Andy: I think I can help clarify this somewhat:
· To simplify a bit, there are two major migratory Monarch populations in North America, east of Rockies and west of Rockies. Well discuss the former here. · Each year, the final brood of summer Monarchs in the East fly down to overwinter in Oyamel Fir forests in the Transvolcanic mountains of Michoacán, Mexico (at 2400 to 3600 meters). · In the spring, new broods travel north, repopulating North America · Historically, millions of Monarchs have congregated in a small areas in Mexico each winter. · Many of these southbound emigrants come from the East (incl. southern Canada), but numerically most hail from the upper Midwest. · Lately, illegal logging in Mexico has damaged the overwintering sites · More importantly, perhaps, much of the corn grown in the Midwest is genetically modified to be resistant to the herbicide Roundup; farmers douse the landscape with this herbicide to eliminate weeds, thus destroying the host plant for Monarchs (milkweeds), while leaving the corn unaffected (at least by this; their specialized genetics seem to be leaving them susceptible to other blights, however, such as Gosss wilt, as recently reported in NYT.) · Some are now suggesting this will lead to a loss in the biological phenomenon of Monarch migration. · A number of factors led to a small northern return flight of Monarchs in 2013 · Some reached northern climes late in the summer, however where milkweed was profuse this year, so there is at least some eastern southbound migration this fall · It is likely to be small trickle compared to earlier years, however · Invertebrates are hearty and resilient, but no telling how long they will be able to withstand the headwinds they now face That is the story for the moment . Thanks for asking, Rick Cech From: bounce-108492854-3714...@list.cornell.edu [mailto:bounce-108492854-3714...@list.cornell.edu] On Behalf Of andya...@aol.com Sent: Tuesday, October 08, 2013 10:01 PM To: nysbirds-L@cornell.edu Subject: [nysbirds-l] Monarch Butterlies I have heard comments on the decline of quantities Monarch Butterflies this fall. I have also found a great decrease in the migration in the east on Long Island. The fall monarch nature trips also have found very few. I would appreciate it, if someone who is knowledgeable about this would care to comment. I have heard all kinds of speculations from birders, but no comments from those who study this, and are knowledgeable about the reason and have statistics showing how much this Monarch Butterfly migration is much lower than previous years. In fact I think the migration has been lower every recent year, but this year is the worst. Thanks for your input, I realize this is not birding, but I think it is of interest to birders. And Murphy -- NYSbirds-L List Info: <http://www.northeastbirding.com/NYSbirdsWELCOME> Welcome and Basics <http://www.northeastbirding.com/NYSbirdsRULES> Rules and Information <http://www.northeastbirding.com/NYSbirdsSubscribeConfigurationLeave.htm> Subscribe, Configuration and Leave Archives: The Mail Archive <http://www.mail-archive.com/nysbirds-l@cornell.edu/maillist.html> <http://www.surfbirds.com/birdingmail/Group/NYSBirds-L> Surfbirds BirdingOnThe.Net <http://birdingonthe.net/mailinglists/NYSB.html> Please submit your observations to <http://ebird.org/content/ebird/> eBird! -- -- NYSbirds-L List Info: http://www.NortheastBirding.com/NYSbirdsWELCOME http://www.NortheastBirding.com/NYSbirdsRULES http://www.NortheastBirding.com/NYSbirdsSubscribeConfigurationLeave.htm ARCHIVES: 1) http://www.mail-archive.com/nysbirds-l@cornell.edu/maillist.html 2) http://www.surfbirds.com/birdingmail/Group/NYSBirds-L 3) http://birdingonthe.net/mailinglists/NYSB.html Please submit your observations to eBird: http://ebird.org/content/ebird/ --
