WESTRALIAN CRESTED TERN. 
Collection of a series of birds nesting on the islands off South-west Australia, 
has revealed the fact that Australia possesses not only one of the smallest 
races of Th. hergii, but also one of the largest. While South-east Australian 
birds rarely, if ever, have the wing-measurement reaching to 350 mm., and 
the other measurements proportionately agreeing, the flying young of the 
South-western form reaches this figure, the adult in the first year surpassing 
it, and the full-grown equalling in size the very largest subspecies. Why 
tins anomaly should be is not apparent, the method of distribution being 
apparently via North Australia in each case. The birds travelling down the 
East Coast have become smaller, culminating in the least form in Tasmania, 
while the birds travelling along the North Coast and down the North-west 
have grown larger, culminating in the largest form in the South-west. 
While investigating the forms of this species as outlined {antey p. 340) 
under Th. h. poliocercuSy I was struck by the diversity in coloration of the 
juvenile of some of the subspecies. Series have not been collected so that the 
exact characters of the juvenile cannot be definitely stated, but the difference 
between the juveniles of Th. h. gwendolenoB, Th. h. cristatusy and Th. b. recti- 
rostris seems worthy of remark. I have carefully described the juvenile of the 
first-named, and irrespective of size I note that the juvenile of Th. b. cristatus 
has none of the deep brown coloration there noted, but it is only a light 
brown, the bird having quite a faded appearance in comparison. The 
juvenile of Th. b. rectirostris is about the same size as that of Th. b. cristatuSy 
but the light brown coloration is now lost, ashy-grey predominating, so 
that comparatively speaking this bird looks washed out. The juvenile of 
Th. b. cristatus seems remarkable, as the adult of that form is much darker 
than the adult of Th. h. gweudolenoe. 
351 
