Four of these glaciers actively calve icebergs into the bay. These shelves then melt or calve off to give icebergs that eventually melt. As the ice reaches the sea, pieces break off, or calve, forming icebergs. In Antarctica, ice shelves calve large tabular (table top) icebergs. Thus, a female can calve twice a year, and even thrice if one calf dies. Also, moose cows may not calve without adequate summer weight gain. Endangered North Atlantic right whales calve off the city's shoreline. Unlike on the mainland, these glaciers calve directly into the open ocean. Southern right whales come to the nearby waters to calve and to mate. Both Miles Glacier and Childs Glacier calve directly into the river. Endangered right whales calve off the city's shoreline. Female reindeer keep their antlers until they calve. Cows first calve at five years of age, after a gestation period of 11.5 months. Females are believed to calve on average once every three years. Calve Island is an uninhabited island in Tobermory Bay.