Sources: Marshall, Joe T., Jr., 1956, Summer Birds of the Rincon Mountains, Saguaro National Monument, Arizona, The Condor 58:2:81-97.
Rincon means “corner” in Spanish, and these mountains have their highest summit at the corner of this roughly L-shaped metamorphic complex toward its northeastern end on Mica Mountain, a great dome (see above) that tops out at 8600 feet above sea level. The map below shows the overall shape more clearly than can be gained from any ground view. Click on the image for a larger view.
From Mica Mountain dome, one long ridge of the L slopes gradually down westward to end near the Visitor Center Headquarters of Saguaro National Park East, while a second runs roughly southward to a second apex at Rincon Peak. The east side of this latter, north-south ridge exhibits steeply vertical cliffs located along the Martinez Ranch Geological Fault, a structure evident in the lie of the east face of Rincon Peak on the map above, and visible below in this image of faulted strata taken from Happy Valley in February 2002. The peak itself is here obscured by clouds.
At the top of Mica Mountain, the land spreads out in rolling hills with broad drainage basins, and supports a continuous stand of Ponderosa Pine forest that contains some of the largest of these trees to be found in Southern Arizona. Some twenty square miles of boreal forest extends ringwise out along both arms of the L and verges into almost 70 additional square miles of pine-oak woodlands. Chihuahua Pine,Blue Oak, Arizona Oak, Silver-leaf Oak, and Arizona Madrone, all more widely distributed in Mexico, are plentiful here, as are the migratory birds frequenting such woodlands who come from points further south. Gambel Oak and Arizona Rosewood attain exceptionally large size on these mountains. While the Rincons lack the alpine fir and Apache Pine found toward the summits of the nearby Santa Catalina and Santa Rita Mountains, Douglas fir and White Fir do appear near the top on the north-facing slopes, and Aspen and Mexican Locust on the very steep northern side. Below, snow caps the northeastern slopes on May 13, 2008.
On these eastern (and northern) sides, soil moisture is retained significantly longer than elsewhere on the mountain, so the "Canadian Zone" trees do gain a purchase here. Unlike the Santa Catalina Mountains just to the north, whose deep canyons and flanking high ridges support interpenetration of different vegetation zones at various altitudes, the Rincons largely lack these features, but strong differences in vegetation can be seen between the east and west slopes of the mountain. On the western slopes the oak woodland, except on flood-plains, is dwarfed compared with the east and includes Mexican natives like Mexican Pinyon Pine, Alligator Juniper, Agave schottii, Garrya wrightii, and Arctostaphylos pungens, all of which are highly tolerant of dryness and of terrain containing much exposed rock. The eastern slope, in contrast, supports gardens of deciduous shrubbery, ferns, robust trees, and a meadow. In this woodland one sees, along with the pines, aspens, and New Mexican locusts, the largest oaks, madrones, chokecherries, and buck-thorns on the mountain.
Below, we focus on this eastern side, framing the two main peaks of the Rincons complex -- Mica Mountain and Rincon Peak -- as well as the Little Rincon Mountains, relative to Cascabel, Corridor Central in this portion of the Madrean Sky Island - Desert Valley complex:
The north-south strike of the Martinez Fault runs roughly along the flanks of the mountain range here. Happy Valley, visible in the lower left quadrant of the map, contains some of the meadows mentioned above, and with the springs nearby it draws many birds. The Paige Canyon - Happy Valley Corridor is a significant ecological feature of this landscape.
Below, a view from the Oak Woodland vegetation zone, looking out over Happy Valley. In the near background, the Little Rincon Mountains are in shadow, flanking the valley and Paige Canyon. Manzanita shrubs are visible in the foreground Beyond these, horizon-left, run the Galiuro Mountains on the far side of the San Pedro River Valley and beyond them at horizon-right, the Whetstone Mountains.
Click on the image to enlarge it.
Below a view from the San Pedro River side, along Cascabel Road just north of Pomerene, looking in the opposite direction. The Little Rincons, which have a very complex geology, glow tan at mid-distance, Rincon Peak blue at far left.
In the mid-1950s, Joe Marshall (cited above) compiled the results of his and several other bird collector's visits to Mica Mountain, attempting to relate the presence of breeding summer birds to vegetation zones. the lists below show the results of his efforts: (Note: click on the lists to enlarge them)
First list: Observed Vegetation
Second List: Birds Observed in Vegetation Zones:
Note: regarding this list, Marshall noted that (1) a bar chopped off at the left margin means the species in question continued down into the desert; (2) a bar ending abruptly at a boundary between vegetation zones means the bird is expected beyond that limit but was not observed there in this study; (3) a bullet at the left margin means that specimens of the species from the Rincons are extant in museums.
Note: for a more detailed account of Rincon geology, see this link: Catalina-Rincon Metamorphic Core Compex
February 2003: Rincon Peak at top-center, viewed from the Hot Springs Canyon Windmill. Little Rincons in middle distance.
January 2005: Rincon Peak in the background, Little Rincons in the middle distance.
December 2001: Rincon Peak obscured by clouds.
For geological discussion of the Rincon Mountains, click on Geology Walk: Metamorphic Core Complexes....
January, 2002: Mica Mountain sunset viewed from the Hot Springs Canyon Windmill.
January 2005: Mica Mountain and Little Rincons foothills, morning, from Lower Hot Springs Canyon terrace, after rainfall:
December 2001: Mica Mountain Sawtooth Ridge after snowfall, from lower Soza Mesa. Click on the image for a closer view.