Eric, a gos researcher sez:

> Seemingly irreconcilable differences about the difference in the ecology
> also point to a separation. Goshawks in Europe apparently do well in managed
> forests and active logging areas. In North America, especially in the west
> where most of the work is being conducted , goshawks are declining due in
> large part to logging in foraging and nesting areas. This discrepancy is
> often exlained as a difference in any number of potentially biasing factors
> between studies such as techniques, habitat, competitors, prey base, etc..
> Could a more reasonable and satisfactory explanation be that we are dealing
> with two different species?

I think you want to be careful about using the fact that gos do well
in managed forests in Europe, but not in western North America as an
argument that the two forms are different species. You really need to
understand the underlying forest ecology, logging techniques, and
the resultant second-growth forest in great detail.

For instance, selective logging of Ponderosa pine in western North
American forests coupled with fire suppression have transformed large
tracts of relatively open ("park-like") pond pine forest into dense
thickets of lodgepole. As I'm sure you know, lodgepole grows rapidly,
dies at a relatively young age (the subspecies here in Oregon, that is),
and in such large tracts is prone to disease. Etc etc, I could detail
changes wrought by this transformation for pages but the bottom line
is: does forestry in the coniferous forests of Scandavia, for instance,
lead to the same result? They're certainly formed of different species,
and perhaps genus (are these forests pine forests?).

Gos in North America live in various forests (for instance,
the western Cascades forests, which are VASTLY different than the
limber pine/white fir forests of Great Basin ranges where gos also
thrive, in addition to pond pine forests mentioned above). I imagine
this is true in Europe as well - do they do well in ALL managed
forests in Europe, or only certain types of forest or under certain
types of management?

A good example is 'ole spotty, that night-time mammal muncher. They
thrive in second-growth redwood, but not in second-growth Doug fir.
Are the two populations separate species? Currently they aren't
even considered separate SUBSPECIES. This is an interesting example,
because old-growth redwood forests and old-growth doug fir forests
are very similar structurally (i.e. big trees, multi-layered canopy,
etc) though dominated by different tree species. Similar logging
techniques are followed (clearcuts!). However, the resultant
second-growth forests are sufficiently different that the owl are
able to live and fledge young in one, but in general not the other.

This doesn't reflect a difference in the owl, but rather a difference
in the two forests (after all, doug fir and coast redwood are VERY
different trees).

The above isn't an argument in favor of lumping the two populations
of gos into a single species. I'm merely pointing out that the
bare fact you mention can't be used as an argument for or against
without extremely detailed analysis of the cause of that fact.


-Don Baccus-