302 SWALLOWS AND MARTINS 



eye-witnesses, in one case the victim being a nestling. 1 But it is diffi- 

 cult to understand why a house-sparrow should not be able easily to 

 push out the wet mud, seeing that its bill is strong enough to break the 

 dry, which it does in enlarging the entrance to the nests it seizes. It 

 may be that it is compelled to remain within the nest till too hungry 

 or tired to make the necessary effort. The matter can only be settled 

 by detailed direct evidence, and this is still wanting. The same applies 

 to the statement that individual swallows occasionally hibernate in 

 this country instead of emigrating. The thing is not impossible. 

 There is simply no satisfactory proof that it has happened. 



There is evidence that swallows' nests are occasionally appro- 

 priated by sparrows, but they do not suffer to the same extent, a 

 fact that they owe no doubt to the partiality of the sparrow for 

 holes. 



House-martins have sometimes to defend their nests not only 

 against sparrows, but against their own kind. I have seen (June 9) 

 two martins fighting in a nest, and continuing the fight in the air out- 

 side, as they descended almost vertically to the ground. Stevenson, 

 on June 12, saw three enter a nest, where they struggled together, 

 wings and tails alternately projecting from the aperture. Here two 

 pairs were engaged, and sometimes all four birds would fall fighting in 

 a " feathered mass " through the air. The engagement lasted twenty 

 minutes, one pair being finally left in possession of the nest, where 

 they remained for some time twittering with excitement, and evidently 

 determined to remain on guard. 2 The cause of these fights, having 

 regard to the late date of their occurrence, is not easy to understand. 

 It is possible that the attacking pair had lost their own nest, and that 

 the hen was in haste to find a place for her first egg. 



Ill ...^, 



The young of swallows and martins are hatched after about a 

 fortnight's incubation, and are then fed by both parents. 



1 Zoologinchea Garten, 1904, 312 ; Field, 1860, xv. 509. Birds of Norfolk, i. 334. 



