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March 2007


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Vermont Birds <[log in to unmask]>
Thu, 29 Mar 2007 11:49:11 -0500
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Just playing devil's advocate...

Wouldn't an escaped goose, given the birds' deeply social instincts, 
join up with a flock and stick with it through its migratory travels 
thereafter?  Certainly the growing number of flocks of non-migratory 
Canadas often have an escaped domestic goose or two permanently attached 
to them.

Whatever their origin, I wonder why the preponderance of the Barnacle 
sightings are one-time-only events.  Assuming individual flocks of birds 
follow the same route, using the same stopping places year after year, 
wouldn't one expect to find a Barnacle fellow traveler at roughly the 
same time and place at least a few years in a row?  Are these presumably 
captive-born birds so bereft of migratory urgings that they stay behind 
or wander off and lose the flock at some point?  Or are they almost 
invariably taken by predators somewhere along the way because they lack 
the hair-trigger reflexes to escape and/or are targeted because they 
stand out visually?

Anybody have a hypothesis?

<In any case, it's a gorgeous bird I'm thrilled to see in the wild, and 
I don't much care one way or the other about its origins, except as an 
interesting puzzle.>


hector galbraith wrote:

> Interesting data Kent. 
> As I read it all of the last 5 (non-historical) occurrences have either
> appeared in October (3 records) or April/May. These occurrences are
> obviously during the migration seasons for arctic-nesting geese. To
> dismiss these birds as "origin uncertain" one would have to hypothesize
> that they somehow jumped their cages and then got caught up in the
> north-south migrations of genuine wild geese. This is feasible, but is
> it not equally likely that they are genuine wild birds that have gone
> astray? 
> My point is that BRCs have got themselves into a cul de sac by assuming
> that for a bird to be fully accepted as a genuine vagrant we need to
> show beyond a reasonable doubt that it is not an escapee. This, as well
> as being unscientific, is impossible for most individual birds (how do
> you prove a negative?). The barnacle goose that was banded by Steve
> Percival in Scotland and turned up in the US is the very rare exception.
> Is it not much more reasonable to assume that such a bird is a genuine
> vagrant, unless there is some definite evidence to the contrary?  
> Hector Galbraith PhD
> Galbraith Environmental Sciences LLC
> 837 Camp Arden Rd., Dummerston, VT05301
> 802 258 4836 (phone)