NORTH AMERICAN GREBES. a 
among the growths of aquatic vegetation, so that until they are at 
least two-thirds grown it is difficult to observe them. After the 
_ young are well grown, the adults disappear for a time in order to 
molt, resorting for the purpose to dense growths of rushes, where 
_ they remain in seclusion for a period of three or four weeks. Like 
_ ducks and geese, they shed all the wing feathers simultaneously 
- and are then unable to fly. 
ECONOMIC RELATIONS. 
The food of the grebes, as would be expected, is made up largely 
of aquatic organisms belonging to a variety of groups. Of these, 
_ fishes are perhaps of greatest importance in establishing the economic 
status of these peculiar birds. The western and Holboell grebes, 
the largest of the six forms of the family found within our limits, 
_ take more fishes than do the smaller species, but on the whole they 
- can not be considered actually injurious, as the kinds eaten are in 
most cases of little or no value to man. 
| From the basis of the present studies it can not be said that any 
_ species of grebe is directly inimical to the fishing industry. Grebes 
which alight during migration in ponds at fish hatcheries may do 
serious damage, and in such places it is advisable to drive them away 
_ or destroy them if Federal and State laws permit.? This stricture 
applies in the main, however, to only one species, the pied-billed 
grebe, as only occasionally do the other forms appear in such locali- 
ties. ‘The sacrifice of the few pied-billed grebes which it may be 
necessary to kill for this reason can have little or no effect upon the 
abundance of these widely distributed birds. 
_ With the exception of the large western grebe (which so far as 
_ known at present feeds only upon fishes), all of our grebes feed 
_ extensively upon crustaceans, and when more material is available 
_ for study it is possible that this species also may be found to eat 
this kind of food. The Holboell grebe takes many marine crusta- 
eeans, as do the horned and eared grebes. The two last mentioned 
_and the pied-billed grebe destroy also many crawfishes. The feeding 
of the pied-billed grebe is especially beneficial in this manner in 
localities where crawfishes are destructive to crops. 
Aquatic Coleoptera (beetles) and Heteroptera (bugs) figure 
largely in the food of the smaller grebes, and that of the pied- 
billed grebe shows that the birds prey extensively upon giant water- 
bugs and predacious water beetles, insects that are reputed to be 
_ seriously destructive at times to the small fry of fishes. Eared 
and horned grebes in summer often act the part of scavenger in 
_ feeding upon the masses of miscellaneous insects found floating on 
the water. During the flights that occur as these forms emerge in 
the adult state, frequently bays and ponds are covered with the 
bodies of such of these creatures as have attempted to alight, only 
to be entrapped by the water and drowned. From this source 
these grebes secure a greatly varied insect fare, but one, however, of 
no particular economic significance. 
*For a summary of the provisions of Federal, State, and Provincial game laws, see 
_ the latest annual Farmers’ Bulletin on the subject (that for the season 1923-24, Farmers 
_ Bulletin No. 1375, U. S. Department of Agriculture). 
