(Sula leucogaster)
Like the other birds in his family,the dark sula is a medium-sized seabird.The length varies from 64 centimeters to 76 centimeters,weighs from 700 grams to kilo and a half,wingspan from 137 to 145 centimeters depending on the subspecies.The liveries are similar in both sexes.The back,the tail,the upper part of the chest,the upper part and the lower edges of the wings and the head are dark brown,while the belly and the lower central area of the wings are white.The legs and feet are yellow in the females and grayish-green in the males,like the beak,which however tends to gray even in the females.The wings have special air bags that,together with the long and narrow body,mitigate the impacts with the water.The beak is conical,long and sturdy,suitable for catching fish.