Sunday, February 19, 2006

Unlike humans, hawk mates don't fight: Blakeman

Photo by Cal Vornberger

Website correspondent Jan Lipert sent in the following question and asked me to forward it to John Blakeman:

You have mentioned the hawks' nonsocial behavior, and I have often read about it in my bird books. Yet Pale Male and Lola seem to 'hang out' together all year long. Do you think that perhaps the abundant prey has reduced their need to be competitive, and allows the bonding to have more of an influence on them even when it's not mating season? Do you think that their isolated location might also have something to do with it?

Blakeman responds:


A very good set of questions. I don't think I've been completely clear with my descriptions of red-tails' social behaviors in the fall and winter, when they aren't directly prompted by sex and breeding hormones.

We all understand that a pair perches together, hunts together, feeds together, works on the nest together, and often "mates" (well, I mean here "copulates") in winter, spring, and into the summer under the strong influence of behavioral hormones that pour out when days are lengthening.

But what keeps the big female from attacking her smaller mate in August through January, when breeding activities are generally nil? In fact, the mated (I mean here, "pair bonded") birds continue to perch together and share the territory. In these later seasons, they often don't sit so closely, and they seldom work on the nest and almost never copulate. But to even the most inexperienced observer it appears that the pair is bonded. To be anthropomorphic (dangerous), the two birds appear to "like" each other. They hang around together and seem to be mutually contented in the territory.

Here's where I wasn't clear. By "non-social" I meant that the birds just don't like the presence of other members of their species to which they aren't pair bonded. But the pair bond tends to last, in varying degrees of strength, throughout the entire year. Once bonded, the pair never considers any aggression against the other pair member. That's what's so interesting. If a new, unidentified red-tail flies into a mated pair's territory, it is usually driven off quickly and decisively. Mated pairs never have internal aggression. They never fight (unlike many of us humans). But they will often aggressively drive off a new territorial interloper.
And that, I think, is the essential and interesting explanation of a mated pair's internal non-aggression. It appears that the mated birds are mated both to themselves (anthropomorphically, they "like" each other), and also to the territory (they accept and like where they live -- and at the same time allow just the other member of the pair to live there, too).

So it's also a territory thing, a "stay out of my yard" expression. The other bird in the pair is instinctively permitted "in the yard," on the property. But no other bird during the breeding season is.

Can we see how non-mammalian, how non-human this arrangement is? The two hawks abide the presence of each other within the territory, but any other red-tail that drifts in is very non-socially driven off. This is the remarkable aspect of the pair bonding I referred to.

To summarize: mated (pair bonded) red-tails never, at any time of the year, fight or have aggression to each other. Both birds perceive they have a biological right to be in the territory, while at the same time acting as though any other red-tails don't. This delicate social arrangement works, a remarkable feat for a species that is otherwise so non-social.


John A. Blakeman