Pigeons and exhaustion.

Tootled over to Gullane this morning.
Stopped on the way to capture these pigeons.
When I got to the scenic seascape my camera told me the battery was exhausted.
I felt rather tired myself, but never mind.
Reached in my bag for the spare battery, did the necessary swapping only to find that somewhere along the line I have been carrying a 2nd exhausted battery. How did that happen to an, hmm, organised person like myself.