摘要:

The investment of time and energy in reproduction by male and female sandgrouse (genusPterocles) was studied. Energy expenditure was estimated using time budgets and laboratory measurements of metabolism. Female parental expenditure was greatest during laying and incubation. Females took the larger share of daytime incubation, which reduced their time available for foraging (3.6 h compared with 4.8 h for males). To remain in energy balance, they required a higher food intake rate than males (97 kJ/h compared with 79 kJ/h, respectively) and consequently were likely to lose condition during incubation. Male parental expenditure was greatest during chick‐rearing, especially when the young were well grown but still dependent on the male for water. The role of males as water carriers increased their energy expenditure and decreased their time available for foraging. Males also took the greater share of time spent in vigilance on behalf of the young, which further reduced their foraging time (3.2 h compared with 4.9 h for females). To remain in energy balance, males with young required a higher intake rate than females (62 kJ/h compared with 44 kJ/h, respectively

ISSN:0019-1019    

DOI:10.1111/j.1474-919X.1994.tb01094.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

The pattern of chick feeding in Little ShearwaterPuffinus assimilison Selvagem Grande was examined by weighing chicks at 4–h intervals throughout eight successive nights and daily for a further 11 days (19 days in all). Individual meals fed to chicks averaged 23.2 g (s.d. ±4.7) or 13.6% of adult mass. Mass increments over 24 h (NET) were linearly related to the sum of positive mass increments over 4–h intervals during the night (SUM) by the equation NET = 0.36SUM ‐ 5.89 (r2= 0.60). Using this relationship, I estimated that over a period of 18 nights, a mean of 95% of chicks were fed each night, and the mean interval between feeds was 1.05 nights, with a maximum of three nights. There was no significant day‐to‐day variation in feeding rate. These results were not compatible with the prevalent idea that the purpose of large fat deposits in Procellariiformes is to tide chicks over periodic fasts resulting from poor feeding conditions. On average, chicks required 16 g of food per day to maintain constant mass and converted 33% of their intake of food above this requirement into biomass. Meal size and feeding frequency were independent of chick size and body condition (body‐mass corrected for body‐size), and the masses of food received by individual chicks each night varied in direct proportion to previous values. These results suggest that the rate of food supply to chicks was not regulated by adjustment according to chicks' nutritional requirements. To some extent, this supports the hypothesis that lipid accumulation among Procellariiformes is related to stochastic variation in food supply rate, resulting from an absence of regulation of feeding. However, feeding was not stochastic, in that adults tended to deliver consistent amounts of food to their chicks, and the pattern of feeding among even the worst‐fed chicks was inconsistent with a need for large lipid stores based upon chance variation

ISSN:0019-1019    

DOI:10.1111/j.1474-919X.1994.tb01095.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

King PenguinAptenodytes patagonicuschick growth is interrupted by a winter fast which extends the length of the breeding cycle (laying to chick independence) to 14–16 months, so that continuous annual successful breeding appears to be impossible. The 3–month laying period imposes further constraints with respect to timing of breeding attempts in relation to the onset of fasting. By the frequent resighting of individually marked birds at Marion Island, we examined the frequency of breeding and the relationships between timing, outcome and frequency in the same and in consecutive years. A total of 3101 adult King Penguins were banded between 1984 and 1991, yielding continuous breeding histories spanning a maximum of 5 years. Most penguins attempted to breed in consecutive years, although the likelihood of taking a year off increased with the number of consecutive attempts. In any one season, about 19% of potentially breeding adults did not breed. Early breeders were more likely to succeed than late breeders and comprised 84% of breeding attempts of known timing. Successful birds in one season usually bred late in the following season, whereas failed attempts were usually followed by an early attempt. Non‐breeding was more likely to occur after a successful outcome than a failed one, and after a year off 93% of birds bred early. It is incorrect to refer to the King Penguin as a biennial br

ISSN:0019-1019    

DOI:10.1111/j.1474-919X.1994.tb01096.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

The incubation routine and mass changes of male and female Blue PetrelHalobaena caeruleawere studied at the Kerguelen Islands to investigate factors influencing the durations of incubation stints and foraging trips at sea and the factors determining nest desertion and return to the nest.The body mass at the start of an incubation shift and also when the bird was relieved varied throughout the incubation period, whereas the mass when birds deserted the nest was stable. Birds deserted the nest when their mass decreased to threshold, independent of the duration of the fast. Temporary egg neglect was observed in successful as well as in unsuccessful breeding attempts, but it increased the risk of breeding failure. The net and daily massgained at sea during the second part of the incubation period were higher than during the first part, suggesting an increase in food availability. During the first part, the mass gained at sea and time spent foraging were inversely related to the mass of the bird before it left the burrow, whereas a similar relationship did not occur thereafter.The results suggest the occurrence of a fixed mass threshold when birds decide to leave the nest if not relieved by their partner. The mass when a bird left its nest inffuenced the time spent foraging or mass gained when food was scarce. Although decision rules to leave the nest or return from the sea are related to body condition. the possibility of neglecting the eggs temporarily enables Blue Petrels to regulate the trade‐off between risks of breeding failure and risks of an increase in adult mortality. A model for behavioural decision to stop incubating or stop feeding, based on a variable set point, is propose

ISSN:0019-1019    

DOI:10.1111/j.1474-919X.1994.tb01097.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

The brood‐parasitic indigobirdsViduaspp. mimic the songs of their foster species, which for many species of indigobirds areLagonostictafirefinches. We report additional associations of indigobirds with estrildid finches in west Africa. Quail‐finch IndigobirdsVidua nigeriaein northern Cameroon mimic the songs of Quail‐finchOrtygospiza atricollis. Gold‐breast IndigobirdsVidua raricolain Cameroon and Sierra Leone mimic the songs of Gold‐breastAmandava subflava. Both indigobirds are distinct in male breeding plumage from other indigobirds. Also, a population of blue indigobirdsViduasp. in Cameroon mimics the songs of Brown TwinspotClytospiza monteiri. They are similar in colour and size to blue indigobirds associated with Dark FirefinchL. rubricataand Black‐bellied Firefinch L.rara. Mouth patterns of fledged young Quail‐finch Indigobirds and Goldbreast Indigobirds resemble those of their song‐model and presumed foster species, but the mouth pattern of a fledged young associated with the Brown Twinspot mimic was not distinct from the mouth of young Black‐bellied Firefinch. The field observations show associations of certain species of indigobirds with finches other than the firefinches. The results are consistent with mitochondrial DNA estimates of greater genetic similarity among indigobirds than among their foster species. The field observations support the hypothesis of evolutionary associations of the brood parasite and foster species by colonization with switching from one foster to another rather tha

ISSN:0019-1019    

DOI:10.1111/j.1474-919X.1994.tb01098.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

We removed male Eastern BluebirdsSialia sialisto examine the importance of male parental care and the behavioural responses of unaided females to loss of male assistance. Unaided females fed young significantly more than control females (females with male assistance) fed young, but young in experimental nests were fed significantly less frequently in total than young in control nests. Unaided females had significantly lower nesting success (fledged at least one young) than control females. At control nests, males defended the young more strongly than did their mates. Unaided females defended their young as strongly as control females. Unaided and control females spent the same amount of time brooding young, and there was no tradeoff between feeding and brooding young. Most early season experimental nests failed, but late in the season many unaided females were as successful as pairs. Unaided females were able to match the feeding rat'e in control broods at late nests but not at early nests, where control nestlings were fed at a higher rate. In our population, male bluebirds played an important role in provisioning young, and early in the season unaided females were unable to provide sufficient bod to raise any young to fledging.

ISSN:0019-1019    

DOI:10.1111/j.1474-919X.1994.tb01099.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

JackdawsCorvus monedulabreeding in old holes of the Black WoodpeckerDryocopus martiuswere studied during 6 years in central Sweden. Of 131 breeding attempts, only 56% were successful. Nest predation caused 74% of the breeding failures. The most common predator was probably the Pine MartenMattes mattes, as fresh hair was found in 42% of the nests whose contents had been predated. Predation risk of nest contents was not related to the height above ground, but it was significantly reduced with increasing colony size. Since Jackdaws are known to communally defend their nests, a likely explanation is that the Jackdaw benefits from group defence against predators. During the study, the number of breeding Jackdaw pairs in Black Woodpecker holes declined, probably linked with a recent increase in the numbers of Pine Martens in the area.

ISSN:0019-1019    

DOI:10.1111/j.1474-919X.1994.tb01100.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

We made intensive observations of 50 pairs of Lesser Spotted WoodpeckerDendrocopos minorin southern Sweden from 1989 to 1992. Between 7% and 22% of the pairs each year defended a territory but laid no eggs. Overall, 76% of the pairs laying eggs raised fledglings, but this proportion was only 33% in 1991 when the weather was cold and wet. The mean clutch size (5.9) and brood size (4.5) in successful nests did not vary significantly between years. Incubation time was 1 day longer in 1991 (11–12 days) than in 1990 and 1992 (10–11 days). Number of young fledged per nesting attempt (3.5) and per pair (2.7) in the population also varied significantly between years. The initiation of egg laying varied between years but coincided each year remarkably well with the date when oak came into leaf. Breeding success is discussed, and comparisons are made with other hole‐nesting sp

ISSN:0019-1019    

DOI:10.1111/j.1474-919X.1994.tb01101.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

The seasonal pattern of sperm storage was examined in a wild population of Yellow‐headed BlackbirdsXanthocephalus xanthocephalusby collecting females at eight different stages of their breeding cycle. Sperm storage tubules (SSTs) were present in simiktr numbers throughout all stages of the breeding season, from arrival on the breeding grounds to departure for winter. In contrast, the size of SSTs varied enormously over the season, reaching maximum size just prior to clutch initiation, when SSTs were more than three times the length of those found in post‐breeding birds. The amount of sperm stored also varied over the season, in parallel with the growth and regression of SSTs. Sperm were first observed in SSTs approximately 2–5 days before laying and increased rapidly in abundance until clutch initiation. The amount of sperm stored then decreased gradually during the egg‐laying period so that by clutch completion approximately 70% of stored sperm had disappeared from the SSTs. The rapid seasonal development and subsequent regression of SSTs in the Yellow‐headed Blackbird contrast sharply with the pattern found in domestic poultry, where the imposition of continuous laying regimes has; led to the maintenance of SSTs at maximum size for extended period

ISSN:0019-1019    

DOI:10.1111/j.1474-919X.1994.tb01102.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

The aims of this study were to test whether or not JaysGarrulus glandariusstore stones and, if so, to examine the conditions under which they store stones. By directly observing the behaviour of five captive Jays that were housed individually in flight cages, we found that stones were stored only in the absence of food items or when food items were no longer available to store and that there was a strong preference for storing stones that resembled acorns in both size and appearance (in terms of colour, shape and smoothness of the surface) and were undamaged rather than heavily chipped. These results are discussed in terms of Tinbergen's classic ethological model in which animals respond selectively to certain key features and ignore other features of the stimulus.

ISSN:0019-1019    

DOI:10.1111/j.1474-919X.1994.tb01103.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY