As with the rest of the folks on this list, thank you for bringing this question up - proves there are no "dumbest" questions when it comes to bird biology. I do think there is a clear takeaway, however, some crossbills are left-billed, while others are right-billed - a genetic quirk that highlights the diversity of Nature, something to be appreciated and celebrated. I hope this discussion has encouraged some of you to fall further down the rabbit hole when it comes to crossbill ecology and evolution. As I've mentioned here previously, crossbills are our Darwin's finches and we are lucky to live in the heart of this evolution-in-progress story. While an oldie-but-goodie, this article from Sibley (https://www.sibleyguides.com/2010/09/red-crossbill-call-types-act-like-species/) is a good summary of what is going on with these guys, There has obviously been a ton of science conducted since this article came out, so if you now have piqued curiosity, check out the postings by the Finch Research Network (https://finchnetwork.org/) to get up to speed on the current science. Again, thank you Catherine for asking about your crossbills, I've learned a lot. Good Crossbilling, Doug
-----Original Message----- From: Inland-nw-birders <inland-nw-birders-bounces...> On Behalf Of Catherine Temple via Inland-nw-birders Sent: Tuesday, February 24, 2026 1:43 PM To: David McNeely <davmcneely40...> Cc: Ken Pitts <kenp...>; Inland NW birders <Inland-nw-birders...> Subject: Re: [inland-NW-birders] Crossbills
Thanks to everyone who jumped in with explanations for me! The links and additional searches made for some interesting (although somewhat confusing with all the scientific words) reading. I don't know if I came away with a clear answer, but I now know a bit more than I did before.
On Mon, Feb 23, 2026 at 12:15 PM David McNeely <davmcneely40...> wrote:
> Probably not. Genetics is suspected, though not proven, despite my > earlier assertion that it is well known. Red crossbill chicks show > morphological differentiation of the bill crossing phenotype BEFORE > they start feeding on their own, that is, while the parents are still > feeding them partially digested seed mash in the nest. But there is > evidently no definitive genetic data. > > https://bootstrap-analysis.com/2005/12/crossbills.which.html > > On Mon, Feb 23, 2026 at 8:41 AM Ken Pitts via Inland-nw-birders < > <inland-nw-birders...> wrote: > >> Hi Catherine! >> >> Your question about the curve direction of Red Crossbills is really >> interesting. I did a quick Google search of Red Crossbill photos and >> saw that some go to the left and some go to the right. I then found >> an explanation that when the Red Crossbills are young, they have >> pretty typical finch beaks. As they attempt to get seeds out of >> cones, they tend to always pry one direction that is not the same for all the others. >> Constant prying in the same direction causes the beak to warp that >> direction, thus determining the lifelong result. >> >> The best! >> >> Ken >> >> On Sun, Feb 22, 2026 at 10:42 AM Catherine Temple via >> Inland-nw-birders < <inland-nw-birders...> wrote: >> >> > Yesterday I saw a pair of red crossbills gathering grit in the road >> > so I took some lovely photos of them. Later I noticed that each >> > birds bill (a male and female) curved in a different direction. I >> > know a lot has been said about the difference in bill size and the >> > different "types" based >> on >> > the types of cones they eat. But if the birds are the same species >> > or >> type >> > shouldn't the bills curve in the same direction? Or is it common to >> > have left and right curved bills within the same type? Or is this a >> difference >> > between male and female? I'm really curious as this is the first >> > time >> I've >> > been able to get close enough to see the differences. I've attached >> > a >> photo >> > of the pair. Thanks in advance if you can enlighten me. >> > Catherine >> > >> > >> > -- >> > >> > *Catherine Temple* >> > >> > *Pet Portrait and Wildlife Artist* >> > >> > *Clarkston, WA.(208) 791-7052* >> > <ctemple99...> >> > >> > www.catherinetemple.com >> > www.flickr.com/photos/ctemple/ >> > _______________________________________________ >> > Inland-nw-birders mailing list >> > send email to: <Inland-nw-birders...> manage >> > subscription: >> > https://mailmanlists.us/mailman/listinfo/inland-nw-birders >> > >> _______________________________________________ >> Inland-nw-birders mailing list >> send email to: <Inland-nw-birders...> manage subscription: >> https://mailmanlists.us/mailman/listinfo/inland-nw-birders >> >
--
*Catherine Temple*
*Pet Portrait and Wildlife Artist*
*Clarkston, WA.(208) 791-7052* <ctemple99...>
www.catherinetemple.com www.flickr.com/photos/ctemple/ _______________________________________________ Inland-nw-birders mailing list send email to: <Inland-nw-birders...> manage subscription: https://mailmanlists.us/mailman/listinfo/inland-nw-birders
