796 
BULLETIN OF THE UNITED STATES FISH COMMISSION. 
and a typical specimen measures 67 by 45 millimeters. We found one white, downy nestling, and 
most of the eggs were considerably incubated. 
We saw only one red-tailed bow’s’n bird near the French Frigate Shoals, but on Necker they 
were rather common. Contrary to the very pronounced nesting habits on Laysan, the species here 
has accommodated itself to the rocks and lays its egg in any rounded cavity. One nest I examined 
consisted of old torn feathers, a few stray sticks, and similar rubbish. The birds sat facing the wall, 
and were as noisy as usual when disturbed. 
The species is scarce at Bird Island, where it was observed in August. 
Among the windward islands of the group, that is from Niihau and Kauai to Hawaii, we did 
not observe this species, although Phaethon leplurus was frequently seen. Mr. Wilson in “Aves 
Hawaiienses” states that “it breeds in several places in the group, especially on Kauai and Niihau, 
and chooses holes in almost inaccessible cliffs wherein to deposit its eggs.” 
SUULLE. 
Sula cyanops. Blue-faced Booby. 
Dysporus cyanops Sundev., Physiogr. Siillsk. Tidskr., 1837, p. 218, tab. 5. 
On Laysan the masked, or blue-faced booby lives only on the sedgy slope facing the ocean, 
exposed to spray-laden winds and close to the booming surf. On the inner slopes of the island the 
species is entirely absent, being replaced by its somewhat smaller congener Sula piscator. We found 
cyanops most plentiful on the northeast, east, and southern exposures, where the narrow littoral slope 
is broadest, but on the west side, where a little bluff replaces the seaward slope, the birds are absent. 
The homes of these boobies are not crowded, but are scattered here and there over the greensward 
and from a distance are easily recognized by a little round patch of sand and the sentinel bird. Two 
limy, white eggs are laid on the bare sand, with usually no semblance of a nest, or occasionally there 
may be a little dried sedge scratched about the eggs or young. As is well known the eggs are a light 
blue underneath, and the coarse limy coating covers this to a greater or less extent. Sometimes the 
blue shows through, or is revealed by scratches made when the outer layer is soft. All the eggs we 
saw were very untidy. There is, of course, variation in size and shape, some eggs being ovate, and 
others elongate oval or short fusiform. 
We found young and eggs in about equal numbers, and most of the eggs were far advanced in 
incubation. The young varied from about a week old down to newly hatched individuals. It is a 
curious fact that although there are two eggs, only one young is reared. Often all signs of the second 
egg were removed, as if the young had hatched and had been devoured by a parent or some marauding 
Fregata. But more frequently there would be one nestling and one egg. Sometimes this egg was 
spoiled, sometimes contained an embryo. In one case I found two newly hatched young, one of 
which had already been trampled to death. Professor Nutting saw one large nestling and one small, 
still alive, but I doubt if it lived long. The presence of only one young bird has been noted in the 
eastern Pacific at Clipperton Island by R. H. Beck,« and Rothschild ,J mentions the same fact for 
Laysan. The voracity of the bird first hatched is probably responsible for the death of the second. 
The young bird nearly always keeps its head under the parent, although the greater part of its 
body may be exposed to the sun. Both old birds take turns in sitting on the eggs or watching the 
nestling. Occasionally both will be seen standing guard together, in an absurd statuesque pose, or 
gazing seaward or at the sky on the lookout for winged marauders. From time to time they utter a 
very hoarse strident cry. (Figs. 33, 34, 36. ) 
We derived no little pleasure on the first afternoon of our visit from watching an old bird feed the 
young. The young one inserts its head fairly into the throat of the parent, in a decidedly gruesome 
manner, and catches the disgorged food. In fact, the young one’s head went so far into the parent’s 
throat that I became solicitous for its safety. Flying-fish, swallowed whole, seem to be their favorite 
food, judging by remains scattered about nests and a stomach examined. (Fig. 35. ) 
When the old birds exchange places, one slips off the nestling and the other immediately takes 
its place, as if fearing an attack from a frigate bird. The boobies appear to exhibit affection for their 
young. I have seen them gazing at the fuzzy-white ball with evident pride in their otherwise stolid 
Condor, IV, 1902, p. 61. 
1 Avifauna of Laysan, p. 26. 
