April 10, 2005
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