I thought Doug Firs and other conifers had multiyear cycles of cone
production e.g. Doug Firs have large production every 7 years on
average and other North American conifers produce good seed crops at
two to four year intervals. A large group of trees sync to these
cycles to try to provide an overabundance of seeds to "defeat" losses
to the seed eaters.

e.g. see

<http://www.cof.orst.edu/cof/teach/for442/cnotes/sec1/intro.htm>

It's certainly an adaption used by some trees and plants to enhance
their chances of propagating seeds.

I believe this strategy is also mentioned in one of Bernd Heinrich's
books (the Winter book or the first Raven book) but obvious it would
be in a forestry text

On Jan 24, 2009, at 4:54 PM, Eugene and Nancy Hunn wrote:

> Just curious. Does anyone have any idea how frequent a winter
> visitation
> such as we had last year might be? How often should we expect such an
> abundant cone crop at a given location and how can we predict such
> events? I
> know there have been other winters with interesting winter finch
> concentrations at Stevens Pass, but not this time.

--
Kevin Purcell
kevinpurcell at pobox.com