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The pine & the jay - symbiosis between blue pinon jays and pine trees - Forest Facts
American Forests, Jan-Feb, 1992 by Terry Heiner
There's more than symbiosis going on between these two denizens of the Southwest. By TERRY HEINER
The October afternoon is quiet, the pinon pine forest seemingly dozing in the autumn sun under a clear blue New Mexico sky. The air is filled with a resinous pine scent, and an occasional breeze whispers through the needles, lightly shaking the cones that are opening in the warm afternoon air. The more vigorous breezes are followed by the pitter-patter of pinon seeds falling to the ground.
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The afternoon tranquility is suddenly shattered by the clamoring racket of a flock of several dozen blue pinon jays screeching to each other as they swoop into the forest. Landing in the tops of the pines, they begin to pluck the dark, plump seeds from the sticky cones. Storing the seeds in their throats, they fly away to hide them in secret locations before returning to repeat the process.
This scene has been repeated in New Mexico for probably thousands of years, and benefits both the pinon and the pinon jay.
A complex and fascinating interdependent relationship exists between the pine and the bird (including both the gregarious pinon jay and the more solitary scrub jay). The reproductive cycle of the jay seemingly coincides with the ripening of the seed crops of the pine; likewise, the pine depends on the jay for the dissemination of its seeds.
Over thousands of years of evolution, the jay may have played a major role in the selection of pinon seed characteristics, including its large size. When scrub jays are allowed to choose from pinon seeds of differing sizes, they invariably select the larger ones first. Seedlings from those seeds will experience greater success, and the next generation will tend to produce larger seeds.
Another characteristic of the pinon seed is the absence of a wing. Pines of other species whose seeds are not harvested and planted by birds have seeds that are small and have wings that assist in wind dispersal. Not so with the pinon.
With their probe-like bill, the jays plant the pinon seeds in the soft ground under the canopy of other trees, to be stored for later consumption. jays have been observed to transport seeds from as little as a few feet to as far away as several miles. Early observers often found pinon seedlings growing beneath other tree species, far from any seed source, and wondered how the seed reached such distant sites. The answer is clear: The seeds flew there on feathered wings ! When close to human dwellings, scrub jays have frequently been observed putting the seeds in flower beds or even flowerpots. Since the jays do not consume all the seeds they store, gardeners may find pinon seedlings growing among their pampered petunias. Thus we consider the jay to be the architect of some of the pinon's unique features.
The selection of the seed-storage site is an important decision that may affect the jay's survival. They may store their seeds in cracks in the bark of trees or, more commonly, in the ground under the canopy of a gray oak or a juniper. The bird's wisdom can be appreciated on the days following a heavy snowstorm. The tree's canopy catches much of the snow, and as the snow melts, the ground under the tree becomes bare earlier, making the stored seeds available to the hungry jay.
The jay has a throat that can expand to hold and transport a large number of unshelled pinon seeds at one time. One pinon jay is reported to have carried more than 50 seeds in a single trip, truly an amazing number. When preparing to eat the seed, the jay will brace it against a branch with its foot and hammer at it with its bill in woodpecker fashion until the shell cracks.
When compared to other pines, pinons produce a higher percentage of cones in an upright position with scale membranes that delay the release of the seeds. The longer the time the seeds remain in the cones, the better for both the pine and the jay. Once the seeds fall to the ground, they become available to animals that tend to eat the seeds rather than plant them. From the jay's point of view, the seeds in the open cones are presented in a manner that seems to say, "Here are my seeds-help yourself." It is possible that over eons of time, our feathered architect helped create this manner of seed presentation.
When next we take a fall stroll through a southwestern forest and see a flash of blue beneath an oak tree, we should realize that a feathered planter is hard at work. As the jay flies away, he may have left several plump pinon seeds nestled in the ground, either to await his return or to germinate when the warmth of spring arrives. Thus a small fragment of the pinon pine forest arrives at a new location.
COPYRIGHT 1992 American Forests
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