4. Experimentation is affording data as to the amount, kind, and 

 preference of food, and to the time of digestion. 



5. Field investigation is furnishing evidence as to the depredations 

 of birds, their general habits and abundance, and their value in main- 

 taining a natural equilibrium of insect life. 



6. Investigations which have been undertaken to determine the rela- 

 tion of birds to insect outbreaks are demonstrating the economic value 

 of birds at such times. 



7. A comparison of all the helpful qualities of a bird with all of its 

 qualities injurious to the welfare of mankind is affording a dependable 

 criterion of its economic status. 



Next to the knowledge of the food of a bird in determining its 

 economic status, is a knowledge of the habits of a bird. Its abundance, 

 feeding habits, nesting habits, food preferences, its depredations, etc., 

 are all factors that must be considered. Evidence along this line can 

 be afforded only by field investigation. 



The field work carried on thus far can be grouped under three heads: 

 studies of the abundance, feeding habits, nesting habits, etc. ; studies 

 of the food of birds ; and studies of the relation of birds to insect out- 

 breaks. 



STUDIES OF THE ABUNDANCE, FEEDING HABITS, NESTING HABITS, ETC., 



OF BIRDS. 



A month's time has been spent at Lathrop, San Joaquin County, Cali- 

 fornia, studying the abundance, feeding habits, nesting habits, depreda- 

 tions, etc., of birds, especial attention being given to the meadowlark 

 and blackbird. This particular locality was chosen because it afforded 

 not only an abundance of birds, but also a favorable proportion of culti- 

 vated and uncultivated land, thus allowing a study of food preference. 



Censuses and studies of the rate of reproduction have been carried on 

 to ascertain the relative abundance. Work in the spring of 1911 and 

 1912 substantiated the fact that meadowlarks. Brewer blackbirds, and 

 red-winged blackbirds usually nest twice each } r ear. 



The average brood of the meadowlark is four, although the number 

 of eggs laid is usually five. Second nestings examined have usually 

 showed an incomplete set of* eggs. A preference for pasture land for 

 nesting sites was shown, at least 86 per cent of these found being so situ- 

 ated. The time of incubation was found to be fourteen to sixteen days. 

 The young stay in the nest but a short time (eight to ten days). Nest- 

 lings are subject to many enemies, such as the skunk, weasel, mice, and 

 hawks, and the number of broods successfully reared is less than that 

 of most other birds. That over 15 per cent of the nests in most localities 

 are destroyed by predaceous animals and birds seems a very conserva- 

 tive estimate. 



These facts have an important bearing on the economic relations of 

 the meadowlark. Their particular habitat influences the amount of 

 damage done, due to the locality in which they are found. Their rate 



