boreal blocking effect
birdeland at pasty.net
Fri Mar 10 22:54:23 EST 2006
Brian : I think you are on to something whatever it may be! I've discussed this very thing with veteran birders over the years with great interest by a few and a "ho-hum" attitude by others. It seems with all the data, data-bases and all the research being done some conclusions would have or could be done. It works both ways--ie: in reverse look at the range maps for neo-tropical migrants.
Several show their summer range extend farther north into Wisconsin and points west and up into Ontario and points east but sometimes no farther north into Michigan but about 43:00 latitude. Why would this be? Not to be overly lengthy here I could list many examples but one can look and see for themselves those species. Yes, different field guides have different range lines in some cases and yes many species have expanded or withdrawn their ranges but my point being the overall range status.
Just for discussions sake lets say we lose all Red-Headed Woodpeckers and Bob White Quail in the LP. Where would a new natural population have to come from? The fact of the matter is the only way any bird ( or anything for that matter) can get into or out of the LP is through Indiana or Ohio, Detroit & St. Clair Rivers, OR the Straits of Mackinac if the species is prone to cross the 5 to 7 miles or the many more across Lake Michigan and Lake Huron. Point being the LP is almost entirely surrounded by large bodys of water except for Indiana & Ohio!
Anyhow I agree the habitat is probably no worse here then Wisconsin or Ontario. Probably some cases better.
Russ Emmons, St. Clair county
----- Original Message -----
From: Brian A
Sent: Friday, March 10, 2006 2:11 PM
Subject: boreal blocking effect
The other day I was out walking the dog/birding some "boreal" habitat (white-cedar, tamarack, balsam fir, white pine) forest near my house and as usual noticing the paucity of any boreal birds.
I had the idea that possibly Lake Michigan and Lake Huron block the normal distribution of boreal birds (at least to some extent) from northern lower Michigan from what would be expected at this latitude.
In comparing maps of several species (red crossbill, evening grosbeak, pine grosbeak) It looks like the species do extend down to about latitude 45 in Wisconsin and Ontario but not (with a bit of exception in Pine Grosbeak) in Michigan. see http://audubon2.org/birds/cbc/hr/map.html
From my travels I do not think the habitat is any worse in Michigan in this area for boreal species than either Ontario or Wisconsin.
Anyway, just trying to justify my lack of birding success I guess.
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