2o6 Sparrow-Hawk 



breed until their fourth or fifth year * when they have acquired 

 the full plumage. 



It would be interesting to know why the Sparrow-Hawk has- 

 developed this precocious habit, and what has led up to it ; for it 

 seems certain that the maturity of the plumage, and the maturity 

 of the sexual organs are meant to run side by side in birds, as in 

 other animals. 



Number i female in Table II, which was trapped at the remains 

 of a female Partridge she had just killed, was certainly a bird of the 

 previous year's hatching, being then, April 13th, about ten months 

 old. I dissected this bird myself and made the following note : 

 " Right and left ovaries well-developed, with numerous good-sized 

 ova in both ; would certainly have bred this season, though it was 

 only a bird of last year." 



That raises another point of some importance, though it has no 

 direct connection with the subject of this paper ; namely, the 

 frequency with which the right as well as the left ovary is found to 

 persist in certain members of this familv (Falconidae), especially 

 the Sparrow-Hawk, Kestrel and all the Harriers. Out of twenty 

 consecutive female Sparrow-Hawks examined, fourteen had paired 

 ovaries. Mr. Gunn published a valuable paper on this subject in 

 the Proceedings of the Zoological Society, March, 1912. A great 

 deal of his material was obtained from the specimens now in my 

 collection. 



Finally, an examination of the three broods of nestling Sparrow- 

 Hawks reveals a very remarkable excess of females over males, f 

 There are, in all, sixteen nestlings, and of these, kaelve were females, 

 and only four males, or three females to every male. My small 

 series of sixteen chicks is too small to base any very definite 

 conclusions on, but while the proportion of one to three may very 

 easily be too high, I think it probable that in a large series of nestlings 

 the females would be found to outnumber the males very largely. 

 The reason for this excess, if it exists, is not very obvious. With a 

 polygamous bird, like a Pheasant or Black-cock, a preponderance 

 of females might conceivably be beneficial to the species, but the 

 Sparrow-Hawk is monogamous ; it would theoretically serve the 

 species best that the sexes of the young should be as nearly even as 

 possible. 



* See footnote on p. 23. — Editor. 



+ (i) May 28, 1913 5 very small nestlings, 2 males & 3 females 



(2) July 4, 1913 5 half-f^rown nestlings, i male & 4 females 



(3) July 7, Hjoo 6 three-tjuarter-grown nestlings, i male & 5 females- 



[Table IL 



