3§8 THE ZOOLOGIST. 



steadily increases and whose movements daily become more vigorous ; 

 if the nest is not considered safe, I feel sure the old birds entirely 

 demolish it, and scatter the debris in very small fragments at a dis- 

 tance, so that one does not find them ; and this they do even when 

 they build the new nest on a fresh site. At any rate, nests disappear, 

 leaving marks on the walls so that their former existence is indis- 

 putable, but no remains are visible on the ground, as is the case when 

 a nest falls. Mr. Wood (he. cit.) says that " the material of which 

 the nests are built is a kind of mud, which becomes tolerably hard 

 when dry, and is strong enough to exist for a series of years, and to 

 serve for the bringing up of many successive broods." I believe, how- 

 ever that this lasting property depends on two factors : the consis- 

 tency of the mud when used owing to the amount of the recent 

 rainfall, and also on the geological or chemical composition of the 

 material ; anything of a stiff clayey nature would surely last much 

 longer than anything of a light sandy nature. 



That House -Sparrows are apt to appropriate the nests of House- 

 Martins is very well known, but it is perhaps not so well known that 

 the builders and rightful owners may kill the young of the invaders. 

 I think there can be no doubt this vengeance was inflicted here this 

 season. My eye was caught one day by a fully-fledged young Sparrow 

 lying dead on the ground under the thickest group of the Martins' 

 nests ; and I saw that the entrance to one nest had been enlarged, 

 the lining of poultry feathers protruding ; so going up by ladder I 

 found that the nest contained a single young Sparrow, dead like the 

 one on the ground ; but, while the latter was quite fresh, the one in 

 the nest was rather stale ; and I therefrom infer that the Martins had 

 not time to kill both the young birds before the old Sparrows returned, 

 but had to wait to complete their full resolve until they found the 

 coast again clear, two or three days later. Perhaps the second victim 

 had tried to escape, and was only given the coup de grace after it was 

 actually outside the nest. I regret not having skinned the heads of 

 these birds to look for peck-scars, but it must take a good many 

 blows from so soft and feeble a weapon as a House-Martin's beak to 

 kill a tough, nearly fully-grown young Sparrow. The nests are cer- 

 tainly inaccessible to Eats and Cats, or even, I am sure, to Squirrels ; 

 besides which, any of these animals would have pulled the nest 

 down. No other cause of death that seems in the least probable has 

 occurred to me. — Alfeed H. Cocks (Poynetts, Skirmett, near 

 Henley-on-Thames) . 



White Wagtail Nesting in Yorkshire. — There is little doubt that 

 this year the White Wagtail has nested at Scarborough, thereby 



