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NATURE HAPPENINGS October 2012

The Migrations of Autumn
by Damian Fagan

Damian Fagan's blog

 

Cottonwood

Monarch butterfly

Collared lizard

Aspen leaves

merlin


October marks the passage between the seasonal bookends of summer and winter. Though the desert can still experience warm days – average highs hover around 75˚F, but nighttime lows rarely dip below the freezing mark - October weather can suddenly go south with snow and rain. The weather is just one migration that defines October in the desert.

The big reason for this seasonal fluctuation is the position of the earth on its yearly migration around the sun. After the summer equinox on June 21, the sun’s position changes in respect to where it rises and sets. In October, the sun sets or rises south of true east and west, respectively, for each day until the winter equinox. Daylight duration also shifts with a trend towards shorter days; by the middle of the month the length of daylight is around 11 hours.

As the world turns, nature also responds to this seasonal shift. Birds, which are attuned to photoperiod changes, respond, in some cases, by moving south towards warmer climates or regions with appropriate prey bases. Warblers, vireos, orioles and flycatchers, birds dependent upon insects, head towards or over the US/Mexico border and into parts of Central America, Other birds like chickadees, nuthatches, jays and siskins migrate down slope, not necessarily southward, but to lower elevations. The idea that the shorter daylight period reduces time spent foraging results in a lowered ability to sustain metabolic rates during the long, cold nights. So the birds move to where the gettin’ is good.

Birds like the rough-legged hawk, an Arctic breeder, descend into the lower 48 and show up in western states where winter may lay heavy on the landscape. The cold desert is still a better deal than the frigid Arctic.

Plants also reflect this seasonal migration. A mosaic of leaf colors erupts as chlorophyll pigments break down and unmask underlying pigments of yellow and red. Fall creates a Crayola™ moment as leaves migrate through the color wheel.

Another vegetative migration is the rain of deciduous leaves from their tenuous holds on slender stems. Aspens, cottonwoods, oaks, roses, and other plants drop their leaves and move into a “leafless” state to pass the winter months.

Perhaps less noticeable, is the scarcity of lizards, snakes, butterflies and insects that blossomed during summer. Snakes can den up together, a temporary truce between species to survive the winter. Larger lizards like the collared lizard or leopard lizard, also go underground into burrows or protective crevices, but not together, to avoid the cold. Many adult butterflies die, except for the mourning cloak which overwinters as an adult. Of course, there are larvae of butterflies and other insects that survive the winter.

Other indicators of this seasonal change bring us back to the human element. English is once again the dominant language heard in City Market, the European contingency having migrated home. Making a left turn off of Main Street once again becomes possible, and trails seem devoid of traffic.

October in the Canyon Country may be a period of “comings and goings,” but for those that stay, there is the quiet and solitude of the trails and canyons that may postpone their migration.



Damian Fagan is an accomplished writer who has published a number of guide books as well as numerous articles. If you would like to read more or find out what Damian is up to follow this link to Damian Fagan's blog.


 
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