212 BULLETIN" 196, UNITED STATES NATIONAL MUSEUM 



there is a decided falling off in daytime singing. The early afternoon 

 in particular seems to be a rest period for the thrushes, but as the 

 sun approaches the western horizon singing is gradually renewed, 

 with flight ceremonies at twilight as the culminating feature of the 

 day. 



Song is at its height before and during nest-building early in June. 

 The obvious decrease in song past the middle of the month is coin- 

 cident first with incubation and later into early July, with care of 

 the young. Singing during late June is due at least in part to inter- 

 rupted breeding schedules, with a renewal of singing by males of the 

 unsuccessful nests. At none of the nests studied did the male sing 

 much during incubation or feeding, although before the nest was 

 built, or if it was broken up, the nest site was the chosen location for 

 song. Singing is renewed early in July at the end of the nesting cycle, 

 regardless of whether the young are safely fledged. Such a recurrence 

 of singing suggests renesting, but in only one case was a second nest 

 found. This short July revival of song then abruptly wanes into 

 almost complete silence late in July and in August. 



Another feature of special interest in relation to song is the occur- 

 rence of singing among the females. At most of the nests under close 

 observation the sitting bird was known to sing on the nest occasionally 

 during incubation, hatching, and brooding. In one case the incubat- 

 ing bird stood up in the nest and sang repeatedly in broad daylight 

 while an egg was hatching, but otherwise the singing was confined 

 largely to the morning or evening hours. Nests were watched at all 

 hours of the day and during every stage of the nesting cycle, and in 

 all cases incubation and brooding seemed to be entirely the work of 

 one bird, the female, without any substitution on the part of the male. 

 The male often visited the nest and occasionally inspected the eggs, 

 if the female was away, but was never known to sit on the eggs or 

 brood the young. The female song does not differ materially from 

 that of the male, except that it seemed to be of an inferior quality, 

 and was usually, though not without exception, hoarse, thin, and 

 weak. 



The most characteristic call note of Bicknell's thrush is a harsh, 

 penetrating, slurred whistle, similar to but harsher and higher- 

 pitched than the familiar when of the veery. At times it approaches 

 the sharply whistled call of the red-winged blackbird. Most other 

 call notes are modifications of the typical one, adapted to express a 

 variety of moods: high and piercing when used as a scolding or alarm 

 note, lowered to an inquisitive pe-irt when used to express curiosity, 

 or warbled more or less musically when the adults are at the nest. 

 The female in particular often chirps and warbles to herself while 

 nest-building, incubating, and brooding. And the parents seem to 



