摘要:

SummaryVisual and vocal displays of Brown‐capped Rosy FinchesLeucosticte tephrocotis australis,observed in Rocky Mountain National Park, Colorado, and of Aleutian Grey‐crowned Rosy FinchesL. t. griseonuchaon Adak Island, Alaska, are compared and contrasted with general behaviour among the Fringillidae.Visual display behaviour of the two subspecies is very similar. Vocal displays, as shown by sonagrams, are by comparison divergent. Most of the sound energy in the flock call ofgriseonuchais concentrated in a single band of frequencies. The range of these frequencies is small, and the call is whistle‐like to the human ear. The flock call ofaustralis,more like that of other finch species, consists of three major bands of frequencies. Based on this difference, it is hypothesized that the flock call ofgriseonuchamay be specialized for penetration of high background noise, which characterizes the windy environment of the Aleutians. In ambient noise that extends across the frequency range of the flock calls, the narrow‐range flock call ofgriseonuchais relatively high in signal/noise ratio. Some divergence in vocal display may also result from social mimicry in the respective habitats. The flight call ofaustralisis click‐like, and more like the flight call of the 8ympatric Violet‐green SwallowTachycineta thallasineathan that ofgriseonuchaor of descriptions of the flight call of other finches.The two races differ also in general breeding habits. The breeding season, from first sexual chasing to fledging of young, ingriseonuchaspans nearly seven months; the study population was sedentary. Inaustralis,individuals migrate in summer to alpine breeding grounds, and the events of breeding occur within about two months. Males were observed to feed their mates during the nesting period, in both races. Male and female fed the young and removed excreta from the nest, with about equal frequency.Bothaustralisandgriseonuchahave marked excesses of males in the mature populations, but both are monogamous. It is considered that the unbalanced sex ratio may have selective effects on the behaviour associated with reproducti

ISSN:0019-1019    

DOI:10.1111/j.1474-919X.1980.tb02657.x

出版商:Blackwell Publishing Ltd    

年代:1980

数据来源: WILEY

摘要:

SummaryYellow‐billed Shrikes were found to live in groups throughout the year. Within the group, each member helped to defend the group's territory, warn against predators and feed the breeding female, nestlings and fledglings.During the study there was little change in the location of the boundaries and in the areas of the territories occupied by the majority of the groups. The densities of the larger groups were in general two to three times that of smaller groups. Numbers within one group varied by ±24% of the average (12) during a period of three years.Progeny remained in a group for some years before dispersing, sometimes in parties of the same sex. Both sexes exchanged groups, the females moving on average further than males. During successive periods in the history of a group the representation of the sexes varied from a surplus of females to a surplus of males. In the population as a whole the sex ratio was probably parity.Only one female bred in a group at a particular time and she alone incubated. Eggs were laid on consecutive days. Breeding started at the height of the dry season; the first peak in egg laying occurred at the beginning of the rains; laying continued through the wet season and ceased usually in August. The most frequent clutch size was four, and varied little within a breeding season or between seasons. The incubation period ranged from 15 to 18 days, the most frequently recorded being 17 days. The nestling period was 19 days. The percentage of total eggs laid that produced fledglings was 25% and yearlings 11%.Young shrikes were independent in the seventh week, participated in group displays in their tenth week and fed fledglings in their fourteenth week.The age of first breeding was not discovered. Two females in their sixth year were still helpers in a group at the end of the stu

ISSN:0019-1019    

DOI:10.1111/j.1474-919X.1980.tb02658.x

出版商:Blackwell Publishing Ltd    

年代:1980

数据来源: WILEY

摘要:

SummaryThe paper presents data on the breeding and predation of Puffins in two areas of different nest density within a single colony on Dun, St Kilda group, Outer Hebrides in 1973‐78.Within a season birds laying early had a slightly higher nesting success than birds laying late, but laying date had little influence on the peak and fledging weights of young. The main disadvantage in late laying was a reduced chance of relaying if the first egg was lost.Breeding success and chick weights varied from year to year. The 1974 season was the least successful with the lowest nesting success, lowest frequency of feeds, lowest calorific value of feeds, lightest chicks and slowest growth. Overall breeding performance was not related to the annual mean laying dates.In all years pairs nesting in the area of high nest density did better than pairs nesting at low density. The effect is attributed to differential predation and disturbance by predatory gulls. At least 4.2% of adult Puffins breeding in the area of low burrow density were killed by gulls each breeding season; this is higher than the total annual mortality found in three other studies. Only 0.9% of adults from the high density area were found killed. The subpopulation in the low density area cannot survive without much immigration, yet there is no evidence that this happen

ISSN:0019-1019    

DOI:10.1111/j.1474-919X.1980.tb02659.x

出版商:Blackwell Publishing Ltd    

年代:1980

数据来源: WILEY

摘要:

SummaryA population of about 15 pairs of Grey Phalaropes was studied during one season. Observations were made of behaviour and feeding habits at all stages in breeding.Females advertized to males with Circle Flights over the breeding grounds, and became gregarious and mutually intolerant during the latter part of the season. Females also took the initiative in courtship, but males defended the pair bond against intruders and incubated the eggs. Pair bonds were believed to be stable until after egg‐laying. Descriptions are given of ritual activities and the context in which they were witnessed. Courtship Touching followed intrusion by a strange female, expelled by the male's Driving Flight. Rattling occured at moments of general excitement. None of these rituals appeared to be pre‐copulatory. A ceremony leading to the selection of a nest site, in which the female takes the initiative, is described for the first time. Females deserted their mates during incubation. A qualitative model is proposed to explain the variability in the time between laying and female desertion, in terms of opportunities for polyandry and risk of nest predation.For food, the birds depended largely on a rich supply of chironomid midges, though aquatic larvae and spiders were also important, particularly early in the season. Three feeding techniques were distinguished and some assessment was made of the profitability of each, in the light of data on feeding rates.The mating system (monogamous role reversal) is believed to have evolved from the habit of double‐clutching. It is proposed that a factor in the emancipation of females and their assumption of the courtship initiative is the small size and fragmented distribution of breeding groups, in which sex ratios tend to be un

ISSN:0019-1019    

DOI:10.1111/j.1474-919X.1980.tb02660.x

出版商:Blackwell Publishing Ltd    

年代:1980

数据来源: WILEY

ISSN:0019-1019    

DOI:10.1111/j.1474-919X.1980.tb02661.x

出版商:Blackwell Publishing Ltd    

年代:1980

数据来源: WILEY

ISSN:0019-1019    

DOI:10.1111/j.1474-919X.1980.tb02662.x

出版商:Blackwell Publishing Ltd    

年代:1980

数据来源: WILEY

ISSN:0019-1019    

DOI:10.1111/j.1474-919X.1980.tb02663.x

出版商:Blackwell Publishing Ltd    

年代:1980

数据来源: WILEY

ISSN:0019-1019    

DOI:10.1111/j.1474-919X.1980.tb02664.x

出版商:Blackwell Publishing Ltd    

年代:1980

数据来源: WILEY

ISSN:0019-1019    

DOI:10.1111/j.1474-919X.1980.tb02665.x

出版商:Blackwell Publishing Ltd    

年代:1980

数据来源: WILEY

ISSN:0019-1019    

DOI:10.1111/j.1474-919X.1980.tb02666.x

出版商:Blackwell Publishing Ltd    

年代:1980

数据来源: WILEY