Sky Island Spring

Close to the US-Mexico border, where New Mexico and Arizona meet Chihuahua and Sonora, lies one of the world’s biodiversity hotspots.  More than a dozen small mountain ranges rise from the surrounding desert, and are often referred to as “Sky Islands”, as their forested slopes appear to be islands in a sea of grassland and desert scrub.  But what actually makes this area so rich in plants and animals is not the 5-6,000 foot change in elevation from the valley floor to the peaks, but rather the intersections of 4 major biomes.  For it is right here where the Sonoran and Chihuahuan Deserts meet, and where the Sierra Madre mingles with the Rocky Mountains.  

These little mountain ranges actually form an achipelago between the Rockies and the Sierra Madre, and the area is sometimes referred to as the Madrean Archipelago.  This creates an almost continuous chain of mountains in North America, from central Mexico to central British Columbia.  This area also served as a refugia during the glacial periods of the Pleistocene, leaving little pockets of the Rockies or Sierra Madre far from where they would be expected.

Another factor that contributes to the biodiversity is climate.  This area lies at the northern edge of the Mexican Monsoon.  This weather phenomenon brings heavy rains during the summer, when plants are growing the fastest.  It also creates good habitat for animals, including insects and the birds and mammals that feed on them.  Without the monsoon, this area would be much more like the Mojave desert.  The monsoon starts in the tropics in April, and slowly moves its way up Mexico, arriving in Arizona in late June or early July.  By late August, it starts its retreat back to the tropics.

The monsoon is preceded by a hot, dry spell, which usually runs from early April to late June.  In these parts, it is usually referred to as the “pre-summer” because it bears little resemblance to what most people think of as spring.  It is very hot and dry.  But in late June or early July, the winds shift, and thunderstorms start to build in the afternoon.  Hot and dry changes to hot and humid.  Flash flood warnings become a common occurrence, as many of the thunderstorms produce torrential rains – usually a lot of rain in a small area.

Much of the wildlife in the area have geared their annual cycles to the monsoon.  Many birds, deer, coatis, and skunks all hold off producing offspring until right before or right after the rains are due to start, to take advantage of all the new, green vegetation and insects.

But it’s still June here.  I took a hike a couple of weeks ago up into the Huachucas, a lovely mountain range that touches the border at its southern end.  High up in the oak-pine forest, the birds were acting like it was spring, singing up a storm in spite of the heat.  I found one last little pool of water along Sunnyside Creek, and placed the microphone there.   A strong breeze was roaring through the canyon, but I was lucky enough to record a few of the iconic species that draw birders in from all over the world.

As I was leaving the mountains, I looked back to see thunderheads building over the mountains.  Looks like the monsoon is almost here.

For more sounds from the Madrean Archipelago, download my album, Crossroads.

Recorded using a PCM-M10 and Audio Technica AT2022 mic with Felmicamps preamp.