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The natural tree holes and nest holes of hole-nesting birds were surveyed in four forest types in the west Khentii Mountains of NE Mongolia. The utilization patterns of species, size and condition of trees, as well as hole types, were investigated. The average density of tree holes in the study area approached 30 holes/ha, while that of hole-nesting birds was 2.4 nests/ha only. The riparian mixed forest had the greatest number of species and individuals of hole-nesting birds, while the spruce-fir forest had the lowest numbers. Excavating bird species preferred larger, deciduous trees, and snags. Non-excavators did not select holes according to tree species or size, but preferred holes in living trees and branch holes. In view of the low occupancy of holes among the four habitats, we suggest that the density of secondary hole-nesting birds is not limited by availability of holes in the study area.
117 nests of Red-breasted Flycatchers in Białowieża primeval forest (NE Poland) were characterised. Most nests (79%) were built in Hornbeam Carpinus betulus and lime Tilia cordata. Three types of nest sites were distinguished: chimney shaped (26.4%), half cavities (46.4%) or shelves — the nest was wedged under a piece of bark against the main trunk (27.3%). Most cavity entrances were exposed to the south. Compared to other species of secondary cavity nesters in Białowieża National Park, Red-breasted Flycatchers used cavities of a different shape, with a smaller bottom area and at a relatively low height above the ground (x̅= 4.9 ± 3.13 m). Nesting trees had a smaller diameter (x̅= 31.2 ± 21.4 cm) and were more often dead (29.8%) than trees used by the other secondary cavity nesters. Only four nest sites were used in consecutive seasons.
Broods of Pied Flycatcher nesting in natural tree holes and nest-boxes in Białowieża Forest (E Poland) were compared. Natural holes in primeval stands of the Białowieża National Park were located by following singing males, then monitored several times during the season. Nest-boxes situated in the managed part of the forest were inspected weekly. Flycatchers breeding in natural holes started laying eggs on average two days later (15 May) and laid smaller clutches (6.4 eggs) than birds breeding in nest-boxes (13 May and 6.7 eggs). The predation rate was significantly lower in natural holes (av. 47%) than in nest-boxes (av. 65%). This result indicates that generalisations regarding the evolution of adaptations to predation by nest-box populations should be treated with caution.
The study of tree-hole breeding mosquitoes was carried out in the tropical rainforest of Imo State Nigeria (two rural areas and two forest reserves in some parts of Orlu Senatorial Zone) between May – October 2002. Using standard entomological procedures, two macrohabitats (natural tree-holes and bamboo traps) and two microhabitats (leaf axils of cocoyams/pineapples and leaf axils of plantain/banana) were sampled for various mosquito species. Mosquitoes were recovered from all the various biotypes sampled. Types of mosquitoes species encountered, their relative abundance, as well as genera varied signifi cantly during the study (p<0.05). Four genera of mosquitoes: Aedes, Culex, Anopheles and Toxorhynchites were recovered while 16 species of mosquitoes encountered include: Aedes aegypti, Ae. africanus, Ae. simpsoni, Ae. albopictus, Ae. stokesi, Ae. taylori, Ae. apicoargenteus, Culex quinquefasciatus, Cx. nebulosus, Cx. trigripes, Cx. decens, Anopheles gambiae, An. funiestus, An. coustani and Toxorhynchites viridibasis. Most of the mosquitoes showed oviposition preferences for one or more habitats. The presence of Ae. africanus, Ae. simpsoni and Ae. aegypti indicate that the study areas were at risk of yellow fever epidemic. The presence of Anopheles and Culex species ensured endemicity of malaria and fi lariasis, while the recovery of Ae. albopictus in this region suggests a possible outbreak of dengue fever in future if not properly controlled.
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