336 GENERAL ORNITHOLOGY part ii 



family Phalaropodidce, and some other Limicoline genera, the male 

 incubates. Most birds attend to their own eggs ; many cuckoos 

 (CuculidfCe) and the species of Molothrus, are parasitical, laying in the 

 nests of other birds, which are thus forced to become foster-parents 

 of alien offspring, generally to the destruction of their own. This 

 seems to result from some peculiarity of the egg-laying process, which 

 does not permit several eggs to be incubated and hatched simultan- 

 eously. It is not so unusual among American cuckoos as generally 

 supposed. The degree of development to which birds attain in 

 the egg differs in AUrkes and Prceeoces (see p. 131). They break 

 the shell by pecking at it, and struggling ; for the former operation 

 the bill is often tempered at the tip by a hard knob which is after- 

 ward absorbed. The necessity of providing a receptacle for eggs, 

 in which they may be incubated, results in nidificaUon or nest-build- 

 ing ; and the extraordinary taste and ability .many birds display in 

 this matter, as well as the wide range of their habitudes, furnishes 

 one of the most delightful departments of ornithology, called caliology 

 (Gr. KttAta, halia, a bird's nest; see p. 81, note). Many birds 

 burrow in the ground ; others in trees ; the most beautiful and 

 elaborate nests are furnished by various members of the Oscines, 

 the weaver-birds of Africa (Ploceidce) probably taking the lead. 

 The male sometimes constructs his own " nest " apart from that in 

 which the female incubates. "Certain conirostral Cantores still 

 practise in the undisturbed wUds of Australia the formation of 

 marriage-bowers distinct from the later-formed nesting-place. The 

 satin bower-bird (Ptilonorhynchiis Jiolosericeus), and the pink-necked 

 bower-bird {Ghlamydodera maculata), are remarkable for their con- 

 struction on the ground of avenues, overarched by long twigs or 

 grass-stems, the entry and exit of which are adorned by pearly 

 shells, bright-coloured feathers, bleached bones, and other decorative 

 materials, which are brought in profusion by the male, and vari- 

 ously arranged to attract, as it would seem, the female by the show 

 of a handsome establishment " (Owen). The extraordinary nests of 

 the Crotophaga are used in common by a colony of the birds. " Edible 

 birds' nests," constructed by swifts of the genus Colloealia, consist 

 chiefly of seaweeds and inspissated saliva. Perhaps the most re- 

 markable of all the receptacles of eggs is that which the penguin 

 makes of its own body, the egg being taken in a sort of pouch 

 formed by the integument of the belly, something like that of a 

 marsupial mammal. 



