A fish hawk hovering over the meadow and my boat (a raw cloudy afternoon).

November 17. 

Paddled up river to Clamshell and sailed back. 

I think it must have been a fish hawk which I saw hovering over the meadow and my boat (a raw cloudy afternoon), now and then sustaining itself in one place a hundred feet or more above the water, intent on a fish, with a hovering or fluttering motion of the wings somewhat like a kingfisher. 

Its wings were very long, slender, and curved in outline of front edge. I think there was some white on rump. 

It alighted near the top of an oak within rifle-shot of me and my boat, afterward on the tip-top of a maple by waterside, looking very large.

H.D. Thoreau, Journal, November 17, 1854

I think it must have been a fish hawk. See May 12, 1855 (“ It comes on steadily, bent on fishing, with long and heavy undulating wings, with an easy, sauntering flight, over the river to the pond, and hovers over Pleasant Meadow a long time, hovering from time to time in one spot, when more than a hundred feet high, then making a very short circle or two and hovering again, then sauntering off against the wood side.”); April 6, 1859 ("A fish hawk sails down the river, from time to time almost stationary one hundred feet above the water, notwithstanding the very strong wind.”). See also November 6, 1854 ("Was that a fish hawk I saw flying over the Assabet, or a goshawk? White beneath, with slender wings.") and A Book of Seasons, by Henry Thoreau, the Osprey (Fish Hawk)