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Me First! Whooping Crane Pecking Order
Photo Operation Migration

Background
If you are in a fa
mily with siblings, you might feel like a bigger or older sibling has more "power" or "rights" than those who are younger or weaker. That's how it is for Whooping cranes, but did you know that most wild Whooping cranes don't grow up with brothers or sisters? Wild Whooping cranes almost always lay two eggs, but only about 60 percent hatch. Babies face so many dangers in the wild that over one-fourth of the hatchlings die in their first month of life, especially during the first two weeks. Only about 1.5 percent of wild Whooping crane nests have three eggs (none have more than that!) and all in all, only about 8 percent of nests produce two chicks that both survive to reach the wintering grounds.

When two baby cranes in a nest DO survive, they can't waste time bickering, especially in years when food is scarce. Fortunately, they don't usually have to. The smaller chick (the one who hatched out one or two days after the bigger one) can see that its sibling is stronger and bigger. It keeps out of the way! If the smaller chick isn't careful, the bigger one may grab it by the back of the neck, peck at it, or chase it. But the littler chick quickly figures out that it's best to simply avoid its big sister or brother. The bigger chick is usually first to be fed and cared for, but as long as there is enough food to support both babies, they both have a good chance of surviving.


One Big Happy Family: Cohorts and Pecking Order
Photo USGS

The baby cranes that were costume-raised in captivity to start forming the new Eastern flock must deal with something that wild Whooping cranes never do: a whole group of other baby cranes, all in the same "family." But since these birds aren't necessarily related at all, they're called a cohort. There's plenty of food for all of them, but they still instinctively need to sort out who's top dog—or rather, top bird.

Scientists have been raising Whooping cranes in captivity for many years now. They have learned that when they raise a cohort, the birds eventually fall into a linear hierarchy. This means that Crane A can "boss around" all the other cranes. Crane B can boss around all the cranes except Crane A. Crane C can boss around all except A and B, and so on. Other birds that have this kind of linear hierarchy include barnyard chickens and chickadees. Sometimes a whole group of baby chickens will gang up on the bird at the bottom of the hierarchy, and even peck it to death. Chickens were the first birds observed developing a linear dominance hierarchy, so we often call this arrangement a pecking order. Chickadees also have a dominance hierarchy, but they work it out without hurting each other.

Young cranes sometimes fight to figure out their dominance hierarchy. But as soon as everyone knows exactly where they fit in, they can settle their disputes in a surprisingly peaceful way. This is because the dominant bird always wins
whenever two birds both want the same morsel of food, or the same particular place.

Socialization: Helping Cranes to Get Along
A pair of wild crane siblings are usually two days apart in age, and because they are different sizes it's easy for them to figure out which bird is dominant without much fighting. Crane chicks in a captive-bred cohort can be closer in size than sibling wild cranes. The tiniest one might have a few days or a week of being fed alone before it meets other birds in the cohort. When the cranes finally meet one another, it can take a while before they figure out their dominance hierarchy.

Kelly Maguire, Aviculturalist for International Crane Foundation

The pilots at Operation Migration want their crane chicks to work out their pecking order without too much actual pecking. They call their process socialization. The work on socializing crane chicks starts at the Patuxent Wildlife Research Center when the cranes are still tiny. The process is off to a good start by the time the young cranes are delivered to what will be their summer home and future breeding grounds at Necedah National Wildlife Refuge in Wisconsin. Aviculturist Kelly Maguire worked with the young cranes being trained to follow the ultralight on their first migration. Kelly described the very first chicks for the project in 2001:

When the chicks first arrived at Necedah National Wildlife Refuge, it was difficult for me to see an obvious hierarchy. But within weeks, both cohorts began showing a definite and consistent one. Hierarchy can change, but much of it is reinforced during exercise. When the chicks get out of the pen, before the ultralight takes off, they are jumping and flapping to burn energy—but you will also see some dominate and submissive behaviors. If a lower-ranking chick gets a bit too rowdy, a "higher" chick may grab the back of its neck, or mildly chase the submissive one just to keep it in line. We see very little intense aggression at this point, which seems to mean that the main structure of the hierarchy has been established.

Flying Order With the Ultralight
As the hierarchy works out among the birds in each cohort, and between the two cohorts, the birds will find their "place in line" for following the ultralight. This is a very important process. Once the socialization is complete, the birds won't have to argue or fight about where they fly. When 10 or 20 cranes are flying in formation, two bickering birds could disrupt the whole line. When they all stay in proper formation, each bird can take advantage of the air currents of the ultralight and the birds in front of them, to make flying as easy as possible. Getting along helps everyone!


Try This! Activities
  • Write a paragraph explaining why it's important for the trainers and ultralight pilots to thoroughly understand and work with the cranes' dominance structure.
  • Explain how you think having a "pecking order" order might help a species survive. Do you think it holds true for humans (who have broader social skills)?
  • Play the Pecking Order Simulation Game.
  • We humans have many things in common with animals, including an urge to fit into a social hierarchy. Discuss how school classes are "cohorts" too, with a large number of students all close to the same age.Think about the way kids in a class sort themselves out socially. How is their "pecking order" similar to that of a whooping crane cohort? How is it different? Write your thoughts in your journal, or discuss as a class.

National Science Education Standards

  • An organism's behavior patterns are related to the nature of that organism's environment, including the kinds and number of other organisms present.
  • An organism's behavior evolves through adaptation to its environment. How a species moves, obtains food, reproduces, and responds to danger are based in the species' evolutionary history.

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