126 BRITISH BIRDS. [vol. xv. 



which may or may not fetch her mate off, according to the 

 stage of incubation. If no Merhns are seen, a two-hour 

 wait in hiding is mostly enough to determine the presence of 

 the birds as the male is but seldom absent for a longer period. 

 As he almost invariably feeds the hen upon his return and 

 relieves her at the nest, such a watch is frequently rewarded 

 by the finding of the exact site. 



The locating of the nest by means of the " chalked " 

 boulders may be rendered more complex and even impossible 

 by the use of the same area by a pair of Kestrels, Tawny or 

 Short-eared Owls, and occasionally Sparrow-Hawk, if the 

 site chance to be near a suitable wood. 



The finding of an eyrie may sound, from the above remarks, 

 far simpler than it actually is. On the twenty square miles 

 dealt with in these notes, there are almost countless sites 

 that appear to fulfil all requirements, and yet not more than 

 four pairs of Merlins have ever been recorded thereon in a 

 single season. This is, no doubt, explained by the Law of 

 Territory, and the demands of the Merlin in this respect are 

 extraordinarily great. It is a common thing to find the 

 Tiercel hunting two miles from his eyrie, and at times he 

 may be seen even farther afield. That the law of territory 

 is respected is certain, for two eyries are never found close 

 together. Birch informs me that he has known a couple 

 only a mile apart, but he considers such proximity very 

 exceptional. 



On the eastern slope of Barden Fell there are two gills, 

 known respectively as Lesser and Greater Hay Gills. Their 

 heads are separated by nearl}^ a mile but they rapidly 

 converge. No year passes without a nest on one or the 

 other, as they both offer ideal conditions, but two nests in 

 the same season, one on each gill, have yet to be recorded 



The law of territory may account for the limiting of 

 numbers, but it throws no light on the actual choice of sites, 

 which offers a most interesting problem. With a very large 

 number of possibilities to choose from, most of which have 

 at some time or another actually been used and have thus 

 proved their ehgibility, the Merlins show an extraordinary 

 preference for a small minority which will hold an eyrie 

 year after year without a break. It is in this case not a 

 question of the same pair of birds returning to a favoured 

 haunt in successive seasons, for it is but rarely that a hawk 

 attempting to breed on these moors survives to tell the 

 tale, but rather one of certain sites attracting new birds 

 annually. Two concrete examples of what I mean will 



