nomes no trilho de navegação
Generally populations are stable or have increased slightly in most parts of the species range. Habitat loss has resulted in declining numbers in some areas (Burleigh, 1972; Tomback, 1998).
Perception Channels: visual ; tactile ; acoustic ; chemical
Limited data is available on actual population density of Clark's Nutcracker. Currently no specific management plans are in place. Long-term fire suppression has resulted in advanced forest succession. This coupled with loss of conifer stands due to disease or insect outbreaks has resulted in loss or degradation of some historic habitat areas. Changes to piñon pine communities related to grazing have also resulted in some decreases in habitat quality. These factors may result in a reduction in their numbers in certain areas (Tomback 1998).
US Migratory Bird Act: protected
US Federal List: no special status
CITES: no special status
IUCN Red List of Threatened Species: least concern
Again, future research is needed to determine the actual effects of the role Clark's nutcracker has in pine population structure, with regard to the selective pressures it exerts as a seed predator (Tomback, 1998).
Though additional studies are needed, Clark's nutcracker plays a role in the dispersal and establishment of conifer species. Its spatial memory abilities are an area of interest for future research as well (Tomback, 1998).
Positive Impacts: research and education
Clark's Nutcracker plays a major role in the dispersal of wingless pine seeds. Ranges of seed dispersal by these birds affect the population structure of various conifer species (Tomback, 1998).
Ecosystem Impact: disperses seeds
Though conifer seeds make up the majority of this nutcracker's diet, they will feed opportunistically on other food resources. Other food items present in their diets include flying insects and ants, small vertebrates, eggs and nestlings, and occasionally carrion. They use their sturdy pointed bills to pry seeds out of unripe cones, or to hammer and crush seeds out of their shells. Then they will either eat the seeds or place them in their sublingual pouches for caching later.
Ponderosa seeds are their most important food by volume but seed use changes with annual variations in seed availability. Seeds are cached at varying elevations, with each cache averaging three to four seeds. A single individual may have thousands of caches. Seed stores are recovered using visual cues and spatial memory up to nine months after being cached (Tomback, 1998).
Animal Foods: birds; eggs; carrion ; insects
Plant Foods: seeds, grains, and nuts
Foraging Behavior: stores or caches food
Primary Diet: herbivore (Granivore )
Clark’s nutcracker has a wide distribution in zones of coniferous vegetation from the coastal ranges in Canada throughout the mountainous areas of the western United States. It is a native, permanent resident of the mountainous regions of western North America. Migration is only altitudinal with a shift to lower elevations beginning in late September (Burleigh, 1972; Coues, 1874; Tomback, 1998).
Biogeographic Regions: nearctic (Native )
In summer it prefers habitat in the sub-alpine zone near the tree line. The habitat of choice is semi-open, mixed stands of pines, fir and spruce growing on steep slopes and ridges interspersed with meadows and streams. Species of trees within the habitat varies geographically. Nutcrackers will remain on their summer range as long as food is available. In winter they migrate to lower elevations and spend the winter foraging and retrieving caches there (Tomback, 1998; Coues, 1874).
Range elevation: 1000 to 3840 m.
Habitat Regions: temperate
Terrestrial Biomes: taiga ; forest ; mountains
Little is known about the average lifespan of Clark's nutcracker. However, the longest recorded lifespan was seventeen years.
Range lifespan
Status: wild: 17 (high) years.
Average lifespan
Status: wild: 209 months.
Clark’s nutcracker is a chunky, jay-sized bird averaging 11 inches long. Its plumage is powder-gray and of loose texture. Wings and central tail feathers are glossy black. Wings are long, when folded reaching nearly to tip of tail. Flight is crow-like with deep wing beats and when in flight white wing patches and white outer retricies can be seen. There is moderate size dimorphism between sexes with males being bigger. (National Geographic Society, 1999; Tomback, 1998).
Average mass: 141 g.
Average length: 28.8 cm.
Other Physical Features: endothermic ; bilateral symmetry
Clark's nutcrackers respond to predator threats with mobbing behavior. Alarm calls (squalling) alert other flock members (Tomback, 1998).
Known Predators:
Apparently monogamous with long lasting pair bonds. Pairs form in winter months. Courtship displays can be seen throughout the year but are most intense in the breeding season. Courtship behavior includes rapid flights where one bird follows its mate at high speed, both performing various swoops and dives. Begging calls, feeding and other vocalizations have been observed as part of courtship. Territories are only established for nesting purposes and a pair may hold the same nesting territory for several years.
Mating System: monogamous
Both members of the pair contribute to nest construction. Timing of nesting vary seasonally based on elevation, weather, and food availability. Nest location is often near food stores and may not be well concealed. Nests, which average 11 inches in diameter, are placed on the more sheltered side of nesting tree, often on a south-facing slope. Height of nest varies from seven to 70 feet above ground depending on the nesting tree. Placed on one or more branches, the nest platform construction materials include small twigs woven together. The nest bowl is well insulated with the outer part built of rotten wood pulp and the inner bowl lined with fine material.
Brood size averages three eggs, which are laid usually two days after nest construction is completed. The altricial young with sparse down hatch almost synchronously after an 18 day incubation. Growth is rapid and fledging occurs approximately 20-22 days after hatching. The family group forages together for the remainder of the summer but the young are completely independent by the end of summer (Tomback, 1998).
Breeding season: Late winter to spring
Average eggs per season: 3.
Average time to hatching: 18 days.
Average fledging age: 21 days.
Average age at sexual or reproductive maturity (female): One years.
Average age at sexual or reproductive maturity (male): One years.
Key Reproductive Features: iteroparous ; seasonal breeding ; gonochoric/gonochoristic/dioecious (sexes separate); sexual ; fertilization (Internal ); oviparous
Average time to hatching: 17 days.
Average eggs per season: 2.
Unusual for corvids, both males and females incubate. Male has well developed incubation/brood patches, which allows him to tend the nest while female retrieves seeds from her caches. Both also care for the young after they hatch.
Parental Investment: altricial ; male parental care ; female parental care
