The Three-Minute Outdoorsman: Wild Science from Magnetic Deer to Mumbling Carp

23. Looking Back at Turkey Season

I N T H E W O O D S 95 that hunting has little to do with turkeys choosing multiples mates (the Krakauer study was in a no-hunting zone), and I’d bet it’s the norm whether there is hunting or not. But until the recent DNA evidence became available, we could say little about the consequences of the mating rituals of Wild Turkeys. Now when we see those broods in summer, we’ll know the young turkeys might not be too sure who was their daddy or their mommy. 23 looking back at turkey season what you might not have seen A quick glance is usually all that is needed to tell whether the turkey approaching your decoy is a mature tom, a jake, or a hen. Obviously, tom turkeys are larger than females and jakes, and toms are the most brightly colored, resulting from iridescent feathers and vividly colored patches of skin. What exactly does a hen see in a tom, anyway? Since Charles Darwin’s time we have known that females choose males that somehow indicate their superior features. What sort of features? Well, first of all, to be gaudy in the extreme, like a tom turkey, means you are visible not just to hens but to predators as well. So, simply being alive may mean you possess superior characteristics that have helped you survive in spite of your outrageous appearance and behaviors. This is sometimes referred to as the “handicap principle.” But what if there are multiple toms to choose from? Do females choose males based on their beard length, feather brightness, how well they gobble, body size, or spur length, things we tend to emphasize? Or are there characteristics of toms that only another turkey can see? Here, we should note that birds and humans see colors very differently. First, birds see an expanded color spectrum, because t h e t h r e e - m i n u t e o u t d o o r s m a n 96 their eyes have our set of cones (color sensors) plus a fourth set. Second, birds see in the UV spectrum, whereas humans do not. So, when we look at turkeys, we may not see what it is that piques the interest of a hen in a particular tom. You might ask, so what if toms differ in their true coloration and UV reflectance in ways we cannot see? Are hens making choices about which tom to mate with out of vanity? Maybe not. Turkeys are often infected with a protozoan parasite, and males with these infections can have altered feather colors. What if the more parasites a turkey has, the less bright or iridescent its plumage will appear? If true, females could choose males with “better ” feathers to father their young because they have the fewest parasites, which would be a decided advantage for the offspring. In other words, if some toms have more genetic resistance to parasites than others, turkeys might see it in their feathers. And we, with our vision, would be none the wiser. At least that’s the theory. Geoff Hill and his colleagues at Auburn University decided to investigate this question experimentally using three groups of captive-reared young male Wild Turkeys. One group was infected with a single strain of a common turkey protozoan parasite, the second group was infected with a mixture of different species of protozoans, and the third group was kept free of infection. Their idea was to compare the newly molted feathers of males and see if having a parasite infection affected feathers. They found that exposure to the protozoan parasites affected certain aspects of the iridescent coloration, namely, brightness and ultraviolet reflectance . A male with a higher parasite load might look a little different to you and me, but it probably looks very different to another turkey. So, unbeknownst to us, turkeys can check each other out and determine who is more infected than whom! Now, the next step is to do the critical experiments to see if females actually do prefer males with lower parasite loads and brighter plumage. But it won’t necessarily be that easy. As we try to remember in scientific studies, “correlation doesn’t prove causation.” In I N T H E W O O D S 97 fact, in another study, Richard Buchholz from the University of Mississippi found that...