Habitat selection of Dartford Warbler Sylvia undata on Elba Island (Tuscan Archipelago,Italy)

Capsule Habitat selection of Dartford Warbler Sylvia undata on Elba Island (Tuscan Archipelago, Italy) was analysed, considering 1-ha square plots (104 occupied and 104 unoccupied). Dartford Warbler occurrence was positively associated with garrigues, maquis and meadows, whilst the urban areas have a negative effect. The most used vegetation types were the garrigues with Cistus and degraded tall maquis with Erica arborea, Arbutus unedo and Cistus monspeliensis.     

Habitat type determines the effects of disturbance on the breeding productivity of the Dartford Warbler Sylvia undata

Numerous studies have examined the causes and impacts of human disturbance on birds, but little is known about how these impacts vary among habitats. This is of applied importance both for predicting bird responses to changes in disturbance and in planning how to reduce disturbance impacts. The Dartford Warbler Sylvia undata , a key heathland breeding species, occupies territories in a range of heathland types. Three territory habitat groups were identified: heather-dominated territories, heather territories with significant areas of European Gorse Ulex europaeus and territories containing Western Gorse U. gallii . Productivity was significantly affected by the timing of breeding in all habitats, but disturbance only appeared to have a significant impact on the productivity of birds in heather territories. Disturbance events in heather territories delayed breeding pairs for up to 6 weeks. This significantly decreased both the number of successful broods raised and the average number of chicks fledged per pair. Nests situated close to territory boundaries in heather territories, with high numbers of disturbance events, were more likely to fail outright. It was determined that an average of between 13 and 16 people passing through a heather territory each hour would delay breeding pairs sufficiently to prevent multiple broods.     

Foods of the Dartford warbler Sylvia undata on southern English heathland (Aves: Sylviidae)

This paper describes the invertebrates of Callunetum and gorse on lowland heaths in Dorset and relates how these were exploited by the Dartford warbler Sylvia undata , a scarce bird of interest to nature conservation and one of the small number of wholly insectivorous resident passerines in Britain. Gorse had a denser invertebrate fauna than Callunetum and was used for feeding at a frequency out of proportion to its abundance. Diets of adult birds closely reflected the taxonomic composition of the gorse and Callunetum faunas exploited in the observed proportions, though some noxious taxa were avoided and below a certain limit, creatures of above average size were selected. Major foods were beetles, spiders, lepidopteran larvae and bugs. Nestling birds received a diet differing in taxonomic composition and size from that of the adults, and variations between habitats were found which accorded with observations on the habitat preferences of the Dartford warbler. An experimental investigation showed the importance of gorse as a source of food for young and the adults flew considerable distances ignoring extensive deep stands of heather nearer to the nest. The possible influence of competing insectivorous vertebrates on Dartford warblers is discussed. Various mammals and reptiles appeared to be the major vertebrate predators in Callunetum, but little competition was anticipated in gorse. Scarcity of gorse on the heaths and low densities of invertebrates in heather explained the low densities at which Dartford warblers occur.     

Home range and territory of the Sardinian Warbler Sylvia melanocephala in Mediterranean shrubland

Capsule Singing territories were well separated.

Aims To examine the spatial distribution of Sardinian Warbler males during the breeding period in Mediterranean shrubland and, specifically, their territories, home ranges and spatial overlaps.

Methods We studied a 12-ha plot of Mediterranean shrubland in the 1997 to 1999 breeding seasons. Sardinian Warblers were captured using mist-nets, colour-ringed and their territories mapped. In 1999, seven breeding males were radiotracked in order to map home ranges.

Results The Sardinian Warbler had an average of 7.3 breeding pairs/10 ha in the study plot. The mean territory size was 8779 m² and the mean home range was 22 321 m². A positive relationship was found between the area of the home range and singing territory. Home ranges of males born in 1998 were about half the size of those of the oldest males. Paired males who moved with a female had smaller home ranges than those that were either unpaired or whose mate was incubating. The degree of home range overlap was high with some overlap between neighbouring territories. The estimate of home range area increased by 10% when the information generated by a mapping method was added and the estimated territory area increased by 31% when data generated by radiotracking were added. Transmitters remained attached to birds for an average of 9.63 ± 3.46 days (mean ± se).

Conclusions Singing territories were segregated to a considerable degree. In contrast, the wide overlaps among home ranges was best explained by the presence of food resources that the males exploit at the same time and also by the search for extra-pair copulation in nearby territories. We consider radiotracking in this species to be feasible and valid, with no evidence of negative effects on activity levels, weight or mortality.     

Geolocator reveals migratory and winter movements of a Prothonotary Warbler

Prothonotary Warblers (Protonotaria citrea) are Nearctic‐Neotropic migrants that have experienced declining populations over the past 50 yr. Determining their migration routes and wintering areas are critical steps in identifying habitats used by species and populations of conservation concern. We captured a male Prothonotary Warbler on its breeding territory in Louisiana in June 2013 and attached a geolocator. We recaptured this male in March 2014 and analysis of the geolocator data revealed that the male traveled an estimated 7950 km through seven countries. Fall migration was characterized by movements south into Central America on 13 August 2014, then east to the Greater Antilles for about 1 mo, followed by a second movement south to Panama or Colombia on 15 November 2014 where the male remained for the rest of the winter. Spring migration occurred rapidly, with the bird leaving its southern wintering area on 4 March 2014 and returning to its breeding territory on 23 March 2014. The movements of this male Prothonotary Warbler add to accumulating evidence that many migrant birds exhibit either prolonged stopover behavior or secondary migratory movements. Factors contributing to prolonged stopover behavior or additional migratory movements of the Prothonotary Warbler in our study warrant further investigation.     

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.     

An unexpected pattern of migration revealed in the Subalpine Warbler Sylvia cantillans complex by mitochondrial DNA analyses

Genetic markers are often used to trace the geographical origin of migrating birds. Such an approach has been used to attribute individuals of a given species to a given population, but it could also be applied to cryptic species, which are not fully diagnosable on the basis of their morphological appearance alone, despite often being genetically distinct. We sampled migrants of the Sylvia cantillans complex, which include cryptic taxa not readily identified on the basis of their appearance, at spring stopover sites in the central Mediterranean. We identified these individuals taxonomically using mitochondrial DNA sequence data. Molecular analyses enabled us to establish that four different taxa/clades of the Sylvia cantillans complex (two S. c. cantillans clades, S. c. albistriata and S. subalpina) migrate through the central‐western Mediterranean from Africa.     

The winter fattening model: a test at low latitude using the Clamorous Reed Warbler

Small birds at high latitudes accumulate fat during the day so that they can survive long and cold winter nights. The winter fattening model suggests that birds increase their minimum (morning) mass in cold weather, build up their mass during the day, and then rely on the energy reserves so accumulated until the morning. While data from mid and high latitudes support this model, little is known about the strategies of birds inhabiting lower latitudes (< 40°N). We use an 18-year data set to investigate whether the winter fattening model holds in a mid-latitude (32°N) population of the Clamorous Reed Warbler Acrocephalus stentoreus . We show that morning mass and fat score vary as predicted by the winter fattening model. In addition, adults appear to be better adapted to long and cold winter nights than first-year birds. A long-term trend of increased body mass may be attributable to character release following reduced interspecific competition.     

Modelling the winter distribution of a rare and endangered migrant, the Aquatic Warbler Acrocephalus paludicola

The Aquatic Warbler Acrocephalus paludicola is one of the most threatened Western Palearctic passerine species, classified as globally Vulnerable. With its breeding grounds relatively secure, a clear need remains for the monitoring and protection of the migration and wintering grounds of this rare and endangered migrant. Recent research has shown that the Aquatic Warbler migrates through northwest Africa in autumn and spring. The wintering grounds are apparently limited to wetlands of sub-Saharan West Africa, with records from only about 20 localities in Mauritania, Mali, Senegal and Ghana. Given the lack of knowledge of its whereabouts, we decided to use the available data to predict the wintering distribution of the Aquatic Warbler with the help of Geographic Information Systems (GIS). We used a novel approach to model the distribution of rarely recorded species, which is based on a combination of presence-only and presence–absence modelling techniques. Using the program BIOMOD, we thus generated four progressively more conservative predictions of where the Aquatic Warbler overwinters in Africa. Whereas the most permissive model predicts the Aquatic Warbler to be found in a latitudinal band stretching from the Senegal river delta all the way to the Red Sea coast, the most restrictive model suggests a much smaller area concentrated within the regions around the Senegal river delta in northern Senegal and southern Mauritania and around the Niger inundation zone in southern Mali and eastern Burkina Faso. Such model predictions may be useful guidelines to focus further field research on the Aquatic Warbler. Given the excellent model predictions in this study, this novel technique may prove useful to model the distribution of other rare and endangered species, thus providing a means to guide future survey efforts.     

Birds of a feather winter together: migratory connectivity in the Reed Warbler Acrocephalus scirpaceus

To investigate migratory connectivity in the Reed Warbler Acrocephalus scirpaceus, we analysed (1) all available sub-Saharan ringing recoveries and (2) stable isotopes in feathers grown in Africa sampled at 17 European breeding sites across a migratory divide. A cluster analysis of ringing recoveries showed remarkable connectivity between breeding and non-breeding grounds. Two main clusters represented populations taking the two main migratory routes [southwesterly (SW) and southeasterly (SE)]. Stable isotope analysis confirmed the separation of wintering areas of SW- and SE-migrating populations. Higher δ¹⁵N values in feathers of SE-migrating birds indicated that they occupied more xeric biome types. Values of δ¹³C that did not differ significantly among populations were higher than those from feathers of known European origin and indicated a C4 biome. Three populations with an unknown migratory direction were assigned to the SE-migrating populations on the basis of δ¹⁵N values.     

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.     

Dispersal and population expansion in a direct developing marine snail (Littorina saxatilis) following a severe population bottleneck

Most marine benthic invertebrate species have planktonic larvae, and in species in which juveniles and adults have low vagility a larva is obviously an efficient way of active dispersal. A minority of benthic invertebrate species develop without any pelagic phase at all. A largely unsolved question is how and at what rate do these species disperse. We have addressed this question using the marine littoral snail Littorina saxatilis (Olivi) as an example of a species that completely lacks larval dispersal. In the Koster archipelago (north part of the Swedish west coast), L. saxatilis occupies rocky island habitats of different sizes, from large islands to small intertidal skerries (islets). In 1988 an extremely dense bloom of a toxin-producing flagellate killed more than 99% of this snail species in this area. Populations of larger islands were reduced, often to less than 1%, but were restored over 2–4 yr. In contrast, populations of small intertidal skerries were completely wiped out and thus could not increase by local recruitment. Four years later, however, four of 33 skerries (12%) were successfully recolonized with relatively dense populations, and another five had received a few founder individuals. These results indicate recruitment through founder individuals, and are rough estimates of dispersal rate in a snail species that lacks a pelagic developmental stage.     

Year-to-year changes in the age structure of a caddisfly population following loss and recovery of a springbrook habitat

A severe drought in 1977 resulted in cessation of normally permanent flow m a northern California (USA) springbrook, and no individuals of the numerically dominant macroinvertebrate, the caddisfly Gumaga nigricula (McL), survived Prior to habitat loss (1976) this population was multiple cohort, two years after habitat recovery (1979) a single-cohort population was present The shift m age structure back to pre-drought conditions occurred gradually median head capsule width in 1976 (pre-drought) 0 39 mm, 1981 (post-drought) 0 95 mm, 1982 0 99 mm, 1983 0 59 mm, 1984 0 63 mm, 1985 0 63 mm, 1986 0 45 mm Age structure from 1981-1985 was significantly different (p < 0.001) from that occurring before habitat loss in 1976, age structure m 1986 was not significantly different from that in 1976 The ten-year time for return to the original population age structure could be influenced by the isolation of the springbrook from other colonization sources, gradual increases in population density, and differential growth reflecting food availability     

Low genetic variability of the koala Phascolarctos cinereus in south-eastern Australia following a severe population bottleneck

Genotyping of koalas at CA-repeat microsatellite loci has revealed significant differences in the levels of allelic diversity ( A ) and expected heterozygosity ( H¯ _E) between populations from north-eastern and south-eastern Australia. In the 10 populations studied, allelic diversity ranged from 8.0 in the Nowendoc population to 1.7 in the Kangaroo Is. population, and values of H¯ _E ranged from 0.831 in the Nowendoc population to 0.331 in the Kangaroo Is. population. Data from pooled populations revealed koalas from the north-eastern region had significantly higher levels of allelic diversity ( A = 11.5 ± 1.4) than those from south-eastern Australia ( A = 5.3 ± 1.0). Furthermore significantly higher heterozygosity levels were found in the north-eastern ( H¯ _E= 0.851) vs. the south-eastern ( H¯ _E= 0.436) regions of Australia. Following a near-extinction bottleneck in the 1920s, mainland Victorian and Kangaroo Is. koalas have been involved in an extensive program of relocations. The source populations of the relocated animals were islands in Westernport Bay, which were founded by very few individuals in the late 1800s and early 1900s. The significantly lower levels of variation between south-eastern Australian populations suggests that human intervention has had a severe effect on levels of genetic diversity in this region, and this may have long-term genetic consequences.     

Unregulated hunting and genetic recovery from a severe population decline: the cautionary case of Bulgarian wolves

European wolf (Canis lupus) populations have suffered extensive decline and range contraction due to anthropogenic culling. In Bulgaria, although wolves are still recovering from a severe demographic bottleneck in the 1970s, hunting is allowed with few constraints. A recent increase in hunting pressure has raised concerns regarding long-term viability. We thus carried out a comprehensive conservation genetic analysis using microsatellite and mtDNA markers. Our results showed high heterozygosity levels (0.654, SE 0.031) and weak genetic bottleneck signals, suggesting good recovery since the 1970s decline. However, we found high levels of inbreeding (F _IS  = 0.113, SE 0.019) and a N _e/N ratio lower than expected for an undisturbed wolf population (0.11, 95 % CI 0.08–0.29). We also found evidence for hybridisation and introgression from feral dogs (C. familiaris) in 10 out of 92 wolves (9.8 %). Our results also suggest admixture between wolves and local populations of golden jackals (C. aureus), but less extensive as compared with the admixture with dogs. We detected local population structure that may be explained by fragmentation patterns during the 1970s decline and differences in local ecological characteristics, with more extensive sampling needed to assess further population substructure. We conclude that high levels of inbreeding and hybridisation with other canid species, which likely result from unregulated hunting, may compromise long-term viability of this population despite its current high genetic diversity. The existence of population subdivision warrants an assessment of whether separate management units are needed for different subpopulations. Our study highlights conservation threats for populations with growing numbers but subject to unregulated hunting.     

Kin-related social organization in a winter population of the voleClethrionomys rufocanus

Kinship amongClethrionomys rufocanus was investigated during the winter of 1992/93 in a 3-ha enclosure using both molecular and catch-mark-release techniques. Forty-six adult voles (22 males and 24 females) having high heterozygosities, which were collected from several natural populations, were released into the enclosure on 29 September 1992. Most fall-born individuals of both sexes stayed in their natal site during the non-breeding period (December–March), although reproductively active females dispersed during the fall breeding season (October–November). These philopatric individuals aggregated and formed an maternal family in the winter. Several females which failed to reproduce were solitary during this season. Some individuals which were derived from several families also aggregated into a mixed lineage group. Survival rate of fall-born voles from earlier litters was higher than that from later ones. Maternal families broke up soon after the onset of spring reproduction. Most females established a territory near the wintering site and made a kincluster, in which close relatives neighbored each other. Maternal families in winter bring about female kin-clusters in spring, which may influence reproductive output in the breeding season.