And sometimes you get lucky. I had changed out the memory cards in one game-cam and was sitting in the shade watching swallows play with the effect of wind hitting a treeline--one swallow went from almost-straight-winged to delta to vee in just one swoop--when I spotted a hawk high overhead, soaring. A big hawk. Not a red-tailed.
BIG hawk. I didn't have Bird One lens with me, but cranked out the zoom to its full 300mm and did my best. Not a great shot but good enough to compare to the bird book and find out that it was a Swainson's Hawk, Buteo swainsoni. A lifer for me and a first for the land.
And the species count is up to 788.