Date: 1/7/26 9:23 pm From: Jeff P <jeff.percell...> Subject: Re: [cobirds] Interesting goose at Dodd Reservoir, Boulder County
(apologies for 2nd email, but looks like the images didn't go through on
the first one)
[image: image.png]
[image: image.png]
On Wed, Jan 7, 2026 at 10:20 PM Jeff P <jeff.percell...> wrote:
> 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.
>
> - Snow x Cackling Goose <https://ebird.org/species/x00692/US-CO> > (a.k.a the Waneka Goose -- credit TF for that moniker) is our most
> prominent hybrid goose in Colorado - 1,039 reports in eBird -->* that
> is 83% of all records in eBird for this type of hybrid! Colorado is truly
> the best place on earth to see this type of bird.*
> - Snow/Cackling x Canada/Cackling Goose
> <https://ebird.org/species/y00765/US-CO> - 806 Colorado eBird records.
> - Greylag (domestic) x Canada Goose
> <https://ebird.org/species/x00758/US-CO> 720 Colorado eBird records --
> I wouldn't be surprised if more than half of these are from Belmar Park in
> Jefferson County.
> - Ross's x Cackling Goose <https://ebird.org/species/x00694/US-CO> -
> 416 Colorado eBird records --> less than half as frequent as Snow x
> Cackling, which makes sense as that is a similar proportion to Snow vs
> Ross's Goose observations.
> - Snow x Canada Goose <https://ebird.org/species/x00197/US-CO> - 347
> Colorado eBird records.
> - Greater White-fronted x Cackling Goose
> <https://ebird.org/species/x00414/US-CO> - 193 Colorado eBird
> records.
> - Domestic sp. x Canada Goose <https://ebird.org/species/x00759/US-CO> > - 136 Colorado eBird records.
> - Greater White-fronted x Canada Goose
> <https://ebird.org/species/x00415/US-CO> - 54 Colorado eBird records.
> - Swan (domestic) x Canada Goose
> <https://ebird.org/species/swagoo3/US-CO> - 12 Colorado eBird records.
> - Ross's x Canada Goose <https://ebird.org/species/x00693/US-CO>- 15
> Colorado eBird records.
> - Snow x Greater White-fronted Goose
> <https://ebird.org/species/x00627/US-CO>- 13 Colorado eBird records.
> - Barnacle x Cackling Goose <https://ebird.org/species/x00416/US-CO>- > 1 Colorado eBird record -- what a rare bird!.
>
> 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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>
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