Monday, February 22, 2016

In the winter a young bird's fancy lightly turns to thoughts of love

 Appropriately enough, I first noticed loud, urgent birdsong of several different kinds around Valentine's Day.  (I'm not able to identify more than a few birds by their songs, though I would dearly love to learn.)  I had imagined that spring was mating time for local birds, but some, at least, get a head start much earlier. 

In most birds it is the male who sings to attract a mate, and the female who does the choosing.  For the same reason, the male is often the more brightly-colored.  (Females are more often dull: they don't need to show off.)  The male may sing, "keep out! this is my territory!" to other males, while to the females he sings, "Am I not the most beautiful guy you've seen, and with the most impressive song? and wouldn't you like to raise a large brood of fine, strong chicks with me on this wonderful territory?"

The coloration and singing are textbook examples of sexual selection.  This is a variant of natural selection in which characteristics such as bright plumage are selected for, not by directly improving survival or reproduction, but indirectly--the males most attractive to the females are more likely to succeed in getting a mate and contributing those very genes conferring bright color to the next generation.  It makes evolutionary sense that females, which make the enormous resource investment of gestating the young, will be very choosy about who their partner is.  (This choosiness of female holds true in a great many other animal species as well--likely even in humans.)

 A well-attired White-Breasted Nuthatch on February 19th.  
These birds walk up, down and around the tree trunk looking for food.

On February 19th I spotted a handsome pair of white-breasted nuthatches working their way around the gnarled limbs of an old red maple.  If I'd had any doubt they were lovers instead of mere dining companions, my copy of the Sibley Field Guide to Birds of Eastern North America set me straight: "usually solitary."   

 This Downy Woodpecker is probably the female; the male looks the same
but with a prominent red patch on the back of the head.  These birds brace their tails
against the tree while they hammer their beaks into the bark probing for insects.

Today, February 22nd, the sound of gentle, companionable tapping drew my eyes to a pair of downy woodpeckers searching for food in the bark of some dead oak branches.  Later my wife called my attention a pair of tufted titmice in a big Norway maple tree in the backyard.  

It's worth mentioning that these three particular birds don't differ much from male to female, though the male downy woodpecker does have a bright red patch not shared by his mate.  And in the tufted titmouse, at least, both male and female sing.

I will look and listen more carefully in the coming days.

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