[TN-Bird] Re: More on "Canada" Geese

 
Jan. 25, 2007
 
Canada Geese in the area.
 
This all might be "carrying coals to Newcastle" but here goes:
 
I think separation here, at this time, in this area, is mainly  between the 
"interior" Canada and "hutchinsii" Cackling. As changing  as all the goose 
species and subspecies' distribution has been in recent  times, we might find 
ourselves looking through these birds for "parvipies" so  that's a good study 
for 
their possible future encroachment. 
 
However, forget the size, color and body shape of these three as all of  
these points overlap extensively, instead look closely at head and bill  
structure. That is considered by the people working with these birds  to be the 
primary 
indicator and these feature hold true to species even in  the many smaller 
birds and even the runts. The runts we see are the results of  poor food during 
early stages of development. These birds never over come the  deficit, never 
catching up in growth. Some geese, due to cross and back  breeding just like in 
other species will just not be ID-able but still fun to  deal with.
 
Time spent with a scope, even on distant birds, will prove helpful in  noting 
the subtle differences. I was shown some of this years ago on the Texas  
coast when suspected "parvipies" were pointed out in with "Lesser or moffitti"  
all this long before the split but even then we were taking notes in TN and  MS 
on "hutchinsii" because of the impending split being banded  about. 
 
The differences are there and used by many researchers as THE key  to 
separation. They are subtle but consistent and most of all it takes TIME  to be 
comfortable with them in the field but it is not magic or imagination.  Nothing 
beats time spent just looking at the details in variations of  the common birds!
 
There is much to be read on the net about these geese and a lot  of it is 
dated material. New, up to date research is always coming to the  fore. Take 
the 
geese that are a slam dunk ID, study and file the  rest.
 
This is my quick and much simplified take on what I look for  around here as 
a guide line for most of these geese: 
 
Head shape:
 
"hutchinsii"- steep incline to top of forehead and then rounded to a  
noticeably flat top, peaked at rear before turning down at nape, so a square  
headed 
appearance overall.
 
"parvipies" - head slopes back from the bill base and their crown is  rounded 
and not angular at front or back.
 
"interior"- usually larger bird with similar head shape as "parvipies' but  
longer forehead, slightly concave slope and rounded rear to nape, 
 
Bills shape:
 
"hutchinsii" - small triangular shaped, culmen relatively straight, bill no  
more than half the depth of the head.
 
"parvipies" - slope of culmen about the same as forehead sometimes showing  
no concaveness (if that is a word) bill length is 70% or so of the head  depth.
 
 
"interior" - slope of culmen slightly concave following up the  forehead.
bill length 80% or more of depth of the head.
 
 
Good Birding  !!!

Jeff R. Wilson / TLBA
6298 Memphis-Arlington Road
Bartlett, TN  38135



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