Love 'em and Leave 'em or Sit There and Breed 'em?

Ever wonder how birds decide to mate? I know I sure do. And for now, so do you.

So, just how do male birds decide how to mate? Do they? Do they just take what comes, or do they have plans of their own? Is it all hormones? Is it the media?

One way to think of it, it turns out, is hormonal. Conventionally, it has been long known that levels of hormones can influence the behavior of birds, especially during the mating season. However, this isn't quite as clear cut as it seems. It might just be that the ability for birds to quickly increase or decrease the amount of testosterone in their system may be more influential, in the 'short' run, than the total amount of testosterone in the system. A study by researchers at the Universities of Indiana, Virginia, and Southern Mississippi hint at this new way of conceiving the impact of hormones on a bird's behavior.

In this view(which, of course, needs much more study), birds whose levels of testosterone quickly fluctuated were more likely to seek multiple matings, while those whose testosterone levels were more stable tended to stick around one mate and invest more energy in their young. This study points to an idea that the individual history of a bird can influence the way it adapts to reproductive success. More specifically, the local environment and present surroundings of a bird can have a larger impact than previously thought. The data also suggest that there may be more than one way to skin a cat:

"Our data also suggest that there is more than one way to be successful at reproduction. Some males may seek mates at the expense of parental behavior, but other males are doing the opposite. They are being more parental at the expense of aggression. And apparently both ways of being in the world work." -IUB biologist Ellen Ketterson

So what it comes down to is the individual bird trying to maximize reproductive success based on some well-worn strategies. The manly Juncos can maximize the amount of offspring they have, and minimize parental care, or they can minimize the amount of offspring and maximize the parenting. Actually, this conception seems to present a n either-or situation - in reality, the system is more complicated. Not every bird can cruise around the woods spittin' game to fly honeys, (That's right, not only did I type that, I meant that pun.) some homely bird may just have to be a homebody. In fact, the whole system is probably dynamic, a continuum, which influences different birds in different ways.

In the near future, the biologists hope to study just to what extent this hormonal variation occurs. The real question, though, is how this modification is achieved in birds - is it purely an environmental factor, or can it be influenced by the bird himself? And how would you test that?

Posted by Brad Garvey (5)