Comparative Breeding Bata -- Laysan and Lisianski 
Bate aof Population and Breeding 
Survey Bata -- Laysan _ 
GRAY-BACKEB TERN 
Population and Breeding 
Bata --Lisianski 
1964- -- data poor- no clear difference indicated 
Relationship of Lisi- 
anski Cycle to Laysan 
early 
Mar. 
1965 
mid 
July 
1965 
3000 - 5000 . Fr. eggs, 
girds laying 
5000 , 
2000 yg. l/2 gr. to 
flged. 
2000-3000. At least 
1000 n/e but only 1 
rhyg seen 
300, Only gledged + 
nr. fledging imm. 
present. 
Bata poor but suggests 
slightly earlier 
initiation of laying 
on Lisianski 
Cycle appears to be 
aterminating earlier 
on lisianski. Suggests 
earlier initiation 
1965 summ - data suggests slightly earlier cycle on Lisianski 
mid 
June 
1966 
late 
Oct. 
1966 
12000, mostly h inc. e 
& sm. chks.- also many 
flying imm. est. ca. 
1000 e & 4-000 chks 
0 - cycle completed 
7500. Ca. 1000 n/e and 
2500 yg. Mostly flged 
young but some small 
young present. 
0 - cycle completed 
Suggests cycle -will 
terminate, for bulk 
of birds poss. somwhwat 
earlier on Lisianski 
1966 summ - data suggests slightly earlier cycle on Lisianski nut not quite as good as 
for preceding year 
mid 
March 
1967 
early 
June 
1967 
early 
Sept. 
1967 
1000 - 15 e. found 
low hundred, 2 $ n/e fd, 
1 at least sli. inc. 
Bo clear difference 
in cycles apparent. 
[4-0000] E laying to 
flying imm. est.10, 000 
n. 
4-0- ca. 10 yg, app. 
abandoned, v few ad. 
15000 e to l/2 grown young Lot clearly different 
most n/e. Est. 5000 n. but sufgests slightly 
earlier cycle on Laysan 
20 - a few Ig. abandoned 
yg, starving found. 
1967 summ - data on the whole show no certain difference, possibly slightly earlier on Laysan 
1968 Mar. 5000, most pre-nesting, 
2 eggs. fd. 
1000 only e. present 
Bifference not clear, 
possibly slightly earlier 
cycle on Lisianski 
Summary Similar, possibly cycle 
in some years ( 1965 , possibly 1966). 
be 
tends to initiated slightly earlier 
