CHIRICAHUA National monument wilderness area in southeast Arizona is home to plants and animals from four ecosystems.

There's an area bordering the southwestern U.S. and northwestern Mexico where the Rocky Mountains and Sierra Madres and the Sonoran and Chihuahuan deserts meet and mingle.

Conservationists say the valleys act as barriers to the movement of woodland and forest species the way salt-water seas isolate plants and animals on oceanic islands. So they call the forested mountain ranges that rise abruptly above this "sea" of desert and grasslands "sky islands."

One is Chiricahua National Monument, a stunning wilderness area in southeastern Arizona. It's home to plants and animals from four ecosystems. So you may spot something as recognizable as a white-tailed deer or as seemingly out of place as a coatimundi. Or glimpse the Chiricahua fox squirrel, found nowhere else.

A 13-km scenic drive from the grasslands goes through seven vegetation zones. Cactus and mesquite in ranch country yield to sycamore, juniper and oak, then cypress, pine and fir woodlands, topping off with Douglas fir, the kind you find in Canada.

The road ends at Masai Point, the 2,094-metre mark.

The view can literally stop you in your tracks. Standing like sentinels were hundreds, perhaps thousands, of slender pinnacles of grey rock made of rhyolite, ash from volcanic eruptions 27 million years ago.

The pinnacles average 40 metres in height, and balanced, seemingly precariously, on top of some were massive boulders.

It was to protect the pinnacles that Chiricahua was established as a national monument by presidential proclamation in 1924. In 1976, Congress designated most of it Class 1, pristine wilderness.

The Masai Point Nature Trail, less than a kilometre long and wheelchair accessible, offers several dramatic vistas. There are numbered signs: Balanced Rock at Station No. 12 is one of the best photo opportunities.

Five other trails are described as "short, smooth walks with little change in elevation," and four more rated moderate and four strenuous.

A free shuttle service takes hikers from the visitor centre to either Masai Point or Echo Canyon trail heads and drops them off, leaving them a 7 km hike back down.

There's a campground for tents, trailers and RVs, open year round on first-come, first-served basis. Phone 520-824-3560 or visit nps.gov/chir.

Spring and fall bring pleasant temperatures. December through February is the coolest, with daytime highs between 13C and 15C. Summer highs reach the low 30s and there's heavy rain.

More than half the bird species in the U.S. have been observed in Chiricahua, making it a prime birding area.

Willcox, 56 km away and one of the nearest towns, is Arizona's mecca for wintering sandhill cranes, sparrows and raptors.

Homer Hansen, an environmental scientist who runs the annual Wings Over Willcox festival, says the cranes start arriving the first week of November and stay three or four months. Wings Over Willcox is on Jan. 13-16.

Hansen says most people register in advance at wingsoverwillcox.com.

Chiricahua National Monument is 6 km east of the junction of state highways 186 and 181, 193 km from Tucson and 372 from Phoenix.

For more information on the sky islands, visit skyislandalliance.org.