48 BRITISH BIRDS. 



It shows the left ovary and its duct functional and 

 develoiDing ova, and it retains remains of the right ovary, 

 which is reduced to one half the size of the left one. 

 d* A second year's bird. Differs from c. in being a little 

 more striped below, and with the streaks becoming 

 drop-shaped towards the tip 

 of the feathers. Ovaries as in 

 c, but it shows also remains 

 of the right oviduct, in the 

 shape of a band from the ovary 

 to the cloaca (see figure), 

 e.* This appears 3'ounger than d., 

 and was probably a " last 

 year's" bird. Crown of a 

 dark £^reyish-broA^ n with an ^ . , „ , , . 



. ^ J Ovaries of Falco vespertmus, 



admixture 01 rusty-red and specimen rf, May, 5th, 1908. 



black shaft-streaks; mantle (Exactly natural size.) 



brownish-grey, with the feathers edged with rusty-red or 

 greyish- white ; some feathers recently moulted are ashy- 

 gre3^ barred with darker grey ; four outside tail- 

 feathers with large reddish- white spots, and the four 

 central ones (recently moulted) blackish, barred with 

 ashy-grey ; below it is of a cream-colour, washed with 

 light reddish on the breast, and much paler on the 

 rest ; breast, abdomen, and flanks with blackish stripes 

 and spots larger than in d. Ovaries as in d., but the 

 right oviduct is almost as wide as the left one. 



Kestrel {F. tinnunculus). Out of six female specimens : — 

 a. Immature, March 3rd, 1890. Both ovaries well de- 

 veloped and nearly equal in size. 

 h. Adult, October 6th, 1899. Shows remains of the right 

 ovary, which is reduced to about two-thirds of the size 

 of the left one. 



Short-eared Owl {Asio accipitrinus) . Out of five female 

 specimens : — 

 a. Adult, May 27th, 1892. The right ovary is present, 

 but atrophied, being about half the size of the left one. 



Rook {Corvus frugilegus). Out of six female specimens : — 

 a. Adult, December 10th, 1893. Both ovaries present, 

 but the right one less developed, and containing 

 very small ova. 



* 6. c. d. and e. were obtained on May 5th, 1908, from a flock of 

 several other specimens of both sexes ; two more adult females were 

 secured, but they showed only single left ovaries. 



