Subject: [Tweeters] Hand Warmers and Hummers?
Date: Dec 17 14:10:59 2008
From: johntubbs at comcast.net - johntubbs at comcast.net


Hi Jim and Everyone,

Migration in birds is in fact defined as a normal pattern of (usually) seasonal movement by a species as a whole, not individuals. Otherwise, the Variegated Flycatcher found in Washtucna, WA earlier this year clearly proves that Variegated Flycatchers are migrating into or through northern tier states in the US - clearly not the case. Or, from several years ago, we could conclude that the Baltimore Oriole which stayed for a summer in Marymoor Park in Redmond, WA indicates migration of Baltimore Orioles to the west coast - also clearly not the case.

Following is from Merriam-Webster online:

Migration: ...to pass usually periodically from one region or climate to another for feeding or breeding.

A good general discussion of bird migration can be found in The Handbook of Bird Biology (2004, Cornell Lab or Ornithology in conjunction with Princeton University Press), pp. 5-51 through 5-99. Or, for the truly dedicated (obsessed?), there is always The Migration Ecology of Birds by Ian Newton (2008, Academic Press/Elsevier Ltd.) - all 976 pages of it...! All the discussion in the Cornell text (which forms the basis of Cornell Lab's home study course in bird biology) clearly and consistently refers to migration in the context of an overall activity by a species, not individuals.

Many/most species have unusual movements by individuals that are not part of a normal species migration pattern - the correct term for this relative to birds is vagrancy. Then there is irruption (yes, the correct spelling, not eruption as in volcanos), which is movement by larger numbers of a species outside of their typical migration (or non-migration) pattern - usually attributed to availability (or lack thereof) of normal food sources in their regular range. Then there is dispersal (post-breeding or post-fledging) in which individuals of a species leave a locale, to avoid established territories or find adequate food supplies on their own - but still to areas within the species' general range. There is also nomadic movement by species that don't truly migrate, but which follow specific preferred food sources within the species' general normal range - and which may mean they are absent for years at a time where they had once been common (e.g. Pine Siskins).

Migration also does not necessarily imply long distance movement. Altitudinal, or elevational, migration occurs in some species in which many/most of a given species seeks (typically) a lower elevation in the winter. This type of migration could mean movements of only a few miles.

Individuals of a species found in atypical locations may be random events due to who knows what (internal 'compass' screwed up, blown off course by a storm, etc.) or for some entirely different reason not currently understood by science (there are many aspects of bird behavior that are not well understood presently).

I do not believe any ornithologist would term the presence of an individual Anna's Hummingbird in Pennsylvania (or Montana) or an individual Ruby-throated Hummingbird in Washington state as evidence of migration.

Regards,

John Tubbs
Snoqualmie, WA

-------------- Original message --------------
From: Jim Greaves <lbviman at blackfoot.net>

> I think it's absurd to assert that Anna's Hummingbirds "do not
> migrate", unless one ONLY means a normal pattern of moving from one
> area to another... but I would contend that some areas see an influx
> of ANHU in the fall and winter due to what (with Robins at least) was
> and always has been called "local" or "regional migration"... The
> term "migration" does NOT just mean "heading south of the border"!
> How else did Dan Casey get one in Somers Montana a month or so ago
> [many observers and photos], and how else do they get to places like
> the Bitterroot Valley in Montana, or for that matter the eastern
> states? Just a question, and not at all intending to disrespect
> anyone... - Jim Greaves, Thompson Fall s MT
>
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