PARENTAL CARE AND NEST-MAKING 303 



the welfare of the young, it is of real value to have records 

 like that given by Professor Robert Newstead, who calculated 

 that a single pair of Great Tits destroyed between seven and 

 eight thousand caterpillars during the twenty days occupied 

 in rearing their young. What a quaint picture some of the 

 Antarctic explorers have given us of the penguins toiUng up 

 the steep ice-cliff with their crops heavily laden with small 

 shrimp-like Crustaceans (Euphausidae) which they have 

 collected for their offspring — sometimes so heavily laden 

 that they lose it all in the course of their climb ! 



Some peculiarities in connection with the feeding of the 

 young deserve careful consideration. Certain birds of prey 

 hunted off their nest will drop food on their young ones. 

 Male and female pigeons give their squabs a readily digestible 

 creamy fluid which serves, like mammal's milk, for the 

 education of the food-canal. This " pigeon's milk " is not 

 a secretion of the walls of the crop, for these are non- 

 glandular ; it is produced by a fatty degeneration and 

 internal moulting of the cells Hning the crop. A curious case 

 is that of the Storm-petrel, the well-known bird of the open 

 sea, which only comes to land to breed. The parent bird 

 sits close on the single egg, which is laid in a hole among the 

 rocks, or perhaps in the disused burrow of a rabbit. When 

 the young one is hatched out, the parents seem to leave it 

 all the day long, for they are nervous of the land. They 

 return to it at nightfall, however, and give it a heavy, lasting 

 meal of oil from their crop — apparently the concentrated 

 essence of many minute crustaceans and other small fry of 

 the sea. 



The parent puffins brood on their single egg for about 

 a month, and for as long again the fluffy youngster requires 

 to be fed. Both the parents share in the labour of love, and 

 it is a familiar sight to see them bringing in small fishes, 

 several at a time, held crosswise in the mouth. As many as 

 eleven have been counted in one mouthful, and there are 

 often four or five. It is an old puzzle how the number of 

 fishes can be added to without loss of previous captures ; 

 perhaps the solution is to be found in the grip of the tongue 



