TREE SWALLOW 389 



Burleigh (1930) found a nest "ten feet from the ground in a cavity in 

 an old rotten willow stub in underbrush bordering a stream, * * * 

 built entirely of large chicken feathers." 



The tree swallow commonly nests in isolated pairs, showing none 

 of the strictly communal habits of the purple martin and the cliff 

 swallow, but the birds are frequently found nesting in groups, their 

 nests scattered about, not far apart, in favorable feeding localities. 

 Ralph Works Chaney (1910) speaks of such a case in Michigan. He 

 says: "Large colonies of these swallows nested in cavities of dead 

 stumps which projected out of the lake." Charles L. Whittle (1926) 

 sums up an investigation on the distribution of nests by concluding 

 that "the determining factor is the adequacy of a nearby feeding 

 area, or areas, be they meadows (old, filled lakes), marshes or w^ater, 

 to furnish the necessary quantity of food for the young at the 

 requisite period." 



The female bird builds the nest, aided little or none at all by her 

 mate. Winton Weydemeyer (1934b) says: "Although the male often 

 makes a pretense at gathering straws, and occasionally carries feath- 

 ers to the nest, his principal job is that of overseer. * * * Only 

 occasionally do the male birds share the task of incubating the eggs; 

 frequently — especially during days when few insects are in the air — 

 they carry food to their mates in the nests. Generally, however, 

 (he females during the day leave their eggs long enough to secure 

 food for themselves." Both parents feed the young and remove 

 excreta from the nest, dropping the sacs from the air a few yards 

 away. 



Winton Weydemeyer (1934b) states: "As a rule, at no time during 

 the entire season do the males share the houses at night. * * * 

 Frequently the males perch on the houses for an hour or more after 

 their mates have retired, not leaving for their own sleeping places 

 until after darkness has settled." The same observer (1935) reports 

 from Montana : "In the case of sixty nests a full record has been 

 obtained of the percentage of hatch and survival of the nestlings." 

 The latter shows 94.7 per cent for the first brood and 84.6 for the 

 second brood. Austin and Low (1932) calculate a reproductive 

 efficiency of 56.5 percent from 278 eggs. 



Eggs. — [Author's note: The tree swallow usually lays four to 

 six eggs; as many as 10 have been found in a nest, but any over five 

 or six eggs may be the product of two females. The eggs vary from 

 ovate, the usual shape, to elliptical-ovate or, rarely, elongate-ovate. 

 They are pure white, unmarked, and usually without gloss. The 

 measurements of 50 eggs average 18.7 by 13.2 millimeters; the eggs 

 showing the four extremes measure 20.3 by 13.5, 19.3 by 13.7, 16.8 

 by 13.2, and 17.8 by 12.7 millimeters.] 



324726—42 26 



