68 BIRDS OF SWOPE PARK 



According to this estimate, there will average about one 

 and one-half male birds to the acre in the Park. Or, sup- 

 posing that each was mated, there would then be three adult 

 birds to the acre. But since numbers of the birds no doubt 

 escaped notice, we may grant two pairs or four birds to the 

 acre for the Park. Are conditions such that more could be 

 furnished with food and nesting places? What is the limit? 

 What determines the number? These are questions that are 

 difficult to answer. I cannot answer them, but I may venture 

 a few opinions. 



The number of birds found in a certain locality is de- 

 termined by a combination of factors, and the dominant fac- 

 tor may be different in different regions and for different 

 species. 



The alfalfa field and meadow of the Rifle Range in Sec- 

 tion Number 14, one of the most densely bird-populated re- 

 gions in the Park, could well furnish food and nesting places 

 for more birds than were found there. There seemed to be no 

 rivalry or conflict among the Dickcissels themselves, for two 

 males would be sitting only a few feet apart on the wire fence 

 singing happily and seemingly oblivious of each other's pres- 

 ence. Certainly there was shortage in the supply of weed 

 seed or grasshoppers for food. The Meadowlarks and the 

 Field Sparrows seemed to have no dispute concerning food or 

 nest. Why, then, will there not be double the number of Dick- 

 cissels and other birds next year, or at least an increase until 

 the limit has been reached? 



In my opinion, the number of birds in this region of the 

 Park is kept in check by the interference of man; by their 



