Demon divers

A bird bom­bard­ment rekin­dles mem­o­ries of Al­fred Hitch­cock’s clas­sic movie.

Boating NZ - - Contents - BY LIND­SAY WRIGHT

The weird and won­der­ful world of gan­nets.

Watch­ing takapu/gan­nets at work, it’s easy to imag­ine be­ing in the front lines of a me­di­ae­val bat­tle­field when en­emy archers let fly with their ar­rows. Even their Latin name – Morus ser­ra­tor – has a sharp abra­sive edge to it. High-speed, feath­ered pro­jec­tiles plum­met from the sky all around the boat as streaks of yel­low-headed gan­net, trav­el­ling too fast for the eye to fol­low, hit the sur­face with a sizzling rush and dis­ap­pear un­der­wa­ter.

Straight away the scenes from Al­fred Hitch­cock’s 1963 hor­ror thriller The Birds spring to mind. In the movie, flocks of aber­rant birds ter­rorise a small Amer­i­can town. Lo­cally, though, our gan­nets are fo­cussed on food – schools of pilchards, an­chovy or jack mack­erel.

The feed­ing boot was on the other foot when Cap­tain James Cook’s HMS En­deav­our first came across the Three Kings Is­lands on the 24th De­cem­ber, 1769. With Christ­mas just a day away, her crew were also fo­cussed on food – an English-style, slap-up Christ­mas din­ner in this strange land where the sum­mer sun shone brightly at Yule time.

Nearby gan­nets fell foul of the sailors’ guns, be­cause of their re­sem­blance to solan geese – northen gan­nets – from the English home­land. “On 25th De­cem­ber, Christ­mas Day, our goose pie was eaten with great ap­pro­ba­tion,” botanist Sir Joseph Banks noted. “By evening all hands were as drunk as our fore­fa­thers used to be upon like oc­ca­sions.”

You’d imag­ine a gan­net pie would have a strong fish flavour – but no men­tion was made of it, so maybe ine­bri­a­tion helped make the din­ner go down – or per­haps, af­ter months on RN ra­tions, any­thing tasted good.

The Bri­tish matelots had mis­named their din­ner. The Aus­tralasian gan­net, in fact, be­longs to the fam­ily Sul­i­dae and is re­lated to shags, pel­i­cans and (this will get the pri­mary school­ers gig­gling) trop­i­cal boo­bies.

Un­like other na­tive seabird species, gan­nets are flour­ish­ing and breed at 28 colonies around our coast­line. The near­est to Auck­land are Gan­net Rock near Wai­heke Is­land, the new colony at Mo­tuora and the 2,500 or so pairs nest­ing at Mahuki Is­land in the Bro­ken Is­lands on the west coast of Aotea/great Bar­rier. But the big­gest colonies are at Gan­net Is­land, Kawhia and White Is­land in the Bay of Plenty.

The gan­nets’ prac­tice of breed­ing on off­shore is­lands has re­moved them from the range of the com­mon preda­tors that have dec­i­mated other seabird pop­u­la­tions. It’s es­ti­mated there were 325 pairs at Mahuki Is­land in 1946 but or­nithol­o­gists say there may be a re­turn to pre-hu­man pop­u­la­tion num­bers since gan­nets be­came pro­tected in 1924. Sci­en­tists say num­bers are now in­creas­ing by about two per­cent per an­num.

To be among feed­ing gan­nets is to ex­pe­ri­ence an in­ter­min­gling of awe, fear and won­der. The birds sweep down from about 30m and skim the wave tops. They climb back to div­ing height, wheel and plunge, reach­ing about 145km/h ve­loc­ity be­fore pierc­ing the sea, leav­ing barely a rip­ple to mark their pas­sage. Hun­dreds – or even thou­sands of the el­e­gant 2.5kg birds – hit the water at high speed within cen­time­tres of each other.

A net­work of air sacs on their lower neck and breast in­flates to take the pres­sure of sud­den immersion and the long, high-as­pect 90cm wing span is folded back but ex­tended once they’re in the water. Com­bined with their big, webbed feet, these can power them down to 43m in pur­suit of prey.

An­other adap­ta­tion to tackle this life­style is the long, sharp grey beak. I once heard that older gan­nets go blind due to re­peated dives and starve to death. Still, they are one of the long­est liv­ing seabirds – all three of the gan­net species live to 2538 years and mate for life.

The guano-speck­led nest­ing colonies are de­serted from au­tumn to early win­ter un­til, de­pend­ing on location, late July, when the first gan­nets ar­rive. They ex­change fronds of sea­weed (prime nest­build­ing ma­te­rial) and per­form a rau­cous dance to show own­er­ship of the nest­ing site – proof of their abil­ity to raise chicks.

When the fe­male ar­rives, she set­tles in at home and a sin­gle egg is laid. Unsea­sonal cold spring weather has been known to wipe out a gen­er­a­tion of gan­nets but they can lay an­other egg to com­pen­sate.

About 14 weeks af­ter hatch­ing, the chick has lost its fluffy plumage and, gorg­ing on food re­gur­gi­tated in turn by both par­ents, it weighs in at about 3kg. Or 500g more than its par­ents.

At four months old, time has come to leave home and the young gan­net soars off on its first ocean pas­sage – 2,800km to Aus­tralia. They’ve been recorded from Queens­land as far south and west as Fre­man­tle, feed­ing in coastal waters be­fore they an­swer the call to breed back in Aotearoa. At be­tween three and five years old they wing home across the Tas­man and claim a nest­ing site to be­gin breed­ing.

Like a lot of seabirds and fish species these days, the peril comes from plas­tic flot­sam which tan­gles in the gut and starves the birds to death – or mech­a­nised fac­tory fish­ing com­pet­ing for the same food stocks.

But the sight of great clouds of gan­nets, plung­ing from the sky in fren­zied feed­ing mode to graze on school fish is one of the most ex­cit­ing things you’ll see at sea.

Long may it last. BNZ

To be among feed­ing gan­nets is to ex­pe­ri­ence an in­ter­min­gling of awe, fear and won­der

LEFT Div­ing gan­nets are a sure sign of hun­gry fish – but watch your head. BE­LOW Feath­ered pro­jec­tiles hit­ting the water at speeds of around 145km/h.

Newspapers in English

Newspapers from New Zealand

© PressReader. All rights reserved.