Black Swift nesting failure??

[andrew melnykovych]

All-

Visited Box Canyon Falls Park in Ouray today - once in mid-afternoon and again at around 7 pm. 

Located 4 nests - one empty and three with single eggs. All were unattended throughout both times I was there. That is consistent with what the woman at the park visitor center told me has been the case for several days. I would assume that the eggs are unviable as a result.

Does anyone know what might have cased all these nests to be abandoned? My guess is that the unusually cold and wet weather in the last few weeks has impacted their favored prey (flying ants, according to Birds of America Online) and that the food shortage has caused the nest abandonment. (BofA has no info on nest abandonments)

Would be interested in everyone's thoughts.

I later saw at least two Black Swifts above the town at about 730 pm. They were high up, far above a large flock of Violet-green Swallows. So at least a few birds are around, if not necessarily nesting.

Andrew Melnykovych

Louisville KY

[Erik Hendrickson]

I believe this is consistant with obervations of Black Swifts at Black Canyon from 1996-2017, as reported in "Breeding Phenology and Success of Black Swifts in Box Canyon, Ouray, Colorado" in the Wilson Journal of Ornithology, Vol. 119, No. 4, pgs. 678-685, 2007 by Sue E. Hirshman, Carolyn Gunn and Richard G. Levad.  Since publication of the original article, my understanding is that Sue Hirshman continues to closely monitor and record data on nesting swifts at Box Canyon, and Dr. Carolyn Gunn works with the data to update statistics (and continues to publish scientific papers about Black Swifts).  The updated statistics were presented by Carolyn Gunn at the 2019 Ute Mountain Mesa Verde Birding Festival, and included the following:

Egg Laying - mean June 28 (range June 15 to July 22, n = 118)

Incubation Onset - mean July 1 (range June 16 to July 23, n = 131)

At her presentation, I recall Carolyn Gunn commenting that Black Swift eggs can remain unattended after laying for several days, and the eggs will not addle, and will remain viable.

As Rich Levad said - this is the coolest bird.

http://www.aba.org/thecoolestbird.pdf

[andrew melnykovych]

Thanks for the update. One less thing to worry about.....   They are  fascinating birds.