| 1. |
- Larsson, Kjell, et al.
(författare)
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Intraspecific nest parasitism and adoption of young in the barnacle goose : effects on survival and reproductive performance
- 1995
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Ingår i: Animal Behaviour. - : Elsevier. - 0003-3472 .- 1095-8282. ; 50:5, s. 1349-1360
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Tidskriftsartikel (refereegranskat)abstract
- DNA fingerprinting was used to determine the proportion of extra-pair young in a population of barnacle geese, Branta leticopsis, breeding in the Baltic area, Sweden. Of 137 analysed fledged young 17% were found to be extra-pair young. One or more extra-pair young were found in 27% of the 63 analysed families. The proportion of extra-pair young differed between years. No case of extra-pair fertilization was detected. All extra-pair young at fledgling originated either from intraspecific nest parasitism or from adoptions of foreign hatched young. Broods with extra-pair young at fledgling were significantly larger than broods without extra-pair young. However, the number of within-pair young did not differ significantly in broods with and without extra-pair young. Body mass, survival or subsequent reproductive performance did not differ between parents with and without extra-pair fledged young. Post-fledgling survival and age at first breeding were not significantly different between the three analysed classes of fledged young, i.e., within-pair young in families without extra-pair young, within-pair young in families with at least one extra-pair young, and extra-pair young. It is concluded that possible costs or benefits associated with caring for extra-pair fledged young are small or absent in this population.
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| 2. |
- Larsson, Kjell, et al.
(författare)
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Population dynamics of the barnacle goose Branta leucopsis in the Baltic area : density-dependent effects on reproduction
- 1994
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Ingår i: Journal of Animal Ecology. - : British Ecological Society. - 0021-8790 .- 1365-2656. ; 63:4, s. 954-962
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Tidskriftsartikel (refereegranskat)abstract
- 1. The three largest breeding colonies of barnacle geese Branta leucopsis in the Baltic area were studied from their natural establishments in 1971, 1982 and 1987, respectively, to 1993. The number of breeding pairs increased from one pair in 1971 to 1550, 225 and 150 pairs in the largest, second largest, and third largest colonies, respectively, in 1993. 2. Data on clutch size and number of hatched and fledged young were collected from the beginning or the middle of the 1980s. In the largest colony most data on reproductive success were obtained from observations of individually marked geese. 3. Mean clutch size differed among years and colonies. However, there was no trend for decreasing mean clutch size with increasing density in any of the colonies. Hatching success did not decrease with increasing density in the largest colony. 4. The production of fledged young per breeding pair declined drastically in the largest colony as numbers of breeding pairs rose. This decline was mainly caused by an increasing proportion of the breeding pairs failing to produce any fledged young at all. 5. The relative contribution of the smaller colonies to the total production of fledged young in the Baltic area increased considerably over the study years. In 1993, colony 2 hosted only about 13% of the number of breeding pairs in colonies 1 and 2 combined, but it produced about 38% of the fledged young. 6. Our results point out the need to study populations of colonially nesting geese on a colony by colony basis in order to detect density-dependent effects on reproduction.
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| 3. |
- Larsson, Kjell, et al.
(författare)
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Body size declines despite positive directional selection on heritable size traits in a barnacle goose population
- 1998
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Ingår i: Evolution. - : Society for the Study of Evolution. - 0014-3820 .- 1558-5646. ; 52:4, s. 1169-1184
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Tidskriftsartikel (refereegranskat)abstract
- Analyses of more than 2000 marked barnacle geese (Branta leucopsis) in the largest Baltic colony, Sweden, showed that structurally large females generally produced larger clutches and larger eggs, hatched their broods earlier in the season, and produced more and heavier young than smaller females. In males, the corresponding relationships between reproductive parameters and structural body size were weaker or nonsignificant. Because structural body size traits have previously been found to be significantly heritable and positively genetically correlated, an increase in mean structural body size of individuals as a response to selection might have been expected. By contrast, we found that the mean adult head length and mean adult tarsus length decreased significantly in the largest colony by approximately 0.7 and 0.5 standard deviations, respectively, in both males and females during the 13-year study period. Environmental factors, such as the amount of rain in different years, were found to affect the availability of high-quality food for growing geese. As a consequence of this temporal variability in the availability of high-quality food, the mean adult structural body size of different cohorts differed by up to 1.3 standard deviations. Comparisons of mean body size of cohorts born in different colonies suggest that the most likely explanation for the body-size decline in the main study colony is that a density-dependent process, which mainly was in effect during the very early phase of colony growth, negatively affected juvenile growth and final size. We conclude that large environmental effects on growth and final structural body size easily can mask microevolutionary responses to selection. Analyses of environmental causes underlying temporal and spatial body size variation should always be considered in the reconstruction and prediction of evolutionary changes in natural populations.
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| 4. |
- Forslund, Pär, et al.
(författare)
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Age-related reproductive success in the barnacle goose
- 1992
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Ingår i: Journal of Animal Ecology. - : British Ecological Society. - 0021-8790 .- 1365-2656. ; 61, s. 195-204
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Tidskriftsartikel (refereegranskat)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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