question about habitat for biologist or anyone with the knowledge

[borrowed time]

After discussing this subject with another landowner thought I would throw it out here. At one time in Wi sharptail grouse outnumbered ruffed grouse. This happened because of fires favoring the sharpies and ruffed grouse liking the logged areas. The sharptails are now rare enough because of declining habitat that tags are issued for limited harvest. Perhaps 20 or so years ago a pine or spruce bug hit thousands of acres of trees in northwestern Wi. After logging and cleaning up the area, which may included burns, that part I don't know, the sharptails moved in.

Now my question is, if a certain species comes back into a favorable habitat, do they come from small pockets that are out of the way and no one knows about, or do they migrate. If migration happens, how do they know where to go. Anyone have a take on this?

[Land_Owner]

Time...I don't know about your birds.  I would suspect some are there always, at the edges, awaiting a fire and the possibility of moving into new territory.  I would also guess they move around from place to place into and out of agreeable forage and less hostile environments for the preservation of the species.  As they are birds that fly, seeking favorable places, from their perspective, is a "No Brainer".

[mogwai]

Think about islands near the mainland.  If there are plenty of sharptails on the mainland, and the islands are nearby, odds are that some birds will stray to the islands over time.  If an island is not suitable one year, it might be suitable in a couple years.  Birds from the mainland will always be exploring within some range from the mainland, or nearby islands.  If the birds on any given island are eliminated, the island will be repopulated in short order.

Now, move those islands farther apart, and make them smaller.  The odds get more slim that birds will move from island to island, and that they will find suitable habitat if they wander.  It becomes easier to wipe out the population on any given island.  Populations that are eliminated may not be re-established for many years, if ever.  The farther away the islands get, and the smaller the populations get, the easier it is for populations on a given island to snuff out and stay snuffed out.

This is happening to sharptails in northern WI.  That big patch of new habitat was close to some major population, like in the Barrens or eastern MN. 

In northcentral WI, the islands are getting smaller, and farther apart....