Took this a while back while at the Phoenix Zoo DPC GTG.
Processing:
Silver Efex Pro to convert to duotone
Color Efex Pro tonal contrast filter
Levels adjustment
Paint black on new layer in soft light blending mode to darken background
Original
And if you prefer more colorful flamingos (still with a mostly dark background), check this one out
Beautiful image. Flamingoes are such a fantastic colour that you'd think conversion would lose too much - but in fact this is even more beautiful, with the emphasis on form and texture.