The bird may be engaging in “canopy feeding”, a stance where the shadow cast by the bird’s outstretched wings attracts (or maybe, just startles) fish in the water below making them more visible and thus, easier to catch. This photo was taken along the Rio Lagartos (river) in Yucatan, Mexico with a Nikon D7000 and a 70-300 mm VR lens at 300 mm. The exposure was f/11 and 1/1250 sec.