I have photographed two subspecies of Brown Booby (Sula leucogaster). I photographed the Atlantic subspecies (Sula leucogaster leucogaster) in Honduras and the Colombian subspecies (Sula leucogaster etesiaca) in Costa Rica and Panama. I was able to photographs of both the adult, juvenile, and an infant.
Brown boobies (adult – white breasts, juvenile – brown or molted breasts), Punta Sul, Parque Nacional Jeannette Kawas, Tela, Honduras, May 28, 2007
Brown boobies, Punta Sul, Parque Nacional Jeannette Kawas, Tela, Honduras, May 28, 2007
Brown Booby, adult, near Corcovado National Park, Costa Rica, January 12, 2009
Brown Booby, adult, near Corcovado National Park, Costa Rica, January 12, 2009
Brown Booby, juvenile, near Corcovado National Park, Costa Rica, January 12, 2009
Brown Booby, infant, Otoque Oriente Island, aboga District, Panama, January 15, 2009
Your second to last photo appears to be a young Red-footed Booby 🙂