The osprey (Pandion haliaetus), also called sea hawk, river hawk, and fish hawk, is a diurnal, fish-eating bird of prey with a cosmopolitan range. It is a large raptor, reaching more than 60 cm in length and 180 cm across the wings. It is brown on the upperparts and predominantly greyish on the head and underparts. Ospreys prefer habitats with plenty of shallow water where fish are plentiful. They often built nests on small islands or structures over bodies of water that are difficult for predators to get to. Manmade structures such as power poles and other stable structures are common nesting sites. The osprey’s diet is almost exclusively fish, a unique characteristic among raptors. They are opportunistic about the species of fish they catch, but they can only catch fish swimming within three feet (1 m) of the water’s surface. They rarely take fish over 16 inches (40 cm) long. Ospreys have high-pitched, whistling voices. Their calls can be given as a slow succession of chirps during flight or as an alarm call—or strung together into a series that rises in intensity and then falls away, similar to the sound of a whistling kettle taken rapidly off a stove. This second type of call is most often given as an unfamiliar Osprey approaches the nest. As the perceived threat increases, the call can build in intensity to a wavering squeal. Here is a link so you can listen to this bird too.