If December’s exceptionally warm La Nina weather pattern lulled you into a false sense of security regarding winter’s frigid potential, the last few weeks have surely left no doubt as to the season.
One way to keep winter blues at bay is to delve into the lives of our local trees. Be they deciduous and barren or evergreen and sporting a verdant cloak, our diverse array of species can brighten any winter day. Sentinels standing guard until life once again swells in spring. Some trees offer sustenance to wildlife and humans alike—the food. Other trees threaten the very habitats they grow within—the bad. Finally, many host insects that you can investigate and which serve as food for various species—the bugly.
Perhaps my favorite winter food tree is netleaf hackberry. Named for both its finely veined leaf undersides and its fruit (not a true berry, but rather a hard-pitted drupe), even the tree’s bark wiggles its way into the moniker. “Hack” is likely a reference to the tree’s warty bark, derived from old English meaning haggish or warty. Indeed, these distinct deciduous trees often have warty protuberances along their trunks—all the better for some mammal species to scale the boles in search of calories.
The number one local mammalian consumer of hackberries is surely the white-nosed coati. In winter, lacking many of their normal dietary fare, coatis eagerly scale hackberry trees to gorge upon the fruit. Other more crepuscular and nocturnal mammals take care of the night shift—Virginia opossums, common gray foxes, ringtails, and northern raccoons also get in on the act. Look for orange scat with the hard-pits as evidence of these sometimes frugivorous (fruit eating) mammals.
Some of the same species may consume the rather sweet cones—they also are misnamed as berries—of alligator juniper and/or the more medicinal-tasting cones of Arizona juniper, as evidenced by their purplish scat. A variety of local birds, including wintering sage thrashers, also partake of the latter tree’s cones as part of their winter fare.
Meanwhile, our collared peccaries avail themselves of any lingering nuts strewn beneath Arizona walnut trees. Each time I partake of this treat, I require a hammerstone and anvil to liberate the nutmeat. Javelina succeed solely via their prodigious jaws—yikes! Throw in a bevy of tree species tapped into by red-naped sapsuckers and you begin to fathom the supreme importance of local tree species to our Sky Islands wildlife.
Some local trees are, sadly, mere ecological mirages, as they harm rather than support our biodiversity. Go on a walk near Patagonia Lake to visit this rogues gallery of “bad” trees—all courtesy of a landscape disturbed by cattle. Introduced from other parts of the globe and hence liberated from their normal biological constraints, these species wreak havoc wherever they lay roots. Public enemy number one is tree of heaven (or hell, as I prefer). Introduced from Asia as a pollution-hardy urban tree, this handsome yet deadly species can swiftly take over riparian forests. Able to clone itself into dense stands, it also employs root chemicals to help prevent native plant species from growing in its understory. The result is an ecological desert utterly devoid of any true benefits to wildlife. Factoring in increasingly common white mulberry trees—also from Asia—the growing risk of tamarisk from Eurasia, and spreading tree tobacco plants from South America, it soon becomes clear that we had better aggressively remove these foreign botanical villains or forever suffer the ecological consequences—the bad.
Returning to native tree species, we arrive at those that benefit wildlife by the invertebrates they host. As you scan various tree branches, look for odd little insect cases—oothecas—laid down by female mantids. These egg cases house would-be baby mantids that hatch out in warm weather—if parasitic wasps haven’t commandeered them as food for their own larvae! Sometimes, the hungry birds of winter also break into the oothecas, searching for a few meager calories. Keep a keen eye peeled as birds hunt across a wide array of native tree species for seemingly invisible insects—often various moths and flies. Frenetic ruby-crowned kinglets, flycatchers and others remind us that some trees are indeed “bugly”!
Now you have even more reasons to either hug our native trees or to help vanquish nonnative ones.
Vincent Pinto and his wife, Claudia, run Ravens-Way Wild Journeys (RRWJ), their Nature Adventure & Conservation organization devoted to protecting and promoting the unique biodiversity of the Sky Islands region. RWWJ offers a wide variety of private, custom-made courses, birding & biodiversity tours.