2 notes on UV light and birds

[dgulb...@gmail.com]

Surprising facts from An Immense World by Ed Yong:

  - "More than 90% of songbirds whose sexes are indistinguishable to us, including swallows and mockingbirds" look different to each other because of UV markings.

- an oft-repeated claim is apparently false:  Kestrels can't, after all, track voles because of UV reflecting off urine.  The amount of reflection is small, not distinguishable from water, and unlikely to be seen from afar.

David Gulbenkian, Lakewood, Jeffco