Estrella Mountains
Maricopa County, Arizona

The word ‘estrella’ means star in Spanish and indeed the highest peaks in this range reach for the stars above the low surrounding deserts. The name could also refer to the abundant, sparkling flakes of mica present in the Precambrian schist. The eastern half of the range is part of the Gila River Indian Community and access there is restricted. The northwest quarter of the range lies within Estrella Mtn. Regional Park and is now bordered by housing developments incorporated into the city of Goodyear. The park, exceeding 8000 ha. in size, offers recreation opportunities to a diverse population of outdoor enthusiasts such as picnickers, golfers, equestrians, ball players and mountain bikers. The recent addition of a system of trails designated for mountain biking has greatly reduced the pressure on the horse and pedestrian trails making them more enjoyable. There are over 40 kms of trails ranging through the lower foothills of the Estrellas, but there are no trails into the high country from Estrella Mountain Park. Several kilometers east of the park is Phoenix International Raceway - at times the roaring engine sounds disturb the desert peace.

From Phoenix drive west on I-10 and exit at Estrella Parkway. Turn south and just after crossing the Gila River turn east passing Estrella Golf Course and following signs to park entrance on the south side of the road. There are several hiking trails available.

Field Trip Reports:
January 16, 2005

The day was bright and warm after a period of wet and coolish weather. Sara Orange Tip (Anthocharis pima) butterflies were on the wing with the males patrolling about the summits of the hilltops and females moving across the desert looking for mustard seedlings upon which to lay their eggs. Quite a number of Painted Lady (Vanessa cardui) butterflies were seen all of which were worn and old-looking. Their eggs are now being placed mostly on Brittle Bush; these worn adults will soon die, but the caterpillars will hatch into new adults during the next two months and begin a northward migration. A Funereal Duskywing (Erynnis funerealis) and a Mourning Cloak (Nymphalis antiopa) butterfly were also seen.

I hiked a total of fifteen kilometers and found dozens of wildflower species in bloom including spectacular California Poppies and patches of yellow bladderpod. Carpets of green covering the hills and flats predict a really good show in a few weeks. Birds were mostly scarce - I spotted only 47 total birds of 10 species. A big swarm of feral, and likely Africanized, Honey Bees flew by as I sat for a rest. The temperature was near 24°C.

I took the trailhead from the east end of the horse staging area labeled ‘RB’ for Rainbow Valley Trail (@ W112° 22.226' N33° 22.108'). It follows a gravel road for a few hundred meters before cutting south on the left side of the road. The most abundant wildflowers were pink filaree, white comb-burr, and yellowish mustards. Wolfberry shrubs were covered with tiny tubular flowers which were in turn attracting plenty of feral honey bees (Apis melifera). At about 2km the trail begins to climb into some foothills where I took a short spur to a small hill top (@ W112° 22.233' N33° 21.613') where the orange tips were. Half a kilometer further I found a large beautiful ocotillo and an exceptionally large, 1/2m tall, Lance-leaf Ditaxis growing in a small narrow wash (@ W112° 20.834′ N33° 21.865′). Very shortly their is a trail junction where the return Gadsen Loop connects from the north. After three and a half km hiking southeast I met the Gadsen Trail (@ W112° 21.503′ N33° 20.556′) which loops northeast in and out of a large wash, then west to rejoin the Rainbow Valley Trail after 5+ km.

 

Painted Lady (left) and Dusky Wing.

Male House Finch (Carpodacus mexicanus). Females lack red coloring.

Birds

More frequent towards top of list
Seasonal occurrence: (S)ummer, (F)all, (W)inter, (Sp)ring

1. Rock Wren -- Salpinctes obsoletus -- S,F,W,Sp --
2. White-crowned Sparrow -- Zonotrichia leucophrys -- W,Sp --
3. Black-throated Sparrow -- Amphispiza bilineata -- S,F,W,Sp --
4. Anna′s Hummingbird -- Calypte anna -- S,F,W,Sp --
5. Mourning Dove -- Zenaida macroura -- S,F,W,Sp -- Grass areas and along Gila
6. House Finch -- Carpodacus mexicanus -- S,F,W,Sp --
7. Gilded Flicker -- S,F,W,Sp --
8. Black-tailed Gnatcatcher -- Polioptila melanura -- S,F,W,Sp --
9. Cactus Wren -- Campylorhynchus brunneicapillus -- S,F,W,Sp
10. Common Raven -- Corvus corax -- W -- occas. rest of year
11. Ladder-backed Woodpecker -- S,F,W,Sp --
12. Turkey Vulture -- Cathartes aura -- S,F,Sp -- rare in winter

Cactus Wren
(Campylorhynchus brunneicapillus) -
Photo by Mike Plagens.

Side-blotched Lizard (Uta stansburiana) - Photo by Mike Plagens.

Reptiles

1. Side-blotched Lizard (Uta stansburiana) -- most active lizard during cooler parts of year. Dark patch behind forelegs; bluish throat.

More common species first ...

1. Buckhorn Cholla -- Cylindropuntia acanthocarpa -- Most of the chollas are of this species.
2. Saguaro Cactus -- Carnegiea gigantea --
3. Engelmann Hedgehog Cactus -- Echinocereus engelmannii
4. Teddy Bear Cholla;Jumping Cholla -- Cylindropuntia bigelovii -- just a few located on the upper foothill slopes
5. Graham′s Pincushion Cactus -- Mammillaria grahamii -- uncommon at this location

Buckhorn Cholla
(Cylindropuntia acanthocarpa).
Photo by Mike Plagens.

Shrubs and Trees

In order of Abundance:
The more common species are listed first.

1. White Bursage -- Ambrosia dumosa -- The most common bursage in the lower foothills. Often leafless after periods of drought or hard frost.
2. Creosote Bush -- Larrea tridentata
3. Foothills Palo Verde; Yellow Palo Verde -- Parkinsonia microphylla -- This is the most common tree many specimens are only shrub-size.
4. Brittlebush -- Encelia farinosa -
5. Desert Ironwood -- Olneya tesota -
6. Desert Globe Mallow -- Sphaeralcia ambigua -- Bears peach colored blooms after periods of rain otherwise it is difficult to find
7. Anderson Thornbush;Wolfberry -- Lycium andersonii -- fairly common along the washes. 1 to 2 meter tall shrub with noticeably dark twigs.
8. Lance-leaf Ditaxis -- Argythamnia lanceolata -- low-growing, silvery-green plant
9. Ocotillo;Coachwhip -- Fouquieria splendens --
10. Desert Lavender -- Hyptis emoryi -- a few can be seen along washes adjacent to shady cliffs
11. White Ratany -- Krameria erecta -
12. Joint Fir -- Ephedra aspera -
13. Trixis -- Trixis californica -- a few along washes and under trees
14. Triangle-leaf Bursage -- Ambrosia deltoidea -
15. Burro Bush -- Hymenoclea salsola -
16. Cat-claw Acacia (Acacia greggii) - Found growing along washes
17. Velvet Mesquite -- Prosopis velutina - a few only - and only shrub sized

Ocotillos bloom mostly March to May, but the bright red flowers may also appear at almost any time of year.