[cobirds] Chipping or Brewer's? (Boulder) Answers!

Hi folks,

I heard back with IDs and rationales from several of you, as well as requests for answers from several more.  The consensus was that both birds are......... tada!......... Brewer's Sparrows!

Key field marks for these two individuals:

1. No black stripe in the lores (between the eye and bill).  This isn't 100% diagnostic because it can be faint or smudgy in juveniles, but it's a good first field mark to check for birds that seem intermediate between species archetypes.

2. Mostly prominent eye ring, although the second bird's eye ring isn't complete.

3. Rump color....

The field mark that was new to me but that isn't clear on my photos is the color of the rump and lower back.  Chipping sparrows show a gray that contrasts sharply with their dark brown patterned upper back; Brewer's Sparrows show a brown or tan back that does not contrast sharply with their upper back.  In the second of my photos, the bird's lower back is slightly visible between the wings, and it shows a tan/beige lower back, not a gray back, making this bird a Brewer's. The rump color is said to be more diagnostic in separating the species, more so than the loral stripe or the full eye ring.

One person pointed out the difference in call note tone, which I've noticed in the Boulder Community Gardens.  Chipping Sparrows have a sharper, more defined chip, whereas the Brewer's Sparrows have a wispier call note with a less over-and-out definition. (Kind of like their plumage: Chippings are more sharply defined while Brewer's are vaguer.)

If you're in Boulder, the Community Gardens on Hawthorn Ave are a great location to try your sparrow ID skills this time of year. At the moment, it's mostly Chippings and Brewer's, but, especially in September,  you can often find 5-10 sparrow species in a late afternoon hour.

Over the years, in September I have seen the following sparrows at this location:

Grasshopper Sparrow

Chipping Sparrow

Clay-colored Sparrow

Brewer's Sparrow

Lark Sparrow

White-crowned Sparrow

Vesper Sparrow

Savannah Sparrow

Baird's Sparrow (only once)

Song Sparrow

Lincoln's Sparrow

Green-tailed Towhee

Spotted Towhee

Best,

Richard Trinkner

Boulder

On Aug 13, 2024, at 2:48 PM, Richard Trinkner <rtrinkner@icloud.com> wrote:

Every fall I agonize over juvenile spizella sparrows at the Boulder Community Gardens.  Are the attached photos of a juvenile Chipping Sparrow or Brewer's Sparrow? I'd appreciate any comments!

For the bird with its chest toward the camera, I'm leaning towards Brewer's:

Reasons it could be a Brewer's:

1. No dark loral stripe

2. Complete eye ring

3 "Dopey" face (at least seems that way to me...)

4. Steeper forehead

Reasons it could be a Chipping:

1. Bill seems bigger than the "tiny" Brewer's bill. Does this trump the four Brewer's field marks above?

For the bird with its back toward the camera, I'm leaning toward Chipping:

Reasons it could be a Brewer's:

1. No dark loral stripe. 

Reasons it could be a Chipping:

1. Incomplete eye ring

2. Bill seems largish

3. moustachial stripe seems darker and more distinct

Thanks!

Richard Trinkner

Boulder

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