Posted by: momecology | January 18, 2008

it could be worse: they could actually kill each other

As I may have mentioned before, I have two sons. Lovely, affectionate boys; they kiss me even when I don’t ask, even the 10 year old. And yet, daily, I am forced to ask myself: why the hell can’t they keep their hands off each other? The whacking, the shoving, the tackling, the kicking …. it drives me around the bend. (Anybody else got this going on? I am collecting data with which to test the idea that boys are even capable of keeping their hands to themselves. Preliminary results: NO.) Not infrequently just the decibel level causes me to teeter close to behavior not sanctioned in your better parenting books (such as roaring “SHUT UP and get away from each other!” Not that I would actually ever do that. Ahem.). On those days, I take deep cleansing breaths, and remind myself that if they were herons, one of them would likely already be dead. And not in the figurative sense. Dead dead. Actually dead.

Now I know this is a thought that only a bird geek such as myself would have, but stay with me for a minute. Herons are long-legged water birds. They eat fish for a living. And, in most years, the oldest in a group of heron kids can be depended upon to kill one or more of its siblings. Heron chicks make human brothers look tender-hearted and polite in comparison. They exclude one another from the food their parents bring back to the nest. They peck one another mercilessly. They drive the youngest chick right out of the nest.

This might seem like random cruelty. While it certainly is behavior that would qualify as cruel in a human, it is definitely not random. Herons make their babies in very uncertain environs. They get down to doing the deeds that will result in chicks too early in the spring to be sure whether there will be enough food to to raise more than one chick. So they lay two or three eggs, because an egg is a relatively cheap investment in the possibility of more kids. If a good season follows, and there’s plenty of food, it’s all good, and they bring off a bumper crop of kids. If there isn’t enough food to go around, they are left with a Sophie’s Choice of either feeding every kid too little food to ensure it survives, or feeding some kids and not others. In lean times, in a strategy that biologists call brood reduction, they employ the second option, and allow one or more chicks to starve to death.

Now, a heron has not got the kind of brain that would even allow it to play a game of I Spy. It isn’t using some complicated emotional thought process to decide which kid it likes best when fat juicy fish are in short supply. When it gets back to the nest with some food, it simply feeds the chick that begs most vigorously, that screeches the loudest, that muscles its way to the front of the line. Kind of like us dispensing french fries at the end of a long day — the parents just react with whatever behavior will reduce the racket.

Grey heron feeding chicks

© BBC Natural History Unit

(Click on the picture to see a short video of the scrum at a Grey Heron nest. And you thought your kids jump on you when you get home at night. And yes, they are puking the food up into their babies’ mouths. Ew.)

If your kids are close in age, they may be evenly matched, but heron chicks almost never are. When an animal is going to reach full adult size in less than 2 months, 24 hours’ difference in hatching time makes a significant difference in size and strength, and the first chick to hatch has an advantage in size over any younger siblings. That chick uses its advantage; it stands up taller, screeches louder, and shoves harder to get closer to any adult returning to the nest with food. Because it gets fed more, it grows faster, which makes it bigger and stronger than its siblings, which in turn makes it even better at hogging all the grub.

Despite our supposed civilization, this is not an unfamiliar story. Them that has, gets. In a good season, even the advantaged eventually get full. When they are snoozing off their equivalent of a three-martini lunch, the younger kids get enough meals to survive and leave the nest, with never a look backward, no, not even a call at Thanksgiving or Christmas. In a bad season, when the oldest and strongest never get full, the younger chicks never get near a meal. Starvation in situ is the simplest outcome; in a season where the oldest chick is really hungry most of the time, it will attack younger chicks until they leave, or fall out of, the nest. Because herons are not cosmologists, they only identify their chicks by position: In The Nest = My Chick. Out Of The Nest = Not My Chick. (Possibly Not Even A Chick, Maybe A Space Alien.) Out Of The Nest, in other words, equals Not Even A Possibility Of Getting Fed. (The Capitals! They Are Taking Over This Post! Stopping…….NOW.)

The heron system of parenting may seem quite horrible to you, but it is efficient. The parent preferentially feeds the biggest, strongest chick; in uncertain times, that chick is also the one most likely to survive. So the parent is investing food where it is most likely to produce living offspring. Every chick is competing to get fed as much as it can, as often as it can. The chicks with the tendency to compete most aggressively are the ones most likely to survive to reproduce, and produce aggressive babies, themselves. It may not be pretty, but there’s a brutal elegance to it.

Naturally, we can congratulate ourselves on having come way past all that; our children don’t have to kill each other to get enough attention and resources from their parents. Of course, there is that matter of the Cain and Abel story……

I guess it’s a good thing that Santa brought two Nintendo DS’s.


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