32 ARKIV FÖR ZOOLOGI. BAND 14. N:0 25. 



development, but become with increasing age more and more 

 obsolete and cease finally completely for the pattern of the 

 adiilt. In a similar way the tail-coverts of the young birds 

 have a banded pattern, but those of the adult are pure white. 



The general pattern of Milvago chimango agrees on the 

 Avhole with that of the young /. carunculatus. On the tail- 

 feathers the banded pattern is retained, although to a certain 

 extent specialised. In a similar way the small upper tail- 

 coverts are transversely banded. It seems probable that M. 

 chimango in this respect has retained characters, which, be- 

 cause they appear in the juvenile stages of a species, which 

 in adult plumage is so greatly different as /. carunculatus, 

 must have been characteiistic to the primitive Polyborinae. 

 In the genus Polyborus itself the pattern of the plumage has 

 reached rather far in specialisation, but nevertheless the pat- 

 tern of the tail is still rather primitive. With the exception of 

 the broad black apical band the tail is light with dark cross- 

 bars, as also is the case with the upper tail-coverts of P. cheri- 

 ivay. We are inclined to consider that among the Polyborinae 

 mentioned Milvago is with regard to the pattern of the plumage 

 the most gener alised, while Polyborus and I by eter represent more 

 advanced stages. Among the latter there are in the pattern 

 of the adult more primitive features retained in Polyborus 

 t han in I by eter. 



Salvadori & Festa have (Boll. Mus. ZooL, Torino 1900) 

 made some short remarks about the plumage of the young 

 birds of this species, which, however, seemed to deserve to be 

 made more complete by our description above. 



Circus cinereus Vieill. — Adult males: ^76' Pichincha 

 above Lloa, 11000 f.; ^^^ & ^'U, M:t Corazon, 12000 f.; ^'U, 

 northern slopes of Iliniza, 10000 f. Adult females: 7io ^ ^7i25 

 Pichincha, 11000—11500 f.; ^V^ & «7e, Iliniza 11000 f.; ^7^, 

 Romerillos E. of Iliniza same altitude; 74 ^ "/s^ Corazon, 

 11000 f.; 7, north of Cotopaxi, 12000 f. A young male in 

 moult to adult plumage, ^7i25 Romerillos. A female in tran- 

 sition-plumage ^74' Zambiza, 8000 f.; young males ^72 ^ ^°U 

 the same locality 7500 — 8500 f.; young females ^j^, east of 

 Iliniza, 11000 f.; Vjq. Pichincha 12000 f.; 7^, Corazon, '73, 

 Mindo, 5000 f. & one 79 ^^ certain locality. 



This beautiful series displays in an interesting manner 



