Great catch of the tern on its reed nest. Although the fill flash probably helped some, the light is still a little harsh here. A lower perspective (which might mean waders or getting wet) might help seperate the bird from the background
I like it, not often we see a tern photographed on it's nest. I would consider cloning out the dark grass running up from below the bill and visible through the open mandibles. Also toning down the bright diagonal stem just in front of the bill. If it was impossible for a lower angle you could have use a wider aperture to blur the BG some more. :-)