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Clark's Nutcracker and
Pine Forests

Introduction

Mutualism, the ecological relationship between two or more species, is defined as one where the growth and survival of both populations is benefited, and neither species can survive indefinitely under natural conditions without the other (Odum 1971).

Closely associated with the distribution of pine trees across the northern hemisphere is the occurrence of the corvids, the jays, crows, magpies and especially the nutcrackers.

The soft pines produce wingless seeds that are food for man and many animals. Since the seeds are wingless, these pines are dependent on animals for seed dispersal. In return for the food supply, animals collect and cache the seeds of pine trees, sometimes in distant areas, thus dispersing the seeds and reforesting open or disturbed areas.

Of the many species that feed on pine seeds, none is as well adapted for this task as a group of birds known as the nutcrackers.

The mutual dependence between nutcrackers and pines is one of the important ecological relationships between birds and conifer forests that remains largely unnoticed by ornithologists, foresters, naturalists, biologists, botanists, and bird watchers (Lanner 1996).

 

Mt. Rainier, overlooking Seattle, is the largest volcano in the Cascade Range. It is a spectacular setting to observe the mutual association between nutcrackers and the pines.

Mt. Rainier, Washington
Figure 1 - Mt. Rainier, Washington

Pine Forest on the slopes of Mt. Rainier
Figure 2 - Pine Forest on the slopes of Mt. Rainier

The high pine forests of the Cascade Range are home to many species of forest dwelling animals, including chipmunks, red squirrels, marmots, deer, porcupines, weasels, ermine, black bear, Grizzly Bear, elk, Big Horn Sheep, and a host of bird species including several species of jays, and the ecologically important Clark's Nutcracker.

Clark's Nutcracker (Nucifraga columbiana), first observed on 22 August 1805 by William Clark of the Lewis and Clark expedition, is one of three nutcracker species that occur worldwide, all in the northern hemisphere. The Eurasian Nutcracker (Nucifraga caryocatactes) occurs across Europe and Asia, and the third, the larger Spotted Nutcracker (N. c. multipunctata), occurs in the forests of the western Himalayan Mountains (Madge and Burn 1994).

Clark's Nutcracker
Figure 3 - Clark's Nutcracker

Adult Clark's Nutcracker
Figure 4 - Adult Clark's Nutcracker

Nutcrackers have an amazing ability to gather and cache seeds, and to remember where they put them, even when covered under deep snow. Seed caches may be located many miles from the tree source. The birds carefully select seeds to get the best energy return for their effort, a behavior that ecologists call optimal foraging.

The Nutcrackers have a sublingual pouch capable of storing dozens of seeds, much like a chipmunk stores seeds in its cheek pouches. This pouch can hold as many as 28 single leaf pinyon nuts, 90 seeds of Colorado pinyon, and 82 whitebark pine seeds. Asian nutcrackers can store up to 134 Swiss stone pine seeds, 167 Siberian stone pine seeds and 218 Japanese stone pine seeds (Lanner 1996). A single nutcracker can harvest well over 100,000 seeds in the fall, then use them to feed their young in the following breeding season.

Nutcrackers cache nuts and seeds
Figure 5 - Nutcrackers cache nuts and seeds

Juvenile Clark's Nutcracker
Figure 6 - Juvenile Clark's Nutcracker

The bulge in the chin of this juvenile bird is the sublingual pouch that is filling up. This bird has been collecting nuts fed to it by tourists. Once this bird has filled its sublingual pouch, it will fly to an open area to cache its seeds for later use.

Other species also cache pine seeds. The Red Squirrel (Tamiasciurus husdonicus) harvests and stores conifer seeds on the forest floor in large middens that may be up to 30 feet across. These middens serve as a winter food source for the squirrels, and are sometimes raided by bears and other forest creatures.

Red Squirrel (Chickaree or Pine Squirrel)
Figure 7 - Red Squirrel (Chickaree or Pine Squirrel)

Red-breasted Nuthatch
Figure 8 - Red-breasted Nuthatch

The Red-breasted Nuthatch also forages on seed and nuts, but does not play a significant role in seed dispersal.

The Scrub Jay, Stellar's Jay and Pinyon Jay forage on and cache pine seeds. The Scrub Jay's bill is not well adapted to feed on these seeds, so it often acts as a kleptoparasite on other species, startling them and making them drop their own seeds so it can then steal them.

Scrub Jay
Figure 9 - Scrub Jay

Gray Jay
Figure 10 - Gray Jay

Another corvid of remote pine forests is the Gray Jay, better known as the camp robber. It has the unique ability among corvids to produce a sticky mucous from glands inside the bill. The sticky mucous coats the tongue, allowing the bird to extract food from crevices, and also to form berries into sticky balls that are attached to branches for later use.

Ultimately, man and many species of animals benefit from the mutual relationship between the nutcrackers and pine trees. Mule Deer, named for their large ears, are the only deer with black on the tail. They range throughout the Western US in mountainous regions, and tend to prefer forested areas.

Mule (Blacktail) Deer
Figure 11 - Mule (Blacktail) Deer

Clear Cutting of Pine Forests
Figure 12 - Clear Cutting of Pine Forests

It is unfortunate that man continues to clear the pine forests, especially in the old growth forests. Clear cuts are increasingly seen throughout the northwestern US. One wonders how much physical damage and loss of biodiversity this ecosystem will sustain until it finally collapses.

Nesting Behavior

Clark's Nutcracker is a solitary nester. It builds a crow-like cup nest of twigs and bark, usually close to the end of a branch of a juniper or conifer tree. From 2 to 6 eggs, incubated by both sexes, hatch in 16-18 days. Young leave the nest after 3 weeks, and are cared for by the parents for another few weeks.

Banding Recoveries

The Bird Banding Lab web site reports that between 1955 and 1997, a total of 1,718 Clark's Nutcrackers were banded. Of these, 68 have been recovered, a recovery rate of 0.0395%.

Banding studies show that Clark's Nutcrackers are resident birds that do experience population irruptions every 15 years or so when the pine seed crop fails. One bird banded at Crater Lake, Oregon in the late 1950's was recaptured in 1969 in the same area when 17 year, 5 months old (Terres 1991).

If you should recover a banded bird, please report the band number to
the Bird Banding Lab by calling 1-800-327-BAND.

Conservation Status and Economic Importance

Populations of Clark's Nutcrackers are increasing. In view of the importance of these birds to the long term survival of many pine species and forest ecosystems, and to the many other plant and animal species that ultimately depend on this mutualistic association, this is good news.

Literature Cited

Lanner, R. M. 1996. Made for Each Other. A Symbiosis of Birds and Pines. Oxford University Press, New York, NY. 160 Pp.

Madge, S. and H. Burn. 1994. Crows and Jays. A Guide to the Crows, Jays and Magpies of the World. Houghton Mifflin Co., Boston. 1291 Pp.

Mearns, B. and R. Mearns. 1992. Audubon to Xantus. The Lives of Those Commemorated in the North American Bird Names. Academic Press, London. 588 Pp.

Odum, E. 1971. Fundamentals of Ecology, 3rd Edition. W. B. Saunders Co., Philadelphia. 574 Pp.

Terres, J. K. 1991. The Audubon Society Encyclopedia of North American Birds. Wings Books, Avenel, NJ. 1,109 Pp.

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