Gila Woodpeckers and Saguaro Cactus, Illustrating Neighborliness

Dr. James J. S. Johnson

Thine own friend, and thy father’s friend, forsake not; neither go into thy brother’s house in the day of thy calamity: for better is a neighbor that is near than a brother far off.  (Proverbs 27:10)

[Gila Woodpeckers in Saguaro /  photo credit: North Mountain Visitor Center]

Like friends who help each other, the Gila Woodpecker and the Saguaro Cactus (Carnegiea giganteus, f/k/a Cereus giganteus)make good neighbors.

A photogenic icon of the hot desert, the Saguaro Cactus,  thrives in America’s arid Southwest – is what ecologists call a “keystone” member of that hot desert community. For example, the Sonoran Desert (which overlaps Arizona, California, and parts of Mexico) hosts the equivalent of “forests” of these jolly green giants, growing amidst other succulents, xerophytic shrubs, and ephemeral flowers.

[ Saguaro National Park, Arizona, near Tucson   /  photograph by Joe Parks ]

But, looking at Saguaro Cactus from a distance, would you guess that these prickly-spined tree-like columns provide homes for many desert denizens, including a variety of birds? They do!

The Saguaro cactus is in every way a keystone species on the Sonoran Desert’s bajadas [drainage-slope terrains]. Without it, much of the [desert neighborhood’s] richness of species would soon be dramatically reduced. For instance, many of the birds of the bajada either feed or nest (or both) on Saguaros. Gila Woodpeckers, Ladder-backed Woodpeckers, and Northern (Gilded) Flickers hollow our nest cavities that are later used by American Kestrels, Elf Owls, Western Screech-Owls, Purple Martins, and Brown-crested and Ash-throated flycatchers, as well as various species of bats.

Approximately 30 bird species, most recently the European Starling, have been documented to nest in woodpecker-carved Saguaro cavities. House Finches, Chihuahuan Ravens, Harris’s and Red-tailed hawks, and Great Horned Owls use the tall cactus arms as nest sites. Saguaro blossoms are fed upon by White-winged, Mourning, and Inca doves, Scott’s and Hooded orioles, House Finches, Cactus Wrens, and Curve-billed Thrashers. Sparrows and finches consume the [Saguaro] seeds.

[Quoting John C. Kricher, A FIELD GUIDE TO THE ECOLOGY OF WESTERN FORESTS (Houghton Mifflin, 1993), pages 279-280.]

Interestingly, the Saguaro Cactus is sometimes helped by its Sonoran Desert “neighbors”, in situations that ecologists call “mutual aid” relationships—with neighbors being neighborly. One example of this “mutual aid” is seen in the behavior of the non-migratory Gila Woodpecker.  (Like a good neighbor, Gila Woodpecker is “there”.)

A Saguaro whose stem is injured is subject to rapid and fatal necrosis from bacterial invasion. However, the site of the injury is an ideal place for a Gila Woodpecker to begin excavating a nest cavity. In doing so, the woodpecker may remove all of the diseased tissue [i.e., bacteria-infected soft tissue], essentially curing the cactus of what might have [become] a fatal bacterial infection.

[Quoting John C. Kricher, A FIELD GUIDE TO THE ECOLOGY OF WESTERN FORESTS (Houghton Mifflin, 1993), page 280.] Now that’s an appreciative neighbor, giving help when needed, returning good for good!  “For better is a neighbor that is near than a brother far off.”  (Proverbs 27:10b)

[Gila Woodpecker approaching Saguaro Cactus, Arizona /  Photo credit: Brian Small]