Arizonensis --> Sonoran Desert Naturalist --> Sonoran Desert Places --> Hedgepeth Hills

Hedgepeth Hills -- Thunderbird Park
Glendale, Arizona


This is Glendale's only mountain preserve. It is located north of State Route Loop 101 via 59th Avenue. About a mile north on 59th Ave. there is low pass through the Hedgepeth Hills. Just before the pass is the main entrance to Thunderbird Park on the left. There are hiking trails here as well as ball fields and other recreational facilities including parking. Another parking area lies just northeast of the pass at 55th Ave. and Pinnacle Peak Rd. on the right (south). The trails are broad and easy to hike but the sharp-edged rocks require sure-footedness. There are several trails to choose from that will take you to various hilltops or onto perimeter areas.

Adobe Dam to the east catches the water draining down through Skunk Creek. A broad area of fine clay and silt has accumulated behind the dam. It is often nearly bare of vegetation: Typical desert plants cannot sustain the occasional flooding. Weeds predominate including those known to aggravate people's allergies.

The geology is predominately basaltic lava of early Tertiary age with a summit elevation of 570 m. The soil is very thin on the hills and so the few trees are diminutive. Bajadas are poorly developed. The picnic areas are situated within a well developed desert wash where there are many good sized desert trees including a number of Desert Hackberries, Blue Palo Verdes, and Ironwoods. The hackberries are highly attractive to wildlife, especially when in fruit ... mid spring and and again in early autumn.

Photograph © Mike Plagens

A pair of stately saguaro cacti frame a view of the northwest Valley, including Sun City and Peoria. The infamous brown cloud of particulate air pollution is visible on the horizon.

Thunderbird Park is located north of Loop 101 and west of I-17. Drive north on 59th Ave. from the Loop 101 exit. Google Map

     The city of Glendale widened 59th Ave. which removed 40 some acres of desert habitat and added traffic and noise! An awareness march was held on Sat. 7/24/2004 at 8AM and was attended by nearly 200 people.

Field Trip Report: Aug. 1, 2013

At 6 am the temperature was 32°C. A week ago some locations in the Sonoran Desert got good soaking rain, and others just 10mm or so. Many shrubs had small amounts of fresh green growth, including creosote bush, foothill palo verde, New Mexico ditaxis, brittle bush, triangle-leaf bursage, and desert globe mallow. When walking through creosote stands many Desert Clickers were singing. A few cicadas and some crickets were also calling. A family of cactus wrens were the most amusing to watch as four fledglings eagerly followed the parents looking for meals of freshly caught insects. Side-blotched and Tree Lizards were actively hunting for insects. Temperature by 10:00 am was 37° and I required several liters of water.

Field Trip Report: Feb 3, 2008

With three good installments of winter precipitation these desert hills were verdent with new spring annuals. Within the next few weeks this will be quite a show. So far not much is in bloom. A few Orange Fiddleneck -- Amsinckia intermedia; Narrow-leaf Popcorn Flower -- Cryptantha angustifolia; Peppergrass -- Lepidium lasiocarpum and Eucrypta chrysanthemifolia. The upper slopes are just loaded with fresh growth of Blue Dicks Dichylostema.

Field Trip Report: May 7, 2000

The recent hot temperatures and breezes have dried out the wildflowers that were so abundant just weeks ago. Still borne by many plants they appear as dried flower arrangements. Twenty-three species still had a few withering blooms left.

At the park entrance the few Ironwood trees were in full bloom, covered with lilac-colored flowers. The first of the Saguaro Cactus flowers have opened up, revealing their huge, white, waxy blooms. Several Wolfberry shrubs are covered with a thick crop of edible orange-red berries. The flavor is like tomatoes.

Most of the Foothill Palo Verde trees have hundreds of little silken tents in them, about 3 to 7 cm long. They were spun by the caterpillars of a gelechiid moth (Bryotropha inaequalis). The caterpillars feast on the tiny palo verde leaves before the plant would shed them anyway in a few weeks. Because the trees will shed these leaves soon, they do not contain heavy doses of protective phytochemicals, that is, they are easy for the caterpillars to digest. Little if any harm is done to the trees.

At the hill tops there were a number of Pepsis wasp males flying about. These are the spider wasps that hunt tarantulas and trapdoor spiders, but only the females hunt and only the females have stingers. The fearsome looking blue-black males with orange wings are harmless. A single butterfly species was spotted: Leptotes marina, the Marine Blue.

Desert Clicker

Desert Clicker

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Marine Blue

Marine Blue

The Marine Blue, Leptotes marina, is a small butterfly with a wingspan of about 1 cm. It visits flowers of mesquite and acacia. The caterpillar eats the leaves of these desert shrubs as well.


In general order of Abundance:

  1. Verdin -- Auriparus flaviceps --S,F,W,Sp - Tiny birds, barely larger than a hummingbird. Drab gray brown with a majestic yellow head. Esp. in trees in wash/picnic area.
  2. Rock Wren -- S,F,W,Sp -
  3. Black-throated Sparrow --S,F,W,Sp - These pretty birds were abundant in May 2000. They were busy feeding on the seeds and insects that developed on the many wildflowers that bloomed during the month of April. They have a jet-black throat and bib contrasted by bright white on the sides of the face. Beautiful singers. A very nice description of the black-throated sparrow can be found at Twentynine Palms Cyberzine (California). These birds will migrate away when the really blistering days of summer arrive.
  4. Anna's Hummingbird -- S,F,W,Sp - Common. Green back; forehead and throat of males magenta.
  5. Mourning Dove -- S,F,W,Sp
  6. Curve-billed Thrasher -- S,F,W,Sp - also likely along the wash near the picnic areas.
  7. Cliff Swallow -- Sp,S - Common because of the lakes and ponds at Arrowhead.
  8. Gambel's Quail -- S,F,W,Sp - No doubt a bit more common than would be otherwise because of feeders put out in the nearby housing areas.
  9. Gila Woodpecker -- Melanerpes uropygialis -- S,F,W,Sp -
  10. Cactus Wren -- S,F,W,Sp -- These birds require more food than would normally be available in this sparse habitat, and so are generally restricted to areas near the picnic tables where they find supplemental food in the form of crumbs and handouts.
  11. Northern Mockingbird -- S,F,W,Sp -
  12. House Finch -- S,F,W,Sp -
  13. Phainopepla -- W,Sp - in the winter season especially. Jet-black (males), crested birds with red eyes will gather in the wash where there are desert mistletoes growing in the trees (females are dark gray). They eat the mistletoe berries.
  14. Black-tailed Gnatcatcher -- Polioptila melanura -- S,F,W,Sp
  15. Ash-throated Flycatcher -- Sp,S - spring time esp.
  16. Turkey Vulture -- Cathartes aura -- Sp,F - Mostly seen in spring and fall during migration. Observed at Hedgepeths on 20 April 2008 by Paul V. & Family.
  17. Greater Roadrunner -- S,F,W,Sp -
  18. Inca Dove -- S,F,W,Sp - Most likely in areas adjacent to residential areas
  19. Great-tailed Grackle -- S,F,W,Sp - Post-picnic pickers.
  20. Brown-crested Flycatcher -- Myiarchus tyrannulus -- S - strictly a summer bird -- heads south into Mexico come autumn.
  21. Loggerhead Shrike -- Lanius ludovicianus -- S,F,W,Sp - A nesting pair found in May 2000 near the Adobe Dam recreation area.. <
  22. White-throated Swift -- F,W,Sp - might be seen cavorting in speedy dives and swoops around summits

Quite a number of water birds can be seen at the ponds at the north end of Arrowhead. You can hike down along the edge from the mountain trails. There are egrets and herons. In the winter there are often many ducks, coots and grebes.

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Inca Dove, photo © M.J.Plagens

Inca Dove (Columbina inca) Photo by Mike Plagens.

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Phainopepla  Greater Roadrunner
Verdin  Rock Wren

photo © M.J.Plagens

Western Whiptail (Cnemidophorus tigris) Photo by Mike Plagens.


In order of Abundance:

  1. Side-blotched Lizard (Uta stansburiana) -- most active lizard during cooler parts of year. Dark patch behind forelegs; bluish throat.
  2. Tree Lizard (Urosaurus ornatus) -- gray or brown ... forages about on boulders or tree trunks
  3. Western Whiptail -- Cnemidophorus tigris -- banded and spotted lizard digs holes beneath creosote.
  4. Desert Spiny Lizard -- Sceloperorus magister -- large pale-colored lizard with conspicuous, pointed scales. Males have blue on belly and neck.


  1. Audubon's (Desert) Cottontail (Sylvilagus audubonii)- common rabbit species.
  2. Round-tailed Ground Squirrel (Spermophilus tereticaudus) - small squirrels that burrow incessantly and are often mistaken for gophers or prairie dogs.
  3. Harris' Antelope Squirrel (Ammospermophilus harrisii) - small squirrel with a long bushy tail. White stripe along flank. Very common around people areas.
  4. Black-tailed Jackrabbit (Lepus californicus) -- huge rabbit with huge black-tipped ears. A number seen on the flood retention basins.
  5. Rock Squirrel (Spermophilus variegatus) - large rusty brown or gray squirrel without stripes and having a large bushy tail. These squirrels rarely climb trees, but near the picnic area in the wash I found them climbing into the Blue Palo Verdes to gather seeds to eat.
  6. Coyote -- Canis latrans

Harris' Antelope Squirrel (Ammospermophilus harrisii) Photo by Mike Plagens.


Mostly in order of abundance:

  1. Buckhorn Cholla (Opuntia acanthocarpa) --
  2. Teddy Bear Cholla (Opuntia bigelovii) --
  3. Compass Barrel Cactus (Ferocactus acanthodes) -- Spines tinged with red and yellow.
  4. Saguaro Cactus (Cereus giganteus) -- Many have been repeatedly vandalized by rock-throwers.
  5. Engelman Hedgehog Cactus (Echinocereus engelmannii)
  6. Graham's Pincushion Cactus -- Mammillaria grahamii --
Buckhorn Cholla  Teddy Bear Cholla;Jumping Cholla

Shrubs and Trees

In order of Abundance:

  1. Brittle Bush (Encelia farinosa) -
  2. Triangle-leaf Bursage (Ambrosia deltoidea) -- Often leafless after periods of drought or hard frost.
  3. Creosote Bush (Larrea tridentata)
  4. Foothills Palo Verde (Parkinsonia microphyllum) - Most are only shrub size due to the thin soils.
  5. Lance-leaf Ditaxis (Argythamnia lanceolata) -
  6. Wofberry (Lycium andersoni) -
  7. Sweet Bush (Bebbia juncea) - Fairly common.
  8. Desert Globe Mallow (Sphaeralcea ambigua) - Bears peach-colored blooms after periods of rain otherwise it is difficult to find
  9. Wire Lettuce (Stephanomeria pauciflora) -
  10. Velvet Mesquite -- Prosopis velutina - a few smallish ones in the picnic/wash area
  11. Desert Lavender (Hyptis emoryi) - a few can be seen near the summits
  12. Bigelow's Four O'Clock (Mirabilis bigelovii) - common but withers down to crown with hot dry summer.
  13. Canyon Ragweed (Ambrosia ambrosioides)
  14. Desert Senna (Senna covesii) - found mostly at roadsides
  15. Desert Broom (Baccharis sarothroides)
  16. Climbing Milkweed (Sarcostemma cyanchoides)
  17. Burro Brush (Hymenoclea salsola)
  18. Ironwood (Olneya tesota) -
  19. Blue Palo Verde (Parkinsonia florida)
  20. Desert Hackberry (Celtis pallida)
  21. Wolfberry -- Lycium exsertum
  22. Cat-claw Acacia (Acacia greggii) - along the wash adjacent to the picnic area
  23. Desert Mistletoe (Phoradendron californicum) - parasitic in the larger trees along the washes.
  24. Desert Tobacco (Nicotianna trigonophylla) -
  25. Trixis (Trixis californica) -
  26. White Bursage (Ambrosia dumosa)
  27. Joint Fir -- Ephedra aspera -
  28. Yellow Felt Plant -- Horsfordia newberryi -- a few at scattered locations close to the summits.

© Mike Plagens

Creosote Bush Larrea tridentata

Late Winter Wildflowers (obs. January 24, 2010)



Desert Globe Mallow

Desert Globe Mallow

Desert Lavender

Desert Lavender

Desert Tobacco

Desert Tobacco

Lance-leaf Ditaxis

Lance-leaf Ditaxis

Spring Wildflowers (obs. March 2, 2003)

White Flowers

  1. Emory Rock Daisy -- Perityle emoryi
  2. Arch-nutted Comb Bur -- Pectocarya recurvata
  3. Peppergrass -- Lepidium lasiocarpum
  4. Lacepod -- Thysanocarpus curvipes
  5. Narrow-leaf Popcorn Flower -- Cryptantha angustifolia
  6. California Mustard -- Guillenia lasiophylla
  7. New Mexico Ditaxis -- Argythamnia neomexicana
  8. Small-seed Sandmat -- Chamaesyce polycarpa

Pink/Lavender Flowers

  1. Red-stemmed Fillaree -- Erodium cicutarium
  2. Locoweed -- Astragalus nuttallianus
  3. Cheeseweed -- Malva parviflora -- minute flowers
  4. Desert Globe Mallow -- Sphaeralcia ambigua

Yellow Flowers

  1. Brittlebush -- Encelia farinosa
  2. Sahara Mustard -- Brassica tournefortii
  3. London Rocket -- Sisymbrium irio
  4. Wolfberry -- Lycium exsertum
  5. Foothill Deervetch -- Lotus humistratus
  6. California Sundrop -- Camissonia californica
  7. Creosote Bush -- Larrea tridentata

Purple-Blue Flowers

  1. Lupine -- Lupinus sparsiflorus
  2. Eucrypta chrysanthemifolia
  3. Notch-leaved Phacelia -- Phacelia crenulata

Red-Maroon Flowers

  1. Buffel Grass -- Pennisetum ciliare

Orange Flowers

  1. Orange Fiddleneck -- Amsinckia intermedia
  2. Desert Globe Mallow -- Sphaeralcia ambigua
  3. Coulter's Globe Mallow -- Sphaeralcea coulteri

Green Flowers

  1. Canyon Ragweed -- Ambrosia ambrosioides
  2. Triangle-leaf Bursage -- Ambrosia deltoidea
  3. Pellitory -- Perietaria hespera
  4. Indianwheat; Woolly Plantain -- Plantago ovata
  5. Hairy Bowlesia -- Bowlesia incana
  6. Six-weeks Three Awn -- Aristida adscencionis

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