survival and mortality rates from egg-laying to fledging are calcu- 
lated. These data are as follows: 
Number Number of 
of eggs young Mortality Survival 
Black-footed albatross, on -- laid fledged rate rate 
Sand Island 4,280 1,780 58% 427, 
Eastern Island 2,290 1,470 36% 64% 
Total 6,570 3,250 51% 49% 
Laysan albatross, on -- 
Sand Island 60,000 36,000 40% 60% 
Eastern Island 45,000 30,000 33% 677% 
Total 105,000 66,000 37% 63% 
These figures confirm the suspected higher mortality rates 
for the black-foots, as compared with the Laysans. However, it is 
interesting to note that there is very little difference in mortality 
rates between the two species on Eastern Island, which is not subject 
to much human disturbance. 
Taking the Laysan albatrosses on Sand Island as an example, 
even if we assume that the juvenile mortality was 60 percent rather 
than 40 percent, we would get an estimate of 24,000 young which reached 
the flying stage. If we further assume that only two-thirds of these, 
or 16,000, survived their first few weeks after leaving the island, 
we still get an annual increment of about 7,000 or 8,000 over the 
estimated annual adult mortality on Sand Island (estimated at 8,000 to 
9,000; see 1956-57 report). It seems apparent that, even under the 
abnormally heavy mortality which prevailed on Sand Island during the 
1956-57 season, the biotic potential of the Laysan albatross is still 
sufficient to maintain the population. Mortality of adults at sea is 
very low - not over 5 percent a year, based on returns of birds banded 
at Gooneyville Lodge 18 years ago. The big unknown factor is the 
mortality of young birds at sea during the first few years of their 
life, before they return for the first time. Until that is known, we 
cannot predict how much mortality the population can sustain on Sand 
Island. 
Nest Mortality Due to Tidal Waves 
Under the term "tidal waves" are two distinct phenomena, the 
results of which are the same as far as nesting albatrosses are 
concerned. The first of these phenomena is the "tsunami," or seismic 
tidal wave. The second is the storm tide created by typhoons (or 
hurricanes, depending on whether they originate west or east of the 
180th meridian). Their effects on nesting albatrosses are irregular 
and infrequent, but often disastrous and of far-reaching effect 
throughout the Leeward Chain. 
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