Interesting goose at Dodd Reservoir, Boulder County

[Randy Siebert]

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

Randy Siebert

Lafayette, Boulder County

[Peter Ruprecht]

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

--
--
You received this message because you are subscribed to the Google Groups "Colorado Birds" group.
To post to this group, send email to cob...@googlegroups.com
For more options, visit this group at
http://groups.google.com/group/cobirds
* All posts should be signed with the poster's full name and city. Include bird species and location in the subject line when appropriate.
* Join Colorado Field Ornithologists https://cobirds.org/membership/
---
You received this message because you are subscribed to the Google Groups "Colorado Birds" group.
To unsubscribe from this group and stop receiving emails from it, send an email to cobirds+u...@googlegroups.com.
To view this discussion visit https://groups.google.com/d/msgid/cobirds/a7a293af-a374-45a5-8e73-2457bbd48aban%40googlegroups.com.

[Jeff P]

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, 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 (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 - 806 Colorado eBird records.
• Greylag (domestic) x Canada Goose 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 - 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 -  347  Colorado eBird records. 
• Greater White-fronted x Cackling Goose - 193  Colorado eBird records. 
• Domestic sp. x Canada Goose - 136 Colorado eBird records.
• Greater White-fronted x Canada Goose - 54  Colorado eBird records. 
• Swan (domestic) x Canada Goose - 12 Colorado eBird records.
• Ross's x Canada Goose - 15  Colorado eBird records. 
• Snow x Greater White-fronted Goose - 13  Colorado eBird records. 
• Barnacle x Cackling Goose - 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)

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! 

Best,

Jeff Percell

Erie, CO

To view this discussion visit https://groups.google.com/d/msgid/cobirds/CAHPXVBZgjEpaRoovuwXFRfRjiYyX6DDMcO6Og%3DKmvFybOCxhBQ%40mail.gmail.com.

[Jeff P]

(apologies for 2nd email, but looks like the images didn't go through on the first one)