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- Forslund, Pär, et al.
(author)
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Age-related reproductive success in the barnacle goose
- 1992
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In: Journal of Animal Ecology. - : British Ecological Society. - 0021-8790 .- 1365-2656. ; 61, s. 195-204
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Journal article (peer-reviewed)abstract
- 1. We studied age-related reproductive success in a recently established breeding colony of barnacle goose Branta leucopsis on the island of Gotland, Sweden.2. Associations of age and breeding experience with several reproductive parameters were investigated by comparing the success of individuals of 2, 3, 4 and >=5 years of age. Also, we measured the within-individual changes in reproductive parameters as the individuals grew older.3. Associations between survival and reproductive success were investigated by comparing the reproductive success of 2, 3 and 4-year-old birds that returned or did not return, respectively, in the subsequent breeding season.4. The reproductive success increased up to an age of 4-5 years. Thus, clutch size, number of hatched young and number of fledged young increased, and hatching date was advanced with increasing age. This was due to the fact that individuals increased in reproductive success as they grew older.5. A possibly higher probability of survival among individuals that perform well in reproduction could not explain the higher reproductive success in older age-classes as compared to young age-classes of geese, because there were no associations between survival and reproductive success, and very few individuals did actually disappear between any two breeding seasons.6. Path analysis suggested age effects only at earlier stages of reproduction, i. e. timing of breeding and clutch size. These characters, in turn, were associated with number of fledged young. These findings were further supported by measurements of hatching success and rearing success, which did not seem to increase with age.7. Increased breeding experience was associated with early hatching date and larger clutch size in males, and with larger clutch size in females. This was concluded from path analysis and from comparisons of individuals of the same age but with different breeding experience.8. The increase in reproductive success with age in the barnacle goose is probably a result of age-related skills in individuals and the direct effects of these skills on reproductive success, but possibly also because of increased reproductive effort with age owing to these age-related skills.
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- Forslund, Pär, et al.
(author)
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Breeding range expansion of the barnacle goose Branta leucopsis in the Baltic area
- 1991
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In: Ardea. - : Netherlands Ornithologists’ Union. - 0373-2266 .- 2213-1175. ; 79:2, s. 343-346
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Journal article (peer-reviewed)abstract
- We describe the development of Barnacle Goose Branta leucopsis breeding colonies in the Baltic area. The largest colony is situated on the eastern coast of Gotland. Sweden, and consisted in 1988 of 970 breeding pairs. Breeding birds have also been observed in nine other Baltic localities within the 1980s. Differences in reproductive success at different localities suggest that density-dependent effects are important. Young nonbreeding geese frequently move between colonies during the summer. Intraspecific competition may increase the propensity for natal dispersal by geese from the main colony on Gotland
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- Forslund, Pär, et al.
(author)
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Intraspecific nest parasitism in the barnacle gooseFjärrlån IN : behavioural tactics of parasites and hosts
- 1995
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In: Animal Behaviour. - : Elsevier. - 0003-3472 .- 1095-8282. ; 50:2, s. 509-517
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Journal article (peer-reviewed)abstract
- Intraspecific nest parasitism in the barnacle goose,Branta leucopsis, was recorded by direct observations of females trying to lay eggs in the nests of other females. This was observed on 36 occasions. Parasitic egg-laying attempts were observed both in mornings and evenings, and lasted on average at least 20 min. Parasitic females approached host nests very fast and immediately sat down on or close to the nest. Host females attacked parasitic females intensively, but host males were much less aggressive. Males paired to the parasitic females were sometimes seen, but they never took any active part in the parasitic egg-laying attempts. Parasitic females probably successfully laid an egg most of the times, as the clutch size in host nests was on average 0·9 eggs larger than in nests where parasitic egg-laying attempts were not observed. Host females were observed to retrieve eggs laid outside the nest cup. Of 27 known cases, parasitic females made their egg-laying attempts before or at the host's start of incubation on 12 occasions, and after the start of incubation 15 times. It is suggested that parasitic females exploited features in the behaviour of potential hosts, such as egg retrieval and low aggressiveness in host males, to succeed in their egg-laying attempts. Nest parasitism seems to be a facultative, ‘best-of-a-bad-job’ tactic in barnacle geese, as parasitic females were observed to have nests of their own before or after the year they behaved parasitically, but never in that particular year.
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- Forslund, Pär, et al.
(author)
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The effect of mate change an new partner's age on reproductive success in the barnacle goose, Branta leucopsis
- 1991
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In: Behavioral Ecology. - : Oxford University Press. - 1045-2249 .- 1465-7279. ; 2:2, s. 116-122
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Journal article (peer-reviewed)abstract
- Mate retention frequencies and correlations between mate change and reproductive performance were estimated in a population of barnacle geese, Branta leucopsis, breeding on the island of Gotland in the Baltic. About 90% of the pairs remained together from one breeding season to the next. Only 2.4% of the pairs divorced, most mate changes being consequences of the death of one partner. Divorces were not forecast by low reproductive success, and seemed to be accidental. In the season before mate change, there was no difference in reproductive performance, measured as clutch size, hatching date, and number of fledged young, between faithful pairs and pairs where one partner was subsequently changed. However, in the first season with a new partner, clutch size and number of fledged young decreased on average. Hence, because mate change led to a reduction in reproductive success, it was concluded that mate retention is advantageous. Our results suggest that this reduction is more likely due to the lower average age or breeding experience of new partners than to the benefits of breeding experience with one particular partner.
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- Jeppsson, Tobias, et al.
(author)
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Can Life History Predict the Effect of Demographic Stochasticity on Extinction Risk?
- 2012
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In: American Naturalist. - : University of Chicago Press. - 0003-0147 .- 1537-5323. ; 179, s. 706-720
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Journal article (peer-reviewed)abstract
- Demographic stochasticity is important in determining extinction risks of small populations, but it is largely unknown how its effect depends on the life histories of species. We modeled effects of demographic stochasticity on extinction risk in a broad range of generalized life histories, using matrix models and branching processes. Extinction risks of life histories varied greatly in their sensitivity to demographic stochasticity. Comparing life histories, extinction risk generally increased with increasing fecundity and decreased with higher ages of maturation. Effects of adult survival depended on age of maturation. At lower ages of maturation, extinction risk peaked at intermediate levels of adult survival, but it increased along with adult survival at higher ages of maturation. These differences were largely explained by differences in sensitivities of population growth to perturbations of life history traits. Juvenile survival rate contributed most to total demographic variance in the majority of life histories. Our general results confirmed earlier findings, suggesting that empirical patterns can be explained by a relatively simple model. Thus, basic life history information can be used to assign life history-specific sensitivity to demographic stochasticity. This is of great value when assessing the vulnerability of small populations.
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