Bill Curtslnger 



A red-tailed tropic bird, left, soars through the air above the 

 northwestern Hawaiian islands. An unattended red-tailed tropic 

 bird hatchling, below, waits for its parents to return with a meal. 



Erwin and Peggy Bauer; Bruce Coleman, Inc. 



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being trapped in the islands was relatively 

 low compared with other spiny lobster 

 fisheries. Second, sizable areas of the 

 wildUfe refuge were closed to lobster fish- 

 ing. And third, size limits allowed lobsters 

 to mature and spawn at least once before" 

 reaching harvest size, which should have 

 been giving the population a chance to 

 renew itself. Furthermore, I had heard ru- 

 mors of declining numbers of seabirds and 

 monk seals in the area. These two species 

 are often good indicators of changes in the 

 ocean; the number of offspring they raise 

 each year can be strongly affected by the 

 abundance of food in the sea. 



Hoping that other parts of the ecosys- 

 tem would provide clues to the declining 

 lobster catches, I paid a visit to Beth Flint, 

 a seabird biologist working for the U. S. 

 Fish and Wildlife Service. I was fortunate 

 to find Flint in Honolulu; usually, she is 

 out on the islands monitoring seabirds. 

 When I told her my story, she was very in- 

 terested and told me that since 1985, the 

 reproductive success of the red-tailed 

 tropic bird and the red-footed booby had 

 dropped to half of what had been observed 

 in the early 1980s. She explained that the 

 birds' reproductive success is defined as 

 the fraction of eggs that ultimately hatch 

 and become fledgling chicks strong 



enough to fly. The number of eggs laid 

 hadn't changed, but the fraction of hatch- 

 lings that survived to become fledglings 

 had fallen. Although she didn't know the 

 reason for the decline, she was able to rule 

 out factors such as predators, diseases, and 

 habitat loss and suggested that a scarcity 

 of food would force the adult birds to 

 abandon their nests for longer periods 

 while foraging. This would increase the 

 chances that their exposed eggs and chicks 

 would perish in the hot, subtropical sun. 



I spent the rest of the day poring over 

 dusty files of seabird records dating back 

 to the early 1980s. I found that at the be- 

 ginning of the decade, about 70 percent of 

 the eggs laid produced fledghngs, but the 

 success ratio decUned steadily through the 

 mid-1980s, so that by the end of the dec- 

 ade, this fraction dropped to about 40 per- 

 cent, where it has remained. I also learned 

 that red-footed boobies and red-tailed 

 tropic birds feed almost exclusively on 

 squid and flying fish. I wondered if these 

 marine creatures had been reduced in 

 number by some environmental change 

 that had also affected the lobsters. If so, 

 why did the decUne in seabird reproduc- 

 tive success precede the decline in lobster 

 catches by three or four years? 



Maybe monk seal statistics had some- 



53 



