Note 29 — Chapter XVIII · ON THE ADVANTAGES AND DISADVANTAGES OF CHANGED CONDITIONS OF LIFE: STERILITY FROM VARIOUS CAUSES.
Reading edition
A list of the species of birds which have bred in the Zoological Gardens from 1848 to 1867 inclusive has been published by Mr. Sclater in ‘Proc. Zoolog. Soc.,’ 1869, p. 626, since the first edition of this work appeared. Of Columbæ 51 species have been kept, and of Anseres 80 species, and in both these families 1 species in 2·6 have bred at least once in the 20 years. Of Gallinæ 83 species have been kept and 1 in 27 have bred; of 57 Grallæ 1 in 9 have bred; of 110 Prehensores 1 in 22 have bred; of 178 Passeres 1 in 25·4 have bred; of 94 Accipitres 1 in 47 have bred; of 25 Picariæ and of 35 Herodiones not one species in either group has bred.