560 Mr, G. L. Bates on the Breeding-Seasons 



vvitli eggs or young, and the times at which conspicuous 

 breeding-plumages were seen in such birds as Pyromelana. 

 These records I have now tabulated, under the months of 

 the year, for about a hundred species — those for which 

 the greatest number of observations were made. From 

 these tables 1 have drawn the summaries and conclusions 

 which follow. 



Evidences of Breeding. 



In drawing conclusions as to the breeding-season from the 

 condition of the sex-organs, it is assumed that in the 

 male the testes are enlarged only at the period of breeding. 

 This enlargement may last during all the courting, nesting, 

 and incubating period, but surely ceases after the brood is 

 reared, unless preparations are made immediately for 

 another brood. In birds of certain families the size of these 

 organs seems to vary little. This is true in the Accipitres, 

 in the Woodpeckers, and in many other Picarian birds. 

 Extremely small testes have been found generally only in 

 birds shewing by their plumage, colour of bill, tender skin 

 and bones, or otherwise, that they were young. In many 

 species in this country (to be noted later) these organs 

 seem never again to become small after maturity is reached. 

 "Winter migrants from the north have the sex-organs more 

 reduced than adult resident birds are often found to have. 



So, also, in female birds, the condition in which the 

 ovaries are small and thin and hard to see is not often 

 met with except in birds shewing signs of immaturity, and 

 in winter-migrants from the north. Generally there may 

 be seen small ova of various sizes. The growth of the ova 

 must be slow, and they are probably present for a con- 

 siderable period. The absorption of those which are not 

 fertilized takes place, too, rather slowly, for ova are found 

 in the bodies of sitting females, and even of mother birds 

 after the brood has been hatched out. The most exact 

 indication of the laying period, except the presence of large 

 ova or a full-sized egg, is the enlarged oviduct. The 

 presence of the empty sheaths or sacs of the ova, after 



