Eagle Cam Web Log

Eagle Vision

Before we talk about eagle vision, I wanted to answer a frequent question from today regarding the corncob in the eagles' nest.

Not far from the two cam nests is a field where the Refuge staff has grown corn for migrating waterfowl. Eagles do not eat corn (neither do ospreys), but the eagle parents bring cornstalks from the field to the nest for nesting material, and sometimes an ear of corn comes along for the ride. It looks like the eaglets are pecking the corn out of curiosity, but we don't think they're eating it. Eventually the cob will probably get buried or knocked out of the nest. :-)

And now on to the topic of eagle vision...

As the eaglets grow and develop, we continue to see more adult-like features on their bodies. One example is the bony ridge that can now be seen over the eaglets' eyes. Most raptors have this ridge over each eye as it helps shade their eyes from the sun and makes it easier to see and track prey. It serves the same purpose as a visor that a human would put on top of their head.

In addition to the helpful bony ridge, eagles also possess what is regarded as the sharpest, most powerful set of eyes in the animal kingdom. It's believed that their eyesight is about four times sharper than a perfect human eye. In fact, the eagle's vision is so legendary that it's responsible for the idiom "eagle eye," which means a person with unusually keen sight.

An eagle eyeball is almost the size of a human eyeball even though the eagle's head is smaller than an adult head. Along with their large eyeball, eagles also have two foveae, or centers of focus, on each eye, which allows them to see both forward and to the side at the same time. And as a further bonus, eagle eyes have around 1 million light-sensitive cells per square millimeter of retina, while humans only have about 200,000 cells.

Ornithologists state that an eagle can spot a moving rabbit from about a mile away. If the eagle is flying 1,000 feet high in the sky, it's believed it can spot prey over about three square miles.

Despite their tremendous eyesight, one of the hardest tasks for the eaglets will be learning to fish from the air. Fish often have dark coloring on top of their bodies, so they are difficult to see from above. In addition, water refracts objects and makes it difficult to judge their exact location underwater. Many juvenile eagles "catch" dead fish more frequently than live fish until they learn the art of sky fishing, which is an acquired skill that will take time to develop and will impact their chances for survival.

Until next time,
Lisa - webmaster

Life in the Nest

Over the last five months, our wonderful cam watchers have sent in a ton of amazing photos, and this past week was no different. In addition to some great face and feather photos, we also saw a lot of quality behavioral shots that gave us a window into the daily lives of the eaglets. Here is a list of some of the highlights:

Preening: The eaglets are doing a good bit of preening now that they have so many feathers to maintain. As we mentioned awhile back in this log, the eagles' oil gland is located at the base of their tail, and the birds use this oil to clean and waterproof their feathers. This photo offers a good view of an eaglet maintaining his beautiful coat.

Eye Protection: Occasionally when the eaglets are preening, we see their third eyelid -- or nictitating membrane -- move horizontally across each eye. All raptors have this transparent eyelid, which keeps the eyes moist and clean, and protects the eyes during feeding and preening. In this shot you can see the eaglet protecting his eyes during a cleaning session.

Also, you might want to check out this web page where you can see an illustration of the third eyelid and how it works.

Crop Storage: Eagles are diurnal raptors (active in the daytime), and all raptors of this type have a special organ called a crop, which is a muscular pouch located in front of the bird's neck near the throat. This pouch serves as a storage area where food can be held for later digestion.

In these two shots taken during one feeding session, you can actually see the crop on the third eaglet fill up with food.

For the eaglets, the advantage of a crop is that they can quickly swallow food that their siblings might want, and for the adults it means the chicks can go longer between feedings. Besides storing food for later consumption, the crop also stores indigestible material -- like bones and scales. These unusable food pieces are captured in the crop and eventually molded into pellets that are later regurgitated. (Note that owls, which are mostly nocturnal, do not have crops).

Scavenging: While watching the cam, it seems that the eaglets spend a good part of the day just lying around. But after watching the eaglets on the live video feed at the Refuge headquarters, our cam technician reports that sometimes when it looks like the eaglets are lounging, they are actually digging for food bits in the bottom of the nest. In this shot, you can see a good example of an eaglet digging for leftovers while he's waiting for the next meal to be delivered.

Entertainment: And because life in the nest is not just about eating, preening, and napping, there's also time for little contests like the "I'm Bigger Than You Are" game that the eaglets seem to be playing in this photo. Fortunately for the third eaglet, it won't be long before he'll be able to hold his own in any such contests. :-)

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Extra Note: Just an extra post about some recent cam-related events. We have not heard the final word on whether the third eaglet will be relocated to Vermont, but as soon as the final decision is made, we'll announce it in the Web Log.

Also, our "Name the Eaglets Competition" has ended, and word from the Refuge is that they will select a winner or winners by May 6. Thanks to everyone for their creative and imaginative efforts in naming the cam eaglets. We were thrilled with the response from our cam watchers!

Until next time,
Lisa - webmaster

Thanks to Rachel Carson

Because April 22 is Earth Day, we'll celebrate it by paying tribute to the one person most responsible for the fact that we have bald eagles and ospreys to watch on our website -- Rachel Carson.

Although Rachel Carson grew up in Pennsylvania, she lived in Maryland for most of her life, so she is a local hero to those of us living in the state. In the first part of Carson's working life, she made a career with the U.S. Fish and Wildlife Service, eventually attaining the position of editor-in-chief of publications before retiring when she had the means to become a full-time author. During her writing career, she produced several popular books about the sea (including a National Book Award winner), but her most famous creation was her controversial 1962 work Silent Spring, in which she alerted the world to the dangers of the pesticide DDT and its deadly impact on both animals and humans.

Carson's book was based on a staggering amount of research, including work done at Maryland's own Patuxent Wildlife Research Center. The research done by the U.S. Fish and Wildlife Service there showed that DDT was working its way up the food chain and accumulating in the bodies of birds of prey -- particularly fish-eaters.

A pesticide applicator would spray DDT (a very popular pesticide in the 50s and 60s) in order to control mosquitos. Eventually the DDT washed into streams, rivers, and bays. The fish would feed on small animals contaminated by the pesticide, and after an eagle or osprey ate a large enough amount of fish, the pesticide would accumulate in their system -- a process known as biomagnification. (Click on the graphic).

Once a bald eagle or osprey had enough DDT in its system, the pesticide's breakdown product -- DDE -- would begin to inhibit the production of calcium for the bird's eggshells, and the eggshells would come out too thin. The end result was often that the egg would not hatch or the raptor would sit on the egg and it would crack, ending the life of the chick inside.

During the height of DDT use in America, the populations of bald eagles, peregrine falcons, ospreys, pelicans and similar birds began to plummet. In the 1930s, the Chesapeake Bay area saw an average of 1 to 2 eaglets produced per nest, but by the 1960s that average dropped to 1 for every 5 active nests. In America as a whole, the bald eagle population in the lower 48 states had dropped to approximately 400 pairs by 1963.

Rachel Carson's book was the catalyst that began to change all that -- it created awareness, outrage, and eventually political action. Despite intimidation from the chemical industry, Carson wrote her book and then continued to speak out after its publication, eventually appearing in front of Congress. In 1963, Carson's work was officially validated by President Kennedy's Science Advisory Committee. Carson died of cancer in 1964, but she lived long enough to know that her book had made a difference -- in America and throughout the world. Today many give her credit for sparking the modern environmental movement.

In 1972 the EPA officially banned the use of DDT in America, as evidence had grown about its impact on wildlife, its cancer-causing properties in humans, and its impact on unborn children. Since the banning, amazing efforts have been made by the U.S. Fish and Wildlife Service and conservation groups to rehabilitate bird populations using tools such as the Endangered Species Act, habitat conservation, captive-hatching and transplanting of young birds. As a result, osprey and pelican populations have grown dramatically throughout the country, the peregrine falcon has been removed from protected status, and talks are under way to remove the bald eagle as well. In the Chesapeake Bay area, eagle pairs have grown from a low of around 80-90 pairs in 1970 to a 2004 count of almost 400 nesting pairs in Maryland alone. The numbers nationwide are equally impressive. (Click on the graphic).

In 1980 Rachel Carson was posthumously awarded the Presidential Medal of Freedom -- the highest civilian award in America. She earned the medal for having the courage to stand up to intense pressure from the chemical industry -- pressure that would have intimidated most scientists into abandoning the book and staying silent. But even when the attacks turned personal, Carson stood her ground, and those who love the bald eagle and the osprey will be forever in her debt.

Rachel Carson:
"We still talk in terms of conquest. We still haven’t become mature enough to think of ourselves as only a very tiny part of a vast and incredible universe. Now I truly believe that we in this generation must come to terms with nature, and I think we’re challenged, as mankind has never been challenged before, to prove our maturity and our mastery, not of nature but of ourselves.”

Read more about Rachel Carson:
Rachel Carson website
Rachel Carson National Wildlife Refuge

Read more about how birds have rebounded from DDT:
Bald Eagle
Osprey
Peregrine Falcon

Read the EPA's warning about DDT:
DDT

Happy Earth Day!
Lisa - webmaster

Eagle Calls

Since the images on the Eagle Cam are without audio, we can't hear the cries and calls of the bald eagles via the website, but we can provide some sound clips below.

The adults and eaglets "talk" in different ways. The eaglets are reported to have a language all their own, from general yips to demanding screams when they're hungry.

And as for the adults, they don't have a wide range of calls, but their cries can carry a long distance. Some ornithologists have described the eagle's most common call as a gull-like cackle accompanied by thin squeals. It's reported that the female's voice is lower-pitched, and some biologists state that they can tell the sex by the call.

Bald eagles will often toss their heads back when making a call while perched. Calls can be given in greeting, as a declaration of ownership of food, as a demand to a mate, as a warning to new visitors at a favorite roosting site, or as a warning to an intruder telling him that he is flying too close to the nest or to the eagle's territory.

Below are several samples of adult bald eagle calls. All clips are in the MP3 format. Click to play, or right-click and save the files to your computer.

Eagle Call #1 (143KB) Eagle Call #2 (35KB) Eagle Call #3 (77KB)

Until next time,
Lisa - webmaster

Chick Development II

It's time to take another look at the eaglets' ongoing development. The chicks seem to change more every day, and they are rapidly reaching the time when they will look and act like true raptors.

On Monday April 18, all three eaglets will be at least 6 weeks old. To put this in perspective, at 7 weeks old, the oldest eaglets will have almost all their feathers. At 8-9 weeks they'll begin branching -- or flapping and hopping -- to different parts of the nest and maybe even branches of their tree. At 10-12 weeks, they'll be almost as big as their parents and will be ready to leave the nest for their first flight.

As for the feathers, both of the oldest chicks have extensive feather development. The third eaglet still has a good bit of down, but black feathers are now visible on his body as well. Also, we're starting to see more of the eaglets preening themselves as they maintain their new body coverings.

Along with the feather growth has come more wing flapping from all three eaglets, and it's an activity that will only increase in frequency as the eaglets approach their first flight. Here are photos of all three eaglets exercising their wings:

• Chick 1
• Chick 2
• Chick 3

When it comes to eating, the oldest chick is now tearing off his own food and the second chick shouldn't be far behind. It's interesting to see how the parent beak-feeds the ones that continue to need it.

As for thermoregulation, the eaglets have been managing their own body temperature for some time now -- as evidenced by the fact that the birds are left uncovered in varying types of weather -- and having all their feathers will help further insulate them from the elements.

Despite all the eaglets' growth, they are still reliant on the protection of their parents, so the mother and/or father are often nearby, even when we can't see them in the cam image. At this point, both parents are hunting for the family's food and taking turns watching over the eaglets.

So what's in store for the eaglets? Below you'll find a set of beautiful photos that show bald eaglets in the latter stages of development. It won't be long before our eaglets will look like these fierce and handsome raptors. Click on the thumbnails below for larger images:

Technical note: Just an FYI, if you see white streaks across the cams in the evening, note that spiders are attracted to the cams and can be seen hanging off them at night. During the daylight hours, however, they are not visible.

Until next time,
Lisa - webmaster

Other Cams on the Net

Over the last couple months, our cam watchers have helped us collect a group of links to other bird cams on the Internet. We're starting to see some major chick action on several of them, so we decided to list the links here in case you want to check them out.

Catalina Island Eagle Cam -- a California bald eagle nest with three adults, where a transplanted eaglet was just moved to the nest

Kent Washington Eagle Cam -- a Washington state bald eagle nest where a mother is incubating

Northeast Utilities Eagle Cam -- a Massachusetts bald eagle nest where an egg just hatched

Puleston Osprey Cam -- a Long Island osprey nest where one egg was just laid

Peregrine Falcon Cam -- a San Francisco, CA falcon nest where four eggs just hatched

Peregrine Falcon Cam -- a Harrisburg, PA falcon nest on the Rachel Carson State Office Building where the parents are incubating four eggs

Peregrine Falcon Cam -- a Pittsburgh, PA falcon nest where a mother is incubating multiple eggs

Peregrine Falcon Cam -- a University of Pittsburgh falcon nest where a mother is incubating multiple eggs

Peregrine Falcon Cam -- a Jersey City, NJ falcon nest where the mother is incubating

Peregrine Falcon Cam -- a Dayton, OH falcon nest where the mother is incubating eggs. The website offers a neat three-cam view

The Birdhouse Network: Nest Box Cam 2005 -- a Cornell Lab of Ornithology collection of live nest cams featuring active barn owl, elf owl, bluebird, and osprey nests.

Note: While you're at the Nest Box website, be sure to visit the 2004 Barn Owl Movies and click on the "Eating Mouse" video. Down in one gulp!

Until next time,
Lisa - webmaster

Eaglet Relationships

Before we talk about eaglet relationships, we have a couple of items to mention. First, it appears that one of the ospreys sat or landed on the Osprey Cam. Fortunately the eggs have not arrived yet, so we will try to get the bucket truck (which we rent from a local utility company) out to the platform to fix the cam before the eggs arrive. We'll post any news about the fix on the cam page.

Second, we wanted to share a link for the Vermont Bald Eagle Restoration Initiative website. It has lots of info regarding the effort to reestablish eagles in the Green Mountain state -- something that might be in store for our littlest eaglet. Also be sure to check out their Gallery section for some amazing photos of young bald eagles.

Now onto eaglet relationships. Quite a few cam watchers have asked whether the eaglets would ever turn on each other, as we often hear accounts of chicks killing other chicks in a nest.

Raptor nests can be very competitive places. The first chick born has the advantage in that it is bigger, frequently feeds first, and often receives the most food.

In places where food is hard to come by, there is a chance that eaglets will kill other eaglets (called siblicide) to eliminate the competition for food. In areas where food is abundant -- such as at Blackwater Refuge and around the Chesapeake Bay -- incidents of raptor siblicide are not as common. If the food supply is adequate, then there is less pressure in the nest, and the chicks are not in such a "do or die" situation.

The ospreys are a good example -- they have access to plenty of fish at Blackwater, and in the two years we've observed multi-chick families on the platform, we haven't witnessed an incident where one chick clearly harassed or attacked another. But siblicide in osprey families does occur -- as author David Gessner found out while observing ospreys for his wonderful book "Return of the Osprey: A Season of Flight and Wonder."

Gessner witnessed a fatal chick attack while observing a nest around Cape Cod, Massachusetts. At a four-chick nest, he saw the third chick violently attack the youngest chick. While the incident played out, the mother osprey made almost no effort to stop the attack, and the chick died.

Gessner admitted that he was at first very angry with the mother osprey for not preventing the attack, but said later that he realized he was judging the mother by human values rather than by raptor values. Osprey expert Alan Poole explained the bird's attitude when he said "Parents never interfere in such squabbles, apparently because it fits their interests to raise one or two well-fed young, instead of the three or four weak ones that would result if scarce food were shared equally." Three or four weak chicks will not perpetuate the species, because it's likely that once they leave the nest, none of them will survive in a harsh world where even strong juveniles struggle to reach the breeding age.

There is possibly another form of natural wisdom at work here as well -- if brood sizes are naturally reduced to match the available food supply, then no unnecessary pressure is being put on the already limited resources of the local ecosystem. Nature is keeping the local population size in check.

In our own cam nest, we've seen some competition between the eaglets, and that is only natural as most broods of young animals will exhibit varying degrees of hierarchic rivalry, and eaglets, in particular, are bound to exhibit characteristics betraying the fierce predators they will one day become. But the abundance of food in the cam nest has relieved some of the tension that might otherwise exist and has also produced three seemingly strong eaglets.

And while we're on the topic of eaglet relations, we wanted to alert you to an entertaining video showing how young bald eaglets "relate" with one another. The video is from the Catalina Island Bald Eagle Cam website; look for the "short video" link at the bottom of the page. The video is only about 530KB in size, but it shows some of the great action we probably missed in our still images back in early March. Even the towel isn't safe in this group of young raptors. :-)

Until next time,
Lisa - webmaster

Cam & Third Chick

As you might have noticed, the cam was repositioned Thursday morning. Craig Koppie, an endangered species/bald eagle expert from the U.S. Fish & Wildlife Service, climbed the tree to inspect the condition of the nest, to check the chicks, and to reposition the camera while he was there.

Craig said the nest is in good condition following our windstorms. He also reports that the third chick is strong, healthy, and has good muscle development. He said it's clear that the parents are providing enough food for all three chicks and are making sure that the third chick is getting his fair share. From what Craig can tell, the third chick is developing normally.

Craig is also part of the USFWS effort to reintroduce bald eagles into the state of Vermont, which is the only state without at least one pair of nesting bald eagles. Within several weeks, the USFWS will be transplanting several eagle chicks from the Chesapeake Bay area to Vermont where they will be raised and, later this summer, released into the wild.

Craig has suggested to our Refuge Manager, and he has agreed, that the third chick would be a good candidate for this program. We should know shortly if our third chick gets the "nod" and when it will happen.

Everyone at Blackwater Refuge is excited that our littlest chick is not only healthy and strong, but might get to play a role in reestablishing bald eagles in Vermont. We don't have any more details now and we want to stress that there is still a chance the eaglet will stay put, but we wanted to share this good news with our many cam watchers who were worried about the condition of the third eaglet.

Until next time,
Lisa - webmaster

Pin Feathers

When the oldest eaglets are within view of the camera, we can sometimes see tiny pin feathers on their wings. Pin feathers are how new feathers are born. The feather comes out wrapped in a thin shaft of tissue, which will eventually split, allowing the new feather to unfurl and grow to its full size.

We'll talk more about eagle feathers in future Web Logs, but for now we'll mention a couple important facts. First, feathers are made of the tough protein keratin, which is the substance that makes up human hair and nails. An adult bald eagle can have around 7,000 feathers on its body, and although the feathers are light, together they will weigh twice as much as the eagle's skeleton.

Bird feathers can be broken down into several categories such as contour feathers (the most visible feathers covering a bird's body), flight feathers (on the wings and tail), and down feathers (kept closest to the skin for protection from heat and cold). Visit this excellent article on feathers if you'd like to learn more about the role that each type of feather plays in a bird's life.

Also visit the Bald Eagle Information website to see close-up photos of beautiful bald eagle feathers.

Note on the cam: Just an FYI, the eagle expert had to cancel a recent visit to the eagle nest because of the stormy weather and large amounts of rain that we've had at the Refuge. We hope that in the near future we will be able to reschedule another visit so we can seek out his advice.

Until next time,
Lisa - webmaster

The Cam Tree

On the morning of March 8, Blackwater Refuge experienced a strong storm with powerful winds -- this was the same day that our eagle nest camera was accidentally pushed down. The staff at the Refuge could see the Eagle Cam on the video monitor in their office, and they said the nest was really rocking.

Eagle nests in general get very heavy because the eagles add to them year after year. It's possible that over time, either the weight of a nest or the age of a tree will bring an eagles' home to the ground, but our cam nest apparently did well in the storm, which had wind gusts as high as 50 mph.

As for the cam tree, it's a loblolly pine. About 60% of eagle nests in the Chesapeake Bay region are in loblolly pine trees. Eagles probably like the loblolly because of its immense height and sturdy nature. These beautiful and majestic trees are a common sight at Blackwater Refuge, and they provide a wonderful canopy for a quiet walk in the woods.

Visit this Ecology page to see photos of the loblolly pine and to learn more about its popularity with wildlife.