Ornithology of Borneo. 31 



creased difficulties. 1 have, however, re-examined the Marsh- 

 Harriers in the Museum collection, and I find that a com- 

 parison of measurements between C. spilonotus and arugi- 

 nosus gives the following result : — 



Wing. Tarsus. 



inches. inches. 



C. spilonotus ad 15-5-16-0 3-45-3-6 



„ 2 ad 15-5 3-1 



C <eruginosus ad 15'7-16'1 3*4-3-6 



„ juv 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. aerugi- 

 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. aruginosus. 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. niaillardi; 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 Reunion sjjecies. 



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 ' (I. 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 

 sec at present, there is no gradual change from the M'hite- 



