Imagine spending most of the Fall, until the snow comes, being able to harvest some 30 whitebark pine seeds, caching them about 2-3 cm deep in soil on sloping subalpine hillsides over a wide area and then being able to remember where most of them are up to nine months later.
This amazing feat is carried out by Clark’s nutcrackers every year. No one is sure how they do this, but clearly, they have remarkable memories. One study suggested that they may be able to remember a cache in relation to a rock, downed wood or standing trees. But what if the rock or log is covered with snow? It is possible that if the slope is windblown, the snow may not be too deep.
Clark’s nutcrackers are corvids with grey bodies, black wings with white wing patches, larger with longer, sharp-pointed bills, but somewhat similar in appearance to Canada jays. The nutcrackers hang out in coniferous forests around timberline, are gregarious and noisy and often move around in groups. They may cache their seeds communally or have their own private stores.
The birds are found in the same range in BC as their favourite food – the seeds of whitebark pine – a long lived, five-needle, subalpine pine tree. The cones of whitebark pine are very dense and woody and the scales do not open to release the seeds like the cones of lodgepole pine do. The long-pointed, heavy beak of the nutcracker is ideally adapted to tear open the cones to access the large, fatty, highly nutritious seeds.
Clark’s nutcrackers extract only healthy, intact seeds, insert them into a pouch underneath their tongue (sublingual pouch) which can hold up to 150 seeds at a time before they take off to cache them in the soil on gentle slopes, usually within about 25 km of their nesting areas.
It does not matter if the birds do not retrieve all the seeds because some of the seeds will germinate and grow into new trees providing food for future generations. In essence the birds are dispersing and planting the trees. This very closely dependent relationship is called obligate mutualism where the birds and trees need each other for continued survival. It is a remarkable example of co-adaptation between different species.
Unfortunately, this important relationship is in jeopardy because of two highly aggressive pathogens (white pine blister rust and mountain pine beetles) that are attacking and killing whitebark pines. More about this and what is being done about the problem next time.
