摘要:

I monitored the incubation schedules of FulmarsFulmarus glacialisin an Alaskan colony by observing nests where the male and female were of different colour phases. Complete shifts of up to 16 days were recorded; the average shift in mid‐incubation was 4–6 days. Mean shift length was inversely correlated with hatching success in 5 years, suggesting that Fulmars adjusted their foraging patterns to annual differences in food availability. Males assumed the larger share (55%) of incubation on average, and a larger share in years with lower hatching success. Serial correlation in the length of incubation shifts had two components—the influence of prior shift lengths on time spent foraging and individual variation. Failure of the male to relieve the female soon after laying resulted in a few breeding failures and egg losses were associated with exceptionally long shifts throughout incub

ISSN:0019-1019    

DOI:10.1111/j.1474-919X.1990.tb00275.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

The breeding season of the White‐headed PetrelPterodroma lessonion Mayes Island off the Kerguelen archipelago was studied between December 1985 and February 1987. The birds returned to land in November, and the chicks hatched at the end of January and fledged in May. These incubation and fledging periods are among the longest known in the family Procellariidae. Successful birds normally bred every two years, which has not previously been reported for any member of this family. The breeding ecology is compared to that of other gadfly petrels from sub‐antarctic and tropical waters, and the breeding frequency is discus

ISSN:0019-1019    

DOI:10.1111/j.1474-919X.1990.tb00276.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

Regurgitations from nestling Grey HeronsArdea cinereaat Loch Leven, Scotland, April‐July 1981–83, contained mainly three types of prey:perch, brown trout and ducklings. The diet varied markedly through the season but not between years. As the heron breeding season progressed, perch occurred in fewer regurgitations and ducklings in more. There was no seasonal variation in the occurrence of brown trout. Regular collections of duckling down from the heronry suggested that the consumption of ducklings peaked in early June. The ducklings taken by herons were less than 10 days old, Mallard ducklings predominating before mid June and Tufted ducklings later. Most ducklings were taken by only a few herons:those that bred earliest and which initially fed their young on perch. Ducklings became a major part of their diet in the late nestling period and broods fed on ducklings fledged no more or fewer young than others. Herons feeding their young on brown trout took ducklings rarely, if ever. It is argued that variation in the contents of regurgitations resulted from three interacting variables; the type of feeding habitat used by individual Grey Herons, the date at which they bred and the date that regurgitations were produced by their nestlings. The numbers of ducklings taken by herons were calculated to be about 230 in 1981 and 291 in 1982, about 5% of Mallard and 3:b of Tufted ducklings estimated to have hatched annually. Assuming herons continued to consume ducklings at the same rate after their young had dispersed, the figures for Tufted ducklings would be higher but still only about 4% in 1981 and 6% in 1982. Compared with total duckling losses of over 75%, predation by Grey Herons was minor and did not affect duckling production in the years concer

ISSN:0019-1019    

DOI:10.1111/j.1474-919X.1990.tb00277.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

The density of territorial pairs, laying pairs and the breeding performance of three raptor species, BuzzardButeo buteo, GoshawkAccipiter gentilisand KestrelFalco tinnunculus, were investigated in relation to rainfall and temperature during the breeding cycle. In all species the density of territorial pairs was not related to spring rainfall and temperature. In the Buzzard the percentage of pairs that bred unsuccessfully was significantly related to May rainfall. The number of young fledged was negatively correlated with rainfall in April and May. In the Goshawk the percentage of laying pairs was negatively correlated to rainfall in March and April. Success in terms of number of young fledged was related mostly to May temperature. In the Kestrel the density of territorial pairs was dependent on March‐April rainfall. The number of young fledged per successful pair was highly correlated with May and June temperature. All these relationships showed that the hatching period and the subsequent two weeks were most important for chick surviva

ISSN:0019-1019    

DOI:10.1111/j.1474-919X.1990.tb00278.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

A discriminant equation based on bill‐depth and total head‐ and bill‐length is provided to sex adult Black‐headed GullsLarus ridibundus. This equation is used to sex birds of known age. Relationships between age and morphometrics and between age and the black extent on the wing are then investigated both in males and females. Size of birds did not change with age but the black extent on the wing tended to decrease with age in both sexes. The tendency to become lighter with age may he an expression of sen

ISSN:0019-1019    

DOI:10.1111/j.1474-919X.1990.tb00279.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

Radio‐tagged NightjarsCaprimulgus europaeusnesting in conifer plantation clearings and on lowland heath in Dorset travelled an average of 3.1 km away from their nesting areas at night to atypical habitats, presumably to feed. Comparison of habitat availability with use showed that Nightjars preferred deciduous or mixed woodland habitats, while they avoided conifer plantations and arable or improved grassland. Absence from the nesting area was recorded on 72 % of bird‐nights and birds were least likely to be away during the middle third of the night. The use of atypical habitats may have implications for Nightjar conservat

ISSN:0019-1019    

DOI:10.1111/j.1474-919X.1990.tb00280.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

Individual time budgets during winter and spring were studied in a population of NuthatchesSitta europaeain south‐central Sweden. In late winter birds spent about 90% of daytime foraging, males feeding somewhat less than females, possibly due to male dominance. In early spring, foraging time decreased to about 65% of daytime activity, and sex‐related differences became more pronounced. Males then increased time spent resting and singing. Females were nestbuilding, spent less time resting and also devoted more time to foraging than did males. Prior to the observation periods, food density for part of the population was experimentally increased by supplying sunflower seed. In spite of this, time budgets in the experimental group were similar to those of the control group. It is possible that the intensity of foraging, rather than actual time devoted to it, was influenced by food density and that, as a result, birds in the experimental group were able to maintain a higher level of vigilance. Also, an increase in food supply may be less important to a hoarding bird such as the Nuthatch. However, the result remains that Nuthatch time budgets in winter and spring are not readily influenced by an increase in food dens

ISSN:0019-1019    

DOI:10.1111/j.1474-919X.1990.tb00281.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

The male's role in feeding young and his effect on the mortality of eggs and nestlings of the Great Reed WarblerAcrocephalus arundinaceuswere studied in Kahokugata, central Japan, during eight breeding seasons. Three potential costs of polygynous breeding for females were examined:(i) a reduction of male parental care per brood, (ii) an attraction of predators due to concentration of nests, and (iii) an increase of unfertilized eggs due to the reduced frequency of copulation per female. Only the first cost was found to occur:polygynous males fed their young, especially of their second broods, less frequently than monogamous ones. The lowered paternal feeding frequency, however, did not increase the mortality by starvation in second‐hatched broods. This was because the warm climate emancipated females from brooding and enabled them to compensate for the deficiency of feeding by males. The paper discusses possible roles of the staggering of the time of laying among harem mates and the shift of breeding status of females caused by nesting failure, in reducing potential costs of polygynous breeding for female

ISSN:0019-1019    

DOI:10.1111/j.1474-919X.1990.tb00282.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

The effect of supplementary food on the reproductive success of Black‐billed MagpiesPica picawas studied in an urban habitat in the city of Edmonton, Alberta, Canada. We provided supplementary food (pelleted dog food) regularly from August 1986 to June 1988 in a feeder situated outside all known magpie territories. Magpies using the supplementary food showed (i) an advancement of 7 days in the initiation of laying, (ii) no increase in clutch‐size, (iii) higher survival of nest contents (eggs and young) during a spring snow storm, (iv) an increase in rate of nestling weight gain, and (v) an increase in fledging success. Supplementary food did not prompt the fed pairs to select nest sites nearer the feeder in 1988 than in 1987. The feeder did not affect the breeding density because the nearest neighbour distances of fed magpies did not differ from unfed magpies in either year, nor did they differ between the two years for either fed or unfed magpies. This study provided evidence that magpies frequently renest even if their initial nests fail after the eggs hatch—a practice that has been reported to be absent or rare in other studies. Although brood reduction was equally frequent in the nests of food‐supplemented and control pairs, the actual number of nestlings disappearing from the former (1.56 per nest) was significantly smaller than that from the latter (2.60 per nest), suggesting that the availability of food plays a major role in magpie reproductive

ISSN:0019-1019    

DOI:10.1111/j.1474-919X.1990.tb00283.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

In a dense population of Egyptian VulturesNeophron percnopterusin northern Spain, nest‐switching occurred between nearby nests. Fledglings obtained more feeds by intruding and pirating than by remaining in their own nests during the same period. Intruder fledglings showed the same behaviour with Foster adults attacked intruder fledglings significantly less than they attacked alien adults and immatures but more frequently than they attacked their own fledglings. Effective rejection behaviour by foster adults to intruders may not have evolved as Egyptian Vultures usually nest at lower densities than that found in the study are

ISSN:0019-1019    

DOI:10.1111/j.1474-919X.1990.tb00284.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY