Date: 11/4/25 10:53 pm From: Joe Morlan via groups.io <jmorlan...> Subject: Re: [CALBIRDS] Cassia Crossbill reports San Mateo Co
I'm taking the liberty of posting from an advanced draft copy of the 50th CBRC report about these records:
"CASSIA CROSSBILL Loxia sinesciurus (0, 0). IDENTIFICATION NOT ESTABLISHED: Large numbers of Red Crossbills (L. curvirostra) were encountered at Skylawn Memorial Park in Half Moon Bay, San Mateo County during a widespread irruption of this species in fall 2023. Among a flock of up to 60 crossbills giving flight calls of several different types included one or more birds that were thought to be consistent with Cassia Crossbill 26 Oct-16 Dec, 2023 (2023-108); this species was considered endemic to the Albion Mountains and South Hills of southern Idaho, but has recently been found in Colorado (Gent 2022). Outside experts agreed that field recordings most closely matched those of Cassia Crossbills recorded in the South Hills of Idaho. However, after two rounds of voting, the majority of the committee felt that there was too much uncertainty in the variation within Red Crossbill call types, and that the recordings did not precisely match those of classic Cassia Crossbill. Some members were also concerned about the likelihood of long-distance vagrancy in an ostensibly sedentary, range-restricted species."
FWIW, the voting was 5-4 in favor, the first round, but 2-7 against on the second round. A recent paper found rapid evolutionary change in Red Crossbill vocalizations in Europe. It is reasonable that some of our birds evolved calls that are similar to, but not exactly like Cassia Crossbills.
In a recent visit to Skylawn, I recorded previously unknown call types that are intermediate between Type 12 and Type 7.
On Wed, 5 Nov 2025 10:33:46 +0530, "Rishab Ghosh via groups.io" <rishab.ghosh...> wrote:
>I heard and possibly saw the supposed Cassia in December 2023 and had the >audio confirmed by Tim Spahr & Matthew Young at the Finch Research network >[1]. The CBRC didn’t accept the Cassia sightings FWIW. This week there were >two reports. One has audio ID’d by Merlin, which isn’t reliable - I >suggested to the reporter to send them to the FRN for review. The Nov 2 >report is a 5 minute duration incomplete checklist with 5 (!!) Cassia >crossbills, no photo or audio or description justifying the ID. > >I would wait for more confirmation before getting on a 7 hour drive up to >San Mateo :) > >Rishab >1. My checklist with the Cassia is >https://ebird.org/checklist/S156444745 > >On Wed, Nov 5, 2025 at 10:06 <tgmiko...> via groups.io <tgmiko= ><gmail.com...> wrote: > >> Hi, >> I just saw the second report in the last couple of days or so of Cassia >> Crossbills at Skylawn Cemetery in San Mateo County. >> If these reports are correct I would like to jump into the car and drive >> up there and maybe actually see them, this time. Any negative or positive >> information would be appreciated. Last I missed them by one day because I >> took too long. >> >> Tom Miko >> Claremont 91711 >> 909.241.3300 >> >> >> > > > > -- Joseph Morlan, Pacifica, CA
