ON BIRDS FROM THE NETHERLANDS. 215 
specimens in interesting stages of plumage, that were totally 
unknown to me and that were not represented in the 
series of this species in our general collection. These specimens 
necessitate me to revert to the example, which [ mentioned 
last year as being a hybrid between Fuligula fuligula (L.) 
and Aythia nyroca (Güldenstädt) (Notes Leyden Museum, 
XXX, 1908—’09, p. 150, pl. 7) but which I consider 
now as an adult female of Fuligula fuligula changing from 
the summer plumage into the winter plumage. 
This year I received two females, shot 26 July (plate 6, 
fig. b) and 12 August 1909 (plate 6, fig. a) at Nieuw- 
koop, in which the whole undersurface is dark brown, the 
feathers being edged with pale brown or with whitish. A 
few pure white feathers are to be observed between the brown 
feathers, when lifting up these. In a female shot 24 Au- 
gust 1909 (plate 6, fig. c) at Nieuwkoop, the feathers 
of the undersurface are dark brown, those of the middle 
of the breast, of the sides of the breast and of the vent 
broadly edged with white, so that the undersurface is much 
more white than in the two preceding specimens. Also in 
this example a few white feathers, especially on the breast, 
are scattered between the brown ones. This specimen is 
much like the female, which I described and figured last 
year as a hybrid. In a female shot at the same date and at 
the same place (plate 6, fig. d) the feathers of the breast 
and vent are white, but some brown feathers with white 
edgings are scattered between them. The two last-named 
birds have been sexed by myself, they were old females, at 
least in their second year. 
The specimens with the brown undersurface are in the 
summer plumage, which is laid on as breeding has com- 
menced and which is worn by the birds for only about 
two or three months, as already in the last of August or 
the beginning of September the white feathers of the win- 
terplumage appear between the feathers of breast and 
vent, and replace the brown feathers of the summer 
plumage. 
Notes from the Leyden Museum, Vol. XX XI. 
