For the past three days, there has been a flock of at least 75 Red Crossbills chowing down on the seeds of sunflower plants at the Boulder Community Gardens in north central Boulder. I've never seen more than a few crossbills on a handful of occasions at this site over the past 25 years, where I bird frequently throughout the year. It's been quite a treat to see the birds perched on the sunflower stalks at my eye level. They seem quite unbothered by my presence, even when I'm just a few feet away. The flock was present again this morning at 7:00.
I watched them feed for about an hour yesterday evening. Every single one was an immature. There were no adults (or at least birds in adult plumage). All had plumage reminiscent of House Finches, many with traces of yellow streaking on their breasts.
Questions:
1. Is it normal to find a large flock of only immature crossbills?
2. Are they migrating? (I had thought our crossbills were resident.)
3. I made recordings of their flight song. How do I use that to identify the species type? Merlin only went so far as identifying them at the species level. Is there software to use? Or do I visually compare waveforms?
Thanks,
Richard Trinkner
Boulder
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