(RBC-7/6/67) 
Table 
20th Century Observations of Gray-backed Terns on Rihoa Island, 
Date of Survey 
(jp Dec. 21-22,1953 
DDec. 9-16,1961 
Mar. 18, 1915 
//'gOfer. 18 , 1954 
Mar. 6 - 7 , 1964 
(ft) Mar. 13-14,1965 
(±3) Mar. 8 - 9 , 1967 
June 10. 
1962 
July 28- 
t>) Aug. 1 , 1966 
3 ) Aug. 7-15, 1940 
>/ 
Size of 
Population 
c.10,000 
12-14 
c. 100 
c. 5,000 
c. 
X) June 11 - 16,1923 C. 10, 000 
8,000 
Reproductive Status 
juNone seen on partial survey] (Richardson, pers . comm .) 
sIcac, (Kramer, 1961 ) 
* 
t! 
,..seen in scattered pairs. ...Two only were 
flushed from eggs.*" (Munter, 19151^ 
(Richardson, pers . comm .)* 
C. 25 nests with eggs observed^ (P0BSP)* 
Rests contained only eggs;* (POBSP)* 
On fresh to slightly incubated eggsx (POBSP)* ' 
Majority with fseesh eggs but some recently hatched 
young and a few half-grown young seen* (Wetmore, 1923 )* 
With eggs and downy young* (Kramer & Beardsley, 1962 )* 
C. 4, 000 young, 5% recently hatched, 25^ from 2-3 
weeks old, and 7 0$> older than 3 weeks# (P0BSP)' 
Found in two small colonies. "Breeding was in its last 
stages and only young were seen* 
_ ^ (Vanderbilt & de Schauensee, 1941 \ #)* 
Sept. 964 c. 50 
Six immatures remaining on the island from the 
preceding season^ 
(P0BSP), 
1964 
f96, 
6 i\ 
1968 
/ <- 25 duly 
■I 
very common 
13-14 September very common 
7-9 March c. 2,000 
Very small chicks to 2/3 grown young (kridler, 1964 
Some near fledging young noted (Kridler, 1967 ). 
Only one nest with egg found. Most ^irds evidently 
pxMkmxding pre-nesting (P0BSP). 
