30 BIRD FRIENDS 



shaped, gradually growing larger till near the bottom, 

 and then tapering to a point. The only materials 

 in the woodpecker's nest are the chips that happen 

 to fall down, and the pointed cavity keeps the eggs 

 from rolling around. 



The marsh wren builds a globular nest attached 

 to the reeds of the marsh and makes an entrance at 

 one side. So strongly developed is the nesting in- 

 stinct in this bird that it builds several extra nests 

 besides the one which it uses. 



Time occupied in building. Observations have 

 been made on birds while building nests and it is 

 found that the time occupied in building the nest 

 varies, both with the species of bird and with the 

 same species at different times. A pair of house 

 wrens was found to occupy seven days in construct- 

 ing a nest. This nest contained one thousand sticks, 

 so that about one hundred and fifty sticks were 

 brought a day, or an average of ten per hour. 



]NIr. Francis H. Herrick watched a pair of robins 

 building and found that they completed the nest in 

 three days. On the first day the birds worked five 

 hours; on the second, fourteen, and on the third 

 four and one half, making a total of twenty-three 

 and one half hours. On the first day, both male and 

 female worked; on the second and third days, the 

 female alone. During this time two hundred and 

 eighteen loads of material were brought to the nest. 

 On the first day an average of seventeen visits per 



