Eagle Update

I’ve seen quite a few bald eagles on the North Shore lately.

Feed me, feed me!
Update from the nest

Our three eaglets are now focused on the business of growing up, eating plenty and getting strong. They’re a full-time job for the adult eagles, in need of frequent feedings and help staying warm, but these adults have proved their mettle as parents. Fish, pigeons, muskrat and squirrel have all made appearances at meal times, and both adults are taking turns keeping the chicks protected from the March winds of Minnesota.

Sibling squabbles

Competition starts early in the life of a bald eagle. As we’ve seen, bald eagle chicks hatch asynchronously, meaning they don’t all hatch at the same time. A few days difference in age means differences in size and strength for the first weeks of their lives outside the shell, resulting in sibling rivalry. At this young age, one eaglet is unlikely to really hurt another, but that doesn’t keep them from trying! Viewers may see tiny grey heads bashing each other during feeding times. This behavior is a normal and healthy part of early life for an eaglet. Working to get to the best food bits first, to have the most comfy spot in the nest and the most parental attention helps eaglets grow strong and smart. Eagles’ lives don’t get easier once they fledge and join the adult population, so it’s very important they develop a competitive spirit early on.

Parental strategies

Parenting human children, someone once said, is like making chili; everyone has their own recipe. That’s true in the animal kingdom, too, where biologists describe two basic approaches to caring for the young. Some species are referred to as precocial – their young are mobile and pretty much able to take care of themselves as soon as they’re born or hatched (what parents of any teenager might occasionally find themselves longing for). Horses, giraffes, domestic chickens, ducks and turkeys – all are precocial. The super-precocial African wildebeest has calves that can stand within six minutes of birth, and outrun their main predator, the hyena, within a day, giving them a significant survival advantage.

Other species are altricial – they need lots of care and feeding for at least a while after being born or hatched. Most backyard songbirds are altricial, as are eagles and other raptors. That’s why we get to be intimate witnesses to all that goes on in our bald eagles’ nest. If eagles were precocial, they’d fly off shortly after being hatched, and there wouldn’t be much to see.

Altricial development may offer benefits to the species, as well as to us spectators. Altricial birds, like eagles, hatch with fairly small brains, but the rich parent-provided diet after hatching lets their brains grow larger and more complex than precocial birds, providing advantages for survival. It certainly seems to work that way for humans. Altricial development also tends to promote greater socialization, as parents may need to work together to provide care for their young. Certainly we see that with our bald eagle pair!

While humans may be at one end of the altricial development scale, taking as much as 18 years for the young to become mature (sometimes more – much more!), such traits are not confined to higher order critters. Some insects such as ants and bees also can be categorized as altricial. One fascinating group of beetles, known as burying beetles, displays a surprising amount of parental care. True to their name, burying beetles chew up and bury the bodies of small animals as food for their larvae. Both parents then guard the larvae and the carcass/food from other intrusions, and they will feed the squiggling larvae a regurgitated liquid protein in response to begging. It is particularly noteworthy that male burying beetles participate in parental care alongside the females. Although the burying beetle larvae are capable of moving about and feeding on their own, the parental care shown by burying beetles is thought to produce fewer but larger and stronger adults.

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