io8 OUR RARER BIRDS 



birds, and flit in undulating course from tree to tree, all the 

 time keeping up an intermittent cliorus of twittering notes 

 which sound something like the syllables si-si-si, sometimes 

 loud and piercing, sometimes low and guttural. When flying 

 from the observer, the brilliant red or yellow plumage on 

 the backs of males and females shows out very distinctly, and 

 is a useful aid in identifying the birds. 



The food of the Crossbill is composed largely of the seeds 

 of coniferous trees ; the bird also eats various kinds of berries 

 and fruits, especially apples, w^hich it splits open to obtain the 

 pips ; and in summer insects and larva3 of different kinds 

 are preyed upon. It is very probable that the young are 

 reared almost exclusively on an insect diet, perhaps varied 

 with the smaller fruits. Crossbills often mix with other 

 birds, apparently for no other reason than that of companion- 

 ship, and may frequently be observed in company with Siskins 

 and other tree-hauntiiig species. 



At the approach of the breeding season much of the Cross- 

 bill's trustfulness passes away, and it gradually becomes a shy 

 skulking bird. It is one of the earliest birds to breed, certainly 

 the earliest of all the British Finches. Its breeding grounds 

 are chiefly in the pine woods, although the nest is occasionally 

 made amongst deciduous vegetation. I once knew a nest of 

 this bird built high up in a dense whitethorn hedge, close to 

 a wood which Crossbills had frequented through the winter. 

 The nest is built at various heights from the ground, the 

 favourite situation being in a fork of the branches, near the top 

 of the tree, or in a prong of some horizontal limb, at some dis- 

 tance from the trunk. It very closely resembles that of the 

 Bullfinch — a rustic structure, in which many fine twigs are 

 used in forming the outside framework. Some nests are 

 made externally, almost entirely of the dead twigs of the fir ; 

 and the inner nest is made of dry grass and moss, and occasion- 

 ally a flake or two of the thin pine bark. It is finally lined 



