Date: 11/5/25 9:16 pm From: Lance Benner via groups.io <lbenner...> Subject: Re: [CALBIRDS] Cassia Crossbill reports San Mateo Co
Hi Everyone, The discussion about red crossbills at Skylawn Cemetery in San Mateo County highlights the gaps in our knowledge of red crossbill vocalizations and the need to obtain more recordings of this species. Multiple flight call types have been present at Skylawn, all of them have multiple known variants, and there could still be other variants from some that haven't been discovered. As Joe mentioned, he _may_ have recorded a type 7 recently, but there aren't many examples from that type (often called the "enigmatic" type) so there's an acute need for more. It's possible to get useful recordings using a phone with a recording app. I recommend using the Song Meter Touch and Voice Record Pro apps, which are both free and very capable. Song Meter Touch also shows audio spectrograms in real time so you can see what the vocalizations look like as they happen. These apps don't attempt to identify the species, though. Although the Merlin app is very popular, and is getting better at species identification, its sensitivity is distinctly lower than those of Song Meter Touch and Voice Record Pro, so I advise against using Merlin. You'll want all the sensitivity you can get, so if the birds are perched, please walk toward them to increase the volume on your recordings. That could also enable us to see more detail in the sonograms, which can be crucial for trying to identify any Cassia crossbills and is, of course, very useful for identifying all of the flight call types, toop calls, and songs. A while back I did a webinar presentation for Los Angeles Birders on red crossbills and their flight call types, which you can view online at: https://www.labirders.org/webinars/crossbills.html Regards, Lance Lance BennerPasadena, CAOn behalf of Los Angeles Birders --------------------
From: "Jim Holmes via groups.io" <jfholmes...> Reply-To: <jfholmes...> To: <rivierastarsong...>, <jmorlan...> Cc: <rishab.ghosh...>, <tgmiko...>, "calbirds" <calbirds...> Sent: November 5, 2025 at 9:26 AM PST Subject: Re: [CALBIRDS] Cassia Crossbill reports San Mateo Co
I was recently in Scotland voice recording Crossbills.
I put several of my recordings into BirdNET (an AI bird sound identification app, similar to Merlin).
Multiple of my recordings in Scotland came back as Cassia Crossbill (albeit with low probability).
Pretty sure the AI is not yet capable of definitively identifying the crossbill “species.”
Thanks,
Jim Holmes
Sacramento
From: <CALBIRDS...> <CALBIRDS...> On Behalf Of James Bailey via groups.io Sent: Tuesday, November 4, 2025 11:33 PM To: <jmorlan...> Cc: <rishab.ghosh...>; <tgmiko...>; calbirds <calbirds...> Subject: Re: [CALBIRDS] Cassia Crossbill reports San Mateo Co
Hi,
In my experience it is difficult to compare European and American crossbills, even within the same species. In Europe the calls of red (and also parrot and “Scottish” crossbill) are indeed variable. The hypothesis is this is because the populations there are a contiguous amalgamation over a huge geographic area, with fluid ecological needs, and so without so established “types”.
This is different to the case in the US. Our crossbills here are much more specialized to specific geographic areas and corresponding ecology. As a result individuals from these “types” are far more consistent. “Intermediate” calls are apparently rare and more often caused by recording error (or in my experiences birds being too far away, and the spectrogram being incomplete…). But that question is better answered by Tim. I don’t believe any past recordings from Skylawn in 2023’s irruption were conclusively intermediate. Last spoken, I don’t think a Cassia-call could be produced as a false positive because it the call structure is not “between” two types.
P.S. wouldn’t be surprised if it turns out Cassia crossbill isn’t sedentary if conditions are dire. Apparently in 2023 their habitat was severely damaged and burned by fires.
JB
On Tue, 4 Nov 2025 at 10:53â¯PM, Joe Morlan via groups.io <jmorlan...> wrote:
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.
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