MENTAL POWEES OF BIED3. 
285 
length of absence, it is scarcely credible, unless by the merest 
chance, that the same bird can hit off the exact haunt of the 
previous year. The swallows that resort regularly to the same 
nest, or even the thrush that builds always in the same fork, 
or the sparrow in the hole on the housetop, are not necessarily 
the exact tenants of the previous year. Each species gives a 
preference to one sort of situation over another, and the fact 
of seeing an unoccupied nest is, with many birds, an induce- 
ment to appropriate it ; although, no doubt, among the indi- 
genous avi fauna of every country there are generations upon 
generations of rooks and sparrows, for example, that build 
in the same tree. Now, notwithstanding the fact that mated 
birds soon forget one another, there is no reason why they 
should not possess^ as in certain higher animals, a greater 
capacity of memory for places. 
In conclusion, it is apparent from the foregoing that birds 
display emotions of a varied character by well-marked vocal 
utterances and gestures, and that although these and other 
mental qualities are to a great extent instinctive, there are at 
the same time clear indications of reason in many instances. 
We may believe, therefore, that although the intellectual powers 
of birds are generally much inferior to quadrupeds, they show the 
progressive development of their class, as do their organism ; 
and as the corporeal structure is suited for the welfare of the 
species, so the instincts and other mental qualities are developed 
and modified. 
