No. 4.] BIRDS AND CATERPILLARS. 319 



pillars situated in a locality where many species of birds 

 are likely to find it. The observer first makes sure as to the 

 kind of insects to be found upon the trees or plants to be 

 watched. He then conceals himself near the insects whose 

 destruction he wishes to observe and watches the birds which 

 come there to feed. 



When this method is followed methodically by trustworthy, 

 painstaking observers, and when results obtained by different 

 observers, working independently, agree in the main, there 

 can be no reasonable doubt as to the value of such obser- 

 vations. When the caterpillars are small, certain marked 

 branches are chosen for observation, or certain nests, webs 

 or tents are marked and watched at close range. One ob- 

 server has even counted the number of caterpillars on a 

 branch, watched the birds feed upon them and then counted 

 the number left alive. 



The results of the earlier observations were published in 

 the report on the gypsy moth issued by the State Board of 

 Agriculture in 1896.* It w^as then proved conclusively that 

 thirtj'-eight species of birds were destroying the gypsy moth 

 in one or more of its forms, and thirty-one of these were 

 feeding on the caterpillars. Since that time several birds 

 have been added to the list, and much more has been learned 

 as to the comparative usefulness in this respect of several 

 species. 



The discovery of another introduced pest, the brown-tail 

 moth (^Euproctis chrysorrhoea), in Massachusetts in 1897, 

 has stimulated further observation, and incidentally the feed- 

 ing of birds on other hairy caterpillars has been noticed. 



It is not the intention of the writer now to republish the 

 result of the observations given in the report on the gypsy 

 moth in 1896, but to place before the reader some facts 

 observed that year and since. From the mass of observa- 

 tions on the food of birds a part has been selected of those 

 M^hich refer to the two introduced European species — the 

 gypsy moth {Portlietria dUpar) and the brown-tail moth 

 (^Euproctis chrysorrhoea) — and two common American pests, 

 — the tent caterpillar (Clisiocampa americana) and the forest 

 tent caterpillar (C. sylvaiica). In these four species we 



* " The Gypsy Moth," Forbush-Fernald, 1896. 



