308 SWALLOWS AND MARTINS 



more than one may be heard singing together. The martin's song, 

 also heard in flight, has been figured as chir-r ruee, chur-r-ruee, ruee, 

 ruee, but it sounds best when he is twittering contentedly to himself 

 inside the nest, which he often does. The usual call-note of the 

 martin is a kind of chirr-up, but the species is said to have a softer 

 note when calling its young in the air to be fed. From the nest- 

 lings I have heard two distinct notes, the usual chirrup, varied occa- 

 sionally by another difficult to describe a more rasping note, 

 something like qrrrr ! The usual note of the swallow is a twitter. 

 The nestlings have a somewhat similar note, the uproarious twitter 

 with which they greet their parents' visits with food, and to which 

 reference has already been made. According to my experience, 

 nestling swallows are usually quiet between the visits. Nestling 

 martins certainly are not, perhaps because they have their parents, 

 or other martins they mistake for such, frequently in view. Their 

 twittering may indicate the interest they take in the movements 

 of the flying birds. On the other hand, there are species like the 

 redstart, whose nestlings may be heard keeping up a continual 

 twittering between the visits of the parents, even when the latter 

 cannot be seen by them. 1 The notes of nestlings, the occasions on 

 which they are used, and the reasons why those of some species are 

 more silent than others, is a subject that has so far received small 

 attention. It is one of those many undiscovered regions of ornithology 

 that awaits its explorer. 



In addition to its ordinary twittering note, the swallow has a shrill 

 alarm-note. 2 It is to this that Gilbert White refers in his letter 

 to Barrington of January 29, 1774 : " The swallow, probably the male 

 bird, is the excubitor to house-martins and other little birds, announc- 

 ing the approach of birds of prey. For as soon as a hawk appears, 

 with a shrill alarming note he calls all the swallows and martins about 

 him, who pursue in a body, and buffet and strike their enemy till they 



1 Cf. vol. i. p. 423. 



* Two, according to Naiimann ; one when the enemy is still far off, the other when close to. 

 Vogel Mitteleuropas, iv. 199. 



