Gulls in Central Pacific — Sibley and McFarlane 
319 
for drinking purposes and that such water is 
usually totally lacking on Pacific islands. 
Amadon replied to this article by pointing 
out that several species of gulls spend long 
periods at sea without suffering ill effects. He 
further argues that food availability would seem 
a more probable limiting factor. In addition, he 
postulates that competing tropical species and 
the apparent aerodynamic disadvantage of a 
gull over tropical oceans may also contribute 
to their lack of success. 
Frings (1965^) cited a specimen of Larus 
argentatus which had washed ashore on Oahu 
and stated that most gulls arrive in the 
Hawaiian Islands in poor physical condition. 
This assumption is not supported by our data. 
Many gulls collected by POBSP personnel had 
considerable deposits of fat; the weights of these 
birds (Table 1) were within the range for im- 
matures of each species; and all were wary and 
capable of strong flight. Although a large num- 
ber of gulls visited Kure Atoll during the 
winter of 1964-1965, only one was found dead 
and it is believed to have died from gunshot 
wounds. 
Not only were the Laughing Gulls from the 
Line Islands in good health, but there is some 
indication that they may have remained in the 
area for some months. Bourne (1965) reported 
a few "Franklin’s Gulls’’ at Fanning Island in 
December 1963. These may have been the same 
birds observed and collected as Laughing Gulls 
(immature birds of the two species are very 
similar) in March 1964. An adult Laughing 
Gull in breeding plumage was seen over Pal- 
myra in June 1964, and an adult in winter 
plumage was collected there in November 1964. 
On Johnston Island a Laughing Gull was pres- 
ent for two months before it was collected; a 
second bird which had been injured and appar- 
ently recovered was seen for almost two months 
before it disappeared. 
Observations concerning the feeding habits 
of gulls in this area are fragmentary and incon- 
clusive. The stomachs of most birds collected 
during the winter of 1962-1963 were empty 
or contained items obviously scavenged from 
garbage dumps. Gulls near Kure and Midway 
atolls habitually frequent the garbage dumps of 
the military facilities. The Laughing Gulls from 
the Line Islands contained local foods (analysis 
incomplete). While gulls as a group are vora- 
cious scavengers, many species are proficient at 
capturing live fish and other animals (Bent, 
1921; Murphy, 1936). 
Frings implied that all gulls reaching Hawaii 
fail to return to their place of origin and even- 
tually die in the islands. However, those gulls 
which do reach the islands apparently do not 
remain long, and there are no summer records 
for gulls in Hawaii. Since they show no reluc- 
tance to depart, it would seem reasonable to 
assume they are not subjected to excessively 
stressful conditions at sea and probably will 
attempt to return to their normal summer range 
if navigational ability is unimpaired. 
Since our observations recently have shown 
that some gulls arrive at the islands in apparent 
good health, and since Frings’s birds were in 
poor physical condition, we are not able to 
agree with him that all gulls arriving at the 
islands after a long oceanic flight suffer from 
ionic imbalance and thirst, resulting in poor 
health, without the actual determination of body 
electrolytes. 
Frings maintained that the salt glands of 
marine birds function primarily to rectify a 
given amount of sea water into a smaller 
amount of fresh water to satisfy their metabolic 
needs and that the elimination of excess salts 
ingested while feeding is to be considered a 
minor function. This view would seem to be 
contradictory to the reports of Schmidt-Nielsen 
et al. (1958) and Schmidt-Nielsen (I960) who 
found no evidence to support the hypothesis 
that sea birds must drink sea water in order to 
cover their normal needs for water. When his 
experimental birds were fed fresh fish the water 
content of the fish was more than adequate for 
the renal elimination of salts and nitrogen. He 
observed nasal secretion only after an osmotic 
load and never in fasting birds or after inges- 
tion of fish or fresh water. 
Frings pointed out that gulls are unable to 
concentrate sodium chloride in their salt gland 
secretion to the degree known in albatrosses 
and petrels (800-1100 meq/1). He feels, there- 
fore, that gulls are unable to exist for long 
periods without recourse to fresh or brackish 
water. It would seem, however, that the salt- 
eliminating capability of the two species of 
gulls tested by Schmidt-Nielsen ( Larus argen - 
