Non-breeding Individuals Research Articles

Activity Patterns and Social Behavior of Non-Breeding Adelie Penguins

This paper completes a three-part study of non-breeding individuals in the nesting population of the Ad6lie Penguin (Pygoscelis adeliae) at Cape Crozier, Ross Island, Antarctica, where many banded, known-age individuals are present. LeResche and Sladen (1970) and LeResche (1971), who also worked with these birds, found that they first visit the breeding rookery as two-year-olds and first breed when three (female) or four (male). Moreover, many do not breed until five to seven years old. These findings suggest that the rates and processes of physiological, morphological, and behavioral maturation related to reproduction may account for non-breeding individuals. Initially, I compared degree of maturity of the reproductive systems of penguins of various ages. I found that males and most females less than four years old are physiologically or morphologically incapable of breeding (Ainley 1974a). This discovery made it even more intriguing that so many fourand five-yearolds, particularly males, failed to breed. I therefore turned my attention to these birds. A preliminary analysis showed their reproductive behavior to be immature in several re-

Migration Reversal: A Regular Phenomenon of Canada Geese

Migration from a nesting to a wintering ground and back again in autumn was detected each year during a 3-year study of individually identifiable Canada geese (Branta canadensis). Reverse migrants were primarily yearling, nonbreeding individuals and others of nonfamily status.

Comparative Ethology of the Ciconiidae. Part 1. the Marabou Stork, Leptoptilos Cr Umenifer Us (Lesson)

A breeding colony of Marabou Storks, Leptoptilos crunieniferus, was studied at Kitale, Kenya, East Africa, in January 1964 and from October 1964 through May 1965. Further observations were made of non-breeding individuals at Kitale and elsewhere in East Africa. An adult Marabou was kept in captivity for six months, and nestlings were hand-reared in order to observe their behavioral development in more detail. A brief description of the appearance of the Marabou is followed by an account of the plumage and soft part color changes occurring in breeding individuals. Sexes are morphologically indistinguishable in the field, except for slight differences in size and bill shape. In normal flapping flight Marabous beat their wings slowly, at a rate of about 145 flaps per minute. When conditions permit they rely on thermal soaring and gliding for long distance movements. They are remarkably agile fliers for so large a bird and often perform aerial acrobatics when descending from high altitudes. Marabous are omnivorous, and their feeding technique depends on the type of food being sought and feeding conditions. Their bill is not well suited for tearing flesh, and when feeding on carrion, their main food outside the breeding season, they frequently allow vultures to tear the meat into small pieces before attempting to grab it. Aquatic prey, which is taken in quantity during the breeding season, is sometimes located visually and sometimes by feel (tactolocation), depending on the turbidity of the water. Marabous also habitually forage in freshly plowed fields and near brush fires. Occasionally they kill largcr vertebrates for food. Comfort movements are discussed, with emphasis being given to those that seem most typical of storks. Close approach between individual Marabous, either at a feeding area or at a nest-site, often results in ritualized social displays by one or both birds. The specific displays given depend upon the locale of the encounter and the social relationship between the birds. Away from the nest, the Forward Tlanent is the most common offensive display and the Upright Display the most common defensive display. At or near the nest-site, the Aerial Clattering Threa-t and Forward Clattering Threat are the most purely aggressive displays, and the Anxiety Stretclz and Erect-Gape seem to show the highest escape or fear tendencies. The Snap Display and Balancing Posture are ambivalent displays, showing a near balance between tendencies to attack, flee from, and pair with the other hird. The Up-Doiom, a common greeting display between mates and between young and parents, appears to be a friendly appeasement gesture, serving to reduce hostilities in the opposite member. Swaying Twig-Grsping, most likely derived from nest-building movements, probably helps to strengthen the pair-bond. During copulation the male performs Copulation clattering alongside the female's bill ; this display may have its roots in latent hostility between the members of the pair. Following the description of social displays in adults, a section on the behavior of nestling Marabous is presented. Some adult displays, such as the Up-Doiun, appear first in nestlings; the development and maturation of such displays are traced. The major elements in Marabou social behavior appear repeatedly, in varying combinations, in many different displays. A summary of these is presented in Table 1.