摘要:

SummaryAspects of the biology ofEudyptes paclzyrhynchusnesting on the west coast of the South Island of New Zealand were studied over six seasons. Nests occur in small scattered groups on steep slopes covered with heavy rainforest, beneath which the birds are protected from temperature extremes.After about four months at sea, the breeding birds return to land at the height of the southern winter. They aggregate in small, loosely organized groups, breed annually and tend to retain the same nest‐site and mate from year to year. They are ashore to breed for about 20 weeks before their chick departs. Incubation lasts for 31–36 days, and is undertaken in long shifts by both sexes in turn. It does not begin until the second and larger of the two eggs has been laid. The hatchling is guarded by the male for about three weeks, during which time it is fed almost daily by the female parent. The chick then joins a crèche and from then is fed by both parents until, at about 75 days old, it leaves for the sea. The parents also leave thereafter.Details are given of egg dimensions and weights, of egg loss, rates of chick‐growth, the fate of twins and of the food brought to the chicks. Egg and chick losses are high. The heavy rainfall and frequent storms seem major causes of loss. The birds seem incapable of rearing more than one chick, and when two are hatched a size disparity soon appears leading to the death of the smaller, apparently through starvation.The adults moult annually in the forest, often on their nests, after some 60 to 80 days spent at sea fattening up for this event. They fast for about 25 days before their new plumage is sufficiently well grown to permit their return to feed. Their whereabouts out of the breeding season are unknown.Display and associated behaviour are complex. They involve many dramatic attitudes in which the flippers and crests feature prominently accompanied by loud vocalizations.In an Appendix figures are given for dimensions of breeding pairs and details of other morphological differences between the sexes and between members of the present species and its closely related congenerE. ro

ISSN:0019-1019    

DOI:10.1111/j.1474-919X.1974.tb00220.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

SummaryThe number and distribution of the White PelicanPelecanus onocrotalus roseusand the Pink‐backed PelicanP. rufescenswere studied in the Ruwenzori National Park, Uganda, by means of aerial surveys carried out at approximately weekly intervals between May 1968 and December 1969.The White Pelican is migratory and was present in the Park at highest numbers in August 1968 and May 1969 when 2510 and 3927 respectively were recorded. It does not breed within the Park. The Pink‐backed Pelican is resident, with a population averaging about 1350 birds.Pelicans are distributed in discrete flocks on loafing grounds. Flocks of the White Pelican tend to be bigger than those of the Pink‐backed. Forty‐three loafing grounds were recognized in the Park, and it is shown that there is no difference between the species in the frequentation of these grounds. The areas favoured by both species are characterized by flat, open stretches close to water; steep slopes and heavily vegetated shore‐lines are avoided.The feeding behaviour was studied by direct observation and through cine‐photography. Only the White Pelican feeds communally in coordinated groups; this species also often feeds singly. The feeding sequence of both species is described, and is divided into four phases:searching, trapping, catching and swallowing. The searching phase lasts about six times longer in the Pink‐backed Pelican than in the White. The White Pelican feeds further from the shore than does the Pink‐backed. There is little difference between the species in the daily feeding pattern. Feeding takes place throughout the day but mostly from dawn to about 10.00 hrs and from 17.00 hrs until dusk. The rest of the day is spent mainly in preening, resting or bathing.The food of pelicans is exclusively fish. The White Pelican takes mainly largeTilupia, andHaplochromisand fish fry to a lesser extent. The Pink‐backed Pelican feeds largely on fish fry, butTilapiaandHaplochromisare frequently taken and by weight are more important than the fry. However, theTilapiuare smaller than those taken by the White Pelican. Ecological separation between the two species is achieved through these differences in their feeding behaviour.It is estimated that the White Pelican takes 1201 g and the Pink‐backed Pelican 776 g of fish each day. The total amount of fish eaten by both species from Lake George during 1969 was calculated to be 591 709 kg. This is small (c. 3%) compared with the estimated total fish production of the lake but quite appreciable (12.7%) as a proportion of the total caught by man. It is concluded that the pelican populations are probably not important as a link in the chain whereby organic matter transferred from land to water by the Hippopotamus is r

ISSN:0019-1019    

DOI:10.1111/j.1474-919X.1974.tb00221.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

SummaryThe 165 000 km2sub‐desert corridor in which Lake Rudolf lies may affect the routes taken by Palaearctic migrants in eastern Africa. A five‐week study was made at Lake Rudolf during the spring migration period. The area is important for water birds, especially waders. It is less important for land birds, although on passage several passerines occur abundantly on Central Island, and some commonly in similarly well vegetated area (Turkwel river, littoral reedbeds). Some may fatten there before emigrating. Evidently the sub‐desert corridor is not so inhospitable that it is entirely avoided or overflown by mig

ISSN:0019-1019    

DOI:10.1111/j.1474-919X.1974.tb00222.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

SummaryThe heaviest clutches (2 eggs) laid by WoodpigeonsColumba palumbusin a Cambridgeshire study area weighed 30% more than the lightest. Yet the variation in egg‐weight within clutches was less than 1 %. Irrespective of initial weight, eggs lost weight at the same constant rate during incubation. Heavy eggs hatched more successfully than light eggs and none weighing less than 16 g hatched. There was no correlation between chicks' weight at hatching and their weight at day 6 during the July‐September part of the breeding season. The ability to feed crop milk at this stage could compensate for low chick‐weight, but this might not be true early in the season. Weight at day 6 was correlated with the weight at day 16 or 17. The growth pattern is discussed.Chicks in broods of one achieved a higher weight at day 17 than those in broods of two. The survival rate both in and after leaving the nest was the same in both brood‐sizes. Chick‐weight in artificially created broods of three was almost as high as in broods of two, but again data refer to the July‐September period when abundant cereal food is available. Survival before and after fledging was lower in broods of three.Clutch‐ and egg‐weight declined from April until September. It is suggested that this is adaptive, in that the adults produce heavier eggs when food supplies are most difficult to collect. The critical period probably occurs during the few days when the adult must produce crop milk and the young cannot be left unattended. Thus egg‐weight depends on the female's capacity to acquire nutrients, and is related to the needs of embryonic development and the amount of compensation in nutrient supply which can be provided immediately after hatching. But clutch‐size is more related to the bird's ability to feed and rear young to the point of fledging, thereby influencing the number of offspring which survive to leave progeny. Egg‐weight and female body‐weight were positively correlated in females weighing less than 480 g but not in heavier females. First‐year birds did not acquire adult weight until midsummer and they would probably produce light eggs if they could breed before this month. However, their gonads do not recrudesce until July and this prevents them breeding in the spring.Seasonal changes in body‐weight and fat content of adults and first‐year birds are described and discussed; differences were noted between adult males and females which were considered to be adaptive.The moult is described. It begins in April and continues until November, approximately one pair of primaries being replaced per month. The moult ceases during the winter months, when it is known that food supplies become limiting.Woodpigeons lay light eggs relative to their body‐weight but can achieve the extra parental care needed for the altricial chicks by producing crop milk. Because the moult is extended, the energy demands of moulting and breeding combined are relatively low and this enables the Woodpigeon to have a long breeding sea

ISSN:0019-1019    

DOI:10.1111/j.1474-919X.1974.tb00223.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

SummaryZonotrichia capensis australisinhabits Argentina from the northernmost limits of the Patagonian steppe south through Tierra del Fuego, and extends westward to the Pacific slope in southern Chile. At least part of the population has a north‐south migration along the Andean foothills of Argentina as far north as southwestern Bolivia. The breeding range ofaustralisis bounded on the north and northwest by subspecies ofZ. capensis (chilensis, choraules, and possiblyhypoleuca) having conspicuous black lateral crown‐stripes. Topotypicalaustralis(Tierra del Fuego) have plain grey crowns, but the frequency of black nuchal markings and faint lateral crown‐lines increases northward in the coastal populations. In inland populations (Andean piedmont) the frequency of black crown markings is apparently reversed, increasing southward. The size (wing‐length, tarsus, bill, and probably body‐weight) ofaustralisdecreases northward in both coastal and inland samples.The nesting season ofaustralisbegins in late November and early December and extends to mid January and early February. Postnuptial moult begins from mid December to early January. Moult proceeds while the testes are apparently still functional. Postnuptial moult terminates from late January through mid March. There is no evidence in the current data of geographical trends in the chronology of nesting and postnuptial moult. The calendars appear to be about the same throughout the range ofaustralis.Postjuvenal moult begins about 4–5 weeks later than the onset of postnuptial moult and terminates in the latest birds in about mid March. Northward migration begins at abou

ISSN:0019-1019    

DOI:10.1111/j.1474-919X.1974.tb00224.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

ISSN:0019-1019    

DOI:10.1111/j.1474-919X.1974.tb00225.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

ISSN:0019-1019    

DOI:10.1111/j.1474-919X.1974.tb00226.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

ISSN:0019-1019    

DOI:10.1111/j.1474-919X.1974.tb00227.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

ISSN:0019-1019    

DOI:10.1111/j.1474-919X.1974.tb00228.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

ISSN:0019-1019    

DOI:10.1111/j.1474-919X.1974.tb00229.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY