118 THE ZOOLOGIST. 



Period of Incubation. Fledging Period. 



Starling 12-13 days 21-22 days 



Magpie 17-18 , 29-30 



Carrion- Crow 18-19 



Rook 17-18 



Long-eared Owl 28-30 



Sparrow-Hawk 30-32 



Moorhen 19-20 



33-31 

 29-30 

 . ? 



28-30 



As individual birds vary to some degree in commencement and 

 constancy of incubation, there is some slight difference in incubation 

 periods to be observed at times. For instance, two Song-Thrushes, 

 nesting close together in a shrubbery, commenced laying on the 

 same day, laid the same number of eggs, and yet one bird hatched its 

 brood at least twelve hours in advance of the other. Amongst 

 Passerines laying is very regular as a rule, one egg being deposited 

 each day until the clutch is complete. There are individual excep- 

 tions, however. For example, I have known an instance of a Grey 

 Wagtail which laid two eggs of its clutch in regular course, missed 

 the third day, and laid again on the fourth and fifth. Hawks and 

 Owls are well known to lay only every second or third day. A 

 Partridge, whose nest was kept under daily observation from the 

 time it contained two eggs, took eighteen or nineteen days to com- 

 plete its clutch of sixteen eggs. It is an interesting fact that some 

 species of birds lay earlier in the day than others. Mistle- and Song- 

 Thrushes, for instance, do not lay as a rule earlier than 8 or 9 a.m., 

 according to my observations, and I have known a Mistle-Thrush 

 delay until almost noon. Rooks also are late layers. Hedge- 

 Sparrows, on the other hand, seem to lay either during the night or 

 at daybreak. Swallows and Starlings are notable exceptions to the 

 average small bird in the period required by their young to fledge. 

 It is possible that young Starlings, if reared in an open nest, might 

 fly at as early an age as young Blackbirds or Thrushes, but young 

 Swallows have no impediment to prevent an early flight. — S. E. 

 Brock (Kirkliston, West Lothian). 



