BRANCH CHORD AT A; CLASS AYES: THE BIRDS 367 



etc. ; also the number of eggs, their size and color mark- 

 ings, the length of incubation, the help or lack of help of 

 the male in brooding, etc. In connection with this 

 gathering of data in the field by note-taking, sketching, 

 and photographing, nests and eggs can be collected (see 

 directions on page 469). Let only one clutch of eggs cf 

 each species be taken for the common high-school collec- 

 tion, and if more than one nest is desired take used and 

 deserted nests. When the nestlings are hatched, the 

 bringing of food, the defence of the home, and the teach- 

 ing of the young to fly should all be observed and noted. 



Some attempt should be made to systematize the mis- 

 cellaneous data obtained. Do all the members of a group 

 have similar nesting habits ? Note the early nesting of 

 birds of prey ; note the nests of the woodpeckers in holes 

 in trees ; note the nesting of the various swallows. Is 

 there any significance in the colors and markings of eggs ? 

 Observe the protective coloration obvious in some (see 

 Chap. XXXI). Are there differences in the condition of 

 the newly hatched nestlings ? Note the helpless altricial 

 young of the robin ; the independent precocial young of 

 the quail. 



The strong influence of the mating passion will be 

 made plain by observations on the fighting, love-making, 

 singing, and general behavior of the birds in the mating 

 season. The expression of the mental and emotional 

 traits, the psychic phenomena of birds, are most empha- 

 sized at this time, and reveal the possession among 

 animals lower than man of many characteristics which are 

 too commonly ascribed as the exclusive attributes cf the 

 human species. 



Local distribution and migration. As explained in 

 Chapter XXXII, the geographical distribution of animals 

 is a subject of much importance, and offers good oppor- 

 tunities in its more local features for student field-work. 



