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[CALBIRDS] Red Crossbill Irruption Update

1:16 pm

Remember to record your crossbills. So far only 5 recordings uploaded to eBird this fall from San Diego.
Matt Sadowski
———- Forwarded message ———
From: Lance Benner <lbenner@…>
Date: Tue, Dec 5, 2023, 18:49
Subject: [CALBIRDS] Red Crossbill Irruption Update
To: <>, <>

Hi Everyone,


Here’s another update on the red crossbill irruption in California, with an emphasis on the southern part of the state and the Bay Area.  


Red crossbills continue to appear in more locations around the state where they don’t often occur and are now showing up near the coast in San Luis Obispo, Santa Barbara, and to a lesser extent in Ventura and San Diego.  A good percentage of these birds have been recorded and most are flight call type 2s, but some in Santa Barbara have been type 4s.  Type 4s have been recorded in the south in Ventura, Los Angeles, San Bernardino, Santa Barbara, and Kern Counties, and in that order.  The  ones in Ventura were on Mt. Pinos in July but weren’t identified as such until months later.  The other type 4s were either in the deserts (San Bernardino and Los Angeles) or otherwise at low elevations (Santa Barbara and Kern).  


To date, the birds on Mt. Pinos are the _only_ red crossbills recorded in the mountains south of the Sierra Nevada that weren’t flight call type 2s.   This covers records dating back more than a decade.   


The other red crossbills recorded in the southern California mountains this fall have been type 2s, most recently in the Laguna Mountains in San Diego County.  Some type 2s have been documented in the deserts and on the coastal slope.


There’s also one type 3 record this fall from the desert near Ridgecrest (Kern County).   During previous irruptions, type 3 was occasionally relatively common in the southern California deserts and on the coastal slope.


To date there haven’t been any red crossbill reports in Orange County this fall.


In the Bay Area, the Peninsula continues to be a hotbed of red crossbills with reports from San Francisco, San Mateo, Santa Clara, and Santa Cruz Counties.  The spot with the largest number of flight call types, by far, has been Skylawn Cemetery off route 92 in San Mateo County where the following crossbills have been found in recent weeks:


Type 1

Type 2

Type 3

Type 4

Type 5

Type 7

Cassia (formerly known as type 9)


_ALL_ of those have been documented with recordings in one small area.  Cassia crossbill is still being reported there but identifying them usually requires high-quality recordings in order to see the diagnostic features in

the flight calls.  By high-quality I mean flight calls that are loud and show a lot of detail.  Most of them have been obtained by observers who were close to the birds and/or had dedicated equipment such as a shotgun mic, parabola, and a dedicated recorder. ` Cell phone recordings have been sufficient to document Cassia crossbills in some instances, but if the sounds are faint, then details in the flight calls often aren’t visible, and Cassia crossbills can be very difficult to separate from type 5s, which have been particularly numerous at the cemetery (along with type 2s).  



Elsewhere in the broader Bay Area, multiple flight call types have also been reported at Bear Creek Redwoods Open Space Preserve (Types 2, 3, and 4; especially around the pond) off route 17 near Los Gatos; in selected spots just north of Santa Cruz, and in multiple locations on the Monterey Peninsula.  There have also been numerous crossbills in counties just north of the Golden Gate but I havne’t checked records there in detail so I can’t comment on the different types.

Numerous reports have appeared in preserve and parks along the San Mateo and Santa Cruz county coasts that could produce multiple flight call types.  Broadly speaking, the most common flight call types south of the cemetery have been type 2s, which are also the most common types in the Sierra Nevada and in the mountains in the southern part of the state. 



One of the main messages here is that it’s important to record red crossbills whenever you find them.  This year, in particular, you might find something truly special with just a couple of clicks on a cell phone. The key is to try.   If you aren’t familiar with how to offload recordings from a phone to, say, a computer or an eBird list, please ask and we’d be glad to help.


On the general topic of recording birds using smartphones, many people are now using the Merlin app to identify bird sounds and to record them (Merlin records them by default).  Merlin is really good and getting better, but it makes mistakes, and for recording faint sounds, I recommend using other phone apps that are more sensitive. 

If I’musing a phone to record, my first choice is Voice Record Pro, which can be configured so it’s several times more sensitive than Merlin, which means it will pick up fainter sounds and provide a better chance for detecting something rare like a Cassia crossbill.  The Song Meter Touch app is also pretty sensitive, and like Merlin, it shows a scrollling sonogram in real time, which is a really nice feature that Voice Record Pro lacks.  There are other apps out there, but I wanted to point out that Merlin isn’t the most sensitive option.


If you have experience with processing audio files, it also helps a lot if you amplify the sounds before uploading them to eBird lists.  There are multiple ways to do this.  The folks at eBird request that you normalize the volume to -3 dB before saving the sound in a separate file and uploading it.  If this is beyond your experience, please ignore the last paragraph, just upload the files, and we’ll help you.



A couple more thoughts:

Red crossbills feed mostly on conifer seeds, so the best place to find the birds is in places with…conifers.

Crossbills have been found in Montery Pines, Douglas firs (but not bigcone Douglas-firs in the south), California redwoods,incense cedar, ponderosa pine, Jeffrey pine, lodgepole pine, pinyon pine, white fir, and non-natives such as Aleppo Pines.  


At really high elevations they’ve also been found in bristlecone pine, foxtail pine, and western white pine. I’m sure there are others as well.


To the best of my knowledge, they aren’t known to feed on gray pine, Coulter Pine, sugar pine, deodars, or Canary Island Pines.   I don’t know about knobcone pines.


To date, Cassia crossbills have been found in California at only one location, but it wouldn’t be surprising if they turn up elsewhere with good numbers of red crossbill types.


For more information about red crossbill flight call types, please see the eBird article from 2017 by Matt Young and Tim Spahr online at:



Thanks for your attention, and please keep recording and reporting red crossbills across the state!






Lance Benner

Altadena, CA

Community Science Chair, Los Angeles Birders