254 BULLETIN 196, UNITED STATES NATIONAL MUSEUM 



States, but this was more local in its effect, and the birds soon re- 

 covered from it. Dr. Musselman (1939) writes: 



In the seven years that I have been banding and studying Bluebirds through 

 the use of bird-boxes, we have had three severe freezes in April after the majority 

 of the Bluebirds had laid their full quota of eggs. Nearly always I found comple- 

 ments of frozen eggs deserted by the mother. Later, a second grass nest was built 

 directly over the old eggs, then the new mother would begin her nesting activities. 

 Seldom did the original mother return to her old nest. The unfortunate feature 

 about such a catastrophe is not alone the destruction of fifteen hundred to two 

 thousand eggs, but it is the fact that the nesting period is advanced about two 

 weeks. This means that these Bluebird boxes which are very much in demand 

 by several types of birds have eggs in them at the time the House Wren (Tro- 

 glodytes aedon) returns. The number of pierced eggs has been correspondingly 

 large on the years of such freeze. During normal years the baby Bluebirds are 

 in the nest at the time of the wrens' return. Generally they are not molested. 

 On normal years the nesting is so timed that when the first batch of young Blue- 

 birds desert the nest, the House Wrens have already established themselves else- 

 where. When the Bluebirds return later for the second nesting, there is little 

 danger that piercing of the second complement of eggs will take place. 



In addition to the frozen and punctured eggs, he found on several 

 occasions the frozen bodies of the incubating birds where they had 

 died on their nests ; and once two birds were found frozen to death in a 

 single box. 



Field marks. — Bluebirds are so well known and so conspicuously 

 colored that they are easily identified. Even the spotted young have 

 bluish wings and tails. 



Fall. — Dr. Winsor M. Tyler has sent me the following sketch: 

 "Bluebirds are all along the roadsides this morning — a windless, 

 warm, October day. They are gathered sociably in companies of 

 half a dozen or more and keep near together like a big family, one 

 bird following another when it flies. They are quietly musical as they 

 flit about, giving the gentle whit call, the soft chatter, the velvety 

 turwy, and sometimes a phrase of song. It is easy to imagine that 

 the bluebird's song was evolved from a repetition of the whit note, 

 perhaps by way of the turwy; a slight change in the tone of voice, 

 making it mellower, louder, and sweeter, lengthening the notes a little, 

 and there is the song. 



"The birds perch on dead branches, wires, or fence rails, scanning 

 the ground as from observation posts, sitting upright with the tail 

 straight down ; they explore holes in the apple trees, peering in, some- 

 times entering the cavities, calling to one another; they drop to the 

 grass or to the hard, surfaced roadway where they catch up some- 

 thing with a deft peck. The bluebird's shadow at this season, the 

 myrtle warblers, come down to the road, too, and act in the same way. 



"In flight the bluebirds are very charming at this time of year; 

 a leisurely flip of the wing carries them along silently with just enough 



