34 ZOOLOGY DIEECTIONS 



plants, has been the wind, by whose action seeds of dandelion, 

 thistle, maples, elms and of many other kinds of plants have been 

 introdnced. Animals like dogs, horses and men have scattered 

 the seeds of bnrs and other fruits which cling to the body or 

 clothing. Squirrels and jays have buried many kinds of nuts, 

 some of which have germinated. Birds and other animals have 

 eaten the seeds of fruits which pass through the digestive tract 

 uninjured. In this present study attention will be directed to 

 the last of these agencies only. 



3. Because of their greater range of movement and prefer- 

 ence for fruit diet, birds have greater influence in distributing 

 seeds than any other group of animals. The stomach contents 

 of thousands of birds have been examined by experts and show 

 that some fruits are favorite foods of many different species of 

 birds. Thus elderberries have been found in the stomach of 67 

 different species of birds, raspberries and blackberries in 60 spe- 

 cies ; mulberries in 48 species ; dogwood in 47 species ; nonpoison- 

 ous sumachs in 44 species ; wild cherries in 39 species ; blueber- 

 ries in 37 species; wild grapes in 29 species; pokeberries in 26 

 species; Virginia creeper in 25 species; juniper in 25 species; 

 strawberries in 16 species; hackberries in 15 species; haws in 12 

 species; hose hips in 11 species; gooseberries and currants in 

 10 species. 



4. Fruits are carried to nestling birds even in species the 

 adults of which do not ordinarily eat fruits. 



5. Not all seeds are capable of bird dispersal. A pulp at- 

 tractive to the birds as food must be present, then if the seeds 

 are small enough they will be swallowed along with the pulp. If 

 the seeds are provided with hard or tough seed coats at least 

 some will escape crushing in the gizzard and pass out along with 

 the excrement. 



6. The undergrowth of this forest is largely cut out each 

 year. 



7. Large flocks of blackbirds usually roost in this forestry 

 in the spring and fall. 



