on the Yellow-rumped Finch. 197


me three specimens, two of which resembled figure 2, but the

third has gone a stage further in the direction of the assumption

of the plumage of M. castaneithorax, and is illustrated in figure

3 of the accompanying plate. As will be seen, the throat has

darkened very considerably, the pectoral band has commenced

to develop and there is a dark spot on the flank.


Now as to the cause of this abnormal state of colour-

ing. Mr. Teschemaker believes that these birds are hybrids

(page 117) and at first this would appear to be a very reasonable

solution of the puzzle, but there is one great difficulty in

accepting this theory. Most of the smaller Passerine birds

assume their adult plumage at a fairly early age. In the case

of M. castaneithorax Mr. Teschemaker tells us that a young bird,

at six weeks old was "showing already the chestnut breast"

though it was slow in assuming the complete adult plumage.

At four months old it was not quite in the mature stage of dress

though nearly so, but. although he does not tell us so, it would

be pretty safe to assume that at six months of age it would be

indistinguishable from its parents. A somewhat shorter period

seems to elapse between the time of hatching and the assumption

of the adult plumage in M. flaviprymna.


It would seem to be reasonable therefore to suppose that

hybrids between these two species would assume their adult

plumage, in which traces of the parentage on both sides would

be shown, at six months of age or less. With the specimens now

under consideration however no trace of the characteristic

markings of M. castaneithorax made an appearance until the

birds were from two to three years of age, before which they

were absolutely typical examples of M. flaviprymna. I am

■greatly hoping that Mr. Teschemaker, who is so very successful

in breeding Australian finches, will, during the present season

produce some hybrids between these two species which would

throw considerable light on this subject. If he does so I

prophesy that they will closely resemble figs. 2 and 3 in the

.accompanying plate, but they will assume this plumage when

from four to six months of age.


My own theory is that M. flaviprymna is merely a desert

form of M. castaneithorax which, to fit it for its desert life has



