74 BULLETIN 196, UNITED STATES NATIONAL MUSEUM 



as threat-colours. Except for this, the attacking male does not usually posture. 

 But on two occasions the wings were flicked open and closed and the body jerked. 

 Nearly always the bird keeps silent, but occasionally give a sibilant "seep" note 

 and on one occasion faint "chucking" accompanied the beak-opening. Com- 

 paratively rarely does the intruder wait to be attacked, but this was seen 

 occasionally. 



Threat-display is also common between two resident males along the common 

 boundary of their territories, and is usually remarkably formalised and unexcited 

 * * * # 



Of course territorial encounters are occasionally more serious, and there are 

 records of one male killing another * * *. But * * * serious fights are 

 rare, and probably occur chiefly when one male is trying to dispossess another of 

 its territory. 



The statement in Niethammer (1937) that choice of territory and 

 pairing up take place at the same time as the beginning of the male's 

 song or soon afterward is|certainly not correct in England. It is 

 one of the peculiarities of the blackbird that it does not start to sing 

 imtil the majority have been paired and in occupation of territories 

 for some time. Just how long is at present a matter of uncertainty. 

 Lack found pairs already formed in January and February and even 

 late in December, and the late T. A. Coward, an excellent observer 

 and author of by far the best of the smaller works on British birds 

 (1920), stated that pairing begins in October and November. He 

 probably had good grounds for this assertion, but unfortunately gives 

 no details. The manner of staking out of territories and of pair 

 formation still awaits elucidation. It will be understood that the 

 observations quoted in the present section refer to resident birds, but 

 in the northern parts of its range the species is migratory. 



Courtship. — Although the blackbird is such a common European 

 species and so regularly frequents gardens it is nevertheless a shy bird, 

 and it is but seldom that any courtship display or the act of coition is 

 observed. The most striking single feature of display, though not a 

 constant one, is the erection of the feathers of the rump, which gives 

 the bird a most peculiar appearance as it runs about in a somewhat 

 crouching posture with the tail usually fanned and depressed, an 

 expression of excitement which may also be observed in other types 

 of display and is common to both sexes. Several writers (Kirkman, 

 1911, et al.) have described this odd erection of the rump feathers and 

 the present writer has also observed it. For the rest, the recorded 

 display actions show wide variation and conform to no well-defined 

 pattern. This inconstancy of pattern is observable in the display 

 actions of a number of passerine species, which seem to be much less 

 stereotyped than in some types of birds. Perhaps such individually 

 variable and erratic posturings under the stress of nervous excitement 

 represent the kind of raw material out of which the more set displays 

 have been evolved. 



