Occurrence Maps

Clark’s Nutcracker

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Clark’s Nutcracker is a highly specialized relative of jays and crows that lives in high and dry conifer forests of the Rocky Mountains, Great Basin, and Sierra Nevada. It is one of the more intelligent birds, at least when it comes to memory, and is able to store many thousands of nuts and remember the location of every one, which helps the bird survive periods of low food production. The general map highlights the correct mountain ranges and areas of concentration: western Colorado, the central Sierra Nevada, and northern Rockies are all important areas for nutcrackers.

The status of its population is the subject of recent study, since the health of some of the pine and fir ecosystems in which they live is in question and the prognosis is not good in many areas. The seasonal movements shown by these occurrence maps may help to focus some of these studies, although they must be used with caution. There are definitely seasonal movements undertaken by Clark’s Nutcracker, but the year-to-year movements may be more significant than the regular seasonal movements. In some years the species can disperse to deserts and isolated mountain ranges were they do not normally occur.

These models are currently drawing on data from more than one year to generate these occurrence maps. In many species, this does not cause problems, since the migration of White-throated Sparrow, Willow flycatcher, or rose-breasted Grosbeak generally does not change much from year to year. But for winter finches, Clark’s Nutcrackers, and certain other species with irruptive tendencies, it should be recognized that these multi-year averages may not accurately reflect the occurrence in any one year (although these models are running for 2009, they are influenced by 2006-2008 as well).

Bird movements are so incredibly complex, with seasonal fluctuations and year-to-year fluctuations, long-term increases and long-term declines, and other movements that we are only beginning to understand. Although we fully believe that our models and vast amounts of eBird data will be able to rise to these challenges, each species model must be considered independently alongside an understanding of the species’ known patterns and the ways in which these models are trained.