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| 3. |
- Berglund, Anders, et al.
(författare)
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Female-female competition over reproduction
- 1993
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Ingår i: Behavioral Ecology. - : Oxford University Press (OUP). - 1045-2249 .- 1465-7279. ; 4:2, s. 184-187
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Tidskriftsartikel (refereegranskat)
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| 4. |
- Berglund, Anders
(författare)
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The operational sex-ratio influences choosiness in a pipefish
- 1994
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Ingår i: Behavioral Ecology. - 1045-2249 .- 1465-7279. ; 5:3, s. 254-258
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Tidskriftsartikel (refereegranskat)abstract
- If more females than males are available for mating in the breeding population (i.e., the operational sex ratio, OSR, is female biased), males can afford to be choosy. In the pipefish (Syngnathus typhle) females compete for males, who are choosy. In nature OSRs are typically female biased, but may occasionally be male biased. In a series of experiments, males were allowed to choose between a large and a small female under a perceived excess of either males or females. Under female bias, males preferred the large female: they spent more time close to her than to the small female; they courted the large female sooner than the small; and they tended to copulate sooner and more often with the large female. Under male bias all these differences vanished and males mated at random with respect to female size. Males reproduced at a faster rate under male than under female bias because they received more eggs in their brood pouches. Thus, males switched from maximizing mate quality (i.e., being choosy) to minimizing the risk of not reproducing (i.e., being quick) as the OSR became male biased.
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| 5. |
- Forslund, Pär, et al.
(författare)
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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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Ingår i: Behavioral Ecology. - : Oxford University Press. - 1045-2249 .- 1465-7279. ; 2:2, s. 116-122
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Tidskriftsartikel (refereegranskat)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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| 7. |
- Nilsson, Jan Åke, et al.
(författare)
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A prudent hoarder : Effects of long-term hoarding in the European nuthatch, Sitta Europaea
- 1993
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Ingår i: Behavioral Ecology. - : Oxford University Press (OUP). - 1045-2249 .- 1465-7279. ; 4:4, s. 369-373
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Tidskriftsartikel (refereegranskat)abstract
- Although hoarding has been studied intensively for many decades, few studies have attempted to measure its actual fitness consequences. To fill this gap, we used ptilochronology, the growth of replacement feathers as a measure of nutritional status, and thus a reflection of starvation risk, of individual European nuthatches (Sitta europaea) during winter. We found that nuthatches are long-term hoarders, retrieving stored food up to at least 98 days after storing it. Long-term hoarding enhanced the nutritional status of individual birds significantly because those individuals experimentally given an opportunity to store seeds during autumn regrew plucked rectrices faster and larger than did control birds. Nuthatches used their stored seeds prudently by adjusting the amounts they ate to meet their requirements, as determined by ambient temperatures. Nuthatches refrained from using stored food during periods of relatively benign conditions so they could use the food during periods of more severe conditions.
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| 8. |
- Smith, Henrik G., et al.
(författare)
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Intrasexual competition among polygynously mated female starlings (Sturnus vulgaris)
- 1994
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Ingår i: Behavioral Ecology. - : Oxford University Press (OUP). - 1045-2249 .- 1465-7279. ; 5, s. 57-63
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Tidskriftsartikel (refereegranskat)abstract
- In southern Sweden, the starling (Sturnus vulgaris) has a variable mating system with some males mating monogamously and others attracting several females. Mating status affected the reproductive success of females: monogamous and primary females laid larger clutches and fledged more and heavier young than secondary females. This pattern was explained by female competition for male help, with the male primarily helping the offspring of highest value (i.e., the oldest brood). However, when the nesting attempt of the primary female failed, the success of the secondary female increased to the same level as that for primary and monogamous females. The success of the secondary female in terms of fledging success and fledgling size was higher when the secondary female hatched her eggs soon after the primary female. This was due to the fact that a male divided his effort between his broods when the age difference between broods was small
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