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THE OOLOGIST. 



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JUNE, 1877. 



THREE PAPERS ON THE BREED- 

 ING HABITS OF BIRDS. 



IIP INCUBATION. 



TNCUBATION is commenced on the day 

 -^ of the last deposition, and at this stage 

 the body of the sitting bird is at a temper- 

 ature of 96° Fahrenheit, the greatest 

 warmth required. "J^he female, and also 

 the male to some extent, now begin to lose 

 their feathers, which accounts for the large 

 number of poorly plumaged birds found 

 during the breeding season. The male 



does not in all cases lose its feathers at this 

 time, as, with many species incubation is 

 performed by the female alone, it being this 

 process that loosens them. When both sex- 

 es incubate, they observe a systematic mode 

 of relief, the female usually sitting from 

 the afternoon of one day till the forenoon 

 of the next, when the male relieves her 

 while she is absent in search of food. When 

 incubation is performed by the female alone 

 she remains in the nest until the young are 

 hatched, the male in the meantime feeding 

 ler. 



According to Dr. Jasper, the eggs, from 

 the beginning of incubation are turned near- 

 ly every day. If this be so, the Sandpi- 

 pers and other birds which universally lay 

 their eggs in the same position,* must nec- 

 essarily exercise considerable instinct and 

 care in their removal in order that they as- 

 sume their original position. Observation 

 would convince us that in the case of some 

 species, this does not apply, for, on several 

 occasions, when on repeated visits to nests 

 containing less than the anticipated num- 

 ber of eggs, their position was carefully 

 noted, and in a large number of instances, 

 when observable, the prominent blotch that 

 appeared uppermost at first, was observed 

 in the same place until the last, though in- 

 cubation had continued several days. 



Many species utilize the heat of the sun 

 and of vegetable fermentation for incubating 

 their eggs ; some species, the Apteryx for 

 instance, sit under instead of over their 

 eggs ; others like the Cow Bird and Euro- 

 pean Cuckoo, do not attempt to facilitate 

 the hatching process, but lay their eggs in 

 the nests of other and usually smaller spe- 

 cies. The length of time required for in- 

 cubation varies generally with the size of 

 the bird and the thickness and toughness of 

 the shell. Humming-birds' eggs require 

 about ten days, those of most Warblers e- 

 leven or twelve, of Sparrows twelve, of 

 Blackbirds about fifteen, of most Hawks 

 and Owls three weeks, and of the Eagle 



* The Sandpipers always deposit their eggs 

 with their small ends in the center. This is 

 also noticeable with a few other Limicolae. 



