Ornithology of Borneo. - } 31 
creased difficulties. I have, however, re-examined the Marsh- 
Harriers in the Museum collection, and I find that a com- 
parison of measurements between C. spilonotus and e@erugi- 
nosus gives the following result :— 
Wing. Tarsus. 
inches. inches. 
Ce SPUR ORNS BOF ip ce ends oe ae oss 15:5-16:0 3°45-3'6 
- a tr ok asthe seat 155 31 
OS TE a eee een 15°7-16:1 3'4-3°6 
+ Ae aisrecighhe atc permet 15°45-16°8 3°35-3'6 
As undoubtedly adult specimens of both species are here. 
measured, it is evident that dimensions will not help much in 
the determination of the species, and although in their adult 
stages they are widely different, in their young plumages they 
are scarcely distinguishable: if this supposition be correct, 
the chances are that the bird identified by me as C. erugi- 
nosus from the Philippines, on the authority of which Lord 
Walden included the species as an inhabitant of that archi- 
pelago, is really nothing but the young of C. spilonotus ; and 
in this case it is possible that some of the young Harriers 
from China and Formosa belong to the latter bird and not to 
C. eruginosus. The fact is, that the plumages of the Philip- 
pine-Islands bird have never been properly worked out; and 
until this has been done, it is impossible to do more than 
guess at the truth. We may, however, learn something by 
analogy from its nearest ally, C. maillardi; and as it is now 
pretty clear that this species has at least three very distinct 
plumages, so we may fairly credit C. spilonotus with a brown 
immature dress, as in the Réunion species. 
The male of C. spilonotus is a very handsome bird with 
white under surface and black-streaked breast. The plumage 
of the female is probably correctly described in the ‘ Cata- 
logue’ (J. c.) ; and that the young male also goes through a 
stage very similar to’the old female, is pretty clear from the 
remains of such moultings on the maturing birds: both wing 
and tail are barred; and it is evident that these bars are gra- 
dually dissolved as the bird becomes adult. As far as I can 
see at present, there is no gradual change from the white- 


