EASTERN BLUEBIRD 253 



were too much for the bluebirds to resist; fortunately, the sparrow- 

 population is not so formidable as it once was, since its numbers have 

 declined some. But the introduction of the starling gave the bluebirds 

 another setback; these large, powerful birds can easily drive out the 

 bluebirds and occupy any of the larger cavities; many old apple 

 orchards that formerly housed bluebirds are now preempted by 

 starlings. Bluebirds are safe from these intruders, however, in many 

 of the properly constructed bird boxes; if the entrance hole is not over 

 1% inches in diameter the starling cannot enter; but a 1%-inch hole 

 might allow the starling to use the box. 



Bluebirds are generally able to contend with tree swallows, to drive 

 them out or to defend their homes against them. A housing feud 

 between these two species is mentioned above, under "Behavior." 

 Flying squirrels, deer mice, and even bumble bees have been known 

 to appropriate suitable cavities for bluebirds. 



Harold S. Peters (1936) lists two species of lice, one fly, and two 

 species of mites as external parasites of the eastern bluebird. Doubt- 

 less there are other forms of vermin that infest the nests. 



I have left until the last the bluebirds' most formidable enemy, 

 Jack Frost, the agency that has destroyed more of them than all 

 other enemies put together; countless thousands have succumbed to 

 extreme cold, snowstorms, and cold, ice-forming rainstorms. Blue- 

 birds seem to be very vulnerable to these elements in winter and even 

 in spring. The most notable of these catastrophes occurred during 

 the winter of 1894-95, the season of the "big freeze" in the Southern 

 States. Amos W. Butler (1898) describes the event as follows: 



The weather was warm until after Christmas. December 27 and 28 it became 

 quite cold in this latitude [Indiana]. The Bluebirds were forced farther southward 

 beyond the limits of the severe weather. There it remained warm until late in 

 January. On the 24th of that month the temperature as far south as South 

 Carolina remained near the zero mark. It turned warmer that night and the 

 next day, January 25, the weather was bright and clear. The day following was 

 Friday. It rained, then snowed; the wind came down from the northwest 

 with great velocity and the temperature fell rapidly. Everything was ice-bound 

 or snow-bound to the Gulf of Mexico. Then followed weeks of unusual severity. 

 By the end of the severe weather in April, it is said, but few Robins or Bluebirds 

 could be found. The destruction of bird life must have been enormous. The 

 Bluebirds seem to have been almost exterminated. Few, indeed, returned to 

 their breeding grounds in the north and from many localities none were reported 

 in the spring of 1895. 



Bluebirds began to increase slowly during the next few years, but it 

 was five or ten years later before they seemed to have reached normal 

 numbers. A lesser reduction in their numbers in the East occurred 

 as a result of the very cold winter of 1911-12 in the Southeastern 



