The Red Notebook

Nature is still red in tooth and claw at the side of the M62 motorway.

Heading out of Liverpool at 70 mph this evening (for to admit any faster would be to admit breaking the law), I noticed a buzzard circling about 30 feet above the carriageway. Suddenly, it wheeled left, plunged down, and took out an unsuspecting rabbit. I had never seen a buzzard make a kill before.

Five minutes later, on the other side of the carriageway, a kestrel assassinates some poor rodent with deadly precision.

Commuting has its moments.

A kestrel hunting behind my house

More kestrel photos »

No, not the latest album by The Fall; I’ve just started reading The Eye: a Natural History by Simon Ings. On page 28, I came across the following fascinating snippet:

Even with their superb visual acuity and excellent colour sense, extending well into the ultraviolet, kestrels find it hard to spot the drab voles which are their favourite food. Happily for the kestrels, however, voles communicate by leaving trails of urine—indeed, they pee almost continuously—and mole urine reflects ultraviolet light. For kestrels, hunting voles is simply a matter of following the arrows.

Amazing.

I must admit, I was initially irked by Ing’s use of the word happily to describe what appeared clearly to be a marvellous hunting adaptation evolved by the kestrel. But not so: all birds can see into ultraviolet wavelengths, apparently; so kestrels can’t have evolved their ultraviolet vision specifically to hunt voles. The apparent adaptation turns out to be a lucky coincidence, which the kestrel has put to good use—possibly refining it over time.

Ultraviolet mole piss detection isn’t so much an adaptation as an exaptation, it would seem.