Backyard Birds – Late September Report

Bluebird Box Monitoring

Barbara Spagnuolo reported on the 2021 monitoring by the Town of Castle Rock of the 190 bluebird nest boxes maintained by volunteers. The results show a significant decrease in activity and fledging: our lowest season since 2010. Six species used our nest boxes: Mountain and Western Bluebirds, Violet-green and Tree Swallows, and Black-capped and Mountain Chickadees. They occupied 85% of the boxes and fledged 531 individuals (739 fledglings in 2020): 239 Tree Swallows, 222 Mountain Bluebirds, 60 Western Bluebirds – and no House Wrens or Black-capped Chickadees.

Cindy Kristensen reported, “Our numbers in the Village at Castle Pines were also down. Both our earliest egg date and latest egg date were delayed by about 10 days compared to usual. The decrease in nest attempts was due specifically to fewer Western Bluebirds; the other species did not seem to be affected and in fact we had more nesting resident birds than usual, possibly because there were more empty boxes available. We had only seven second nest attempts compared to our usual 20-35.” Western Bluebirds dropped from 60 attempts to 20; the other species held normal, and 3 new species used boxes – 4 Mountain and one Black-capped Chickadees and one White-breasted Nuthatch.

Strangely, the few bluebirds that Urling and I have seen – two family contingents – are Westerns.

Late Breeders

Karen Metz sent an interesting note Sept. 10: “A family of begging, calling Plumbeous Vireos is here and being fed this morning in the pines near my front door. At least 4, maybe 5, including the parents, are here and very vocal.

“It’s uncommon for me to see migratory fledglings this late in nesting season. I once saw a Broad-tailed Hummingbird being fed on September 9, and I have certainly seen (irruptive but not migratory) Red Crossbills being fed in early October, but this is quite surprising and really quite joyful because I had not found this species with young earlier this year and a pair typically nests nearby.”

Few Birds, More Butterflies

Dave Leatherman reported Sept. 9 that he spent “two weeks in Lamar trying to find some migrants. A lengthy visit at this time of year usually nets 120+ species. This year I had about 70. Admittedly, I didn’t hit all the tried and true locations as often but in general it seemed remarkably hot and slow. When the birds are slow, I can switch to insects and be easily amused.

“This visit I did just that and had an amazing 39 species of butterflies in Lamar, 37 of them in Janeal Thompson’s nicely landscaped backyard. Many of the butterfly taxa have a distinct southern flavor and are representative of climate changes that are now part of the new normal down there. When I provided Paul Opler the list of what I had seen, including a Florida White (only 4th state record), he said it read more like a roster from south TX. Exciting to see, but scary to contemplate.”