1902. Proceedhigs of Irish Societies. 49 



DUBLIN NATURALISTS' FIELD CLUB. 



December 10 Mr. F. W. BuRBiDGE in the chair. Mr. R. H. NE1.SON 



read a paper on " Fossils and Fossilizatiou," illustrating his remarks by 

 means of specimens and casts. 



Mr. R.J. USSHER then gave a paper on **The Breeding-habits and 

 Architecture of Birds." The peculiarities of the eggs and young 

 of all birds are suited to the parents' mode of disposing of them, 

 and afford a considerable clue to classification on a natural basis. 

 The number of eggs laid by birds of different groups varies greatly. 

 Petrels, and most of the Auks, lay but one; Nightjars, Pigeons, and 

 Divers, have two only; Gulls and Terns, usually three; Plovers and 

 Sandpipers, four ; Passeres usually have four to six, though Goldcrests 

 and Tits lay up to ten ; gallinaceous birds, Ducks, and Rails, from eight 

 to twelve eggs. The shape too, is characteristic, Kggs of Owls and Falcons, 

 and, indeed, of most raptorial birds, are rounded; eggs of Nightjars, 

 Pigeons, Grebes, and Petrels, incline to be equally rounded or pointed 

 at both ends; those of Plovers and Sandpipers are pear-shaped; those of 

 Guillemots are drawn out to a long point ; while the eggs of Divers are 

 elongated, but not pointed. 



Then, as to colour, the eggs of the Thrush and Crow families are blue- 

 green, speckled or stained with brown or black ; those of Tits are white, 

 speckled with rufous; those of Buntings are streaked; the eggs of Wood- 

 peckers and Kingfishers are glossy white ; of Owls white, but wanting 

 polish ; those of Falcons have reidish-brown markings, which usually 

 cover them ; Rails have buff-coloured eggs, speckled with red or purple ; 

 Ducks and Geese lay spotted eggs of a huffish or greenish white ; Cor- 

 morants' and Grebes' eggs are covered with a rough white, chalky coat- 

 ing ; those of Gulls are olive, with brow^n or grey spots ; Au'ks' eggs vary 

 wonderfully in colouring and markings ; and those of Petrels are white, 

 minutely speckled with a zone of brown. White eggs are generally laid 

 in covered nests, or in holes ; as are those of Barn Owl, Dipper, Swift, 

 Kingfisher, Rock Dove, Sheldrake, Puffin, and Petrels. 



Eggs placed openly on the ground are protectively coloured so as to re- 

 semble surrounding objects. Instances of this are afforded by the eggs of 

 the ringed Plover and Lesser Tern, which so closely resemble the pebbles 

 that surround them on the sea beach that one may tread on these eggs 

 before recognising them. 



The state of the young when hatched differs remarkably, as between 

 different orders of birds; thus, the young of Passeres, of most of the 

 Picaria, and of the Steganopodes, are blind, naked, and helpless, and are 

 fed by their parents. Such young birds are hatched in comfortable 

 nests, in which they remain until they are fledged. 



The condition of the young in these birds contrasts with what obtains 

 zxixow^ Anseres^ Galliiice, Fulicarice, and Limicolcc, whose young can— almost 

 at once — run or swim, and feed themselves; and are covered with down 

 protectively coloured, which makes them resemble when they squat 

 lumps of moss or peat. 



