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SUBPHYLUM VERTEBRATA: 



NESTING 



Most birds construct some sort of nest. The nest 

 may be only a few twigs placed upon a particular site 

 or it may be a very complex structure. However, 

 some birds make no preparation whatsoever for the 

 laying of their eggs. Nest building might be a joint 

 eflbrt of both sexes, a phenomenon where one sex 

 supplies materials and the other constructs, or a 

 single effort of one of the sexes. In the various possi- 

 bilities of nest building either the male or female 

 mi?ht take on any of the tasks; in some birds the male 

 is the only sex involved in nest building and incuba- 

 tion of eggs. 



Although many birds tend to nest away from other 

 birds, most show interesting associations with other 

 animals. Birds may nest in colonies of their own 

 kind or mixed colonies with other species. Some 

 mixed colonies do not seem to provide obvious bene- 

 fits; however, instances where small birds nest very 

 close to hawks and owls seem to be "protective" for 

 the smaller birds. In addition, there are often in- 

 vertebrates, usually insects, inhabiting birds nests. 

 Some of these invertebrates are parasites on the 

 nestlings or adults and others are nest-cleaning forms 

 that remove debris from the birds' nests. 



Although birds lay eggs, not all birds lay eggs in 

 their own nests. Some birds, notably cowbirds and 

 cuckoos, lay their eggs in the nests of other species of 

 birds. In these "parasitic" birds the young tend to 

 hatch and develop quite rapidly, factors that usually 

 result in death to the otfspring of the parasitized 

 parents. 



The young of birds are of two types, advanced or 

 immature. The fairly advanced, feathered young 

 hatch in a state that enables them to care for them- 

 selves. There is little if any posthatching care of such 

 birds by their parents. Immature hatchlings lack 

 feathers, have their eyes closed, and are almost com- 

 pletely dependent upon parental care. Advanced 

 young birds include the ostrich and its allies, tina- 

 mous, fowls, gulls, shorebirds, cranes, ducks, geese, 

 grebes, and loons. The immature condition is char- 

 acteristic of penguins, cormorants, petrels, alba- 

 trosses, herons, storks, pigeons, owls, hawks, parrots, 

 swifts, woodpeckers, and perching birds, including 

 the sparrows and their allies. 



iiRRrriiR-i 



Many birds establish territories, areas actively de- 

 fended against their own kind and. frequently, other 



animals. Territories are of two kinds, breeding and 

 nonbreeding. Breeding territories may be for mating 

 purposes only, but may also be for nesting and/or 

 feeding. Nonbreeding territories are used for feeding, 

 wintering, and/or roosting. Territories are usually 

 established by the males and involve pursuit, plum- 

 age display, and fighting behavior toward outsiders. 

 Singing is the proclamation and warning of territory. 

 Females may or may not aid in defending a territory; 

 however, females are almost always less active than 

 males in expressing territorial behavior. Territorial 

 behavior is a strong instinct; moreover, it is for the 

 purpose of defending an area and not such things as 

 protecting a nest, eggs, young, and/or a mate. Of 

 course, this behavior does lead to such protection, as 

 well as being a means of instigating a sexual bond, of 

 limiting the bird population of an area, and of guar- 

 anteeing cover, nesting materials, and food for the 

 birds of a given locality. 



soNc; 



Various functions might be attributed to bird song. 

 It seems to proclaim territory and warn against in- 

 trusion, act as a means of sex identification, and 

 perhaps release excess energy. Most females do not 

 produce true songs. Songs are simple to complex, 

 usually entirely vocal, and few males cannot sing. 

 The duration of individual songs is associated with 

 the annual cycle. Full song comes with the establish- 

 ment of territories, decreases or ceases during mating, 

 resumes during nest-building, egg-laying, and incu- 

 bation, wanes with caring of the young, and usually 

 stops unless a second brood is reared. Most singing 

 is from a conspicuous perch and mostly away from 

 the nest. A singing male can be a very busy bird; one 

 patient observer counted the 2305 songs of a male 

 song sparrow in one day. However, songs usually are 

 not equally rendered throughout the day; there are 

 eai'ly morning and, to a lesser extent, evening peaks. 

 \'oung males start singing relatively soon, within a 

 month after hatching in some species. Experiments 

 have shown that the basic song is inherited but its 

 perfection is learned from the adults; experimental 

 birds can be taught some different or modified songs. 



CLASS MAMMALIA (Mammals) 



Diagnosis: skin dry, more-or-less covered with 

 hair, glandular; typically four limbs, variously 

 adapted for walking, burrowing, climbing, flying, or 



