CHAPTER I. 



THE PROVISION OF NESTING-PLACES FOR BIRDS BREEDING IN HOLES. 



(A) Nesting Difficulties. 



BIRDS building in holes are those birds that breed and spend the night 

 in holes in trees, or more rarely in holes in rocks or other cavities. 

 According to a list of European birds breeding in holes, drawn up by 

 Baron von Berlepsch, we distinguish between those that do not build 

 their nests in regular holes in trees with a narrow opening, but rather 

 in niches and in narrow, half-open cavities, and those which breed in deep 

 cavities with a narrow opening corresponding to the size of their 

 bodies. In the first category are (1) black redstart ; (2) spotted 

 fly-catcher ; (3) pied and white wagtails ; and occasionally (4) the robin. 

 Of large birds (5) kestrels ; (6) jackdaws ; (7) various species of owls. 

 Nos. 5, 6 and 7 also frequently nest in regular holes. 



In the second category we have : (1) tits -(a) great tit, (b) blue 

 tit, (c) coal-tit, (d) marsh-tit, (e) crested tit, (/) willow-tit ; (2) nut- 

 hatch ; (3) tree-creeper; (4) woodpeckers (a) lesser spotted, (b) 

 middle spotted (Dendrocopus medius), (c) great spotted, (d) Syrian 

 (Dendrocopus leuconotus), (e) three- toed (Dendrocopus tridactylus] 

 (/) grey (Picus viridicanus), (g) green, and (h) black woodpecker (Picus 

 martius) ; (5) wryneck ; (6) starling ; (7) common redstart ; (8) 

 pied fly-catcher ; (9) hoopoe ; (10) swift ; (11) roUer ; (12) stock-dove ; 

 (13) various species of owls; (14) kestrel; (15) jackdaw [Nos. 13, 

 14, and 15 are also in the first category] ; (16) merganser (Mergus 

 merganser] ; (17) white-collared fly-catcher. 



The difficulty experienced by these birds, which are so important 

 to agriculture and forestry, in finding nesting-places, has greatly 



