KUNGL. SV. VET. AKADEMIENS HANDLINGAR. BAND 52. N:o |7. 73 
In these specimens the bill is subject to a noticeable variation in length. The 
difference amounts to as much as 7 mm. Besides the individual variation, this fact 
is due to the wearing of the bill. In some of them the point is even quite worn 
off. In others a new growth of the point has taken place, which can be seen from 
an old shell-like horny edge that has remained near the point of the bill. (In 
such specimens the upper bill usually projects a little beyond the lower-bill.) The 
bill of specimen ”/12 (in entire adult plumage) is only 3,2 cm. long, and that of spe- 
cimen ”/h 4 cm. The difference is probably due to the difference of age. 
Moulting. — If we examine the white band on the back of an adult bird, we 
shall find that in a specimen that has lately been moulting, the white is of secondary 
origin, so to speak. At the lower part of the band we shall find feathers with blue 
edges, followed by a fainter dark edge. The blue margin may be partly worn away 
and partly remain in the same feather. Where it is knocked off there is a faint 
dark-brown edge left, or else this edge is also worn away, and the feather is entirely 
white (Plate 2, fig. 9a and 9.b; page 22, fig. 5). In an old bird it is possible for 
the central part of the band to have entirely white feathers as pins. But often 
there is to be seen a faint dark watering in different parts of this band. 
If we examine the juvenal plumage it will strike us, how narrow the collar is. 
It is intermixed with black-margined and black-mottled feathers, no feather seems 
to be quite without a dark admixture. 
It might therefore be correct to suppose that the band in the adults, where 
it is expanded to such a degree, is obtained from feathers that are in the beginning 
white with coloured margins, from which sooner or later the edges are lost by being 
knocked off. 
The species that seems to be most closely related to this one is H. maclaeyi, 
that is also met with in West Australia. The latter resembles the former both 
in size and colour, except for the loral-spot, which in this one is a rusty colour, 
but in maclaeyi white. It is interesting to note that the female of maclaeyi has no 
white on the back, which is present only in the male. In the juvenals of the latter 
it is probable that during the development of the band of the back some traces of 
dark edges are to be seen. The conservatism, with which the black remains through 
the edgings mentioned above, and also the fact that the band of the juvenals has 
more of the black colour indicates that the white is a specific character of a later 
origin. 
If we compare these juvenals with juvenals of a related genus Todirhamphus, 
we shall find a juvenal plumage with black chin and a dark girdle round the back. 
The black chin has corresponding to it the dark edgings on the breast of the juvenals 
of Halcyon. The wings are brown, otherwise the distribution of the colours is the 
same. 
The geographical distribution is also of a certain interest. The species Todi- 
rhamphus belongs to Tahiti, The Society Islands, Somoa; the species H. maclaeyi to 
the islands in Torres Strait, S. E. Guinea, the northern parts of Australia to S. Wales. 
H. sanctus is spread over the whole of Australia, the New Hebrides, N. Guinea, Ce- 
EK. Sv. Vet. Akad. Handl. Band 52. N:o 17. 10 
