摘要:

Summary.This analysis was initiated to examine the relationship between the rate of growth in birds and their development of mature function. The literature was surveyed for data on growth and development, and the growth curves of 81 species were chosen for the analysis. Growth curves of most species were fitted with the Gompertz equation, and the rate constants of the equation were used as an index of the growth rate. For those species whose curves were fitted better by other equations, with a slightly different form, appropriate conversion factors, derived in this paper, were employed.Among species with similar modes of development, growth rate decreases with increasing body weight in an allometric manner, with slopes of –0.26 to –0.42, depending on the group. Between groups, the rate of growth in body weight was found to be closely associated with the rate of development of function, in particular, the acquisition of flight. Among those species that can walk at an early age, but acquire flight relatively late, the rate of growth depends primarily on the relative size of the musculature of the lower extremities.Data are presented to refute the hypotheses that growth rate is adjusted to nestling mortality, or that the energy requirements of the young (and hence their growth rates) are balanced against brood size. It is concluded that most species grow at some physiologically maximum rate, but as yet it is not possible to distinguish between limitation of growth rate at the level of the organism or at the level of the tis

ISSN:0019-1019    

DOI:10.1111/j.1474-919X.1973.tb02636.x

出版商:Blackwell Publishing Ltd    

年代:1973

数据来源: WILEY

摘要:

Summary.Turnstones arrive on Ellesmere Island in late May or early June. Pair‐formation takes place during migration, or after arrival in courtship groups along the beaches, or on the nest territory, depending on weather conditions. Pair‐formation was not observed at Hazen Camp in 1966 as most birds were already paired when observations began on 3 June. The preferred nesting habitat wasDryas‐hummocked tundra closely associated with a marsh, stream, or pond. A census area of 240 ha supported 13 breeding pairs, possibly 14; the total number of pairs breeding in the Hazen Camp study area was estimated to be 70 (3.04 pairs/km2). Egg‐laying began on 10 June, with 46% of the first eggs laid 13–15 June. 62% of the sets were completed between 19 and 21 June. Both sexes incubated, the female regularly and the male sporadically. Hatching was also well synchronised; most clutches hatched between 7 and 14 July. Nest success was high (79%). After hatching territories dissolved and family groups moved freely over the tundra, concentrating at ponds where food was readily available for the young. Both adults attended the young during the pre‐fledging period, but the females apparently departed long before the young fledged. Males left once the young could fly and the adult fall migration was complete by early August with the exception of late breeders. Most of the young departed in the second half of August. Fall migration is complete by late August or early September.The breeding season appears to be timed so that the young are raised when food is most abundant. Food supply (dipterous insects, especially adult chironomids) was highest from 8 to 12 July at the peak of the hatching period. While food supply for the young declined during the growing period, the early departure of half the adult population, and family movements over the tundra, appeared to reduce the food demand correspondingly.Food appeared to influence the distribution of breeding pairs markedly, restricting them to the vicinity of marshes, streams, and ponds. Territoriality displayed by Turnstones is believed to be closely associated with the protection of the nest against predators and adult food requirements during incubation; it also seems likely that territory has at least a local effect in regulating the number of bre

ISSN:0019-1019    

DOI:10.1111/j.1474-919X.1973.tb02637.x

出版商:Blackwell Publishing Ltd    

年代:1973

数据来源: WILEY

摘要:

Summary.Sanderlings on Bathurst Island in the Canadian arctic have two patterns of incubation. At some nests the eggs are covered soon after the fourth egg has been laid and at others incubation is delayed for 5–6 days. Because the delay is about the same time required to lay a second clutch and because a single individual alone incubates at any one nest, we suspected that Sanderlings might normally lay two clutches in a season, the male caring for one brood and the female for the other.Histological and gross examination of the ovaries of two females taken as the birds began incubation showed eight freshly ovulated follicles in each female. The size gradation and histological appearance of the follicles indicated that two clutches of four eggs each had been laid within 8–10 days by a single female. The ovary of one female had additional large yolky follicles, suggesting a physiological capability of further ovulations.Field conditions in the arctic summer are highly variable, and the small eggs and the rapid sequence of broods of Sanderlings may be breeding adaptations that permit them to multiply the traditional wader clutch of four eggs by 2 or 3 in favourable years. Selection for mating systems characterised by brief pair bonds and by polyandry is expected in precocial birds where some broods are incubated and cared for by the male, but further field work is required to determine the precise mating system of Sanderli

ISSN:0019-1019    

DOI:10.1111/j.1474-919X.1973.tb02638.x

出版商:Blackwell Publishing Ltd    

年代:1973

数据来源: WILEY

摘要:

Summary.The feeding ecology of Wigeon wintering in the vicinity of Bridgwater Bay National Nature Reserve is described. The birds roost on mudflats in the Bay during the day and feed, mainly at night, on saltings and wet pastures in the surrounding area. Their food, ascertained from gut analyses, consists largely of grass leaves; with roots, stolons, bulbils and seeds of secondary importance. Analyses including gizzard contents much exaggerated the importance of seeds because they are retained in the gizzard for longer than softer items.An investigation of Wigeon feeding behaviour and food preferences on salting pasture is described, using the density of the birds' droppings on different vegetation zones to assess usage, and faecal analysis to determine the composition of the selected diet. The technique of faecal analysis is discussed in relation to feeding studies on grazing wildfowl.Disturbance is a very important factor affecting the availability of feeding habitat, and this can mask the birds' food preferences. Early in the winter, Wigeon selectPuccinellia maritimain preference toAgrostis stoloniferaandFestuca rubra.They do this initially by selecting the broad zone in which they feed, by selecting feeding sites within zones, and particular plant species from a mixed sward. The birds are more selective when feeding in less preferred zones. The mechanisms and reasons for food selection are discussed in relation to characteristics of the habitat and of the plants. It is concluded that the nutritional value of the plants is important in determining the birds' preference, but that other factors also play a part.Wigeon are flexible in their feeding habits and are increasingly found on inland habitats. They are adaptable in using new roosts, and in modifying their behaviour in response to changes in food supply and changes in disturbance pressures.

ISSN:0019-1019    

DOI:10.1111/j.1474-919X.1973.tb02639.x

出版商:Blackwell Publishing Ltd    

年代:1973

数据来源: WILEY

摘要:

Summary.The equations of motion for gliding flight in a wind gradient have been used to study the way in which the albatross can gain height in non‐powered flight against a purely horizontal wind. It is argued that a type of potential and kinetic energy parameter is convenient for the assessment of climbing performance if the kinetic energy term involves the airspeed rather than the absolute velocity. The gradient with height of this parameter shows a maximum value at a particular climb angle for each speed and wind gradient.Two types of complete flight cycle have been investigated in a logarithmic wind velocity profile having a speed of 15 m/sec at a height of 10 m. The emphasis in the study has been on the possibilities of making progress against the wind. Progress in any other directions is very much easier to achieve.The first cycle is simple and unidirectional with an upwind dive. Although this leads to a fairly rapid progress against the wind it is shown to be impossible without some power input.By contrast, the more usual flight cycle which involves a dive in the downwind direction is completed very easily without loss of flying speed. In fact, by diving steeply, sufficient excess airspeed can be gained to permit a very long final upwind glide at low level. This repasses the starting position and thus gives a slow but definite nett progress against the win

ISSN:0019-1019    

DOI:10.1111/j.1474-919X.1973.tb02640.x

出版商:Blackwell Publishing Ltd    

年代:1973

数据来源: WILEY

摘要:

Summary.Adult Buller's MollymawksDiomedea bulleribanded in 1948 and 1961 at the Snares Islands south of New Zealand have been recovered between 1961 and 1971. Survival curves are presented which indicate the existence of a constant annual mortality rate of not more than 11.1 % with a mean expectation of further life at the time of banding of not less than 8.5 years.Breeding birds show a strong tendency to retain both the pair bond and the nest‐site. One pair was still breeding in 1971 at the same nest at which it bred 23 years earlier. No re‐matings were recorded while the original partner was known to be still alive.The dimensions of eggs laid over the years by particular females are presented. These enable some general indications to be given of the effects of the age of the female on the dimensions of the eggs which she l

ISSN:0019-1019    

DOI:10.1111/j.1474-919X.1973.tb02641.x

出版商:Blackwell Publishing Ltd    

年代:1973

数据来源: WILEY

ISSN:0019-1019    

DOI:10.1111/j.1474-919X.1973.tb02642.x

出版商:Blackwell Publishing Ltd    

年代:1973

数据来源: WILEY

ISSN:0019-1019    

DOI:10.1111/j.1474-919X.1973.tb02643.x

出版商:Blackwell Publishing Ltd    

年代:1973

数据来源: WILEY

ISSN:0019-1019    

DOI:10.1111/j.1474-919X.1973.tb02644.x

出版商:Blackwell Publishing Ltd    

年代:1973

数据来源: WILEY

ISSN:0019-1019    

DOI:10.1111/j.1474-919X.1973.tb02645.x

出版商:Blackwell Publishing Ltd    

年代:1973

数据来源: WILEY