Naturalist Newsletter of January 28, 2008
issued from Yerba Buena Clinic just outside
Pueblo Nuevo Solistahuacan, Chiapas, MÉXICO
about 1740 meters in elevation, ± LAT. 17° 11' 27"N, LONG. -92° 53' 35"W
The chunky, brownish flicker hopping on pine-straw- covered ground outside my window as I type this looks different from the Yellow-shafted Flickers I grew up with in Kentucky, and the Red-shafted Flickers that later I saw out West.
The head-tops, or crowns, of North American flickers are gray to gray-brown, but the crown of the bird outside my window is more reddish, a rich cinnamon color. Moreover, northern flickers are weakly barred across their backs, while the barring on my window bird is much more intense, almost Zebra-like. My window-flicker reminds me of a woman who's spent an hour on her mascara accentuating her most attractive features. What's going on here?
Back in the 60s my old Peterson Field Guide made the flicker situation pretty simple: The East's Yellow- shafted flickers showed yellow in their wings when the flew, the West's Red-shafted ones showed red. But eventually someone reflected on the fact that in the sliver of the country where the two flickers' distributions overlapped they interbred, and flickers flew around displaying orange in their wings. Since two different species aren't supposed to freely hybridize under normal conditions, the Yellow-shafted and Red-shafted forms were "lumped" into one species now called the Northern Flicker, COLAPTES AURATUS.
But, it's much more interesting than that. It turns out that Northern Flickers are
fracturing, or evolving, not into two groupings but... at least FIVE, according to Howell!
auratus group (Yellow-shafted Flicker, eastern NA)
cafer group (Red-shafted Flicker, western NA)
mexicanoides group (ours, the Guatemalan Flicker)
chrysocaulosus group (of Cuba & Grand Cayman Island)
chrysoides group (Gilded Flicker of northwestern Mexico and adjacent US Desert Southwest)
Each of these groups not only looks a little different from the others but also has its own habitat preferences. Members of the chrysoides group, the "Gilded Flickers," are truly iconoclastic, inhabiting deserts where they nest in big cacti instead of trees.
As the Red-shafted form intergrades with the Yellow- shafted form in North America, in northwestern Mexico Red-shafteds intergrade with the desert Gilded form.
Here south of the Isthmus of Tehuantepec we have only the mexicanoides form, inhabiting uplands from Chiapas to Nicaragua.
What a pleasure thinking about all this stuff as I move around, being witness to new species forming before my eyes!