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02/28/09
Twenty-Something Questions About Bald Eagles,
Filed under: General, Birding & Outdoors, Florida & SE US, Bald Eagle Nest
Posted by: Ken @ 11:56 am

Eagle Flying 20090203

While standing watch at our local Bald Eagle nest in South Florida, visitors seek much information. Thrilled to see the two adults and their two chicks at such close range, their curiosity is aroused and they ply me and other eagle watchers with questions. Not infrequently, my answer has to be “I’m not sure about that– I’ll have to look it up.”

Since there is a steady turnover of visitors, the same questions get asked over and over again. My attempt to limit them to a “top 20″ list did not succeed, even when I combined several of the questions. Readers may contact me with more questions, which I will try to answer.

For a wealth of information, visit my collection of  BALD EAGLE INFORMATION LINKS

Q: When was the nest discovered? How was the nest found?
A: In early March, 2008, a local resident found and photographed the nest, which contained a single well-developed chick.She reported it to the Florida Fish and Wildlife Conservation Commission (FWC), and a spotter aircraft confirmed her sighting on April 9, 2008.

Q: How long has the nest been here?
A: We really do not know, but from the size of the nest it appears to have been in use for more than two seasons. Local residents have seen adult Bald Eagles in this area for several years, some carrying nesting materials and prey, but no one ever reported seeing the nest to FWC.

Q: Does the same pair use the nest year after year?
A: Bald Eagles commonly use the same nest, adding to it each subsequent nesting season. They sometimes alternate between another nest in their territory.

Q: How do you tell the male from the female?
A: Both sexes have identical plumage. Females are usually heavier than males, which can be noticeable if they are viewed next to each other. A more subtle difference is that the base of the female’s bill (measuring from top to bottom) is bigger than that of the male. In comparable  photos, I found the ratio of width of bill at its base to the distance between iris and bill tip to be about 0.5 in the male and 0.6 in the female.

Q: How many eggs do they lay?
A: Usually two eggs, though sometimes there may be only one, and, rarely, a third.

Q: When were these eggs laid? How long do they take to hatch?
A: The first of this pair’s two eggs was probably laid on December 13, 2008. The second was deposited about 5 days later. They take about 35 days to hatch, on average.

Q: When did these eggs hatch?
A: The first egg hatched on or about January 17, and the second about 5 days later.Unlike many birds that do not incubate the eggs until an entire clutch is laid, the eagle begins incubation immediately. Therefore the first egg hatches earlier and this chick will be ahead of any subsequent siblings, giving it a competitive advantage.

Q: How could you tell when they were laid and hatched?
A: By changes in the behavior of the adult pair. On December 13 they suddenly stopped bringing in nesting materials, and the female remained sitting deep in the nest nearly all the time. Incubation was continuous until January 17, when both adults spent much time peering down into the nest, and the next day were seen bringing in prey and tearing off small bits of flesh to feed the chick. The female continued incubation and feeding until about 5 days later, when she stood higher in the nest, sheltering the chicks under her wings and not needing to incubate the second egg.

Q: Does only the female bird sit on the eggs?
A; Both parents share incubation duties, though the female is said to spend more time at the task. We often saw them exchange duties early in the morning, and sometimes at various times of day.

Q: How long do the chicks stay in the nest? When do they fly?
A: Eaglets stay in the nest for about 11 weeks. They may begin to climb out on the branches of the nest tree during the last week or so, where they exercise their wings. Their parents begin to bring less food and entice them to clamber after it. The chicks lose some weight as they develop the ability to fly.

Q: Is it true that chicks sometimes kill their siblings?
A: The first hatched chick is larger and stronger. If food is scarce, or if one of the parents dies, the larger eaglet may keep the smaller one(s) from getting enough food, and they may fail to thrive. Older chicks are known to push their siblings out of the nest, and in rare instances, may even eat them. This behavior is actually a survival strategy, as it may assure that at least one eaglet survives when there is a scarcity of food.

Q: How long do the parents keep taking care of them after they fly?
A: The eaglets will stay near the nest tree for about another month, still dependent upon their parents to bring them food. Then they instinctively develop hunting skills of their own and become independent.

Q: What do eagles eat?
A: These eagles catch a lot of fish, or steal them from Ospreys. They often bring in birds such as Cattle Egrets and White Ibises. They have been seen carrying in snakes as well.

Q: Where do they go after fledging?
A: Here in Florida, most eagles migrate northward. In the northern US, Bald Eagles move southward as lakes freeze up. In Florida, there are two general patterns of migration. Eaglets from the central and northern parts of the state go up the east coast, with many congregating on Chesapeake Bay in Maryland. Eagles from the southern tip of Florida tend to wander within the State. All return to the general area of their nest around October. Bald Eagles from Canada and the northern USA tend to return to the nesting territory in late winter or early spring.

Q: Do they come back to the nest?
A: Sometimes they will visit their nest tree, but they will not be welcomed by the adults, as they will already be in the early stages of courtship and nest building. Eagles generally protect the territory around their nest, out to about a two mile radius.

Q: The eaglets look black. When do their heads turn white?
A: The chicks will develop the white heads and tails of adults when they are about 5 years old, which is also when they begin to breed.

Q: How big is their wingspan?
A: Up to about 8 feet. Northern eagles, such as in Alaska tend to be bigger than the Florida race.

Q: Do eagles make a noise?
A: Eagle watchers are sometimes disappointed when, expecting a majestic scream, they hear the birds’ chirping call. The chicks squeak softly as they beg for food, barely audible above the noise of traffic.

Q: Is it true that eagles mate for life?
A. Generally, yes. Around November the pair get closer and start courting as if they were falling in love for the first time. If one of the pair dies, the other will quickly seek another mate.

Q: Does the pair stay together during migration?
A. No. After the chicks become independent, the adult birds go their separate ways for the remainder of the summer and, in the case of Florida’s eagles, until fall, when they both return to the vicinity of the nest. They become re-acquainted and “fall in love” all over again every year.

Q: Are there many eagles in Florida?
A: Florida, with 1133 breeding pairs counted in the last national survey in 2006, was second only to Minnesota (with 1312) in the number of active Bald Eagle nests in the lower 48 States. The  2007-08 Florida count climbed to 1,280, according to FWC. It is believed that another 20% of nests go unreported.

Q: Are eagles still considered endangered?
A: Bald Eagles were removed from the Federal Endangered Species List in 2007, but they continue to be protected by Federal and State laws and guidelines. In Florida, the species is well-established and not in peril statewide; however, as it establishes new territories that can come in conflict with humans, it faces the threat of local extinction.

Q: Why don’t our eagles have white feathers on their legs?
A: All Bald Eagles’ “leggings” are brown, the same color as their body. Only the heads and tails of adults are white. Some other eagle species, such as Steller’s Sea Eagle (which nests in far northeastern Russia) have white feathers on their legs.

Q: Is this really the first eagle nest in Broward County?
A: Before DDT and persecution of eagles had devastating effects on the its population, Bald Eagles ranged all over Florida. After DDT was banned in 1972, The states monitored their eagle populations and tracked their recovery. Since then, a nest was found in the far western part of Broward County, but it never was shown to contain eggs or chicks. The Pembroke Pines nest is the very first active eagle nest to be registered in Broward County. Of course it is possible that other earlier nests went unrecorded, as the species has nested in northern Miami-Dade.

Q: Do eagles always nest high in trees?
A: While Bald Eagles seem to prefer trees, they may nest on the ground or on cliffs. In coastal areas of Florida, they may nest in mangroves, only a few feet above ground level. They may even use artificial structures, such as cell phone towers.
Several now nest in exotic Australian Pines, an unexpected phenomenon,
as it was believed that removal of exotic trees from Bald Eagle habitat
worked to the advantage of the species.
 
Q: Why did these eagles nest in the city, when there is plenty of land for them in the Everglades?
A: Several factors may be at work here. First, Florida’s eagle population is increasing quite rapidly. Second, suitable rural and wilderness nesting areas are disappearing as land is cleared, wetlands are filled and housing is expanded into their historic range. Third, catastrophic events such as fires may suddenly displace large numbers of adult eagles. Fourth, the many quarries and lakes in urbanized areas provide a plentiful food supply. All this adds up to the inevitable need for the birds to seek suitable nest sites nearer to human habitations.

 

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