January 27, 1921] 



NATURE 



69: 



The Sparrowhawk. 

 By J. H. Owen. 



'T'HE sparrowhawk, in a perfectly wild state, 

 ■*■ is one of our most interesting birds to study. 

 During the nesting period, and especially through 

 the latter part of the incubation period and the 

 whole of the nestling period, it is comparatively 

 easy to observe and photograph the bird. With 

 patience, photographs can be obtained at the nest 

 of the birds, old and young, for something like 

 a fortnight after the young have left the nest. 

 This is because the cock, and in some cases the 

 hen, deposit the kills on the nest, which becomes 

 a larder to a large extent, and the young return 

 to the nest for a meal whenever they are in need 

 of food. 



The young are helped to procure food and partly 

 trained by the old birds for a still further period 

 before they are finally dispersed to seek their own 

 living. If the nesting period be considered to 

 start when the building of the nest is begun, and 

 to end at the dispersal of the young, it is of great 

 length. I have seen new nests, practically com- 

 plete except for the lining of the cup and a feu- 

 minor details, as early as February 17. I usually 

 search for new nests during the second half of 

 March, and find quite a lot of pairs building them. 

 Birds that do not start during March appear to 

 use old nests of pigeon, jay, hawk, or even mag- 

 pie as foundations, but they are in a minority in 

 the neighbourhood of Felstead, in Essex, for 

 at least three-quarters of the nests I find are 

 entirely new. Of course, weather conditions 

 have considerable influence on the building 

 of nests; in rough, boisterous, or wet 

 weather and on foggy days operations cease. 

 In a forward year, such as 1916, complete 

 sets of eggs may be found before the end 

 of April ; in a normal year it is unusual to find 

 such sets until between May 14 and 21. The 

 bird lays, as a rule, on alternate days, but occa- 

 sionally there is a period of .seventy-two hours 

 between eggs, and sometimes even more. The 

 full set consists of four to six eggs, rarely of seven 

 or more. Very old birds produce fewer eggs, 

 which are less heavily pigmented as the age of the 

 bird increases, while the eggs of a young hen are 

 not so evenly or so heavily pigmented, as a set, as 

 arc those of a fully mature bird. 



The incubation period varies somewhat, but can 

 be put at approximately thirty-three days. The 

 eggs usually take a long time to hatch, even after 

 they are chipped ; it is quite usual for two whole 

 days to elapse after the egg is chipped before the 

 chick emerges — I have known this period to be 

 as long as four days. This is probably because 

 the eggs are not moistened by the hen, the shell 

 is very thick, and the membrane very tough. I 

 have often watched a hen helping a chick to break 

 free from the shell. In such ca.scs I have seen the 

 hen cat the shells, but I feel convinced now that 

 this is not the usual method of di<;po«;ing of them. 



NO. 2674, VOL. 106] 



Usually they are carried some distance from the 

 nest and dropped. 



Like the chicks of all birds of prey, those of the 

 sparrowhawk are covered with short, thick, white 

 down when hatched, and their eyes are open ; but 

 the plumage does not show until the bird is more 

 than fourteen days old. The nestling period is 

 about twenty-eight days, and by the end of that 

 time the young birds have mostly acquired 

 their juvenile plumage; but the down does 

 not finally disappear until they are some 

 seven weeks old. During incubation the 

 nest gets flecked with down from the hen, 

 and is a beautiful sight just before incuba- 

 tion ends, if the weather has been good. If the 

 first set of eggs has been taken, the second nest 

 never gets anything like so well flecked ; the 

 supply is limited, and has been used up. This 

 may be a survival of what still happens in the 

 nests of ducks and geese. When the young are 

 hatched, this down disappears very quickly ; it is 

 partly removed by the weather, but largely by 

 the hen, which probably mistakes it for the 

 feathers of victims. The nest is kept particularly 

 clean all through the incubation and nestling 

 periods until just before the young leave the nest. 

 Then the nest again becomes beautifully and liber- 

 ally flecked with down ; but this time it is shed 

 by the young birds. 



When the hen begins to lay, she lines the 

 bottom of the nest with bits of bark, touchwood, 

 and dead leaves, and during the incubation period 

 she adds material, sometimes to the rim and some^ 

 times to the well of the nest, with the object of 

 making the nest stronger and more comfortable. 

 During the nestling period more is added, this 

 time probably partly for sanitary reasons, to keep 

 the young off material contaminated by contact 

 with dead, and often decaying, victims. Dr. T. 

 Lewis has even seen the cock bird bring twigs to 

 the nest during the nestling period. 



The hen, in my experience, does all the incu- 

 bating, and usually the cock procures food for her. 

 This she eats on the larger limbs of trees in the 

 neighbourhood of the nest tree. The cock brings 

 it to some position upwind of her and calls. If 

 she wants it she goes to him and takes it, and 

 they remain together a short time; then he 

 goes away. If, after two or three calls, 

 she does not join him, he 'flies through 

 the nest tree calling ; if she still takes no 

 notice he goes to a favourite feeding-place, not very 

 far from the nest as a rule, eats what he wants, 

 and flies off again. The hen normally sits back 

 to wind (Fig. i). The proximity of ah observa- 

 tion hut upsets her, and she will place herself as 

 near back to wind as possible while keeping the 

 hut Still in view. If, however, it rains she 

 will, hut or no hut, turn her back to it. If it 

 rnins hnrd --he will pradiiiilly move hrr wings out 



