SWALLOWS. 27 



food, migrate m great numbers, and then are preyed upon by swal- 

 lows, flycatchers, and other birds. The destructive cotton boll weevil 

 is more or less active during the late summer and early fall months, 

 and it has been learned that the swallows, as they pass through the 

 cotton States on their way to their southern winter quarters, catch 

 great numbers of them on the wing and so perform an exceedingly 

 important service. Engraver beetles (Scolytidae) have frequently 

 been found in the stomachs of swallows. These insects live under 

 bark, and generally are inaccessible to birds, except woodpeckers; 

 periodically they migi-ate from the tree where hatched and matured 

 to search for fresh pastures; at such times they are unprotected and 

 fall easy prey to any fly-catching bird. Swallows are peculiarly 

 adapted to capturing small insects in mid-air. While their bills are 

 weak their mouths are wide, and their long wings enable them to fly 

 swiftly and turn quickly, so that they sweep back and forth through 

 a swarm of insects and gather them b}?^ hundreds. 



Seven species of swallows, with several subspecies, are commonly 

 found within the limits of the United States. Their food habits 

 vary but little. All seven species occur in California, and this num- 

 ber includes one, the violet-green, that does not occur in the East. 



Besides the swallows whose food will be discussed in detail in the 

 following pages, a few stomachs of the tree swallow {Iridoprocne 

 hicolor)^ the w^estern martin {Progne siihis hesperia), and the bank 

 swallow {Riparia riparia) have been examined, but the number is 

 entirely too small to be used as a basis for general conclusions were 

 it not for the fact that their contents agree in all essential points 

 with those of the other swallows, of which a greater number were 

 available for examination. In fact, it may be said of all the members 

 of the swallow family that they subsist upon practically the same 

 kind of food, with slight variation from month to month. It may 

 be laid down as a general rule that the food of all American SA\al- 

 lows is derived from the following orders of insects: Coleoptera, 

 Hymenoptera, Hemiptera, and Dij)tera, with a few individuals from 

 one or two other orders, and an occasional spider. So far as present 

 investigation has shown, 90 percent of their animal food is from the 

 four orders named above, but the relative proportion of each varies 

 somewhat Avith the different species and seasons. AVith one notable 

 exception ''^ the swallows take so little vegetable food that it may be 

 passed by as a negligible quantity, and much even of the little eaten 

 is probably swallowed accidentally. 



After the above statements in relation to the food of the swallows, 

 it is ])erhaps imnecessary to dwell upon the great value of these birds 



oThe tree swallow of the East {Iritlopmrnc hicolor) <luring its southern 

 migration freely eats the berries of tlie bay-berry (Myricu carolincnsis). 



