Barred Warbler Sylvia Nisoria Research Articles

Seasonally divided moult in the Barred Warbler (Sylvia nisoria) is an endogenously controlled strategy

The seasonal timing of moult in migratory birds is an adaptation to cope with time constraints in the annual cycle. Kiat and Izhaki analysed moult patterns in Palaearctic passerines and rejected the proposition that seasonally divided moult is an endogenously controlled strategy. Instead, they advocated the view that it occurs due to a flexible and opportunistic timing of moult. In contrast, we argue that Kiat and Izhaki’s analysis is flawed and that they overlooked several important facts about moult in the Barred Warbler Sylvia nisoria and other species showing seasonally divided moult. These include the facts that juveniles replace a few secondaries already in their first winter, and that the moult sequences of primaries and secondaries are decoupled compared with the typical passerine complete moult sequence. We argue that seasonally divided moult is an adaptive strategy that is largely under endogenous control.

Habitat preferences of Red-backed Shrikes Lanius collurio and Barred Warblers Sylvia nisoria breeding sympatrically in a wetland/farmland mosaic

ABSTRACTCapsule: The Red-backed Shrike Lanius collurio and the Barred Warbler Sylvia nisoria had similar habitat preferences and their territories often overlapped. However, we found that Red-backed Shrikes were more flexible in habitat choice whilst Barred Warblers had more specific requirements.Aim: We aimed to analyse and compare distribution and habitat preferences of Red-backed Shrikes and Barred Warblers breeding sympatrically in semi-natural landscape in a wetland/farmland mosaic.Methods: We examined habitat availability and use by the two species within their breeding territories to identify differences in habitat selection.Results: Territories of both species were similar in habitat composition and used levees, bushes, fallow areas and single trees. However, the spatial characteristics of the territories differed between species. Red-backed Shrikes used a wider range of sizes and shapes of habitat patches, whilst Barred Warblers preferred a more complex landscape structure and a higher diversity of habitat types. We also found that areas of 71% of Barred Warbler and 34% of Red-backed Shrike territories overlapped.Conclusion: Whilst both species showed similar habitat choices, they appeared to differ significantly in terms of landscape structure: Red-backed Shrikes were more flexible and less selective than Barred Warblers in their habitat choice.

Comparative breeding ecology, nest survival, and agonistic behaviour between the Barred Warbler and the Red-backed Shrike

The majority of studies have demonstrated that the Barred Warbler Sylvia nisoria (BW) and the Red-backed Shrike Lanius collurio (RBS), where they occur sympatrically in central Europe, inhabit similar niches and are not averse to nesting in each other’s vicinity. The present work compares the reproductive parameters, nest survival, and behavioural interactions between these two ecologically similar species. The study was carried out in eastern Poland in two types of habitat: a river valley and farmland. Inter-habitat analysis showed both species to have similar reproductive parameters, although nest survival of the RBS was greater in farmland than in the river valley. Interspecific comparison revealed that the BW built smaller nests, laid fewer and smaller eggs than the RBS, but the production of offspring was similar in both species. In comparison to the other populations from Europe, both the BW and RBS in eastern Poland experienced good breeding parameters, and this is likely to be related to the region's extensive agriculture management and abundant food resources. The main factor reducing breeding success in both species was the plundering of their broods by raptors. Analysis using the MARK program indicated that habitat parameters significantly affected brood survival in the RBS to a relatively constant extent throughout the season. While habitat factors were less decisive in BWs, the fate of this species’ broods was strongly dependent on the phase of the reproductive cycle, and its nests were least likely to survive in the middle of the breeding season. The level of aggression between the BW and RBS was low, as demonstrated by experiments with stuffed models; this was a factor in favour of their nesting in close proximity to one another.

Effect of Brood Age on Nestling Diet and Prey Composition in a Hedgerow Specialist Bird, the Barred Warbler Sylvia nisoria.

The composition and quality of food provided to nestling birds influence their growth and development and offers key insight into the ecological requirements of birds. One bird species whose feeding ecology is poorly understood is the Barred Warbler (Sylvia nisoria), which utilizes semi-natural shrubby vegetation in agroecosystems. Because Barred Warbler nestlings vary greatly in body mass we hypothesised that diet and prey properties (size, diversity, taxonomic composition, and chitin content and resulting body hardness and digestibility) would differ as the nestlings aged. We quantified the diet based on faecal analysis, sampling faecal sacs from the nestlings pooled into three age classes: 2-3 days old, 4-6 d old, and 7-9 d old. Nestlings were provided a wide diversity of food and a strong relationship existed between food characteristics and nestling age. The youngest nestlings (2-3 d old) had the lowest values of each dietary characteristic (diversity, number and total biomass of prey, and individual prey weight), that were significantly lower than the oldest nestlings (7-9 d old). Nestlings aged 4-6 d exhibited intermediate dietary characteristics. Differences in dietary composition of the six major food types showed marked differences between the individual broods and age categories. Percentages of the number and biomass of soft-bodied prey were highest in the diet of 2-3 d and 4-6 d old nestlings, and decreased with increasing age, whereas the opposite trend was observed in the percentage of intermediately and heavily chitinised prey. Parent Barred Warblers probably preferentially select soft-bodied prey for the youngest nestlings, and satisfy the greater energy demands of the older ones by providing them with a greater variety of prey containing more chitin, as well as plant food. The provisioning of less-readily digestible prey to older nestlings suggests that as the quality of food decreases the quantity increases, implying that the youngest nestlings may be physiologically limited as regards their ability to digest more heavily chitinised prey.

Protective nesting association between the Barred Warbler Sylvia nisoria and the Red‐backed Shrike Lanius collurio: an experiment using artificial and natural nests

AbstractThe pressure of predators may significantly affects the distribution pattern of nesting birds. Some individuals may reduce the risk of predation by nesting near other species with an aggressive nest defence. In the present study I tested the predator protection hypothesis using experimental (artificial nests) and observational (real nests) approaches on two ecologically similar passerine birds–the Barred Warbler Sylvia nisoria and the Red‐backed Shrike Lanius collurio. Studies have been conducted in eastern Poland in two types of habitat: river valley and farmland. The main predators of natural and artificial nests were birds, and to a lesser extent, also mammals. I found wide variation level of predation of both types of nests in different years. Nest survival rate of artificial nests was significantly lower in the farmland than in the river valley and in natural nests I observed reverse pattern. According to the predictions of the predator protection hypothesis the survival rates of the natural and artificial nests were significantly higher in territories of individuals breeding in the protective nesting association. This type of interspecific positive interaction between two associate species can be classified as facultative mutualism.

Structural heterogeneity of linear habitats positively affects Barred Warbler Sylvia nisoria, Common Whitethroat Sylvia communis and Lesser Whitethroat Sylvia curruca in farmland of Western Poland

Capsule Structural heterogeneity was the most important factor influencing the distribution of Barred Warbler Sylvia nisoria, Common Whitethroat S. communis and Lesser Whitethroat S. curruca in linear habitats in farmland of Western Poland.Aims To investigate the occurrence of three species of Sylvia warblers in relation to the spatial structure of linear habitats in the agricultural landscape of Western Poland where, in contrast to Western Europe, field boundaries are not managed in terms of their size or spatial structure.Methods In 2008, the distribution of breeding territories of Sylvia warblers in linear habitats was estimated in farmland of Western Poland. Redundancy detrended analysis was used to assess the relationship between bird abundance and seven linear habitat variables in ninety-four 150 m sections.Results Sylvia warblers differed in habitat requirements, however heterogeneity affected their distribution to the greatest extent. In addition, Barred Warbler preferred high shrub volume and wider sections, whereas Common Whitethroat was attracted by brambles and nettles and Lesser Whitethroat favoured shrubs. All species avoided a high proportion of low vegetation.Conclusion Structural heterogeneity resulted in highly preferred linear habitats for Sylvia warblers. Thus, maintaining or increasing structural heterogeneity of linear habitats may be a very effective tool for the conservation of farmland bird populations.

Habitat preferences and population trends in the Barred Warbler Sylvia nisoria in the Ottenby area, southeast Sweden

We performed a detailed census of the breeding population of Barred Warblers Sylvia nisoria in the Ottenby area on the southernmost part of the island Öland, SE Sweden, in the years 1999 and 2000. The number of territories in the study area was similar to the census conducted in 1971—1975, although the distribution of territories had changed. In 1999—2000 most territories were located in the grazed Alvar habitat (a limestone rich steppe found on some island in the southern Baltic Sea) in the north part of the study area, whereas areas in which grazing had ceased since 1971—1975 had been more or less abandoned. Data from the standardized trappings at Ottenby Bird Observatory showed no significant changes in the annual number of trapped juvenile Barred Warblers, also suggesting a stable population size. We investigated the vegetation (species composition and spatial structure) in occupied territories and compared these with randomly distributed plots in the same habitats. Occupied territories were overall more spatially varied, with a large proportion of the vegetation consisting of low and middle-sized bushes. We also use these habitat preference data to outline management advice for this rather uncommon species with fragmented distribution pattern.

The orientation system and migration pattern of long‐distance migrants: conflict between model predictions and observed patterns

The requirements of the orientation system of naïve long‐distance night migrants were analysed by comparing data on Barred Warbler Sylvia nisoria, Marsh Warbler Acrocephalus palustris and Spotted Flycatcher Muscicapa striata with data from a computer model of a clock‐and‐compass system. These species show, respectively, a rather restricted winter distribution in East Africa, migration through a very narrow corridor in East Africa, and rather widely distributed recoveries in the Mediterranean with more concentrated recoveries south of the Sahara. For all three species, to obtain the observed concentrations either a very high directional migratory concentration was needed in computer simulations to bring the birds successfully to their wintering areas or misorientating individuals would be subjected to a very high mortality. Neither the very high directional concentration nor the high mortality amongst misorientating individuals fit the empirical data sets. On the basis of the present study, the observed patterns seem difficult to explain by a simple clock‐and‐compass system only, and to account for the exceptionally precise migratory routes shown in this study it is proposed that first‐time migrants might be able to use landscape topography on a regional scale in combination with corrections of directional mistakes/wind displacements.

Juvenile wing shape, wing moult and weight in the family Sylviidae

A study of 56 species of Sylviidae occurring in the western Palaearctic showed a significantly less extensive post‐juvenile moult in those species which incur longer migrations to winter quarters than in species that migrate short distances. Species with the more extensive post‐juvenile moult also undertook their first full moult in summer compared with the less extensive post‐juvenile moult in species with a full moult in the winter. In 11 species, young birds had shorter wings and lower body mass than adults. These differences produced significantly lower wing loadings in young birds compared with adults. Those species undertaking a full moult in the winter had significantly more pointed wings than species with their full moult in the summer. I suggest that this difference is the result of winter‐moulting species evolving from the probably basic strategy of a full post‐breeding (summer) moult. Some species, such as the Barred Warbler Sylvia nisoria, may be in the process of changing the full‐moult season from summer to winter.

Is the nesting association between the Orphean Warbler (Sylvia hortensis) and the Woodchat Shrike (Lanius senator) an anti-predator oriented mutualism?

As already pointed out in the Red-backed ShrikeLanius collurio (and Isabelline ShrikeL. isabellinus) and the Barred WarblerSylvia nisoria, the Woodchat Shrike and the Orphean Warbler form a species pair engaged in a breeding association. Nest recordings of both species in the same bushes along with behavioural evidence in southern France suggests that this association goes far beyond a simple commensalism (for the sole benefit of the warbler) but might be considered as an anti-predator oriented mutualism whose precise extent evidently needs further observations.

Notes on the breeding biology of the Barred Warbler Sylvia nisoria at Ottenby, Sweden

Notes on the breeding biology of the Barred Warbler Sylvia nisoria at Ottenby, Sweden

The Seasonally Divided Flight Feather Moult in the Barred Warbler Sylvia nisoria: A New Moult Pattern for European Passerines

Wing and tail feather moult in Barred Warblers was studied during three summers in SE Sweden. Birds arriving at their breeding grounds had on average 3.2-4.9 fresh secondaries and 3.9-9.4 fresh tail feathers, most certainly moulted in winter quarters. A few primaries and tertials had also been renewed. After breeding, normally all primaries and tertials were moulted. Primary moult duration was approximately 40 d for the individual and 60 d for the population. On average, only 0.7-1.4 secondaries were shed. No individuals renewed any winter-grown secondaries the following summer. Normally, 3-4 (mainly central) tail feathers were moulted. Thus, Barred Warblers moult primaries, tertials and central tail feathers in summer, and secondaries and a varying number of tertials and tail feathers in winter. The juvenile winter moult of secondaries shows that the seasonally divided flight feather moult is actively initiated already in the first winter; this is interpreted as a preparation for an early departure from breeding grounds the following summer. This moult pattern has not previously been documented in European passerines.