| 1. |
- Hiron, Matthew, et al.
(författare)
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Crop damage by granivorous birds despite protection efforts by human bird scarers in a sorghum field in western Kenya
- 2014
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Ingår i: Ostrich: Journal of African Ornithology. - : National Inquiry Services Center (NISC). - 0030-6525. ; 85, s. 153-159
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Tidskriftsartikel (refereegranskat)abstract
- Cereal crop damage from granivorous birds poses a serious food security problem for subsistence farmers in sub-Saharan Africa. In this region, farmers may rely on human 'bird scarers' to limit crop damage. Here we report feeding behaviour and crop damage patterns caused by Village Weavers Ploceus cucullatus and African Mourning Doves Streptopelia decipiens during four days in a 0.12 ha sorghum field protected by two full-time bird scarers in western Kenya. Despite the scarers' efforts, almost 60% of the seed was lost before harvest. Bird abundance was largely determined by the presence of the bird scarers, with seed loss patterns being a function of distance from these people. Throughout the day, an average of 18 weavers (maximum 120) was present on the crop in any five-minute period. The number of mud projectiles thrown at the birds per 15 min showed only minor diurnal fluctuations, further suggesting that seed eaters attacked the crop throughout the day. Village Weaver individuals took an average 16 seeds per visit, whereas dove individuals took 32 seeds (maximum 105 and 455, respectively). Our study illustrates that avian crop pests can be extremely persistent and, even with consistent diurnal bird scaring activity, severely damage a small crop field. Bird scarers need to be active throughout daylight hours and patrol both the centres and edges of fields to create maximum disturbance to foraging seed eating birds. Further research is needed in order to investigate effects of local-and landscape-level land use patterns on the feeding behaviour of crop pests and the effectiveness of crop protection measures.
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| 2. |
- Lisney, Thomas J., et al.
(författare)
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Behavioural assessment of flicker fusion frequency in chicken Gallus gallus domesticus
- 2011
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Ingår i: Vision Research. - : Elsevier BV. - 0042-6989 .- 1878-5646. ; 51:12, s. 1324-1332
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Tidskriftsartikel (refereegranskat)abstract
- To interact with its visual environment, an organism needs to perceive objects in both space and time. High temporal resolution is hence important to the fitness of diurnally active animals, not least highly active aerial species such as birds. However, temporal resolution, as assessed by flicker fusion frequency (FFF; the stimulus frequency at which a flickering light stimulus can no longer be resolved and appears continuous) or critical flicker fusion frequency (CFF; the highest flicker fusion frequency at any light intensity) has rarely been assessed in birds. In order to further our understanding of temporal resolution as a function of light intensity in birds we used behavioural experiments with domestic chickens (Gallus gallus domesticus) from an old game breed 'Gammalsvensk dvarghona' (which is morphologically and behaviourally similar to the wildtype ancestor, the red jungle fowl, G. gallus), to generate an 'Intensity/FFF curve' (I/FFF curve) across full spectrum light intensities ranging from 0.2 to 2812 cd m(-2). The I/FFF curve is double-branched, resembling that of other chordates with a duplex retina of both rods and cones. Assuming that the branches represent rod and cone mediated responses respectively, the break point between them places the transition between scotopic and photopic vision at between 0.8 and 1.9 cd m(-2). Average FFF ranged from 19.8 Hz at the lowest light intensity to a CFF 87.0 Hz at 1375 cd m(-2). FFF dropped slightly at the highest light intensity. There was some individual variation with certain birds displaying CFFs of 90-100 Hz. The FFF values demonstrated by this non-selected breed appear to be considerably higher than other behaviourally derived FFF values for similar stimuli reported for white and brown commercial laying hens, indicating that the domestication process might have influenced temporal resolution in chicken.
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| 3. |
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| 4. |
- Rubene, Diana, et al.
(författare)
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Importance of high quality early-successional habitats in managed forest landscapes to rare beetle species
- 2014
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Ingår i: Biodiversity and Conservation. - : Springer Science and Business Media LLC. - 0960-3115 .- 1572-9710. ; 23, s. 449 - 466
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Tidskriftsartikel (refereegranskat)abstract
- Species adapted to early-successional forest habitats are in managed landscapes largely confined to clearcuts. To improve habitat quality on clearcuts, green tree and dead wood retention is widely applied in forestry; however, its effects on rare early-successional species have rarely been shown. We repeatedly surveyed two red-listed beetle species (Upis ceramboides and Platysoma minus) on clearcuts in a managed boreal forest landscape. We found that U. ceramboides decreased its occupancy over time while P. minus increased, indicating that red-listed species vary in their ability to successfully utilise managed habitats. We found no effect of connectivity on probability of occurrence, colonisation or extinction per clearcut. Trees retained alive improved habitat quality of clearcuts, since both species were more frequent in dead wood of such trees, in comparison to logging residues. We suggest that retention can be improved by protecting and creating dead wood as intact trees during harvesting. Rare specialist species require habitat of high quality, and consequently it is impossible to meet the requirements of these species on every clearcut. To preserve all early-successional species at a regional scale, we recommend focusing retention of green trees and dead wood to one or a few trees species on each clearcut and in each landscape.
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| 5. |
- Rubene, Diana
(författare)
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Insect diversity on clearcuts in boreal forest landscapes
- 2014
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Intensive management and loss of natural disturbance dynamics in boreal forests leads to habitat loss and degradation for forest dwelling species. As a consequence, many species have become threatened, especially those dependent on dead wood. Integration of conservation in forest management is therefore essential for protecting boreal forest species diversity. To optimise conservation efforts, we need to understand species habitat requirements and diversity patterns in managed forests. This thesis aims to increase our understanding of insect species diversity patterns on clearcuts in boreal forest landscapes. I have surveyed beetles, bees and wasps on clearcuts in two boreal forest regions in Sweden and assessed the importance of clearcut properties and composition of surrounding landscape for species occurrence and diversity. Locally, amount of dead wood was positively associated with high species richness and individual species occurrence of certain wood-dependent beetles. Bee and wasp species richness increased with high local flower richness and clearcut size. Landscape composition was at least as important as local habitat characteristics for shaping diversity patterns. Burned forest land in surrounding landscape increased wood-dependent beetle species richness, while burning of clearcuts had only a weak effect on beetles, bees and wasps. This is probably because burned forest land on landscape scale includes higher habitat diversity with larger dead wood amounts, compared to burned clearcuts. Bee and wasp species richness increased with amount of early-successional habitats in the landscape, indicating that most species are associated with open habitats. The bee and wasp fauna differed considerably between landscapes. Therefore, conservation efforts need to be dispersed throughout the region to preserve the entire fauna. To promote insect species diversity on clearcuts in managed boreal forests, larger amount and diversity of dead wood needs to be created. Species dependent on sun-exposed dead wood or flowering plant richness can be favoured by prolonged open-habitat stage on parts of clearcuts. Concentrating certain conservation efforts to some clearcuts in the landscape is probably necessary in order to create high-quality habitats.
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| 6. |
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| 7. |
- Rubene, Diana, et al.
(författare)
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The presence of UV wavelengths improves the temporal resolution of the avian visual system
- 2010
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Ingår i: Journal of Experimental Biology. - : The Company of Biologists. - 0022-0949 .- 1477-9145. ; 213:19, s. 3357-3363
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Tidskriftsartikel (refereegranskat)abstract
- The ability to perceive rapid movement is an essential adaptation in birds, which are involved in rapid flight, pursuing prey and escaping predators. Nevertheless, the temporal resolution of the avian visual systems has been less well explored than spectral sensitivity. There are indications that birds are superior to humans in their ability to detect movement, as suggested by higher critical flicker frequencies (CFFs). It has also been implied, but not properly tested, that properties of CFF, as a function of light intensity, are affected by the spectral composition of light. This study measured CFF in the chicken, Gallus gallus L., using four different light stimuli - white, full-spectrum (white with addition of UV), yellow (590 nm) and UV (400 nm) - and four light intensity levels, adjusted to relative cone sensitivity. The results showed significantly higher CFF values for full-spectrum compared with white light, as well as a steeper rate of increase with intensity. The presence of UV wavelengths, previously demonstrated to affect mate choice and foraging, appears to be important also for detection of rapid movement. The yellow and UV light stimuli yielded rather similar CFFs, indicating no special role for the double cone in flicker detection.
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