摘要:

Some features of the unusual courtship behaviour of one of the world's rarest and most endangered species of bird, the flightless nocturnal Kakapo parrot of New Zealand, are described. They include excavation and maintenance by males of depressions or bowls which are grouped together and connected by tracks. Bowl systems occur in loose groups used by a number of males as traditional courtship areas and are unrelated to feeding or nesting. Bowls are used by males to emit resonant booming sounds that can be heard at distances of several kilometres, and for posturing and display in the presence of females when the latter visit for brief periods. It is concluded that absence of a permanent pair bond, the use of a mating station that is unrelated to feeding or nesting, and the temporally skewed sex ratio at the mating station in favour of males, all indicate that Kakapo are lek birds. They may be the only avian lek species to have evolved in an environment lacking mammalian predators. Further study of lek behaviour in the Kakapo may be needed if current efforts to save the species from extinction are to succeed.

ISSN:0019-1019    

DOI:10.1111/j.1474-919X.1984.tb00250.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

A population of 17 to 20 pairs of Tawny Owls was studied from 1959–79 in Grunewald forest, West Berlin. The breeding success of the Owls (21–77% of pairs raising young per year) and the proportion of yellow‐necked field miceApodenzus flavicollisin their pellets (13–48% of prey items each year) exhibited the same three‐year cycle. Long‐term trends in the diet of the Owls were apparent and reasons for these ar

ISSN:0019-1019    

DOI:10.1111/j.1474-919X.1984.tb00251.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

A GoldcrestRegulus reguluspopulation living in a spruce‐dominated forest near Oslo (c.60°N), in southern Norway, was studied during the winters (November‐March) from 1966–67 to 1971–72. A significant reduction in population size occurred between November and March, the recorded values varying from 76 to 96%, with a mean reduction for all six winters studied of 86%. This winter decline in numbers was significantly correlated with both precipitation (i.e., snowfall) and ambient temperature, but not with bird density. Spiders were the predominant prey items of the Goldcrests, and it is suggested that the birds experience food shortages that affect their survival rate. Although not statistically significant, a mean change in the ratio of males:females from 2:1 in October‐November to 10:1 in December—February was observed, suggesting that a greater mortality of females than males occurs during the winter.Partly based on data for colour‐banded birds, it is suggested that the Goldcrests form social flocks, which move around as individual units within territories of about 9 ha (7.5 12 ha,n= 5) in extent. The mean flock size decreased significantly from 4.57 (n= 157) birds in November‐December to 2.82 (n =74) birds in January‐February, probably because of the reductions in the size of the local population during the winter. The mean flock size in November‐December varied inversely with the ambient te

ISSN:0019-1019    

DOI:10.1111/j.1474-919X.1984.tb00252.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

A brief account is given of the topography and climate of the Sudan and a more detailed survey is made of the vegetation and habitats afforded to wintering Palaearctic migrants in the Sahel and Soudan savannah zones in the central Sudan. Climatic conditions during the migration seasons are mentioned and the utilization of habitats by wintering migrants is broadly surveyed.The status of 196 Palaearctic migrant species is treated briefly. The basic observational data are tabulated to summarize observed patterns of migration in terms of date, relative abundance and region (for which purpose the central Sudan is divided into four from west to east). Hitherto unpublished field notes of the authors and their collaborators are used, together with dated observations (including specimens collected) of earlier authors, to provide the fullest data on each species.Moreau's (1967) paradox is discussed as it relates to the Sahel and Soudan savannah zones in the central Sudan, together with the degree of competition with resident African species in those zones. Some disparities between the spring and autumn abundance and d. istribution of Palaearctic migrants are discussed in relation to 40 species ana some tentative views are advanced on the possible reasons for such disparities. Evidence is adduced which points toLanius minorandCoraczus garrulus(and possiblyCircus pygargus, partially at least) having loop migrations, south through the Sudan and north through Arabia, andFalco wespertinussouth through the Sudan and north through West Africa. An explanation is offered for the greater volume of water birds observed migrating down‐Nile in spring compared with their volume up‐Nile in autumn, and for the reversed situation observed in the region west of the Nile for these same species.ShelduckTadorna tadornais included in the Sudan list for the first t

ISSN:0019-1019    

DOI:10.1111/j.1474-919X.1984.tb00253.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

Some Red‐legged Partridge females lay two clutches in separate nests, one immediately after the other, which are incubated separately by the male and female of the pair. Pairs remained together during the laying of both clutches so that there were delays between the end of laving and incubation at the first nests. Incubation of the two nests began at approximately the same time but discrepancies of up to ten days occurred. Males incubated first clutches and females usually the second, but probably the first if the second was destroyed during laying. The proportion of surviving eggs which hatched was similar in first and second clutches but declined if the delay between laying and hatching was exceptionally long.Yearling females began laying late and few seemed to attempt two clutches compared with older females of which 60–80% showed the double nesting habit. A model predicting reproductive success for both sexes in relation to the rate of nest predation during laying, suggested that attempting two clutches rather than one would be disadvantageous at high predation rates. Females would produce more young if their mates incubated their first clutch immediately it was complete rather than accompanying them during the laying of the second. However, males may benefit by this delay, even though it exposes the nest to predators for a longer time, because they are able to guard their mate and prevent other males from mating with her and fertilizing eggs of her second clu

ISSN:0019-1019    

DOI:10.1111/j.1474-919X.1984.tb00254.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

In south Scotland, most Peregrines returned to the same territories to breed in successive years, though a few females changed territory from one year to the next.Annual mortality among breeding birds was at most 9% among females (or 11% in both sexes combined). There may have been considerable annual variation, however, and excluding one exceptional year out of five reduced the estimate for females to 7%. These estimates are maxima, but are still considerably lower than those obtained from ring recoveries of dead birds reported by members of the public.Among trapped birds, four males first bred at age two years, one at three and another at four or five; two females first bred at one year, 13 at two years old andoneat three. Five other females which were seen to be in first‐year plumage but were not trapped, also laid eggs, and 12 other such paired females held territory but did not lay. Only one paired male held territory in first‐year plumage.In their movements between natal and breeding territories, some females moved further than males, with median distances of 83 and 58 km respectively. In addition, of birds trapped breeding in the study area, a greater proportion of the males than of the females had been born locally, despite an equal sex ratio among fledglings; this was also consistent with a greater dispersal of females. In general, Peregrines made much longer movements in their first year of life than subsequently. Movements were in any direct

ISSN:0019-1019    

DOI:10.1111/j.1474-919X.1984.tb00255.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

Polygyny is widespread among Orkney's Hen HarriersCircus cyaneus. From 1975–81, it was associated with a sex ratio estimated from resightings of colour‐marked birds up to six years of age to be 29 females:ten males. The sex ratio of fledglings changed significantly from a greater proportion of females in the 1950s and early 1960s to a greater proportion of males subsequently. The mean estimated ‘survival’ rates (birds colour‐marked in Orkney which were seen there in later years) of males and of females 0–2 years old were 14 and 29%. The mean estimated annual survival rates of males and females from 2–6 years old were 72 and 90%. It is suggested that the uneven sex ratio resulted in more frequent intra‐sexual encounters and displays by females. The results of temporary removals of two females (immediately replaced) and of two males (not replaced) in spring indicates that there was a shortage of males in

ISSN:0019-1019    

DOI:10.1111/j.1474-919X.1984.tb00256.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

The response was observed of territory‐holding male European RobinsETithacus rubeculato red— and brown‐breasted model Robins which were presented either simultaneously with tape‐recorded Robin song, or with no song. Robins displayed and sang at the silent red‐breasted model, but sang and displayed much more at the models that were presented with song. It is suggested that, while the red breast is one important feature of Robins eliciting aggressive behaviour, song is also important. The relationship of these findings to studies of stimulus features eliciting behaviour in other species is

ISSN:0019-1019    

DOI:10.1111/j.1474-919X.1984.tb00257.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

Observations of sedentary male Starlings at two sites in Brittany from December 1979 to December 1980 showed that the amount of whistled song varies during the year, principally from March to July during the reproductive season. Whistles are not numerous in summer but increase from September. These results suggest a link between whistled songs and testosterone titers. The different whistle types present different evolutions of their relative frequencies. Some are abundant during the nest building phase, others during the feeding phase. The curves were similar at the two sites for a given theme, showing that each theme constitutes an entity and that the different themes are influenced differently by environmental factors. The significance to the learning process in young birds is discussed.

ISSN:0019-1019    

DOI:10.1111/j.1474-919X.1984.tb00258.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

Diets and nest attendance of Fulmars at Foula, Shetland and St Kilda, Outer Hebrides were examined during the breeding season. At Foula, sandeels formed the bulk of the diet, with fish offal and pelagic zooplankton of minor importance. At St Kilda, 71% of regurgitates consisted of pelagic zooplankton, probably captured at night. Dietary overlap between the two colonies was 14% by species composition. Foraging trips from Foula shortly after chick hatching generally lasted for less than 10 h, while trips from St Kilda late in chick rearing often lasted more than 24 h. The diurnal pattern of feeding suggested mainly nocturnal foraging from St Kilda but both diurnal and nocturnal foraging from Foula.

ISSN:0019-1019    

DOI:10.1111/j.1474-919X.1984.tb00259.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY