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A Palo Verde Snag in the Sonora Desert 1
Charles E. Kennedy2
Abstract.--Nearly constant daily use of a dead littleleaf (Yellow) palo-verde (Cer cidium microphyllum) in the
Sonoran , Saguaro Palo Verde Desert by 13 species of bi rds
i s discussed . The bird species are listed with some
discussion r egarding their behavior in the snag .
INTRODUCTION
The snag being discus sed here is approxi mately
15 feet t all , 6 inches in diameter at breast height ,
and has a crown spread of 12- 18 fee t, is hard , and
has no cavities. It occur s with other typical
Sonoran desert vegetation s uch as mesquite
(Prosopis jul ifl ora), blue palo verde (Cercidium
floridum) , and saguaro (Carnegia gigantea).
Shrubs in the area include creosote bush (Larrea
t r identata), white thorn (Acacia constric ts), and
sweet acacia (Acacia fame~ ( some of which
are intr oduced or namentals) . Other acacias a nd
mimosas are in the general area , but are not
common near the snag . The most common s hrub near
the snag and within the general vicinity i s burr
sage (Franseria dumosa).
with native vegetation as described above (with th e
exception of my house--1 50 feet from the snag) .
I n general , the area is only partially developed .
It is an a rea of northwest Tucson , just west of
Oracle and Orange Gr ove which growth skipped over .
Large acreages held by a few owners prevent ed
development .
In addition to the saguaros (appr oximately
one per acre) several species of cacti are
present . Engelmann prickly pear (Opuntia engelmannii) , jumping cholla (Opuntia fulgida) , a nd
barrel cactus (Ferocactus wislizenii) are common.
Grasses are rather uncommon . No perennial
grasses have been observed. Six weeks grama
(Bouteloua bar ba t a) i s a common annual grass .
Snags are uncommon in the Sonoran Desert . In
a recent survey of vegetation of 2 , 100 acres in
nearly iden tical Sonoran Deser t t ype , approximately
12 mil es east , no s na gs we re observed . Occa~ional
dead br anches were seen on palo verde trees .
The snag is at 2400' elevation . Saguaro
densities increase a quarter of a mile away , only
a few feet higher (2450-2500). Mesquite and
palo verde are larger along t he drainages . The
soil type is Paleorthid, of t en i s very ha rdened,
and overlays Caliche (Petrocalcic ). Five to
eight acres west of the s nag a r e undeveloped ,
1Paper presented at th e Snag Habitat Management Symposium. (Flagstaff , Arizona, June 7-9,
1983)
icharles E. Kennedy is Wildlife Biologist,
Coron~do National Forest, Tucson, Ariz .
Personal communication , Dr. Steve Car others ,
1983, Flagstaff, Ariz .
Figure 1.--This dead palo verde has been used by
nine bird species .
165
Table 1.--Findings and opinions.
DISCUSSION
Methods
This paper is based on casual observations
of the use of the snag. The observations have
been made on impulse at no precise time or
period of time.
A few months ago we began listing species
seen in the snag and later added to this by
noting what species were seen together.
Seasonal Use and Daily Use
No obvious patterns have been detected.
Seasonally, use in the spring months appears to
be a little lower than summer, fall, and winter.
This may be due to time spent in reproduction
activities.
Bird Species
Frequency of Use
Mourning dove
House finch
Starling
Cactus wren
White winged dove
House sparrow
Gambel' s quail
Gila woodpecker
Curve-billed thrasher
Anna's hummingbird
Cardinal
White crowned sparrow
Boat-tailed grackle
Cooper's hawk
Most frequent
Very frequent
Very frequent
Frequent
Frequent (when present 1)
Frequent
Occasional
Occasional
Occasional
Occasional (when present2)
Infrequent
Infrequent
Infrequent
One observation-immature
spring migrant
1Not present in winter.
2observed during winter months.
Daily uses are rather constant. The snag
has a bird or birds more often than the rare
times when it is empty.
No aggressive-intolerant behavior between
species was observed. All species seem to
tolerate each other. Six species were observed
together at one time. Twelve individuals--four
species--were observed at one time.
the use of the snag, but since the snag was used
prior to our supplying feed and water, and the
presence of other available water nearby, I do not
feel it has any significant effect upon the amount
of use of the snag by birds.
Implied Behavioral Uses
Loafing appears to be the most common
behavior among nearly every species. Doves,
starlings, and finches rest-loaf commonly.
SUMMARY AND CONCLUSIONS
1. A snag in a partially developed Sonoran
desert type is used regularly by 9 species of
birds.
Cactus wrens, thrashers, gila woodpeckers,
and cardinals may be resting/loafing during their
visits, but stay is nearly always short. They
always seem to be too busy to sit for ~ery long.
2. The snag has values as a loafing/resting
perch for the birds.
Gambel's quail occasionally loaf and sit.
Males call from tip top perches occasionally,
sometimes when alone, sometimes when with a female.
Up to six quail have been together loafing.
3. Regular and scheduled observations would
better identify competition and/or intolerance
between species and within species, and provide
precise data on seasonal and diurnal uses.
Food and Water
4. Persons who like to see birds and have
them around, could install a dead standing tree.
Water and bird seed are available near my
house, 120 feet from the snag. ·This may influence
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