1478 U.S. NATIONAL MUSEUM BULLETIN 237 part 3 



spotted, blotched, clouded, and frequently marked with scrawls of 

 reddish browns such as "Verona brown," 'Trout's brown," "Brussels 

 brown," or "Argus brown," with undermarkings of "pale neutral 

 gray." They vary considerably, but are generally boldly marked, 

 and practically indistinguishable from those of the song sparrow, 

 except in a series it is noticeable that the blotchings and cloudings are 

 heavier; also they are frequently marked with clouded scrawls and 

 they average slightly smaller. The measurements of 50 eggs average 

 19.4 by 14.6 millimeters; the eggs showing the four extremes measure 

 21.8 by 5.1, 20.0 by 164, 17.8 by 15.0, and 19.3 by 13.1 millimeters. 



In one clutch that I incubated artificially, the eggs floated when 

 tested 10 days before hatching. The complete clutch of four eggs 

 weighed 8.25 grams, and the individual eggs from 1.85 to 2.15 grams. 

 I found them more difficult to candle than the eggs of many song birds. 

 The three young that hatched averaged 1.46 grams apiece at hatching. 



Two clutches are laid each year and sometimes more, particularly 

 when early clutches are destroyed by flooding or by predators. 



Young. — Incubation is apparently by the female alone, at least I 

 have never seen the male incubate. I have, however, often seen the 

 male feed the slightly smaller and duller female on the nest while she 

 brooded. Her mouth lining appeared to be the same orange color as 

 that of her 4-day-old young. 



How well the length of the incubation period has been measured is 

 questionable. Lynds Jones (1892) gives it as 13 days, Ora W. Knight 

 (1908) as 12 to 15 days, T. S. Roberts (1936) as 12 to 13 days. The 

 three of a clutch of four eggs that hatched successfully in my incu- 

 bator hatched over an interim period of 12 plus or minus 8 hours; the 

 fourth egg did not hatch. 



During early incubation the female slips off the nest quietly and 

 unobtrusively while the intruder is still some distance away. Later 

 she waits to be flushed and scolds the intruder busily and boldly. At 

 one nest in advanced incubation that was tipped badly by the differ- 

 entially growing substrate, the female returned to incubate immedi- 

 ately after I righted it; indeed she seemed as oblivious to my presence 

 in my crude blind as she was to the green frog croaking beside her. 

 Her attentive periods varied from 6 to 15 minutes, her inattentive 

 periods from 11 to 34 minutes. On hot days she spent much of her 

 attentive time sitting high as though to shade the eggs, although no 

 direct sunshine reached the nest. Her departure was sometimes in 

 response to calls of the male, and sometimes without apparent ex- 

 ternal provocation, though there was usually vocal communication 

 between the pair whenever she left or returned. Her return to the 

 nest was often noisy. 



