Sylvia Melanocephala Research Articles

From species to individuals: combining barcoding and microsatellite analyses from non-invasive samples in plant ecology studies

By means of DNA barcoding and microsatellite analyses, we studied the species and individuals of legitimate seed dispersers of the Mediterranean shrub Pistacia lentiscus, a keystone species that represents the main source of food in winter for frugivorous birds. We collected dropping of birds containing seeds, and after DNA extraction we amplified and sequenced a fragment of the mitochondrial COI gene. Through BLASTN queries of the sequenced fragments against registered sequences in the GenBank database we identified the bird species that are currently dispersing P. lentiscus seeds. Further, through the amplification of specific nuclear microsatellite loci we calculated standard genetic diversity parameters of the population of birds from the genus Sylvia (the blackcap and Sardinian warbler), the most important dispersers of P. lentiscus. Five bird species were identified as seed dispersers through their barcode match. Further, we found that S. melanocephala displayed slightly lower levels of genetic diversity than S. atricapilla. In this study we show how the genetic analyses of environmental faecal samples can be a useful and convenient tool for the study of plant-frugivore interactions through the ascertainment of the identity of the species involved and through the analyses of genetic variability of their populations.

Seasonal Variation in Bird Species Richness and Abundance in Riparian Galleries in Southern Portugal

Riparian ecosystems are critical in maintaining biodiversity on a regional scale, which is particularly important for open agroforestry systems. We evaluated bird species richness and abundance in three different distances from the stream (0, 125 and 250 m) in Cork and Holm Oak forest systems (Montado) in southern Portugal. We used 5-minute point-counts to survey birds in two daily periods (morning and afternoon) of three different seasons (breeding season, summer-autumn migration and winter), to describe seasonal and daily variations in the use of riparian galleries and adjacent areas by birds. To assess whether birds move actively from the surrounding matrix into the riparian gallery, we installed mist-nets in mid-summer, autumn migration and winter periods, in two sites adjacent to streams, and recorded flight direction of all passerines trapped in the mist-nets. Both species richness and bird abundance were significantly higher in the riparian gallery than in the adjacent matrix. Species richness was significantly higher during the summer-autumn migration period, and bird abundance significantly lower during the breeding season. Apart from the Short-toed Treecreeper Certhia brachydactyla, Nuthatch Sitta europaea and Chaffinch Fringilla coelebs, all other species (e.g. Blackbird Turdus merula and Sardinian Warbler Sylvia melanocephala) were generally more abundant closer to the stream than at 250 m away. A significantly higher percentage of birds moved from the surrounding matrix into the riparian gallery in mid-summer, but not during the autumn migration and winter, which suggests that microclimatic conditions are important to explain observed seasonal differences. This study shows the importance of considering seasonal variation for the management of passerine bird populations in riparian galleries of Mediterranean areas. A well conserved riparian gallery appears to be a keystone structure exerting a strong influence on the number of bird species associated with surrounding agro-forestry systems such as the Montado.

Aridity influences the recovery of vegetation and shrubland birds after wildfire.

Wildfires play a determining role in the composition and structure of many plant and animal communities. On the other hand, climate change is considered to be a major driver of current and future fire regime changes. Despite increases in drought in many areas of the world, the effects of aridity on post-fire colonization by animals have been rarely addressed. This study aims to analyse how a regional aridity gradient affects post-fire recovery of vegetation, bird species richness and the numbers of four early to middle-successional warbler species associated with the shrub cover. The database contains bird relative abundance and environmental variables from 3072 censuses in 695 transects located in 70 recently burnt areas (1 to 11 years after wildfire) in Catalonia (Spain), which were sampled between 2006 and 2013. Generalized linear mixed models (GLMMs) showed that plant cover was affected by time since fire, aridity and forest management. However, only the highest vegetation height layer (>100 cm) recovered slower in arid areas after fire. Time since fire positively influenced bird species richness and the relative abundance of the four focal species. The post-fire recovery of Melodious (Hippolais polyglotta) and Subalpine warblers (Sylvia cantillans) was hampered by aridity. Although this was not demonstrated for Dartford (S. undata) and Sardinian warblers (S. melanocephala), their occurrence was low in the driest areas during the first three years after fire. Overall, this study suggests that future increases in aridity can affect plant regeneration after fire and slow down the recovery of animal populations that depend on understorey and shrublands. Given the recently highlighted increases in aridity and fire frequency in Mediterranean-climate regions, improved knowledge on how aridity affects ecological succession is especially necessary.

A sustained decline in Cyprus Warbler Sylvia melanothorax numbers in western Cyprus, coinciding with the colonisation of its breeding range by the Sardinian Warbler S. melanocephala

SummaryDuring 1998–2011, in an area of western Cyprus spanning about one-quarter of the global breeding range of the endemic Cyprus Warbler Sylvia melanothorax, the species declined at a rate of c.59% decade-1, suggesting that there is an urgent need to review its global conservation status. This decline has coincided with the recent, rapid colonisation of western Cyprus by the Sardinian Warbler S. melanocephala, whose numbers have increased substantially within the study area, as might be expected of a newly colonising breeding species. To identify possible causes of the Cyprus Warbler’s decline we compared its rate of change with measures of land-cover, vegetation density, altitude, rainfall and the presence of Sardinian Warblers at survey sites. The rate of decline in the Cyprus Warbler’s abundance was strongly correlated with land-cover and with the duration of site occupancy by Sardinian Warbler; Cyprus Warbler abundance had declined more steeply on sites colonised by Sardinian Warblers early in the survey period than on sites colonised later. Furthermore, on sites surveyed by BirdLife Cyprus in 2006–2014, Cyprus Warbler abundance had continued to decline significantly (also by c.59% decade-1) in western Cyprus, while Sardinian Warbler abundance had continued to increase. In contrast, Cyprus Warbler abundance showed no significant change in central and eastern Cyprus, where Sardinian Warblers were sparse or absent during the breeding season. These findings are consistent with at least two contrasting scenarios: that changes have occurred in land-cover or climatic conditions in Cyprus, to the detriment of Cyprus Warbler and to the benefit of Sardinian Warbler; or that in western Cyprus at least, the two species may compete for similar resources, despite a lack of evidence of this in an earlier, more detailed study. In either case, we suggest the need for a thorough, nationwide breeding survey of the two species.

West Nile virus-neutralizing antibodies in wild birds from southern Spain.

West Nile virus (WNV) is an emerging vector-borne arbovirus with a zoonotic life-cycle whose main reservoir hosts are birds. In humans and horses, WNV infections rarely result in clinical disease but on occasions - depending on factors such as climatic conditions, insect communities and background immunity levels in local populations - they can lead to outbreaks that threaten public and animal health. We tested for the presence of WNV antibodies in 149 birds belonging to 32 different species. Samples were first tested using a bird-specific ELISA kit and then both positive and doubtful results were confirmed by neutralization tests using WNV and Usutu virus. WNV antibodies were confirmed in a resident Sylvia melanocephala juvenile, supporting the idea of local transmission of WNV in southern Spain in 2013. In addition, the serum from an adult blackbird (Turdus merula) showed neutralization of both WNV and Usutu virus. We discuss our results in light of the occurrence of WNV on horse farms in southern Spain in 2013.

Assessing biodiversity and conservation value of forest patches secondarily fragmented by urbanisation in semiarid southeastern Spain

Semiarid Mediterranean areas patchily forested with Pinus halepensis Mill. are often affected by urbanisation plans, which influence the conservation of biodiversity in the remaining fragments. We assessed forest biodiversity in eleven Pinus halepensis patches of the municipality of Murcia (SE Spain), on the basis of the abundance, richness and conservation value of birds and woody flora. Under the hypothesis that biodiversity is conditioned by pine density, modulated by other patch features (age, physical substrate, surrounding land uses), mixed regression models were used to relate biodiversity indicators with environmental gradients, detected through principal component analyses (PCAs) performed on three sets of variables: landscape (L); habitat structure (H); and, stand development (S). PCA-L related patch size and connectivity to the abundance of typical woodland birds and to floral and bird species richness. PCA-H related shrub cover associated with Sylvia melanocephala Gmelin., to rock and dry grassland cover, a feature of moderately disturbed areas preferred by Lanius senator L. PCA-S associated taller trees and better physical conditions with canopy dwelling and soil probing bird species, respectively. The bird or plant conservation value of patches did not generally match their protection status, which was confirmed by the analysis of a larger sample of 36 natural patches. A negative relationship between floristic value and pine density suggests that reducing the density of reforestations can lead to more diverse and self-sustaining wooded formations. In contrast, conservation value for birds did not decrease with reforestation, stressing the need to use ornithological and floristic indexes as complementary assessment tools. The results seem useful for building a municipal network of reserves connecting higher status protected areas.

Acoustic patterns of an invasive species: the Red-billed Leiothrix (Leiothrix lutea Scopoli 1786) in a Mediterranean shrubland

The Red-billed Leiothrix (Leiothrix lutea) is an invasive species which has recently been found to be locally abundant in eastern Liguria (Italy). The song production of this bird was recorded over the course of an entire year (2011) and evaluated using both aural information and applying innovative automatic processing metrics. Our findings revealed that the Red-billed Leiothrix has loud vocalizations that are heard for most of the year, including in July and August when other birds are silent. Its song production has been estimated to amount to 37% of the sounds uttered by the entire bird community. The next most vocal species are the European Robin (36%), the Common Blackbird (18%), the Subalpine Warbler (5%) and the Sardinian Warbler (1%). The Red-billed Leiothrix can be seen as a new acoustically dominant species and, consequently, a potential modifier of the soundscape patterns of the indigenous bird community. The modification of acoustic traits in the repertoire of both indigenous species and the Red-billed Leiothrix is to be expected according to a co-evolution hypothesis.

Diversity and seasonal patterns of ticks parasitizing wild birds in western Portugal

The diversity and abundance of questing ticks and ticks parasitizing birds was assessed during 1year in two recreational forests in western Portugal, a suburban forest and an enclosed game area. The aim of this study was to assess the distribution and seasonality of tick species and to understand the role of bird species as hosts for ticks. Ixodes ricinus was the most abundant questing tick collected in the enclosed game area, whereas in the suburban forest, only three ticks were collected by blanket dragging. Tick species parasitizing birds included I. ricinus, I. frontalis, I. arboricola, I. acuminatus, Haemaphysalis punctata, Hyalomma marginatum and H. lusitanicum. This is the first record of I. arboricola in Portugal. Tick prevalence and intensity of infestation differed between study areas and was higher in birds from the game area where a large population of deer and wild boar may support tick populations. Ground and shrub dwelling bird species such as Turdus merula, Erithacus rubecula and Sylvia melanocephala were the most heavily parasitized by ticks, but the importance of different bird species as hosts of larvae and nymphs of I. ricinus and I. frontalis differed. Therefore, different bird species may contribute differently for tick population maintenance.

Time-window of occurrence and vegetation cover preferences of Dartford and Sardinian Warblers after fire

Wildfires are the most extensive and severe disturbance affecting the shrublands where Sardinian and Dartford Warblers (Sylvia melanocephala and S. undata) abound. Estimating the long-term use of burned habitats by these species (i.e. their time-window of occurrence) is fundamental to understanding their regional distribution and to plan possible conservation measures for the near-threatened Dartford Warbler. In this study, we describe the post-fire time-window of occurrence and cover preferences of the two warblers using an abundance dataset, gathered by point counts over 22 consecutive years, and a density dataset, resulting from territory mapping of four different plots for up to 8 years. Both datasets span before and after fire. The two species colonized burned areas as soon as the second year after fire. The Dartford Warbler showed its highest abundance between 4 and 9 years after fire and disappeared after 16 years or more. The Sardinian Warbler had a peak of abundance at 9 years, but the study was not long enough to record its local extinction. Partial least squares regression showed that abundance at points and plot density of the Dartford Warbler were positively related to the plant cover between 0.25 and 1 m, whereas vegetation between 0.5 and 4 m was important for the Sardinian Warbler. The Dartford Warbler, therefore, depends on the existence of dense and low shrublands, that are often the result of past fires.

Endemic Cyprus WarblerSylvia melanothoraxand colonizing Sardinian WarblerSylvia melanocephalashow different habitat associations

Anthropogenic habitat change and assisted colonization are promoting range expansions of some widespread species with potential consequences for endemic fauna. The recent colonization of Cyprus by breeding Sardinian WarblersSylvia melanocephalahas raised concerns that it might be displacing the closely related and endemic Cyprus WarblerSylvia melanothorax. Habitat associations of both species were examined using models of abundance within the 95% density kernel of the Sardinian Warbler’s range and also outside this range for Cyprus Warbler. Within the Sardinian Warbler’s range, the two species were associated with subtly different scrub habitats. Outside the Sardinian Warbler’s range, the Cyprus Warbler differed again in its habitat association, but this probably resulted from marked differences in habitat extent and availability in different parts of the island rather than from competitive displacement, as none of the habitat or land‐use elements differentially associated with Cyprus Warblers was positively associated with Sardinian Warbler occurrence. This suggests that the Sardinian Warbler has exploited a different niche, rather than displacing the endemic species, and has perhaps benefitted from changing land‐use patterns, particularly recent fallows and abandoned agriculture, in contrast to the stronger association of Cyprus Warblers with semi‐natural scrub.

Host-Parasite Interactions between Birds and Feather Mites

There is current uncertainty on whether feather mites are a cause or consequence of poor body condition in birds. We aimed at investigating the bird-mite relationships and elucidating the functional significance of feather mites on birds found on the Urra Field station, Sorbas, in Almeria province, south-east Spain. We captured birds using mist nest and assessed birds for body condition (weight, fat and pectoral muscles), mite distribution on the wings and tested for diurnal changes in mite abundance. The Kruskal-Wallis test was used to test for differences in mite abundance across species, sex, age and to test for differences in mite distribution on wings across species while the Fisher`s exact test was used to test for diurnal mite abundance. There were no significant differences in mite abundance between males and females in blackcaps, house sparrows, Sardinian and Willow warblers. There were significant differences in the abundance of mites on Blackcaps, house sparrows, sardinian and willow warblers. This study was carried out just before the breeding season, thus the juveniles may have been “mite-contaminated” by adults during the winter. Also, blackcaps could potentially be carrying different mite species, collected enroute during their migration. With more observational data over different time of day and seasons, investigations could be carried out to describe mite movements depending on varying environmental factors.

Tolerance to noise in 91 bird species from 27 urban gardens of Iberian Peninsula

Urban noise is one of the most important factors explaining the abundance of birds in urban areas. If urban planners have information on the effects of noise on diverse avian species, they can design better gardens that can be useful for the conservation of endangered species. In this sense, many studies have been realized in diverse urban areas across the world. However, information on the exact effects of noise on urban birds in SW Iberian Peninsula does not exist. In this paper, we show the first study on the effects of urban noise on 91 bird species in 27 parks in diverse cities and villages of Spain and Portugal. Our study includes from rural areas with noise levels below 40 dB, to parks inside big cities such as Madrid and Sevilla that surpass 70 dB. The range of noise conditions, studied parks and the seasonal and annual replication of this study permits extraction clears conclusions. In this sense, the ten species most affected by noise, in terms of percentage of explained variance, are: Regulus regulus with 34.62% variability associated with noise, Streptopelia turtur (24.24%), Dendrocopos minor (20.39%), Buteo buteo (15.15%), Hirundo daurica (13.15), Corvus corax (11.09%), Oriolus oriolus (10.23%), Cettia cetti (6.47%), Passer hispanoliensis (6.33%) and Sylvia melanocephala (5.82%). Our data demonstrates that many of these protected species could be attract to urban gardens if noise levels were reduced below 50 dB by using, for example, acoustic barriers.

Avian succession along ecological gradients: Insight from species-poor and species-rich communities of Sylvia warblers

Abstract The mechanisms responsible for species replacement during ecological successions is a long-standing and open debate. In this study, we examined the distribution of the Sardinian warbler Sylvia melanocephala along two grassland-to-forest gradients, one in a high-diversity area (Albera-Aspres chain in Catalonia: eight Sylvia warbler species) and one in a low-diversity area (Mount Hymittos in Greece: four species). In Catalonia, distribution models suggested that the apparent exclusion of S. melanocephala from the open and forest ends of the gradient may be explained entirely by the preference of S. melanocephala for mid-successional shrublands. However, a joint analysis of both data sets revealed that: 1) S. melanocephala was more evenly distributed along the vegetation gradient in Greece, suggesting ecological release in the low-diversity area; and 2) a distribution model assuming interspecific competition (based on the distribution of Sylvia species showing a negative co-occurrence pattern with S. melanocephala) had a significantly higher predictive ability than a distribution model based on habitat variables alone. Our study supports the view that species turnover along ecological gradients generally results from a combination of intrinsic preferences and interspecific competition.

Impacts of passage migrant songbirds on behaviour and habitat use of resident Sardinian Warblers Sylvia melanocephala in Gibraltar

Explanations for the coexistence of migratory and sedentary (resident) birds are much debated: some authors have suggested that migrants make use of surplus resources not exploited by residents, whereas others have recorded ecological shifts in residents during periods when migrants are present. These shifts have been ascribed to the presence of migrants but could equally reflect seasonal variation in the distribution of resources required by sedentary species. Here we assess how the abundance of migrants affects the territorial behaviour and habitat use of resident Sardinian Warblers Sylvia melanocephala at a stop-over site on the Rock of Gibraltar. There was a significant positive relationship between the abundance of migrants and the distances moved, time spent calling and the species and functional diversity of plants used by Sardinian Warblers on a daily basis, suggesting that migrants have a significant impact on residents.

Coping with invasive alien species: the Argentine ant and the insectivorous bird assemblage of Mediterranean oak forests

Cork oak forests invaded by the Argentine ant Linepithema humile have a lower abundance and biomass of arthropod prey for birds than uninvaded forests. We studied whether the biomass of breeding insectivorous birds was also lower in invaded areas. We explored this and other possible effects of the ant invasion on the bird community by censusing birds in transects located in four invaded and four uninvaded forest sites in Catalonia (NE Spain) for 3 years. Redundancy analysis showed only slight differences in the community composition between forests. Two insectivorous species, Luscinia megarhynchos and Fringilla coelebs, tended to be less abundant in invaded areas although two others, Phylloscopus bonelli and Sylvia melanocephala, showed the opposite trend. Overall, the differences in prey biomass between invaded and uninvaded areas did not entail a biomass shift in the guild of insectivorous birds, regardless of whether they were shrub or canopy foragers. The main role of the habitat structure in determining bird densities and food resources being non-limiting in the studied forests are two possible non-exclusive explanations for this inconsistency. At today’s levels, the Argentine ant invasion does not appear to have greatly determined the insectivorous bird assemblage of the forests evaluated.

Spatial Neophilia and Spatial Neophobia in Resident and Migratory Warblers (Sylvia)

AbstractResidents and migrants use their environment very differently – the former remain in a given habitat throughout the year, whereas the latter are repeatedly confronted with unfamiliar environments. The difference in ecology may influence decision‐making processes whether, when and to which extent to explore an unfamiliar environment. We have investigated spatial neophobia and spatial neophilia – two important novelty reactions that may underlie decision‐making – in two closely related warbler species, the resident Sardinian warbler and the migratory garden warbler. Individuals of both species could access an unfamiliar room from a familiar cage. We assessed the conflict between the motivation to enter the novel room (spatial neophilia) and the motivation to avoid it (spatial neophobia) as the frequency and duration of perching on the dowel in the cage, which led to the unfamiliar room before entering it. Furthermore, we measured the latency to enter the novel room and compared the number of individuals of each species entering the room. The combination of the parameters measured allowed assessing the degree of both neophobia and neophilia. Finally, the time spent on each branch in the novel room was taken as a measure for spatial exploration. The migrants perched less often and spent less time on the dowel leading to the room, and entered the novel room quicker than the residents. Additionally, more migrants than residents entered the room. The migrants’ decision to enter the novel room can best be explained with a combination of low spatial neophobia coupled with high spatial neophilia, whereas the residents’ decision‐making is best explained with high spatial neophobia coupled with high spatial neophilia. The differences in neophobia support the migrant‐neophobia hypothesis. When in the room, the migrants spent less time on each branch than the residents, possibly indicating that the former collect less spatial information than the latter.

British Ornithologists’ Union Records Committee: 37th Report (October 2008)

British Ornithologists’ Union Records Committee: 37th Report (October 2008)

Opportunistic nectar‐feeding birds are effective pollinators of bird‐flowers from Canary Islands: experimental evidence from Isoplexis canariensis (Scrophulariaceae)

Insular floras, characterized by simple pollination networks, sometimes include novel mutualistic agents such as nonspecialist nectarivores. In this study we confirmed the effective pollination of Isoplexis canariensis by opportunistic nectar-feeding birds in Tenerife, Canary Islands, Spain. This plant is among the ornithophilous species of the Canarian flora that lack past and present specialist nectarivorous birds. Experimental hand pollinations revealed self-compatibility, but cross-pollinated flowers produced a greater percentage of viable seeds than self-pollinated ones. Flowers were visited by five species of birds (Phylloscopus canariensis, Parus caeruleus, Sylvia melanocephala, Serinus canarius, and Fringilla coelebs) and by the endemic lizard (Gallotia galloti, Lacertidae). Insect pollination was absent, and the few insect visitors acted as nectar thieves or secondary nectar robbers. Birds represented 93.1% of total visits, with the Canarian Chiffchaff, Ph. canariensis, being the most frequent visitor. Flowers visited by birds set more, larger, and heavier fruit than flowers from which birds were excluded. Bird visitation also enhanced seed viability. These results demonstrate the active role of these opportunistic birds as effective pollinators of this Canarian bird-flower species. Further, the results reveal the need to consider the effect of these birds on the evolution of ornithophilous floral traits in absence of specialist nectarivores.

Phylogenetic differentiation of Sylvia species (Aves: Passeriformes) of the Atlantic islands (Macaronesia) based on mitochondrial DNA sequence data and morphometrics

Sequences of the mitochondrial cytochrome b gene (1063 bp) of Sylvia species from Macaronesia (Canary Islands, Madeira, Azores), Europe, and North Africa revealed new insights into the phylogeography of these taxa. Subspecific distinctiveness for Sardinian warblers (Sylvia melanocephala) from the Canary Islands was rejected on the basis of very low genetic divergence, distribution of haplotypes, and high variation in morphometrics. Furthermore, blackcaps (Sylvia atricapilla) from Madeira, Canary Islands, and the Azores were not genetically distinct, whereas morphometrics were highly variable. Differences in morphometrics in both Sardinian warbler and blackcap are caused rather by migratory behaviour and ecological traits than by phylogeny. Tentative data obtained in a small sample of spectacled warblers (Sylvia conspicillata) also suggest a low degree of differentiation between Sylvia conspicillata orbitalis (Canary Islands) and Sylvia conspicillata conspicillata (Mediterranean basin). At least for the Sardinian warbler and blackcap, the genetic data suggest a recent range expansion and chronologically different colonization events to the Atlantic islands.

Fruit tracking between sites and years by birds in Mediterranean wintering grounds

Knowledge of the ability of birds to track spatiotemporal variation in fruit distribution is essential for understanding plant‐frugivore interactions. Arguably, although total fruit availability sets an upper limit to the number of birds that can exploit a habitat patch, not all species can equally distribute abundance according to variation in fruit resources. To explore this, we studied bird and fruit abundance in 1999–2005 in Mediterranean scrublands and woodlands of southern Spain. We analysed whether changes of fruit abundance in eight different sites during six winters could predict numerical changes of a set of frugivorous passerines of the area (blackcap Sylvia atricapilla, Sardinian warbler S. melanocephala, robin Erithacus rubecula, song thrush Turdus philomelos and blackbird T. merula). We also investigated if all frugivores together tracked fruits better than individual species, thereby supporting a shared use of resources. Results showed strong inter‐specific differences. Only the most abundant species (blackcaps and robins) tracked the spatial patterning of food despite strong differences in the use of space (vagrant and territorial, respectively). This suggests plastic behaviour of territorial robins, with individuals changing from strictly territorial to wandering, a flexibility that would favour between‐site numerical arrangements according to food resources. Annual changes in bird numbers were independent of the availability of fruits, except for blackcaps, an abundant vagrant bird that tracked inter‐winter changes in fruit abundance. The abundance of blackcaps fitted the spatiotemporal patterning of fruit resources better than the whole guild of frugivorous birds, inconsistent with the idea that these species track together the changing availability of fruit resources.