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Bald Eagle Facts
Q&A with Peter Nye in 2008
New York Department of Environmental Conservation

Characteristics

Q: What is the difference between the two geographical species?

A: There are not two species of bald eagle, just one, Haliaeetus leucocephalus.
The “southern” and “northern” birds you refer to, are not even different sub-species; they are the same. There are, however, morphological (physical) differences between extremely southern versus extremely northern eagles, which disappear as the two approach each other. This species, as in most others, follow something called Bergman and Allens rule, which states that more northern animals are typically heavier and larger than more southerly ones. Such differences relate to climate and physiological differences and needs. I urge you to look further into that rule.


Life Cycle

Q. How long does it take for the eggs to hatch after they are laid?

A:
35 days.

Q: How old are eaglets when they leave home?

A: About 4-5 months old.

Q: How long do nestlings stay in the nest? Once they leave, will they return to the nest or take off for good? My class has been watching an eagle cam in Florida. The chicks hatched in January and are brown and have lost all the baby white fuzz.

A: Florida eaglets will be the same as eaglets from any other US state; they hatch after 35 days of incubation and are in the nest for 10-12 weeks before they fledge or take their first flight. Often, the fledging process is gradual, where the birds may branch, leaving the actual nest but not the tree, and take another few days or perhaps a week to actually fly away from the nest tree. Then, they return after they calm down and realize that wasn’t so bad, and was actually fun! They’ll hang around the nest area for 1-2 months, honing their flight skills and constantly begging for food from their parents. Then, when they think they are ready (and the males always think they are ready before the females), they venture out to parts unknown on their own, beginning wandering that lasts about a year before they return.


Ecology

Q: How did a juvenile eagle cross the Atlantic to Ireland in November 1987?

A: I recall reading about that at the time, but don’t recall what they said about it. I’ll suggest a way here that may or may not have been the answer. I’m not certain that anyone confirmed the juvenile to be a bald eagle, versus a young white-tailed sea eagle which live nearby and look very similar when young. At any rate, let’s assume it was indeed a bald eagle. Really, if no one helped it over there, the only way is that its internal compass was really messed up, and it just got swept up in a strong weather system and got carried over there, unable to fight fierce winds. This is not unusual, and we see all kinds of exotic birds that are not typically found in certain areas after tornados, hurricanes and strong weather carries them to far off places.

Q: When/where can we see eagles in Alaska?

A: You almost cannot go wrong visiting southeast or southern Alaska at almost any time of year. You are guaranteed to see LOTS of bald eagles. I guess it might depend on the weather you are willing to endure. Certainly in terms of numbers, the fall months are when the largest numbers concentrate in the Kenai area or along the Chilkat River in Haines (Southeast Alaska). I’ve been up to Haines in November when it was –10 deg F, crystal clear, gorgeous blue sky, and hundreds of eagles. Nothing like it. Check out web sites for Alaska Fish and Game, U.S. Fish and Wildlife Service Alaska, or search “Haines – eagles."

Q: Is it true that Northern eagles don’t need as much range as Florida eagles?

A. I would think just the opposite, generally. Since Florida has suitable habitat year-round (all else being equal in terms of fish-food supply), eagles don’t need to search out additional habitats, say in winter, and can stay close to home year-round. Northern birds are more forced to move with the weather.

Q: How do the migration patterns of the Southern Bald Eagle differ from those of the Northern areas: distances, times, feeding patterns, breeding, etc?

A: No self-respecting Northern eagle would be caught dead with chicks in January! Of course, it’s just too darn cold, and most of the water they require to hunt in, is frozen. In Florida, of course, this is not a problem; heat is. So, to avoid the hottest time of the year, Florida eagles do their nesting and chick-rearing in the winter months. Those young, and sometimes, a very small percentage of the overall adult breeders, then move north during our late spring and summer months. Mostly, FL eagles have year-round suitable habitat conditions available to them, so they do not have to move. Northern eagles, on the other hand, will move south when conditions force them to (no open water, hence fish). This southerly movement typically begins in November, eagles winter-over somewhere to the south that is suitable, then return north in late March or early April, depending on how far north their breeding territories are. You can glean a lot of this exact information (where they winter and when they arrive and leave) from the Journey North eagle site. In mid-latitudes or even in a place like New York State, when conditions are not severe and open water is available, many eagles will not move at all, and will remain close to their breeding territories throughout the winter.

Q: What types of birds and fish do eagles eat?

A: Whatever is most abundant and easiest to get ahold of...seriously. Although different pairs of eagles can certainly have different dietary make-ups, generally, the list of prey items found being consumed by eagles is HUGE! If it’s available, chances are good they’ll eat it. Having said that, waterfowl are big on their bird list, as are fish in the herring family.

Q: Can eagles become ill feeding on a deer carcass?

A: That is an excellent question, and demonstrates good thinking. You considered potential indirect effects to eagles! The answer is, absolutely! You are correct stating that eagles (and other scavengers) often feed on carrion, so, generally, wouldn’t be negatively affected by a little rotten meat. And, this is generally true. Where such feeding becomes a problem, and particularly in the situation you mention, deer, is when the deer might have lead in it’s body from a hunters bullet. Indeed many raptors, including eagles (both golden and bald), develop lead poisoning and die from consuming animals with lead in them, be it deer, small game, or waterfowl that used to be hunted with lead shot. Lead is known to be an extremely toxic contaminant, to wildlife and to humans, and has therefore been eliminated in many things, such as paint. In the 1990’s, it also became illegal to use lead shot over water for waterfowl hunting, as many eagles were found to be dying of lead poisoning from eating crippled waterfowl. However, there is still much lead out there and it is still used for almost all other forms of hunting. Except for California, who banned lead in all hunting cartridges, I don’t believe any other state has banned lead totally. This needs to happen.

I'd like to further comment on your question, involving an even more indirect result of an eagle or eagles feeding on road-killed deer: death by collision with a vehicle. Believe it or not, we get a significant number of road-killed eagles each year, because they are attracted to other animals (carrion) and are hit and killed on the roadway or railroad tracks, and subsequently run over as they feed at the side of the road or try to fly off the carcass but are too slow and too low and get hit. The only solution to this is removal of carcasses as fast as possible.


Peter E. Nye
New York State Dept. Environmental Conservation
Division of Fish, Wildlife and Marine Resources
Albany, NY
Spring, 2008


 

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