I just read the "Breeding" section about Red Crossbills in Cornell's Birds of the World. I learned that Red Crossbills in North America potentially nest twice each year, once in the early spring and again in the late summer, depending upon the availability of cone seeds.
A hypothesis, based on my limited research: perhaps along the Front Range this year, crossbills nested in the early spring and produced the juvenile birds we are seeing now on sunflower seeds in Boulder and Fort Collins. The absence of adults in these flocks could be explained if the adults are currently nesting in the foothills in their second window of the year.
As a result, juveniles who hatched during the early spring are now separated from their parents -- hence the all-juvenile flocks in Boulder and Fort Collins.
Richard
On Aug 30, 2023, at 10:36 AM, Chip Clouse <chip.clouse@gmail.com> wrote:These posts remind me of when I moved from Boulder up to 8600 ft in North Beaver near Pinecliffe in 1996. While I didn't actually move up until June 1st, the homeowner had me come up to housesit in either late April or early May. They had a big kitchen window planter box that they filled with Black Oil Sunflower and 60-80 Red Crossbills were swarming that box. These were adult birds of both sexes. When I actually moved up, the planter box was gone but I put up a bunch of feeders until a bear showed up a few weeks later. I never again saw the spectacle of sunflower eating crossbills.Good birding,Chip ClouseLakewoodOn Wed, Aug 30, 2023 at 9:09 AM Dave <daleatherman@msn.com> wrote:Richard Trinker just reported to eBird an observation of juvenile red crossbills at low elevation eating sunflower seed obtained from flowers at a public garden in Boulder. I had the same exact experience yesterday in two different yards on the east side of Fort Collins. The individuals I watched were young enough to have mostly straight beaks. Their vocalizations were a better way to quickly discern their not being house finches than their general appearance. Juveniles have also been at Grandview Cemetery in Fort Collins recently. It has been suggested this might indicate local, urban breeding. However, Richard's and the Fort Collins observations suggest to me a widespread Front Range shift of young birds to low elevation of unknown duration to take advantage of an abundant, easy to obtain nutrition source.The next issue of "Colorado Birds" has a "The Hungry Bird" article on crossbills foods OTHER THAN conifer seed but I didn't say much about sunflower seed and juveniles because the literature doesn't address it and I hadn't personally seen it before yesterday.Dave LeathermanFort CollinsSent from my iPhone----You received this message because you are subscribed to the GoogleGroups "Colorado Birds" group.To post to this group, send email to cobirds@googlegroups.comFor more options, visit this group at* All posts should be signed with the poster's full name and city. Include bird species and location in the subject line when appropriate* Join Colorado Field Ornithologists https://cobirds.org/CFO/Membership/---You received this message because you are subscribed to the Google Groups "Colorado Birds" group.To unsubscribe from this group and stop receiving emails from it, send an email to cobirds+unsubscribe@googlegroups.com.To view this discussion on the web visit https://groups.google.com/d/msgid/cobirds/PH7PR12MB7354DD6DA3FADFAC4D102DFDC1E6A%40PH7PR12MB7354.namprd12.prod.outlook.com.
----You received this message because you are subscribed to the GoogleGroups "Colorado Birds" group.To post to this group, send email to cobirds@googlegroups.comFor more options, visit this group at* All posts should be signed with the poster's full name and city. Include bird species and location in the subject line when appropriate* Join Colorado Field Ornithologists https://cobirds.org/CFO/Membership/---You received this message because you are subscribed to the Google Groups "Colorado Birds" group.To unsubscribe from this group and stop receiving emails from it, send an email to cobirds+unsubscribe@googlegroups.com.To view this discussion on the web visit https://groups.google.com/d/msgid/cobirds/CAPHVJejGsP%2BKoseXELGwcQ6Ak54n2pHe6RLKZtnKbvrGOzxR9g%40mail.gmail.com.
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