Begging for Food from Mr. President and the First Lady

No, not that President!  Thousands of people are captivated by the live video stream of a pair of bald eagles, named Mr. President and The First Lady, nesting on top of a Tulip Poplar tree at the U.S. National Arboretum.  The reality peek into the life of a pair of breeding eagles, together with new research just published in the journal Nature Communications, show how parents decide which of their hungry chick gets fed.  Begging is important, but sometimes begging is ignored and the parents feed their favorite.  Now we know why . . .

eaglesgettingfedWe watched the pair of eagles stoically keeping two eggs warm beneath their downy feathers through the rain, snow, and wind, of early spring.  Then we delighted when each chick cracked out of its shell–the miracle of new life–and wobbled naked and feebly in apparent bewilderment before their parent’s yellow beak poking raw fish flesh down their gullets.  Soon both chicks were begging for food, but the older one dominated in the sibling rivalry for seafood meals of fresh fish plucked by their parent’s talons from the Anacostia and Potomac Rivers.

We admire the exhaustive labor of the attentive parents providing for their hungry offspring. For most species, including humans, the production of offspring is the most energetically demanding stage of an animal’s life.  According to a recent study, raising a brood successfully puts a metabolic demand on breeding birds that is equivalent to a human cycling in the Tour de France.baby-eaglets eagles

With many mouths to feed in the nest, which one gets the treat?  The noisy wheel gets the grease, right?  Not necessarily.  In one quarter of all bird species studied, the parents ignore their most demanding chicks that beg.  Why?

Even though they beg ferociously in hunger, the parents of some birds ignore their most demanding chicks and feed their favorite–the biggest one.  The parents give this fat chick the food even though it doesn’t beg for it.  How can this odd preference to give in to begging in some bird nests but ignore the most demanding chicks in others be understood?

A research team led by Zoologist Stuart West at the University of Oxford, studied 143 species of birds to find out, and they found a pattern.  Whether parents respond to their offspring’s begging or ignore it, all depends–not on the family dynamics–but instead on ecological circumstances.  The researchers found that in predictable and bountiful environments, chicks in worse condition beg more and their parents respond to the begging by giving the most demanding child more food.  That’s apparently what’s happening in the nest of Mr. President and the First Lady, which is situated nearby two great rivers teaming with plentiful fish.  But in poor environments, or in environments where food is unpredictable, the researchers found that parents ignored the begging chick.  Instead they favored their chick that was bigger or had physical features that they favor as signs of quality.  (The prettier one.)

This harsh unequal treatment seems to make sense in poor environments, because the strategy of the parents seems to be to put most effort into their offspring that is most likely to prosper.  In a harsh environment, raising one offspring successfully is better than having both offspring fail to thrive, so they put the greatest effort into assuring that the bird that has the most advantages will survive.bald-eagles-t

In this interesting study of communication and behavior in birds, it is difficult not to draw parallels to people.  Children of the well-off are notorious for being demanding and spoiled, but children in families living in hard times don’t beg, and their parents may lavish over a favorite child.  There is no scientific basis for drawing that parallel between birds and people, but the parallel does help to remember the findings of this new research on why birds sometimes favor their most demanding chicks, but in other ecological conditions ignore them in favor of the prettier one.

photo/video credit: © 2016 American Eagle Foundation, EAGLES.ORG.

 

This entry was posted in Animal Research, Awareness and Attention, by Douglas Fields, Sensing, Thinking & Behaving and tagged , , , , ,
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Douglas Fields

About Douglas Fields

R. Douglas Fields is Chief of the Nervous System Development and Plasticity Section at the National Institutes of Health, NICHD, in Bethesda, Maryland, and author of the new book about sudden anger and aggression “Why We Snap,” published by Dutton, and a popular book about glia “The Other Brain” published by Simon and Schuster. Dr. Fields is a developmental neurobiologist with a long-standing interest in brain development and plasticity, neuron-glia interactions, and the cellular mechanism of memory. He received degrees from UC Berkeley, San Jose State University, and UC San Diego. After postdoctoral fellowships at Stanford and Yale Universities he joined the NIH in 1987. Dr. Fields also enjoys writing about neuroscience for the general public. In addition to serving on editorial boards of several neuroscience journals, he serves as scientific advisor for Odyssey and Scientific American Mind magazines. He has written for Outside Magazine, The Washington Post Magazine, Scientific American and Scientific American Mind, and he publishes regularly for The Huffington Post, Psychology Today, and Scientific American on-line. Outside the lab he enjoys building guitars and rock climbing.

The opinions stated in the blog are the personal opinion of the author and not those of the federal government.

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