Date: 1/7/26 9:21 pm From: Jeff P <jeff.percell...> Subject: Re: [cobirds] Interesting goose at Dodd Reservoir, Boulder County
For this bird I'd recommend snow x cackling-- Mottled bill rules out pure
snow, slight grin patch indicative of snow. It appears to be slightly
larger than nearby Cackling indicative of Cackling.
I'll take Peter's cue to provide a write up on keys to identifying
interesting geese such as this (I was actually already in process with this
write up when I noticed his response):
1. Start with the bare parts:
1. Bill color - most hybrids have mottled bills or grayish-blue cast
over pink. Snow & Ross's geese have pink bills.Though note that juvenile
snow geese will transition from brownish (black in the case of
dark morph)
to pink bill as an adult. Canada/Cackling have black legs. Greater
White-fronted have orange bills.
2. Bill size/shape - Apply similar review as you would to the base
species - length/slope with cackling heritage will be more petite, less
sloped though with Snow influence this makes the bill larger, more sloped
than a regular cackler. Likewise Ross's heritage will have a more stubby
bill with a flatter base of the bill, though Cackler influence adds
curvature to the base of the bill. Presence of the grin patch gives good
indication between Snow & Ross's, though note that Ross's base
species does
still have a limited grin patch.
3. Leg color - Snow/Ross's x Canada/Cackling have pinkish gray legs,
whereas Snow & Ross's geese have pink legs, Canada/Cackling have black
legs. Orangish legs indicate GWFG or Greylag influence.
2. Then move to body shape:
1. Snow x Cackling will be slightly larger than Cackling.
2. Snow x Canada will be slightly smaller or similar sized to Canada.
3. You can also apply the birds of a feather flock together rule here
-- a hybrid in a large group of Cackling geese will likely be Cackling x
whatever else... a hybrid in a group of Canada geese is likely Canada x
other xy or z.
3. Plumage:
1. This can be inconsistent and watch out for leucism/melanism - if
you see a mostly white headed goose, refer to the bare parts as if it has
black legs and bill it could well be a leucistic Canada or
Cackling goose (see
for example this bird <https://macaulaylibrary.org/asset/506034251>,
which I think is a Cackling but looks like I decided to list as
goose sp.).
2. Plumage can be helpful in identifying Greater White-fronted
crosses, as the "speckle belly" influence may be evident there.
3. Attention to folded wings can help with differentiation between a
dark (blue or intermediate) snow vs hybrid, as snow x
cackling/canada. The
dark Snow Goose will generally have a thicker white edge to
their feathers,
whereas the hybrid will have more Canada/Cackling feature here and/or a
thinner white edge.
4. Document with photos!
1. This is super helpful not only to have others review and provide
input to your sightings, but also to compare other sightings. While eBird
doesn't make it easy to get to a hybrid "species" page (they do
exist but I
find typing in the hybrid to google is the only way to get there),
the hybrids are easily searchable in the media search tool (as
well as the
range map tool).
2. Focus on good photos of the bare parts - showing bill/legs,
plumage as well as group shots that enable you to see body size
comparison
to nearby species.
Also, remember not every bird is identifiable, so leaving a slash
--Snow/Ross's x Cackling/Canada Goose is not a bad thing, and requested by
eBird reviewers if you don't have documentation.
Looking at the eBird status/trends page for the geese in Colorado is
interesting.
Hybrid's are fun id challenges --> I have 18 on my life list including all
but 4 of the above listed ones. Snow x GreaterWhite-fronted Goose is one of
my favorite bird sightings, though it was in Southern Indiana. (photo here
<https://macaulaylibrary.org/asset/517615751>)
Here's to hoping we all get an opportunity to go outside and sort some
geese on a freezing morning in the upcoming days - I'm looking forward to
some incoming weather to move the geese around!
[image: image.png]
[image: image.png]
Best,
Jeff Percell
Erie, CO
On Wed, Jan 7, 2026 at 8:24 PM Peter Ruprecht <pruprecht...> wrote:
> Hi Randy,
>
> One thing I find useful when identifying dark morph Snow Geese is the
> tertial feathers that flop over the flanks and rump when the bird is
> standing or swimming. On a dark morph Snow, these will be black with
> distinctive white outlines. On hybrids, they're almost always solid brown
> like on the Canada or Cackling parent.
>
> Sometimes you can also see the nice blue-gray leading edge of the wing
> even when a dark morph Snow has its wings folded. Again, the whole wing is
> usually brown on a hybrid.
>
> See for example https://macaulaylibrary.org/asset/36514851 >
> Based on that, I'd call the bird in your photos a hybrid. I personally
> have a hard time deciding what Anser/Branta mix is in most hybrids (except
> for tiny Ross's/Cackling hybrids), so maybe someone else will want to offer
> advice there.
>
> Peter Ruprecht
> Superior
>
> On Wed, Jan 7, 2026 at 4:01 PM Randy Siebert <rlsiebert52...>
> wrote:
>
>> I got photos of a goose which is either a blue morph Snow Goose or a
>> hybrid. A nice Greater White-fronted Goose was around for size comparison.
>>
>> Opinions will be appreciated and may save me dealing with an eBird
>> reviewer.
>>
>> You can see them at:
>> eBird Checklist - 7 Jan 2026 - Dodd Reservoir - 12 species
>> <https://ebird.org/checklist/S292982911> >>
>> Randy Siebert
>> Lafayette, Boulder County
>>
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