Sky divers

By Sophie Bond.  

The first glimpse of a gannet colony is a truly fantastic sight: thousands of elegant golden and white birds, perfectly spaced, each sitting atop a little mound of a nest.

Gannets, Photo; Creative Commons, Thomas Becker

Gannets, Photo; Creative Commons, Thomas Becker

In winter, when the birds are far away and fishing, the empty colony is just as striking: barren and exposed, the ground is covered in uniform hollows.

The Australasian gannet, Morus serrator, is usually found living in large colonies on offshore islands of New Zealand and Australia.

Called takapu in Maori, it is one of three species of gannet and belongs to the booby family. Gannets spend most of their life at sea, feeding on fish and squid with the help of their remarkable diving abilities.

Dropping from heights as great as 30 metres, at speeds of up to 145kmh, they tuck their wings in close to the body as they slice into the water. Their torpedo-like shape and
speed means they can plunge up to 43m into the water in a single dive. Their natural airbags – inflatable air sacs beneath the skin on the lower neck and breast – absorb the
shock of the dive.

At just four months old gannet chicks set out on their first flight, a 2800km journey across the Tasman. After three or four years they will return to their birthplace to find a
mate and breed. Parents take turns to incubate a single egg, and if the first of the season fails to hatch, they will lay a second. Their nests are mounds of dried seaweed,
compacted into a raised crater shape. One partner will travel as far as 100km to get food while the other minds the nest.

New Zealand has the largest and most accessible mainland gannet colony in the world: Cape Kidnappers in Hawke’s Bay. Gannets have been nesting there since the 1870s and it’s estimated that today about 20,000 birds are found there.

Protection of Cape Kidnappers gannets began in 1924, a decade after the land housing the main colony was gifted to the Crown by the station owner. A board was set up and
wardens were appointed to keep an eye on the colonies.

Birds were frequently found shot at the cape until Junior Wildlife Wardens came to the rescue. The young wardens would patrol the cape every weekend and holiday, based in tents until an eight-room bunkhouse was built.

The Department of Conservation now manages the 13-hectare reserve, which is made up of the Saddle, Black Reef and Whalebone Beach colonies. The Plateau colony is on
private land but is also protected.

Gannets also breed on the mainland at Muriwai in West Auckland (where a reserve was established in 1979 with input from Forest & Bird) and at Farewell Spit at
the top of the South Island. The Muriwai gannets can be seen from a walking track around the coast, and those at Farewell Spit can be visited on eco-tours.

Auckland PhD candidate Stephanie Ismar has spent more time than most with the Cape Kidnappers gannets. She is studying the foraging and breeding success of the
gannets and says relatively little is known about them. She is in her third year of monitoring the gannets: putting bands on the fledglings, taking measurements and tracking their flight paths.

“They are very territorial and defensive of their homes – as far as a gannet’s beak can reach, that is his territory and if anyone or anything else gets near to his nest site it’s
a potential intruder.” She says birds will always come back to their nesting site and it’s extremely rare for one to switch colonies. “The gannets have some very interesting habits. They preen their mates and have a lovely fencing ritual where they rub their beaks against each other.”

An unseasonably cold spring last year set the breeding schedule back about five weeks. The first round of eggs at all the Cape Kidnappers Reserve colonies was lost and
parents had to incubate a second round.

Much of the original coastal vegetation at the cape has been depleted. Replanting is under way in the Cape Kidnappers and Ocean Beach Wildlife Preserve – a 2200ha,
predator-free area at the cape, which provides a haven for the reserve colonies. There is also careful control of weeds including nettle and boxthorne.

Overall, the gannets’ future is looking bright, and numbers at the Cape Kidnappers
Reserve are increasing by about 2 per cent a year.

The greatest threat to gannets is from ocean pollution: oil spills and the flotilla of plastic junk in our waters. Like other species that depend on the sea for their survival, the
gannets face depleted food stocks. There are some fishing restrictions around the reserve and ships must keep at least 9.5km from Cape Kidnappers.

The gannets that nest on our coasts give us a fantastic opportunity to see communal birdlife in action.