SYMPOSIUM OX COXSERVATIOX 45 



various future policies necessary to this end, but I must pass it 

 now with the general remark that the most important measures 

 which should be taken at the present time are. in my judgment, 

 the protection of our waters against injurious contaminations, 

 especially from gas works and certain kinds of manufactories; 

 and the preservation, intelligent care, and complete control of 

 selected breeding grounds and feeding grounds of our most im- 

 portant fishes, to be acquired, held, and developed as permanent 

 reservations by the State. The State Fish Commission has, in 

 fact, made a beginning in this direction, and has lately secured 

 a long-time lease of Matanzas Lake, in the Illinois bottoms, which 

 it is preparing to use as a breeding station. It also seeks to main- 

 tain the supply of our more desirable fishes by hatchery opera- 

 tions, and by collecting young fishes from isolated overflow ponds 

 and returning them to waters in which they can survive. 



Whether the insectivorous birds of the State are of sufficient 

 importance to be taken into serious account in cataloging our 

 economic resources, is a question which can not be answered with 

 the definiteness and precision which we are accustomed to expect 

 as the outcome of anything worthy to be called strictly scientific 

 investigation. The value of the services of birds depends upon 

 the kinds of their food and the ratios of its various elements ; 

 upon the variations in their food and feeding habits as coordinated 

 with differences of season, geographical situation, and ecological 

 circumstance : upon the amounts of food eaten by birds of various 

 species at various ages and under the various conditions of their 

 activities: and upon the numbers of the various kinds of birds 

 engaged in the economic services with which they are to be cred- 

 ited. The problem of the food of any bird is thus highly complex, 

 and its primary data are so variable that even final conclusions, 

 however broadly based, must be put in the form of approximate 

 estimates and contingent probabilities, amounting to scarcely more 

 than expressions of an enlightened personal judgment. 



The quantities of food taken by birds, young and old, can not 

 well be stated in terms of definite values, or masses, or numbers 

 of individual objects eaten. Xevertheless. accumulated observa- 

 tions, continuous for days at a time, on the activities of parent 

 birds of various species in feeding their young, furnish conclusive 

 evidence of the fact that a family of nestlings may devour and 

 assimilate a truly surprising amount of insect food : and the rapid- 

 ity of growth and the high rate of physiological activity of birds 

 as a class give theoretical support to statements which might 



