412 U-S. NATIONAL MUSEUM BULLETIN 23 7 part i 



Both Walkinshaw and I have been intrigued by females that brooded 

 an empty nest while we measured their eggs nearby. 



Young. — Information on the early development of redpolls is scarce. 

 I established one 11-day incubation period at Indian House Lake, 

 and Lawrence 1. Grinnell (in litt., 1955) agrees that his "10 or 11 

 days" (Grinnell, 1943) should read "probably 11 days," even though 

 European students (Witherby, 1938) report 10 or 11 days for this 

 species. Walkinshaw (1948), writing of Alaska observations, said, 

 "We found that, usually, three young hatched the first day, and the 

 fourth the following day. With five-egg sets, four usually hatched 

 the first day." 



The following information on development is drawn from Grinnell's 

 (1943, 1947) studies: Except for faint wisps of grayish natal down on 

 the principal feather tracts, the newly hatched young are naked and 

 they weigh less than 1 .5 grams. Motor control is limited to the ability 

 to right themselves when tiu-ned over on their backs, and to spreading 

 and closing the toes. So translucent are they that food can be seen 

 in the gullet, and blood vessels give the skin an orange-red hue. 

 The foiu-th day sees the eyes begin to slit, and they are quite open the 

 next day. The sixth day sees the young vigorous and active, although 

 the first cheep notes are not uttered until the tenth day, when they 

 show the first fear reactions. Perching is first accomplished success- 

 fully on the eleventh day, and the nestlings can fly enough to leave 

 the nest the next day. Growth in weight is rapid and steady until 

 the ninth day, when it tapers off abruptly after attaining 12 grams. 

 Adults weigh 13 to 14 grams. 



The long days of the subarctic summer provide about 20 hours of 

 daylight, including the colorful crepuscular hours, and the redpoll's 

 nesting day is consequently much longer than that of related fringillids 

 from more southern regions. Adult females are sometimes active 

 from 3:00 a.m. to 10:30 p.m., at Churchill (Grinnell, 1943). Some- 

 what farther north in Alaska, Walkinshaw (1948) found activity 

 continued around the clock. Although females average approxi- 

 mately equal periods off and on the nest, the colder June period at 

 Churchill, with a 31° to 63° F. temperatiu-e range, saw an interval 

 of attentiveness only 40 percent that of July, when the temperature 

 ranged between 42° and 77° (Grinnell, 1947), meaning shorter periods 

 of exposure and more frequent feedings. The same adjustment to 

 temperature is evident in the diurnal activity cycle (Grinnell, 1943), 

 the feeding interval being only 8 minutes between 3:00 a.m, and 6:00 

 a.m., but about 24 minutes for the rest of the day. The average 

 interval between feedings diminishes with advancing age, being 38 

 minutes for the fu'st 4 days, 23 minutes for the 5-7-day period, and 19 

 minutes for days 8 through 10. 



