摘要:

This paper describes the pattern of territory usage by male Pin‐tailed WhydahsVidua macroura, and the display postures used by territorial males, intruding males and visiting females are described. Each territory holder used one or two favoured display sites at which he was visited by, and displayed towards females in groups of one to eight. The frequency of display flights and song output reflected the diurnal pattern of visits by females. Each female was courted by up to six males, but the number of copulations observed was too few to indicate the type of mating system used. The operative sex ratio was estimated at 1:6 (females to territory holders), and the results of a removal experiment suggested that a proportion of males was prevented from breedin

ISSN:0019-1019    

DOI:10.1111/j.1474-919X.1984.tb02073.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

Kentish PloverCharadrius alexandrinuspairs generally re‐nest together after the loss of a clutch. In contrast, two females who hatched clutches changed mates before re‐nesting, thus proving sequential polyandry. Observations of adults accompanying broods show that females normally desert the brood about a week after hatching. The majority of birds change mates between seasons, even if their partner from the previous season is al

ISSN:0019-1019    

DOI:10.1111/j.1474-919X.1984.tb02074.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

The effect of spring temperature on first egg date, laying period and last clutch date was studied in the Mallard and Tufted Duck. Seasonal clutch size and egg size trends were also examined. In years When Mallard laid early, Tufted Duck also did so. The first Mallard clutch was started earlier and laying period was longer in years with a high mean February temperature. The last clutch was started later in years with a high mean June temperature. In Tufted Duck the laying period increased and the last clutch was started later in years with high mean April temperatures.Mean hatching date of Mallard clutches was later in years when the date of peak chironomid emergence was late.In both species, clutch size declined through the season. Egg volume was not related to clutch size in either species, but egg volume in the Tufted Duck declined through the season. No difference in Tufted Duck egg size existed between sites, but the significance of egg size on duckling survival is discussed. Genetic factors related to individual consistency in egg size in Mallard may have obscured egg volume trends during the season because of renesting.

ISSN:0019-1019    

DOI:10.1111/j.1474-919X.1984.tb02075.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

Boat‐tailed GrackleQuiscalus majoreggs averaged 8.09 g wet weight. Mean egg weight represented 8 05 % of female body weight. Based on egg weight, Grackle eggs have a shorter incubation period than the general passerine pattern.Egg weight varied significantly with sequence of laying and between clutches in both two‐egg and three‐egg clutches. Last laid eggs weighed less than first laid eggs. The mean weight of the first two eggs laid in three‐egg clutches did not differ from the mean egg weight of two‐egg clutches. The average clutch of two and three eggs weighed 16.33 g and 24.16 g, respectively.Mean egg weight varied between study colonies and with season. Grackles at East Lake laid eggs that weighed less than grackles at either Alligator Lake or North Lake. Eggs laid during March averaged less than eggs laid later in the season. The locality variation reflects the different timing of nesting between sites rather than food abundance. As nutrient provisioning increases with an increase in egg weight, the seasonal change in egg weight probably reflects improved feeding conditions for the female. This suggests that selection favours beginning laying before reserves of the female are sufficient to lay the largest egg possible.The size of the young at hatching was correlated with egg size. Newly hate had young averaged 79.6% of fresh egg weight. Egg weight did not determine the probability of hatching or starvation of the young. Females do not appear to adjust egg size facultatively depending on the sex of the young. Eggs producing males and females did not vary significantly in weight, whether comparisons were made within or between

ISSN:0019-1019    

DOI:10.1111/j.1474-919X.1984.tb02076.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

ChaffinchesFringilla coelebswere introduced to New Zealand from Great Britain over 100 years ago, and since then their songs have diverged from British ones in both syllable structure and basic organization of syllable sequences. The New Zealand populations seem to be unique in that their songs have undergone differentiation of trill segments by progressive elaboration of syllable morphology and hp ascending and descending changes of pitch. Published sonagrams of British song types have significantly more trill phrases and significantly fewer syllables in the end phrase than do Yew Zealand ones. Many New Zealand song types have much elaborated end phrases and concomitantly simpler trill segments, with songs quite commonly having only one trill phrase. This reversal of complexity between the trill and end phrase in New Zealand seems to have been derived by progressive reduction of the ultimate trill phrase to one syllable, and by recombination of end phrase syllables from different song types into one compound end phrase. The significance of the increased complexity in the end phrases of many song types may relate to the sound transmission properties of dense pine forests in New Zealand, in which Chaffinches are ubiquitous. Elaborate end phrases degrade much less from reverberation in pine forests because individual syllables have more dispersed temporal patterning.Recombination of syllables to form new song types is a major mechanism of song differentiation in New Zealand. Although whole song copying is the predominant mode of replication, very few song types in a locality sample are composed of a unique set of syllables. Rather, song types in an area are interconnected by different combinations of shared syllables, suggesting that the incorporation of some local syllables in a bird's repertoire is sufficient to signal its status as a member of a neighbourhood and also allows the evolution of broadcast complexity.

ISSN:0019-1019    

DOI:10.1111/j.1474-919X.1984.tb02077.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

The dynamics of an Eider Duck population have been investigated over 25 years, using census and capture‐mark‐recapture methods. During the study the population increased two and a half fold, with two periods of major increases in numbers, giving a stepped growth pattern. Mean clutch size showed considerable annual variation, the extremes being 5.40 and 3.78 eggs. The variation in clutch size was greater than that recorded in the Netherlands. Adult female Eiders had a high annual survival rate, averaging 0.895, and varying between 0.75 and 1.00 in individual years. The survival rate decreased markedly in the old ducks. There was no indication of any change in the survival rate during the study. Recruitment of ducks to the breeding group was irregular, with most years showing little recruitment and a few years high recruitment. However, recruitment, associated with good duckling survival, appears to have been the main factor associated with increase in the population. In many years, an appreciable proportion of the surviving ducks, which had already bred in a previous year, failed to nest. The extent of non‐breeding increased during the study and in one year, 1973, this reached 65%. Lower clutch size and adult survival were associated with years of high non‐breeding. The ‘red‐tides’ in 1968 and 1975 appeared to have little effect on the Eider. It is suggested that the Eider missed breeding in years in which its survival was potentially poor, in order to maximize its reproductive output during its life span. This is supported by the smaller clutch size laid by those females which nest in years when many females fail to breed. It is suggested that young ducks may also miss breeding in the year after first nesting but this is not associated with the non‐breeding in older ducks, although it may he related to body condition. It is suggested that non‐breeding by adults of long‐lived birds may be widespread. This has important implications in survey work b

ISSN:0019-1019    

DOI:10.1111/j.1474-919X.1984.tb02078.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

The time budgets of Tufted ducklingsAythya fuligulachanged radically as they matured, particularly during the first 12 days of life—the most critical time for survival. The amount of time spent skimming for surface chironomids declined during the period from hatching to 21 days. Time allocated to diving increased during this period. Ducklings between the ages 12–37 days visited land in order to preen and sleep during the day. Time spent preening on land increased up to 21 days of age and declined thereafter. Diving rate was highest in ducklings of the 20–30 day age category and declined in those older than 30 days. The amount of time spent under water on each dive, equated with diving success, increased wit

ISSN:0019-1019    

DOI:10.1111/j.1474-919X.1984.tb02079.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

Barn Owls have only recently colonized Peninsular Malaysia, nesting in the roof spaces of houses in oil palm estates and feeding on the rats which inhabit these plantations. Pellet analysis showed that the prey spectrum was confined almost entirely to three species of the genusRattuswhich are the major pests of oil palm. There was no annual variation in diet. Breeding showed a broad seasonality but occurred in all months of the year. Mean clutch and brood sizes of 6.6 and 4.6 respectively were recorded, most pairs producing two broods a year although on two occasions three were raised. Overall hatching success was 69.0% with first clutches more successful (79.9%) than second (57.3%). First broods fledged 86.1% and second broods 69.1% of young fledged. Comparison of growth rates of different sized broods suggested that there is a physiological maximum at which all broods proceed irrespective of brood size. The behaviour al changes needed in hunting techniques when colonizing dense plantations rather than the more usual open habitat of Barn Owls is discussed. The breeding strategy seems to be one of producing large clutches and broods, and frequent breeding attempts in a habitat with a high potential carrying capacity.

ISSN:0019-1019    

DOI:10.1111/j.1474-919X.1984.tb02080.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

This paper describes the strategies of resource utilization in the course of the breeding season by five radio‐tagged Grey HeronsArdea cinerea. The seasonal changes in exploitation of the environment by two breeding adults, one non‐breeding adult and two non‐breeding first‐year birds were studied from March to August 1982, near Zonhoven in Belgium.Two adult breeding birds could be followed continuously from the end of March until the middle of June. During the first month they explored an extended area all around the colony, but each concentrated its search in a specific direction. From the end of April until the beginning of June, most probably from egg‐hatching until the end of breeding activities, each bird spent a very large proportion of its time at a particular feeding site, from which other herons were actively excluded. In the first part of June they again visited different sites, each maintaining its preferred direction. From the middle of June onwards they seemed to have left the fish‐pond area.The pattern of movements of the first‐year birds differed markedly from that of the breeding adults. In April, although both non‐breeding and breeding birds explored large areas, only the areas used by non‐breeders were centred on the colony. From the end of April onwards, probably after general egg‐hatching in the colony, the non‐breeders very rarely revisited the colony, and from May till August their ranges became more and more restricted to very small areas at an increasing distance from the colony. They were never observed defending particular sites.The results are discussed with regard to recent speculations about the evolution of colonies as an adaptation for the exploitation of food resources. Breeding herons seem to explore a large part of the environment during incubation and defend a particular site while feeding their young. Choice of feeding site by non‐breeding birds may be influenced by the site defence of the breeding birds. Non‐breeding birds exploit a large area when breeding birds occupy feeding territories. Perhaps they are forced to forage in less suitable places at this time. Colonies might have evolved as a strategy to minimize effort in resource esploitation as, especially at the beginning of the breeding season, the colony could act as an assembly point in the exploration of the environment. However, its importance as an assembly point diminishes in the course of the season, as non‐breeding birds no longer visit the colony an

ISSN:0019-1019    

DOI:10.1111/j.1474-919X.1984.tb02081.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

ISSN:0019-1019    

DOI:10.1111/j.1474-919X.1984.tb02082.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY