In the interests of showing how hard it is to distinguish between 
Cackling Goose and Canada Goose, here is a summary with excerpts of 
the varying comments I got from people who ventured to give an ID. 
Thank you all. My apologies if I left anyone out or misrepresented 
anybody's comments.

In the text below,
"Photo 1" is the first one I posted, at
http://birds.southernspreadwing.com/Cackling_Goose_maybe.jpg
"Photo 2" is the second one I posted, at
http://birds.southernspreadwing.com/Cackling_Goose_maybe_2.jpg


Here are two helpful websites explaining how to distinguish between 
these birds. Be sure to scroll to the bottom of both sites, even if 
you don't read all the text.
This site has graphs and a range map:
http://www.sibleyguides.com/canada_cackling.htm
This site has a nice summary table:
http://www.utahbirds.org/RecCom/NewGoose.htm

--
June Tveekrem
Columbia, Howard Co, MD
tweekiebird AT toadmail DOT com

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Rick Hollis - North Liberty, IA and Westminster&Arbutus, MD

(from Photo 1) "Counting from the left, partial Canada, Cackling, 
Canada, Cackling, Canada. I said Cackling based on bill shape and 
relative size."
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Matt Hafner - Bel Air, MD

(from Photo 1) "2nd bird on the left looks very good for Cackling 
Goose.  Also the bird 2nd from the right is possibly as well. It is 
a little larger, but the head and bill shape look right.  I can't be 
sure [about the bird on the right] from the one photo though."

(from Photo 2) "I think this photo confirms that they are both 
Cacklers."
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Ed Boyd - Westminster, MD

(from Photo 1) "The second goose in from the edge is a Cackling 
Goose - and it doesn't matter which edge you start from. There are 
two of them in the photo."
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Bob Moul - Adams County, PA

(from Photo 1) Said he had found and photographed a goose last week 
in PA that looked "identical in bill shape, length and overall size" 
to the bird in my photo. He posted his photos "to several birding 
lists.  The majority thought it was definitely a Richardson's 
Cackling Goose (Branta hutchinsii hutchinsii)."
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Jo Solem - Laurel, MD

(from Photo 1) "My sense is that [the bird 2nd from the left] is a 
"runt" Canada and not a Cackling Goose.  It does have a shorter neck 
and smaller bill than adjacent geese but the head is not blocky, the 
back is not paler (grayer) than our regular Canadas, and although 
small I'm not sure it is really that much smaller than the others. 
Centennial has a history of having smallish Canadas which are not 
other species."

(from Photo 2) Verbal comment that both look like Cackling Geese 
because photo shows blocky head shape of goose in the right 
foreground, and grayer back color of goose in the left foreground.
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Joe Hanfman - Columbia, MD

(from Photo 1) "The second goose from the left looks like a Cackling 
Goose to me. The second goose from the right looks like a small race 
of Canada Goose. There has been a small Canada Goose at Centennial 
Lake for the last couple of years."
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Hans Holbrook - Baltimore, MD

(from Photo 2) "I would have to agree with Ed Boyd, that both geese 
are Richardson's Geese. Note the overall gray coloration of the back 
compared to the near-by Canada Geese. When I am scanning flocks of 
geese for Richardson's, I actually am looking for overall coloration 
of the bird. I look at size and shape afterwards. I guess what I am 
saying is that overall coloration is a huge indicator coupled with 
size and shape and you got it."
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Gail Mackiernan - Colesville, MD

(from Photo 2) "Definitely [two] Cacklers."
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Jay Keller - Arlington, VA

(from Photo 2) "I would say that the right bird looks good for 
Richardson's Cackling, while the one on the left is somewhat 
suspect, despite the size."

I think it's worth showing his entire text because of the detailed 
description.

"We have a lot to learn about what is definitive for Cackling vs 
parvipes (Lesser Canada Goose), but from my experience I would say 
that the right bird looks good for hutchinsii (Richardson's 
Cackling) while the one on the left is somewhat suspect, despite the 
size.  Size alone should never be used to determine parvipes vs 
hutchinsii, as there is considerable overlap between them.  The bill 
is suspect in the left bird in my opinion because it is quite long 
and gradually sloping - a characteristic of Canada Goose.  It might 
very well be a Cackling, but I am not comfortable with the 
structure.  However, the bill on the right bird appears quite 
triangular and blunt, and has the fairly steep angle from crown to 
culmen as well as a hard rear crown angle and other 
structural/plumage features typical of hutchinsii.  I always like to 
see the birds in life to be 100% sure, however."
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