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The Red-backed Shrike and the Barred Warbler are a pair of species engaged in breeding association. Whilst the arrival time of both species from their wintering grounds was not correlated, they differed in median arrival time by only one day. The majority of the Barred Warbler territories were located within those of the Red- backed Shrike, in both forest and farmland plots. Both species differed significantly in their selection of nest sites, at least in farmland. Unlike to the Red-backed Shrike (n = 297), the Barred Warbler (n = 60) preferred blackberry bushes and small deciduous thomless shrubs, and avoided elder, coniferous and hawthorn. The Barred Warbler nests were placed significantly lower than those of the Red-backed Shrike. The results show that no special ecological relationships exist as was suggested in earlier papers for other areas.
The co-occurrence of Redbacked Shrikes (Lanius collurio) and Barred Warblers (Sylvia nisoria) was monitored during the years 1999–2003 at 343 ha of agricultural landscape of eastern Poland. Each year 25–31 pairs of Red-backed Shrikes and 3–8 pairs of Barred Warblers were nesting. In total, during five seasons, shrikes were nesting in the vicinity (within 50 m from the centre of the Barred Warbler territory) of 22 out of 24 (92%) warbler territories. The breeding success of the pairs nesting close to Barred Warbler territories was 89%, as compared with 61% for the remaining pairs and it was statistically significant. No difference was found in the clutch size between Redbacked Shrikes nesting close to Barred Warblers and far from them, but statistically significant difference was found in numbers of fledglings between them. The present results imply that close nesting of these two species reduces the risk of nest predation. This may be due to the aggression of Barrred Warblers towards potential predators, as this species actively attacks predators near the nest.
We used a nested PCR protocol to examine the genetic diversity of cytochrome b (cyt b) lineages from blood parasites of the genera Plasmodium and Haemoproteus in birds in Bulgaria. In total, 460 birds of 43 species and 14 families (mostly passerines) were examined for the presence of infections. Of them, 267 were recognised as infected with haemosporidian parasites. Mixed infections were recorded in 24 individuals (9%). Besides the 24 individuals with mix infections, 114 (43%) were positive for Plasmodium spp. and 129 (48%) for Haemoproteus spp. We identified 52 genetic lineages of haemosporidian parasites: 38 of Haemoproteus and 14 of Plasmodium. Twelve new cyt b lineages of Haemoproteus were recorded; they occurred in the following hosts: grey-faced woodpecker (Picus canus), golden oriole (Oriolus oriolus), jay (Garrulus glandarius), barred warbler (Sylvia nisoria), song thrush (Turdus philomelos), spotted flycatcher (Muscicapa striata), spanish sparrow (Passer hispaniolensis), hawfinch (Coccothraustes coccothraustes), and cirl bunting (Emberiza cirlus). We also detected 22 new host records for previously known lineages. The most common lineage was SGS1 (Plasmodium relictum), which had a total prevalence of 14% and occurred in 8 host species belonging to 5 families. Three of the cyt b lineages of genus Haemoproteus (DURB1, DURB2 and SYNIS2) showed more than 5% divergence from all described morphologically lineages. These lineages probably represent at least 2 different morphospecies which remains to be identified.
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