[texbirds] Cassin's vs. Purple Finch
- From: Keith Arnold <kbarnold2@xxxxxxxxx>
- To: Texbirds <texbirds@xxxxxxxxxxxxx>
- Date: Fri, 21 Nov 2014 11:38:17 -0600
Something about the available photos for the Cameron county bird bothered
me. Indeed, I ID'd the bird as a Purple Finch in my response to Mary Beth.
Yet, most responders suggested that this female bird was a Cassin's Finch.
So, I looked at female specimens of these two species in our collections: 4
Cassin's and 14 Purple Finches. Here are the results:
Exposed culmen [measurement of bill length] - CF 13.3-13.6mm, with an
outlier of 11.0; PF 11.0-12.1mm, with an outlier of 8.9
Tail extension past wings -CF 15.9-25.3mm; PF 20.6-40.8 [highly variable,
depending on the "make" of the skin, but generally, CF has a longer wing
than PF [1 PF lacked a tail].
White superviliary "patch" [subjective, but seems reliable] barely
perceptible [= category 1] in 3 of the 4 CF, 1 category 2; PF 1 category
1, 1 category 2, 1 category 2/3, 3 category 3, 5 category 3/4. 4 category 4.
No PF had an eye ring and 2 of the 4 CF had weak eye tings.
All 4 CF had a whitish appearance around the base of the bill, but so did 5
of the PF
The bill length and exposed tail length support CF, but the superciliary
"patch" supports PF. The eye ring and white around the base of the bill
seem inconclusive. The width and length of ventral striping is highly
variable in PF
I'll let Texbirders draw their own conclusions.
Keith Arnold
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- » [texbirds] Cassin's vs. Purple Finch - Keith Arnold
