CONSERVATION OF MARINE BIRDS IN NEW ZEALAND 



263 



mammalian browsers, grazers, and predators 

 (Williams 1977). 



The destruction, or at least the reduction, 

 of such browsers, grazers, and predators by 

 physical, chemical, or biological methods, or 

 combinations of these. 



The exertion of social influences to pro- 

 mote changes in methods of land use or in tra- 

 ditional harvest for food (the latter can be par- 

 ticularly important as far as the Polynesian 

 [Maori] population is concerned, as nowadays 

 the taking of birds for food is predominantly a 

 cultural rather than an economic matter). 



Translocation has been a valuable technique 

 for increasing the numbers and ranges of a 

 few threatened terrestrial species. The very 

 nature of most marine species, however, 

 limits its application as far as they are con- 

 cerned. Nevertheless, we have considered it 

 worth trying for one nonmigrant wader; and 

 no doubt it could be tried under similar cir- 

 cumstances elsewhere. 



Convincing local experiences have shown 

 that predator or competitor destruction is 

 likely to be practical only on small, not-too- 

 rugged islands, usually no larger than about 

 500 ha. However, special circumstances have 

 prompted us to attempt destruction, or at 

 least control, on much larger and more diffi- 

 cult islands. It is implicit that the predators 

 or competitors are exotic, not indigenous. Re- 

 cently, on those rare islands that are in- 

 habited but still free of either black or Norway 

 rats, we have set up permanent bait stations 

 (at which sodium fluoracetate "1080" is 

 used as the poison) on wharves and jetties in 

 the hope that such a precaution will, with the 

 addition of a propaganda campaign calling for 

 the regular fumigation of visiting vessels, pro- 

 long the charmed lives that these fortunate is- 

 lands have so far enjoyed. It goes without 

 saying that we ask that the greatest care be 

 taken when expeditions land stores on unin- 

 habited, rat-free islands which, if by "rat- 

 free" we mean also free of R. exulans, are even 

 rarer in our seas. 



The sociolegal approach is effective only 

 when ecosystems or communities have not 

 been seriously modified, otherwise it is no 

 substitute for either of the other two meas- 

 ures discussed. 



Some Case Histories 



Translocation 



Last century, an endemic monotypic genus 

 of wader the New Zealand shore plover (Thi- 

 nornis novae seelandiae) was widespread and 

 occasionally very common around the coasts 

 of the North and South islands and the Cha- 

 tham Islands. As a result of European settle- 

 ment and the accompanying predation by 

 feral cats and rats, the species now occurs 

 only on South East Island in the Chatham 

 group (860 km east of the mainland), where it 

 at present seems safe, since there are no rats 

 on the island and it is now a reserve. However, 

 the population numbers only about 120 indi- 

 viduals. Because calamities can always occur 

 (for example, ship rats recently reached shore 

 on three important islets off the southwest 

 coast of Stewart Island), the Wildlife Service 

 is anxious to spread the shore plover to other 

 suitable islands, if they can be found. The 

 species is not a migrant and is rather seden- 

 tary. The first translocation attempts failed, 

 probably because mainly adult birds were 

 used, and we are now continuing our studies 

 of the species with the thought in mind, 

 among others, that success may come if 

 young birds are used instead; the question 

 is how young? 



As is widely known, the New Zealand Wild- 

 life Service has been remarkably successful in 

 recent years in translocating one species of 

 the endemic wattlebird family the forest- 

 dwelling saddleback (Philesturnus caruncu- 

 latus)to other islands than the four small 

 ones it had been reduced to by the early 

 1960's; three of these islands were the ones re- 

 cently invaded by ship rats, referred to above. 



Predator Control 



Some 25 km off the North Island's east 

 coast lies the 3,000-ha, very rugged and 

 forested Little Barrier Island, which has now 

 been a reserve for the protection of flora and 

 fauna for about 80 years. Before that, it had 

 been almost continually occupied by Maoris 

 since their arrival in New Zealand, and about 

 one-third of its forest was felled or burnt, es- 

 pecially after European settlement of the ad- 

 joining New Zealand mainland began. 



