Summary 139 
construction and from the desire of the Larks to have a bare 
ground nest-approach. 
8. Eggs and egg-laying. The egg is described as having a 
background of grey with an occasional greenish tinge, which 
background is almost completely concealed with a fine speckling 
of cinnamon-brown. The cinnamon-brown often forms a denser 
ring about the larger end. Several other variations are noted. 
The average size was found to be 2.25 em. by 1.55 em. The eggs 
of natural second sets seemed to be a trifle larger than first sets 
of the same individual. The number of eggs per set varied from 
two to five; the average is about four; the smaller sets occurred 
early, the larger sets later. 
9. Incubation period. The optimum was determined to be 
eleven days. Only the female incubates. 
10. Reactions of female and male Larks during incubation 
period. The male shows little or no nest solicitude during the 
incubation period. The female has a highly developed series of 
automatic instincts of solicitude which are modified by time of 
day, condition of weather and frequency of disturbance. The 
most highly developed and probably the most recently acquired 
of these has been given the name ‘‘nest concealment by abandon- 
ment’’, or ‘‘casual abandonment’’. The female leaves the nest, 
in this reaction, when an intruder is at a long distance, and flies 
quietly away, low against the ground, and does not show other 
solicitude for a very considerable period. The distances of the 
intruder from the nest during this reaction vary from 25 to 100 
yards or often farther, a greater distance, it will be noted, than 
would disturb even a timid Lark under other circumstances. A 
reaction, that in many ways is the reverse of this, but still a 
marked exhibit of solicitude, is that called “distress simulation’”’. 
The ‘‘distress simulation’’ consists of a precipitate flushing and 
rapid flutter over the ground after the nest has been approached 
closely. This reaction would be given most frequently on very 
cold days, in the dusk of very early morning or evening and 
when the bird was flushed very shortly after a return to the nest. 
This reaction is certainly more primitive than the first here de- 
Scribed and is probably a culmination of the more frequent dis- 
traction display that most birds present when their nests are 
disturbed. Between ‘concealment by abandonment’? and ‘‘dis- 
tress simulation’’ a complete gradation occurred which, since the 
