194 BRITISH BIRDS. [vol. viii. 



iris gets much more yellow. At birth the head is 

 entirely covered with short, thick, white down. Then 

 a space becomes clear of down between the eye and 

 nostril. This bare skin is at first nearly green and has 

 a few hair-like down-filaments on it. As the skin 

 becomes bare it becomes lighter (yellower), and after- 

 wards gradually darkens. It is very noticeable that 

 birds in the same nest, when fully feathered, vary very 

 much in colour. The breast-markings in particular 

 vary from quite a light brown to a very dark reddish- 

 brown. It is possible to tell females from males before 

 they lose the down at all by the greater length of limb, 

 and especially of the tarsus. 



Often the nest is built up as the nestling period pro- 

 ceeds, and is much flatter and some inches higher when 

 the young leave than when they were hatched. The 

 cup of the nest is lined with leaves or bark at the time 

 these additions are made. I think the object is for 

 sanitary purposes, to cover any small bit of food, or 

 dung, or pellets not taken away by the female. 



It is interesting to note a marked difference in the 

 actual feeding of these and many other nestlings : 

 whereas it is usual for a nestling not to swallow until 

 the food touches the back of the throat, these Hawks 

 make a grab for the food and jerk it into position in 

 the throat before swallowing. I do not think the young 

 begin to peck for themselves until seventeen days old, 

 but after that they can do a little self-feeding. 



In a nest a boy and I watched last summer young 

 Starlings were brought most often ; Blue Tits were 

 also brought more often than might be expected. The 

 birds were always plucked before being brought to the 

 nest, and I tliink this was often done on big limbs of 

 the neighbouring trees, as we climbed several and found 

 traces in most of the trees. Except for legs and feet, 

 all bones were cleared away until the young had left 

 the nest. After they leave the nest the young come 

 back to feed, and then bones are allowed to accumulate. 



