PROFIT AND LOSS IN THE BIRDS. 197 
yet. While indications of this sort are not by any 
means always reliable, they are often probable, and 
are valuable in confirming other indications. F're- 
quently they can be verified in some lower group or 
in some near relations. 
Thus little water ousels, when chased before they 
ean fly, run and dodge about, but make no attempt to 
dive, although an old one, slightly wing-wounded, 
will dive at once to escape. Now, when we recall 
that this little bird’s ancestry among the wrens and 
thrushes is not at all aquatic, his dry-land tactics will 
be better understood. Only recently has his tribe 
taken to water. 
Something similar appears among the grebes, 
which have kinsfolk landward. Sometimes, as al- 
ready mentioned, the little ones crawl upon the 
-mother’s back, and she swims away from danger with 
them, and, if pressed, puts her wings above them 
and forces them to dive. Now they can dive as well, 
or better, than she, but it seems strange that they 
have not yet the instinct to do it at once at the dan- 
ger signal, but prefer to scatter and hide in the reeds 
and grass, like their landward cousins, the fowl forms. 
See diagram of kinships in the next chapter. 
In this diagram it will be noted that the hoactzin 
stands as a connecting link between some fowl forms 
on one side and the gallinules, leading to some very 
aquatic kinsfolks, on the other. There is a little habit 
that hints that their ancestors were once more aquatic, 
for, while the adult birds avoid the water, they build 
their nests over it; and should the young, in trying 
