We Met the Ehlers!

Here in the Sonoran Desert, we are blessed to be the home of the Saguaro Cactus.  They are seemingly everywhere.  Animals and especially birds love Saguaros for a whole list of reasons.  When the Saguaro bloom, the white winged dove can be seen sitting on them helping pollinate them as they sip the flower’s nectar.  As a perch and lookout point, all manner of hawks, wrens, quail, and even bobcats find the top of a Saguaro an excellent vantage point from which to survey the area, as a place of rest, or even a platform from which to hunt.

Inside the Saguaro cactus, however, is a place that birds discovered, centuries ago, is a haven from the desert heat and a safe place to build a nest.  High off the ground, a hole drilled into a Saguaro by a Gila Woodpecker or Gilded Flicker provides safety from predators.  More importantly, creating a nesting place inside a Saguaro, where the resulting temperature is several degrees lower than the intense desert heat, is a major plus.

Creating a nesting home or hideout inside a Saguaro, however, is not an overnight job.  First, a hole is created by one of the birds mentioned above or others, which creates a hole that continues inside to become a cavity large enough to accommodate a nest.  The Saguaro, in response to this invasion or injury, responds in order to defend itself and reduce water loss, by secreting a protective substance to “patch,” itself-almost like first aid, called a Saguaro Boot.  This can take a year.  (It should be noted that insects also burrow into and create homes in the Saguaro.  The Saguaro also creates a protective “Boot,” around these invasions, but they are much smaller and are not large enough to be used by birds.)

When a bird compromises the outer skin of the Saguaro, creates a hole and then drills in and downward, the Saguaro responds, by depositing a hard substance, called callus tissue that contains a woody substance, lignin, which surrounds the hole made for a nest.  This response is good for the cactus, because it prevents the loss of water and, it is great for the animals because of the safety it affords, its lower temperatures and, because it is waterproof, it ensures the young will be safe and dry.  The result is a lined cavity which is then used by several different kinds of birds as a hiding place, a place to build a nest, or a respite from the heat of the afternoon sun. Called a Saguaro Boot, these internal chambers can be expanded, over the years, if additional carve-outs and expansions are made by subsequent nesting birds that take advantage of the initial wound.  To protect itself, the Saguaro continues to deposit the resinous protective shield.  In the life of a Saguaro, the Saguaro Boot retains its structure.  Even after the Saguaro dies and the external skin decays, you may see, internal to a Saguaro “skeleton,” a boot that remains fairly intact.

The Saguaro Boot then, becomes a destination for a variety of bird families as a place to raise their young.  Some species will use a specific Saguaro Boot just once, and others, will return.  In a previous post, I mentioned that small owls, such as Screech Owls, Elf Owls and the like will use the Saguaro Boot as a nesting place.  In addition any number of finches, sparrows, purple martins and others also find the Boot, a great nesting option.