lisa - webmaster
(contact)

Posted by Webmaster at 08:45 PM

January 17, 2006

Welcome to a New Season!

first egg
Welcome to our 2006 Eagle Cam Web Log! As our cam watchers from last year know, the Friends of Blackwater use this web log -- or blog -- to keep our cam watchers updated once the nesting season officially starts. Now that we have an egg, we thought we'd start the 2006 web log. If you missed last year's Eagle Cam season, be sure to visit the 2005 web log as it chronicles our fantastic adventure of watching three eaglets grow and fledge last year.

As for our new year: First we want to apologize to our faithful cam watchers for the camera moving again. While we thought we had worked out the problems from last year regarding the camera moving on us, we clearly are still struggling with that problem. The difference between the Eagle Cam and the Osprey Cam is that the ospreys are in a nest we designed and so we have greater control over their setup. The eagles, on the other hand, are near the top of an 80-foot loblolly pine tree in a nest they made themselves, and so the conditions are not ours to control. Also, the eagles are much more sensitive than the ospreys, and they don't appreciate human visitors once the eggs are in the nest.

I can promise that we are now in the process of seeking out a professional camera mount design for next season to ensure that we do not have this problem again. We feel as frustrated as our cam watchers because we did not want to disappoint our viewers this year with another compromised view. But we are actively seeking out technical assistance now, so we hope that this will be our last time of watching the camera slide out of position.

Over the weekend we had discussed making one more trip up to adjust the cam, but this morning the mother eagle laid her egg early before we could make a move. She is eight days ahead of her first egg from last year, which was laid on January 25. Normally experienced raptor couples will lay their eggs early, while inexperienced couples will lay them late, so we don't think it's a bad sign that she's starting her family early. Based on last year's nest, it's clear these parents know what they're doing.

guide
To celebrate the arrival of our new egg, we're posting an Eagle Watchers' Guide for all our cam watchers. This 25-page guide recaps all the highlights from last season, and it's a handy file to have for anyone who has questions about what happened last year or what we can expect to see this year, if we're lucky. The guide is also enjoyable if you'd just like to relive the fond memories of last season's successful brood of three eaglets.

The Eagle Watchers' Guide is a 2.5 MB PDF file. It will be easier to read if you download it to your computer. Right-click the link below and choose "Save Target As."

Eagle Watchers' Guide

You'll need the free Adobe Reader to view it, but most folks have that on their computers already. If you don't, you can download it here.

A couple additional thoughts: If you're new to our web cams, be sure to look for the “Submit” link at the top of the cam pages -- that link contains information about submitting images to our galleries. Also be sure to locate the “Weather” and “Moon Phase” links on the cam pages as well. These will tell you what type of weather the eagles are experiencing at the Refuge and will also tell you how much light they are getting from the moon during the evening hours.

And if you'd like more general information on the eagles at Blackwater Refuge, be sure to check out the Eagle page on our website.

Until next time,
Lisa - webmaster
(contact)

Posted by Webmaster at 08:02 PM