When Sexes are Alike

These Canada jays could be males, females or one of each. It is almost impossible to tell.

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Of the seven bird species that visited my home this winter in Island Park, I could only tell male from female on one species. This was the hairy woodpecker, where the male has a dime-sized red spot on the back of his head that the female lacks. For the remainder, Steller’s jays, Canada jays, Clark’s nutcrackers, red-breasted nuthatches, mountain chickadees and the single visit from a black-billed magpie, they could have all been males, females or a mix and I could not tell.

That isn’t to say that an expert couldn’t tell the difference with enough observation, but the normal things such as size, very different coloration or ornamentation were not obvious giveaways. From my perspective, even when looking at the photographs later, I simply could not determine the sex of the bird.

I can think of many examples throughout the bird world where sexes are similar in appearance. Canada and snow geese, trumpeter swans, bald and golden eagles, gray partridge, chukars, ptarmigan, storks, flamingos, ravens, crows, creepers, song sparrows, cedar waxwings, titmice, gulls and shorebirds such as black-necked stilts and willets, are just a few. They are represented in many families. It is clearly a different strategy than birds with dimorphic (different looking) sexes.

Scientists have been interested in the subject of sexual dimorphism or the lack of it for centuries. For sexually dimorphic species, the evidence points to sexual selection as the driver of bright or even bizarre decoration: the more colorful, ornamented or larger the bird (or other animal for that matter), the more likely that the individual will be selected by a mate. I am careful not to say male, because there are a number of cases where the female is the more colorful, embellished or larger of the sexes.

This actually works in opposition to Charles Darwin’s original theory that all adaptations were selected for their value to the survival of the individual. A peacock’s tail serves no survival advantage; in fact, it is quite a liability except for the fact that the peahens love it. So, in the case of sexual dimorphism, the costlier the trait (to survival), the more valued for breeding because the battle isn’t for survival but for breeding rights. This pushed Darwin into an evolution of his own and he modified his theory by coining the term, sexual selection, as a special case of natural selection.

With sexually similar species, the current belief is that natural selection (not sexual selection) drives their evolution. Genetic traits become more or less common depending on how they influence an individual’s ability to survive and gather resources.

While we humans may have trouble identifying males and females in sexually similar species, that doesn’t seem to be a problem at all for the birds. They use calls, songs and behavior as ways to help recognize individuals and sexes, but in reality, birds see the world differently than humans. They can see a whole range of colors in the infrared spectrum that humans can’t see. To us, the black feather of a crow is just black. To another crow, it may be a color or colors that we can’t even imagine. One study indicated that when using a spectrophotometer to measure color differences, including infrared, between males and females, 92 percent of the species that we consider as having look-alike sexes have distinct plumage differences that only the birds can see.

There is a lesson in this: Just because we can’t see or understand something, doesn’t make it less real. Most of technology we enjoy today is based on things we cannot see.

 

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Help Idaho Wildlife

When we traveled across the state in October 2017, most of the vehicles we saw using the wildlife management areas did not have wildlife plates. Buying wildlife plates is a great way for non-hunters and hunters alike to support wildlife-based recreation like birding.

C'mon folks, let's help Idaho's wildlife by proudly buying and displaying a wildlife license plate on each of our vehicles! 

See below for information on Idaho plates. Most states have wildlife plates so if you live outside Idaho, check with your state's wildlife department or vehicle licensing division for availability of state wildlife plates where you live. 

And tell them that you heard about it from Nature-track.com!

Wildlife License Plates

Idaho Wildlife license plates provide essential funding that benefits the great diversity of native plants and wildlife that are not hunted, fished or trapped—over 10,000 species or 98% of Idaho’s species diversity. Game species that share the same habitats (such as elk, deer, antelope, sage-grouse, salmon, trout) also benefit from these specialty plates.

No state tax dollars are provided for wildlife diversity, conservation education and recreation programs. Neither are any revenues from the sale of hunting or fishing licenses spent on nongame species. Instead, these species depend on direct donations, federal grants, fundraising initiatives—and the Idaho Wildlife license plates.

Both my vehicles have Bluebird Plates. I prefer the bluebird because the nongame program gets 70 percent of the money from bluebird plates, but only 60 percent of the money from elk and trout plates - 10 percent of the money from elk plates supports wildlife disease monitoring and testing programs (to benefit the livestock industry) and 10 percent from cutthroat plates supports non-motorized boat access.

Incidentally, in 2014, the Idaho Legislature denied the Department of Fish and Game the ability to add new plates or even to change the name of the elk and cutthroat plates (very specific) to wildlife and fish plates, a move that would have allowed for changing images occasionally and generating more revenue. It would seem that they believe that we Idahoans don't want a well funded wildlife program.

I think it is time we let the Legislature know that Idahoan support wildlife funding and that we would like to see these generic plates come to fruition.