May 2, 1858. If I were to be a frog hawk for a month I should soon know some things about the frogs. How patiently they skim the meadows, occasionally alighting, and fluttering as if it were difficult ever to stand still on the ground. I have seen more of them than usual since I too have been looking for frogs.
March 24, 1860. I see a male frog hawk beating a hedge, scarcely rising more than two feet from the ground for half a mile, quite below the level of the wall within it. How unlike the hen-hawk in this!
May 8, 1860. How the marsh hawk circles or skims low, round and round over a particular place in a meadow, where, perhaps, it has seen a frog, screaming once or twice, and then alights on a fence-post! How it crosses the causeway between the willows, at a gap in them with which it is familiar, as a hen knows a hole in a fence! I lately saw one flying over the road near our house.
Excerpted from the journals of Henry David Thoreau.