Re: [cobirds] Red Crossbills & sunflowers

In general, if breeding is successful in significant increases in the population and cone crops are small or depleted, Red Crossbills will erupt beyond usual ranges or habitats and pursue atypical food sources.  Red Crossbills tend to wander wherever the food is to be found and so may have less site fidelity than some other species.  I suspect the crossbills in the Boulder area had a successful breeding season and have well-enjoyed the local cone crops and now are dispersing due to their increased numbers to take advantage of a wider variety of foods. It has been noted that immature birds sometimes go through a teenager phase where they hang out together more than with the mature birds.  But the details about bill development and specific food sources is interesting!

Diana Beatty

El Paso County

On Wed, Aug 30, 2023 at 10:12 AM 'Richard Trinkner' via Colorado Birds <cobirds@googlegroups.com> wrote:

Thanks, Dave, for the report about the crossbills in Fort Collins.

Your post got me wondering:

1. If juvenile crossbills are still developing curved beaks, might that explain why we don't see adults in these flocks feeding on sunflowers?  Could the juvenile beaks be more suited to prying seeds from the sunflowers than prying them from pine cones?  Or might adult beaks be less suited to sunflowers? (Although many of the juvies I saw yesterday had less curved beaks, several had very curved beaks, so maybe this theory doesn't work.)

2. Is there a shortage of food in the foothills for the juveniles?  There have long been sunflowers on the plains, but this is the first time I've seen crossbills encamped at the Community Gardens.  (They're still there, as of 6:45 this morning.)

3. Do juvenile crossbills generally separate from the adults and form juvenile flocks?

Here's a shot of one of the juvies yesterday.

Richard

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