10 U. S. NATIONAL MUSEUM BULLETIN 211 



night both parents remained within the bird house. Contrary to the 

 usual custom of these birds, the young were practically grown when 

 they left the nest and began to fly. One of these juveniles, collected 

 late in February, disclosed a body that was fat and in perfect physical 

 condition." 



This was, of course, a very unusual date for nesting, as the eggs were 

 laid in December. J. J. Murray writes to me that he has seen these 

 birds carrying nesting material as early as February 1, and that a 

 neighbor took a practically complete nest out of a wren box on Febru- 

 ary 21. He has also seen them carry material into a hole as late as 

 November 2. These dates indicate possible nesting activities in every 

 month of the year. Weaver (1943), on the other hand says: "The 

 season of nesting is from April to September for most of the United 

 States but may start as early as March 2 in the South and may be 

 delayed until near the first of May in parts of Canada and in Europe." 



Eggs. — The number of eggs laid by the English sparrow varies 

 from three to seven; five seems to be the commonest number, though 

 sets of six are not very rare; as many as nine have been recorded, and 

 four seems to be the normal minimum. The eggs are mainly ovate in 

 shape, with a tendency toward elongate ovate, and they have very 

 little gloss. Niethammer (1937) gives a very good description of them, 

 of which the following is a translation: "Eggs — very variable with 

 basic color almost pure white, greenish or bluish, less often green- 

 gray or brownish. Marks limited to a few gray or brown dots, usually 

 consisting of closely packed, clouded or sharply limited spots, which 

 vary from deep black-brown through all tone ranges to bright ashy 

 gray and can crowd in toward the blunt end, however, without forming 

 a genuine wreath structure. Usually the last egg is abnormally 

 colored; basic color brighter, spotting more pronounced and not so 

 frequent. Likewise the next to the last egg has a darker basic color 

 and very dense marking." 



Weaver (1943) gives the measurements of 54 eggs, of which the 

 average is 22.8 by 15.4 millimeters; the eggs showing the four extremes 

 measure 25.0 by 16.0, 22.0 by 16.8, 20.2 by 15.0, and 20.4 by 14.5 

 millimeters. 



Young. — Weaver (1943) found that incubation was performed 

 wholly by the female, 12 days being the commonest incubation period: 

 "Three of the twenty-two sets required thirteen days, nine required 

 twelve days, one required eleven days, and three sets required ten 

 days." He figured that incubation began with the laying of the third 

 egg. Of the hatching operation he writes: 



A clicking sound usually announces the readiness of the young to start hatching. 

 It is made by contact of the egg tooth with the shell and possibly also by a clicking 

 together of the mandibles. The egg tooth presses against the shell and makes an 



