deby@cs.utwente.nl (Rolf de By) (11/01/90)
I am wondering whether any of you knows some facts about Crossbill movements. This year, we had quite a large influx of Crossbills from the north here in Holland, and as I understand also in Denmark and the UK. Even some Parrot Crossbills have reached Holland, although it's still unclear in what numbers. Also, as I understand from some of the American Rare Bird postings some movement of (Red) Crossbills has occurred in the USA. This induces the question whether Crossbill movements are a global phenomenon. As I have always understood it, Crossbills start moving due to food (i.e., spruce) shortages. I know little of trees in general, but to me it seems unlikely that all spruce forests in the northern hemisphere suffer from a bad year. Anyone? Rolf A. de By Vakgroep Informatiesystemen Tel : (0)53--893753 Faculteit der Informatica b.g.g.: (0)53--893690 Universiteit Twente Fax : (0)53--339605 Postbus 217, 7500 AE Enschede Email : deby@cs.utwente.nl The Netherlands deby@henut5.bitnet
stpeters@dawn.crd.ge.com (Dick St.Peters) (11/04/90)
In article <9011010807.AA24286@utis15.cs.utwente.nl> deby@cs.utwente.nl (Rolf de By) writes: >As I have always understood it, Crossbills start moving due to food (i.e., >spruce) shortages. I know little of trees in general, but to me it seems >unlikely that all spruce forests in the northern hemisphere suffer from >a bad year. Anyone? Spruce are especially vulnerable to either acid rain or some common form of air pollution - I can't remember which (same thing anyway, really). They've been taking ill and dying all over this neck of the woods (upstate NY, New England), and I've heard the same about Canadian spruce forests. I haven't heard anything about this last year being especially bad; all recent years have been bad. Spruce and sugar maples seem to be among the first to go. -- Dick St.Peters, GE Corporate R&D, Schenectady, NY stpeters@dawn.crd.ge.com uunet!dawn.crd.ge.com!stpeters