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Index of Subjects
Index of Subjects --001636456fe6e087290467b127ad Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit thank you for posting that. there is a lot we *can *learn from birds, as long as there *are *birds. habitat conservation should be #1 priority. -m On Wed, Apr 15, 2009 at 11:16 PM, Stephen Shaw <srshaw@dal.ca> wrote: > Not sure what Paul found so objectionable about this story, which was > perhaps > a low grade report (little value-added material) but was actually > excerpting > analyses and quotations from several researchers and the RSPBirds in UK, > not so > much giving the reporter's own opinion (or that of `the media`). > I didn't read it as suggesting that birds fly up seeking a particular > temperature value, but that the southern border of the habitat to which > they > are specifically adapted is moving further north quite rapidly because of > local > warming, presumably itself a result of global climate change. If for > example a > particular bird species is evolutionarily-programmed to migrate north for a > certain average time or distance, &/or is programmed to recognize exposed > tundra before it lands and tries to claim territory, it may wind up > exhausted > in boreal forest instead of tundra within a few decades, if the northwards > trends in vegetation cover observed already continue. Food sources there > might > be sub-optimal. > The argument that small warblers seem to have made it through earlier more > extreme climate changes just fine may be correct*, but misses the point: > other > species of small warblers may not have survived and become extinct, because > the > changes were too extreme for those particular species to adapt to. We do > not > now have these extinct species recorded or left to testify (few or no > fossils). > I don't believe that people who study it think that there is a `motive for > migration` whether food or not. The proximate cause of migration would be > a > newly modified internal hormonal state (probably triggered by daylength > changes) that elicits an anciently evolved behaviour to migrate, in the > brain. > The ultimate cause -- why such migratory behaviour evolved in the past -- > is > generally argued to be the lower density of predators and lessened > competition > for territory and perhaps food in the north; food (insects etc) obviously > needs > to be abundant, but is present in the summer both the winter grounds and > temporarily in the northern habitat -- the difference is the competition. > Certainly no one argues these days that such behaviours are purely > instinctive > and unmodifiable, but equally some species may be less adaptable to habitat > change than others and less able to survive climate shifts. > *or it may not be -- they may instead have survived further south and then > gradually re-colonized the emptied northern zones as these warmed up. > > > Quoting Suzanne Townsend <suzanne.townsend@gmail.com>: > >> I knew if I posted it here, if it were off the wall someone would comment. >> Thank you Paul! Hope you post your comments at the source. >> --ST >> >> On Wed, Apr 15, 2009 at 8:01 PM, Paul S. Boyer <psboyer@eastlink.ca> >> wrote: >> >> This is a good example of GW hysteria by the mainstream media, in this >>> case >>> by the highly unreliable Reuters. The article is pure speculation. It >>> also >>> ignores the fact that the Earth was warmer just 7,000 years ago, and >>> colder >>> during the Little Ice Age, and warblers seem to have made it through >>> those >>> changes just fine. >>> The principle problem for birds migrating between Europe and Africa, like >>> those described in the article, is loss of habitat (particularly in >>> Africa). >>> It is also generally true that the bigger the bird, the more likely it >>> is >>> to be pestered by humans: chased, shot, eaten, &c. >>> >>> The conversion of temperature into an equivalent surface distance needed >>> for migration assumes that temperature is the main control of bird >>> migration, which almost everyone who has studied the subject knows is >>> just >>> not true. Food is the main motive for migration, and the food needs vary >>> according to species. Birds will put up with a wide range of >>> temperatures, >>> if the food is available. That is the reason so many feeder-species have >>> moved north, and now stay longer in the winter: if the food is adequate, >>> they will stay. It is one of the amazing things we observe: tiny little >>> creatures, out in the cold, with nothing but a thin layer of puffed-out >>> feathers to separate them from freezing ? and yet they can handle this, >>> if >>> they have enough food. They certainly can tolerate temperature extremes >>> much better than unprotected humans. >>> >>> Canada Geese have largely given up migration entirely, because they find >>> it >>> easier to graze on man-made lawns than to make an arduous migration >>> flight. >>> This certainly does not indicate that the seasons have ceased to occur. >>> >>> I have not been able to find a single convincing case of a migration >>> problem which would be caused by a change in a fraction of a degree. >>> Indeed, the severity of winters from year to years varies by much more >>> than >>> that. >>> >>> There is much we do not understand about bird migration. There is also >>> much we have to discover about changes in bird population. Our lack of >>> complete knowledge is no reason for us uncritically to believe every >>> tendentious news story which comes along. >>> >>> >>> On 15 Apr 2009, at 2:03 PM, Suzanne Townsend wrote: >>> >>> >>> >>> http://www.reuters.com/article/environmentNews/idUSTRE53D7G220090415?feedType=RSS&feedName=environmentNews >>> >>> > --001636456fe6e087290467b127ad Content-Type: text/html; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable thank you for posting that. <br><br>there is a lot we <i>can </i>learn from= birds, as long as there <i>are </i>birds. habitat conservation should be #= 1 priority.<br><br>-m<br><br><br><br><div class=3D"gmail_quote">On Wed, Apr= 15, 2009 at 11:16 PM, Stephen Shaw <