Sky Islands and flat tires

We were 3 miles from our destination at Cave Creek Ranch in the Chiricahua Mountains of extreme southeastern Arizona when a rear tire on our Highlander went flat (note to self: avoid driving on gravel roads!). And although this was a major inconvenience for my husband who had to drive 60 miles to the nearest Walmart to get a new tire, it meant we could stay at the ranch an extra day.

We had a nice view of the mountains from our room at Cave Creek Ranch, Portal, Arizona. The golden-leafed Sycamores were just past their prime color, but still added vibrancy to the landscape.

The Chiricahua Mountains rise 6,000 feet above the desert floor that surrounds them, making them an “island in a sea of desert”. A variety of life zones occur along the gradient from hot dry, desert to cool pine forest at peak elevation, and this means these montane islands are a hot spot of biodiversity. And like animals on oceanic islands, Sky Island animals are restricted to their mountain environment, and may become locally endemic, not mixing or interbreeding with the rest of their parent species.

Chiricahua mountain oak and sycamore forests, often riparian, give way to higher elevation juniper and pinyon pines in the Cave Creek area.

Such”sky islands” occur in a number of locations in North America, but this one in the Chiricahuas is particularly interesting because it attracts more southern-distributed Mexican and Central American species like Trogons, Mexican Jays, coatis (raccoon relatives), Jaguars, Mexican wolves, javelinas, and some endemic races of white-tailed deer and wild turkeys.

Coues Whitetail deer is a diminutive subspecies of the eastern Whitetail that stands less than 3 feet at the shoulder. Large surface area of its ears helps it dissipate heat, but the deer stay primarily in the oak and sycamore woods and nearby grasslands at middle elevation in the mountains of southeastern Arizona and ranging south into Mexico. Their elfin size may be an adaptation to limited food supply in their range.
Similarly, Gould’s Turkey is a subspecies of the eastern wild Turkey, found only in the Chiricahuas and parts of southwestern New Mexico, but its range extends south into montane parts of Mexico. Gould’s Turkey is the largest of the 7 subspecies of wild Turkey, with longer legs, bigger feet, and all white tail feathers, compared to eastern wild turkeys. That must be a spectacle during the breeding season!
There are at least 5 subspecies of Dark-eyed Juncos, whose coloration varies among their geographic locations. This little bird, however, is a separate species of Junco — the yellow-eyed Junco, found ONLY in the Chiricahua Sky Island and the Mexican montane region. This is a good example of “island speciation”, in which its restricted Sky Island range cut off gene flow to other North American Junco populations.
Mexican Jays lack the crest of feathers seen in Blue Jays and Steller’s Jays, and resemble Scrub Jays but are much larger than their California cousins. They inhabit the oak woodlands in mountain regions of southeastern Arizona, southwestern New Mexico, and central Mexico, where they form large, loosely familial flocks searching for acorns, pinyon nuts, and small vertebrates for dessert.
Broad-billed Hummingbirds are another example of primarily Mexican-distributed birds that will nest as far north as the Chiricahua mountains, but they migrate back south to central Mexico mountains in the winter. Maybe this handsome male found enough nectar and insects at Cave Creek Ranch to stick around a little longer after the breeding season.
The Bridled Titmouse is another primarily Mexican montane bird that just makes it into the U.S. in the Chiricahua mountains. There are actually three Titmouse/Chickadee species in the Chiricahuas, and they divide up the habitat by their preference for trees on which they forage: Juniper Titmice on junipers, Bridled Titmice on oaks and sycamores, and Mexican Chickadees on higher elevation pines.

Quite a diverse place, those Sky Islands of Arizona!


10 thoughts on “Sky Islands and flat tires

  1. Pingback: Sky Islands and flat tires — Back Yard Biology | By the Mighty Mumford

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