158 The Irish Naturalist Jun6, 



be reared every spring by the ten pairs, there would be no in- 

 crease in the total number, because each year forty old birds 

 would have reached the end of their span of life, and the loss 

 would, therefore, exactly counterbalance the gain. 



I now approach what seems to me the crucial point involved 

 in this question. If I am right in thinking the country is 

 "parcelled out" in the wa}' I have described, it appears to 

 follow that we must have a very large number of non-breeding 

 birds of both sexes, prevented from breeding simply by the 

 fact that they have no suitable ground. Have we any evidence 

 that this large reserve exists ? And if we have, can it be ex- 

 plained on any other h3^pothesis than the one I have 

 suggested ? 



Nearly every standard work on ornithology contains some 

 curious cases of the great facility with which a bird that has 

 been deprived of its mate in the nesting season gets another. 

 Gilbert White tells Pennant that at Selborne he found it use- 

 less trying to check the usurpations of the Sparrows on his 

 House-martins' nests by shooting the offending birds ; for the 

 one which was left, he says, "be it cock or hen, presently 

 procured a mate, and so for several times following." Our 

 great Irish naturalist, Thompson, relates of the Peregrine 

 Falcon in this country, that " if either an old male or female 

 be killed in the breeding season (not, he adds, an uncommon 

 circumstance), another mate is found within a very few days, 

 so that the eyries are sure to turn out their complement of 

 5'oung." Dr. Jenner records how one of a pair of Magpies 

 was shot from a particular nest no less than seven times on 

 consecutive days, but all to no purpose, and the last pair 

 reared their young. A similar story has, I think, been 

 more recently recorded of the Carrion Crow. Darwin was 

 told that Sir John Lubbock's game-keeper had repeatedly 

 shot one of a pair of Jays, and had never failed shortly 

 afterwards to find the survivor re-mated. " I could add," 

 continued Darwin, "analogous cases relating to the Chaffinch, 

 Nightingale, and Redstart.'' The illustrious author of the 

 Oiigin of Species (in whose work on The Descent of Man 

 most of the foregoing examples are circumstantially 

 noticed), then proceeds to quote what I must call the most 

 remarkable instance of the whole remarkable series. He had 

 been informed by his correspondent, Mr. Engleheart, that 



