INTRODUCTION. 



an incomplete nest, you must judge for yourself how soon it 

 will be finished. A pair of our smaller birds, in the latter part 

 of May or in June, ordinarily spend from five to ten days in 

 building one, and sometimes end their work sufficiently in ad- 

 vance to allow the female vacation for a clay or even two. 

 Earlier in the season, other birds are generally occupied two or 

 three weeks. Woodpeckers are very uncertain in this respect, 

 and it is often difficult to decide when their nests should be 

 broken into to obtain the eggs, unless one can watch them 

 closely at their work (carried on chiefly in the morning) and 

 observe the final cessation of chips. The creepers, nuthatches, 

 Chickadees, and certain wrens customarily la}' their eggs in de- 

 serted woodpeckers' holes or other cavities, which they line 

 with warm materials, though the Chickadees occasionally exca- 

 vate for themselves with great and long-continued labor. 



After the first egg has been laid, one is generally added on 

 each succeeding day (apparently most often in the morning) 

 until the complement is made, 8 before which time the nest 

 should not be visited, except in cases of necessity. Most 

 birds lay four or five eggs (occasionally three or six) in a set, 

 commonly fewer in that of a second brood than before. Many 

 wrens, titmice, and kingfishers often lay more ; the former even 

 ten, or very rarely twelve. Gallinaceous birds are also prolific, 

 and two or three hen-birds are said sometimes to lay in the 

 same nest. Humming-birds, eagles, and pigeons, usually lay 

 two eggs in a set, as do also old birds of other species, partic- 

 ularly among the hawks and owls. Many sea-birds have only 

 one. If a nest be found with the same number of eggs for two 



8 To this law the chief exceptions are the birds of prey, and the cuckoos, but 

 among the smaller land-birds the average rate of laying is one a day. Thus among 

 different species the time for laying four eggs varies from three to even seven days, 

 generally being four. 



