Bulletin - United States National Museum - si-pddr - Smithsonian ...

132 BULLETIN 133, UNITED STATES NATIONAL MUSEUM
ivnd Kerguelen Island, I do not detect any constant characters that
may seem to serve to distinguish birds from these localities. The
gonydeal angle in two specimens from Kerguelen Island is very
prominent but is approached in this respect by birds from South
America. Two specimens from New Zealand seem to have the wings
and mantle somewhat blacker than others, but here again the differ-
ence may break down when recourse is had to a fair series from elsewhere.
The bird from South Shetland I have not examined. On
the whole, specimens from the scattered localities at hand seem remarkably
constant in their conformity to one type of coloration.
The similarity in color and structure between L. doniinicanus and
L. marinus from North Atlantic and Arctic regions is striking, and
in final analysis birds from the two regions seem separable by dif-
ference in size alone so that one may well question the degree of re-
lationship between the two. In habit and distribution the two are
complementary one to the other, and it seems logical to conclude
that they have arisen from one parent stock. Differentiation in the
two regions has apparently progressed to a point where we may
recognize the two as full species though the propriety of calling
them subspecies of one form may be considered.
Three specimens were taken near Lavalle, Buenos Aiies, a male
on October 25 and a male and a female on November 3. All are
in partial immature dress. The male first mentioned above has
molted in part into adult plumage though worn brown feathers
are scattered over the dorsal surface, the primaries are still old,
and only part of the tail has been renewed. The neck and lower
surface are still more or less mottled. The two secured on Novem-
ber 3 are less advanced in stage of plumage though dark feathers
are appearing on the mantle. The female is small, so that when
I killed it I was under the impression that it w^as an individual of
some other species.
In June the Dominican gull, known as gaviota cocinera^ was common
in the harbors of Rio de Janeiro (June 16), Montevideo, and
Buenos Aires. At Berazategui, Buenos Aires, a number were recorded
along the Rio de la Plata in company with smaller gulls on
June 29. In the vicinity of the coast near Lavalle, Buenos Aires,
the species was common from October 25 to November 13. The
birds ranged along the tidal mouth of the Rio Ajo and in the Bay
of Samborombon, or occasionally came a few leagues inland in search
of refuse about the killing pens at the estancias. On the beach
south of Cape San Antonio they were fairly common. The majority
seen at this season were in immature dress and those taken
were not in breeding condition.
On December 13 I saw a number in the bay at Bahia Blanca,
where they gathered Avith harsh calls to feed on refuse cast over-