nesting area is almost a third again as many as in 1966 . The percentages 
of nests with eggs and young from 1964- through 1968 suggests a remarkable 
consistency from year to year and strongly supports the conjecture that 
Howland Red-tailed Tropicbirds have an annual population breeding cycle. 
(The data from 1963 is not strictly comparable for two reasons. First; 
the nest count data was not -at thoroughly taken as on subsequent July 
visits. Second; 1963 was a year of markedly depressed breeding by most 
species; including tropicbirds; and one in which nesting conditions were 
apparently abnormal.) 
Data were obtained during this survey on the number of banded and un¬ 
banded breeding tropicbirds; we can calculate the proportion of the July 
breeding population which was banded at the time of our arrival and by the 
time of our departure. Calculations indicate that 63 percent of the- breeding 
population was banded when we arrived and that 73 percent was banded when 
we 'departed. 
Hackman; who did almost all the work with the tropicbirds; painstak¬ 
ingly checked and remarked all nests which had been marked and checked from 
month to month in 1966 by Clapp and Tuxson. The results of his work are 
presented in Appendix 1. 
One of the returns was an interisland bird. This tropicbird; 625~ 
85682 ; which was with a small downy young when recaptured on Howland; 
had been captured with a nestling when it was banded on Baker Island in 
July 1964-. 
Blue-faced Booby Estimated population ----- 1300 
Estimated breeding population ------ 925 
Estimated prebreeding population --- 100 
Sample nest count results (Believed 
to be more than 95$ complete ---n: 4-4-6 * 
Ho. of nests whose contents were 
not checked---— 4-3 
Hests/l egg-*---- 74- (l8.4-$) 
Nests/2 eggs ------ 185 (4-5-950 
Total: nests/eggs--- — 259 (64-1.36 ) 
Nests/egg & naked young - ——-"-l”/ .2$) 
Nests/l naked young —--------—-- 12 ( 3 *0$) 
Nests/2 naked young -- 4- ( 1.0$) 
Nests/l small downy young----r-,. 25 ( 6.2$) 
No. of large downy young -- 59 (l4-.6$) 
No. of large feathered young - 35 ( 8 . 7 $) 
No. of near-immatures ----■- 8 ( 2.0$ ) 
Tot a 1: ne's ts/young and r ' loca 1 ;y young! 44 (3 5*1 $ ) 
No. of dependent immatures counted 12 
No. Banded : 51 ( 7 AM; 8 AF; 3 SU; 6 I-U) 
27 N-U -- 15 breeding birds 
No. Returns —: 285 (l38~ _ AM, 14-2 AF; 4- A-u/ U)U- 
177 breeding birds ** 
__ No. Blood-samples --: 30 (15 AM, 13FF, 2 SU ) 
*n does not include dependent immatures counted, n for percentages is 4-03 since 
unchecked nests were not included. indicates # of birds returned - one 
bird was a double banded return. 
