BIRD HELPERS AT NESTING TIME [Ref]
In many a well-run American home the children have definite responsibilities, the older children may help look after the younger, and even grown-up relatives may stay as part of the family group. As in so many cases there may be found parallels to this in the bird world.
The ani, the curious tropical American cuckoo that makes communal nests, is gregarious and the young of the first brood become part of the parent flock. Two more broods may be raised during one season in Cuba, and the young of the earlier brood may feed their younger brothers and sisters of the later brood. The same has been recorded for many other species in the wild: in eastern bluebirds, mountain bluebirds, wheatears, long-tailed titmice, barn swallows, coots, rails, and gallinules young have been recorded as feeding still younger birds. In captivity this habit has been seen a number of times. Young birds hardly able to feed themselves may help feed still younger individuals of the same or other species, and a nestling crowned hornbill has been seen to offer food to its nestmates. This tendency to feed nestmates evidently appears very early in the life of the bird, as Dr. C. O. Whitman, who worked intensively with pigeons at the University of Chicago, recorded a hybrid dove only twelve days old that fed its nestmate.
FIVE JAYS AT A NEST It was rather generally known that occasionally more than the two parent birds attended a nest, but until 1935, when Alexander Skutch, the authority on the biology of Central American birds, published his paper "Helpers at the Nest," few of us realized how widespread this was. Since most birds of a species are difficult to identify individually, one must actually see the extra, unmated helpers at the nest along with the parents to be sure they are there. In the brown jays of Central America that Skutch studied closely the colors of the soft parts, bill, feet, and eye rings were variable and he was able to recognize many individual birds. At five nests he watched he found at least one helper at each nest, and at one there were five helpers, all bringing food. Sometimes, if between an incoming, food-laden bird and the young, they would take the food and pass it on to the nestling. At one nest the unmated helper was more zealous in guarding the nest than were the rightful parents. Sometimes, perhaps, these helpers were unmated young of the parents' previous year's brood, but this could hardly have been the case where there were five helpers, for the brown jay ordinarily raises no more than three young a year. A black-eared bush tit of Central America seems to have a great preponderance of males and at one nest in addition to the parents there were three other males bringing food to the young.
MATERNAL PENGUINS Perhaps the most striking example among birds is the emperor penguin. These birds breed in the dark and cold of the antarctic winter, on the edge of the ice shelf. The single egg is carried on the feet of the brooding bird; indeed one wonders what other adaptation for holding the egg would be possible in this land of ice, snow, and water. Only a few of the adults in each colony lay eggs any year, perhaps one in five, or one in twelve. But all the adults in the colony have the urge to incubate and brood. Thus many old birds, rather than merely the two parents, may take turns caring for each egg or chick, leaving the rest ample time to feed. So strong is the urge to brood that struggles may take place over a chick and it may be very roughly handled. Indeed the chicks may so resent this that they may creep away into ice crevices and freeze to death. Another strange turn this behavior may take is that frozen eggs, dead chicks, and even bumps of ice of suitable size are carried on the feet and covered with the birds' feathers by their "would-be fathers and mothers."