30 BIRD BEHAVIOUR 



and that aerial acrobat the Bateleur Eagle (Helo- 

 tarsus ecaudatus) seem to have gone in for tail- 

 reduction, so that the steerage, etc., is evidently- 

 given over entirely to the wings in their case. 

 The steering action of the tail is particularly- 

 observable in Kites, in which that member is often 

 turned almost into a vertical plane, and this charac- 

 teristic action was noted by the ancient Romans, 

 Pliny suggesting that it was the Kite that taught 

 men the use of a rudder to a ship. 



Generally speaking, however, the most important 

 use of the tail is as a brake when descending ; why 

 it is always expanded at starting is not so obvious, 

 and probably the action is an involuntary one, like 

 the dropping of the legs by Gulls and Crows when 

 they check in their flight, a habit which has led 

 some observers into the mistaken idea that Crows, 

 when picking food off water, do so -with their 

 feet, which is never the case so far as I have 

 observed. 



Mere speed of flight, by the way, is not neces- 

 sarily so indispensable an asset for escaping aerial 

 enemies as may be supposed ; Swallows and S-wifts 

 certainly suffer little from birds of prey, the Hobby 

 being the only Falcon which ordinarily catches 

 them, and the swift Sand-Grouse, among ground- 

 birds, are too much for most Falcons. But some 

 quite slow birds are also very difficult subjects for 

 Hawks, owing to the facility -with which they 

 shift from the stroke, the lioopoe and Lap-wing 

 being notorious for their abiUties in this respect j 



