308 BIOLOGY FOR BEGINNERS 



Nest Building. 



Necessity for nest, warmth for egg and protection of young. 

 Kinds. 



Excavated in earth Kingfisher, bank swallow. 



Excavated in trees Woodpecker, owl. 



Woven cup shaped Warblers. 



Woven hanging Orioles, vireos. 



Built up of clay Robin, eave swallow. 



Built up of sticks Chimney swift (not swallow). 



Eggs (cf. other forms of eggs as to size, covering, fertilization). 



Structure. 



Germ spot develops embryo. 



Yolk for nourishment. 



White for nourishment. 



Membranes Protection, admit air, exit CO 2 . 



Limy shell Protection, admit air, exit CO 2 . 



Causes of decay and means of prevention. 

 Shape, " oval " for better fitting, will not roll. 

 Number, fewer where more parental care and young helpless. 



Larger where young are precocial, average five. 

 Size, larger where chick hatches well developed. 

 Color, protective, white in dark nests. 

 Use as food for man. 



Concentrated, need no cooking, all digestible. 

 Incubation. 



Small eggs less time (13-15 days), larger 40-50 days. 



Female usually ''sits." 



Chicks hatch in series in altricial birds. 



Chicks hatch all at once in precocial birds (why?). 



Migration. 



Causes, food scarcity, climatic changes, breeding. 

 Methods, night fliers; ducks, hawks, swallows, etc. 



Day fliers; shore birds, warblers, thrushes. 

 Distances, from five to eleven thousand miles. 

 Travel in flocks for protection and direction. 

 Routes, rather definite, along coasts, mountain ranges, etc. 



Not known how they direct themselves. 

 Examples of above instances. 



