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- Merilä, Juha, et al.
(författare)
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Interspecific Competition for Nest Holes Causes Adult Mortality in the Collared Flycatcher
- 1995
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Ingår i: The Condor. - : Oxford University Press (OUP). - 0010-5422 .- 1938-5129. ; 97:2, s. 445-450
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Tidskriftsartikel (refereegranskat)abstract
- Interspecific competition for nest sites between tits (Parus spp.) and Collared Flycatchers (Ficedula albicollis) was responsible for the death of 23 flycatchers during one breeding season. Eighteen (78%) of the killed flycatchers were males, and nineteen (83%) of the kills took place in nest boxes occupied by Great Tits (Parus major), and two (9%) in boxes occupied by Blue Tits (P. caeruleus). The number of casualties in different plots increased with increasing proportion of nest boxes occupied by tits (r = 0.76), and decreased with increasing density of nest boxes (r = -0.43). The number of casualties equalled up to 17% of all flycatcher individuals breeding in a given plot, indicating that interspecific competition for nest sites may constitute a significant source of adult mortality in the Collared Flycatcher population studied.
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| 2. |
- Merilä, Juha, et al.
(författare)
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Mass loss in breeding blue tits : The role of energetic stress
- 1997
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Ingår i: Journal of Animal Ecology. - 0021-8790 .- 1365-2656. ; 66:4, s. 452-460
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Tidskriftsartikel (refereegranskat)abstract
- 1. The hypothesis that mass reduction in breeding passerines results from energeticstress was evaluated using data on body mass changes in female blue tits Paruscaeruleus.2. In accordance with both the adaptive adjustment and the physiological stresshypotheses, females with experimentally enlarged broods lost more mass than femalesrearing reduced or control broods. However, the ability to allocate energy to selfmaintenance(as measured by the regrowth rate of a tail feather removed duringincubation) was negatively correlated with the amount of lost body mass.3. In one of the study years, loss of body mass was more pronounced among smallfemales, suggesting that larger females are better able to cope with poor food conditionsduring breeding.4. In a poor-weather year, 30% of the females deserted their clutches, comparedwith 8% in a good year. Females that deserted their clutches before hatching weresignificantly lighter during incubation than non-deserters, indicating that good bodycondition is important for successful reproduction.5. In one year young females lost more mass than older females and therefore theability to maintain adequate body condition in the face of energetic stress appears tobe age-dependent.6. Taken together, these results suggest that mass loss in breeding blue tits is, to somedegree, attributable to energetic stress, although we have not ruled out the possibilitythat flight cost reductions may help explain the phenomenon.
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