Scientific name: Puffinus tenuirostris
Short-tailed shearwaters have a blunt tail, black bill and a wing span of one metre.
Distribution & abundance
Short-tailed shearwaters breed in colonies around Tasmania, on islands in Bass Strait and in South-east Australia. Colonies range in size from several hundred pairs to a single colony in excess of one million pairs on Babel Island (Bass Strait). The total population is presently estimated at approximately nine million breeding pairs with another five million non-breeding birds.
The birds can fly up to 40 knots, and reach their Antarctic feeding grounds in three-to-four days from Tasmania.
Short-tailed shearwaters migrate every year to the North Pacific Ocean and reach the Arctic Ocean, north of Alaska before returning to their colonies in September. Their migratory path is now known to be more directly north-south, and not the figure-of-eight, around the Pacific Ocean as previously thought.
Conservation status: least concern
The birds dig nesting burrows into soft sandy soils. The burrows can be up to two metres long and there is some competition between shearwaters and penguins in some colonies at the start of the breeding season.
Short-tailed shearwaters, like all other petrels, lay only one egg per season. They can live for more than 30 years and generally have the same breeding partner each season.
The chicks are hatched in January and depart the colonies in April. After the last feeding by their parents, the chicks weigh more than their parents. The last meal is large enough to sustain the chick for up to three weeks before it departs the burrow.
Shearwaters convert the food for chicks to an oil which has a lower mass than the ingested prey. This oil is energy-rich and provides an efficient method of transporting food over large distances (e.g. from the Antarctic to Tasmania), when feeding chicks.
Diet and feeding
The diet of short-tailed shearwaters is primarily crustaceans. Around Tasmania, the shearwaters eat Nyctiphanes australis, a small (1cm) crustacean, but in the Antarctic, shearwaters eat antarctic krill (5 cm).
The adults shearwaters return to the colonies at dark after feeding at sea during the day. This behaviour reduces the risk from land-based predators such as eagles, feral cats, possums and rats who patrol the shearwater colonies in search of food.
Short-tailed shearwaters dive to catch their food and can dive to 50m. Most dives, however, are less than to 20m. The birds use their wings to propel themselves through the water.