NATURAL HISTORY OF THE SWAINSON'S WARBLER 71 



Table 4. — Number of songs per 15-minute interval of a territorial male 



Swainson's Warbler 



[Observation made 3 June 1966, at Dismal Swamp, Nansemond County, Va. Sunrise 

 about 4:44 a.m., sunset about 7:28 p.m.; sunny most of day; first song at 4:27 a.m.; 

 sang until 6:45 p.m. previous evening. Data from Meanley, Wilson Bulletin, 1968, p, 76] 



Songs in 15-minute period ending at 



15 30 45 60 Total songs Temperature 



Hour beginning at 



min. 



min. 



min. 



min. 



in hour 



in woods 

 (° F.) 



4 a.m. 



0 



27 



84 



75 



186 



42 



5 a.m 



61 



33 



50 



48 



192 



47 



6 a.m 



. 52 



51 



44 



47 



194 



51 



7 a.m 



54 



53 



48 



43 



198 



52 



8 a.m 



38 



47 



35 



35 



155 



59 



9 a.m 



24 



23 



29 



0 



76 



61 





0 



0 



0 



0 



0 



87 



11 a.m 



0 



0 



0 



0 



0 



67 



12 noon 



0 



0 



0 



0 



0 



69 



1 p.m 



0 



0 



1 



0 



1 



68 



2 p.m. 



0 



25 



7 



3 



35 



70 



3 p.m 



_ 8 



21 



12 



31 



72 



70 



4 p.m. 



21 



1 



20 



17 



59 



69 



5 p.m. 



0 



0 



0 



0 



0 



62 



6 p.m 



0 



0 



0 



0 



0 



60 



7 p.m. 



... 0 



0 



0 



0 



0 



65 



Total in day . 











_-l,168 





Cadence of delivery 



As pointed out by Reynard (1963, p. 139), an additional fea- 

 ture of bird song "unconsciously recognized but not particularly 

 noticed is the cadence of delivery." Reynard defined the cadence 

 of delivery of a song as — 



the average length of time from the first note of a song unit to the first note 

 of the succeeding unit throughout the whole song performance. The period 

 timed includes that in which the song unit is heard and the silent period 

 between song units. 



I recorded cadence of delivery of three territorial males on 

 May 2 in the Dismal Swamp betv^^een 7 and 8 a.m. : the deliveries 

 recorded v^ere 20, 20, and 14. The average cadence for the sample 

 was 13.7 seconds. Reynard (1963, p. 141-142) lists the cadence 



