Blue-footed boobies are large sea birds (with a five-foot wingspan and measuring 70-90 cm in length) that are most recognizable by their stunning sky-blue feet. They can be observed breeding along the coast of Southern California and down the western coast of America to Peru, but are most commonly known to inhabit the Galapagos Islands. Galapagos Blue-footed boobies are one of the most iconic species in the archipelago, and are celebrated for their spectacularly precise plunge-diving and their highly-ritualized (and somewhat comical) mating dances that optimistic males display for onlooking females. However, while they are the most renowned booby birds and the most frequently seen, this is the smallest population of the booby family and, sadly, there numbers are decreasing.
Blue-footed booby males and females can be differentiated most easily by sound, although it is also possible to visually differentiate them if you have an acute eye; females appear to have larger pupils than males, however it is merely the effect of extra black pigmentation. The calls for blue-footed boobies are very important, as they allow them to communicate to a certain extent and, in fact, mates are actually able to recognize each other by their calls. Males make a high whistling noise and females have a low honking call. Additionally, females have slightly darker blue feet and are just slightly larger in size.