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In 1992 the Sardinian Warbler was first recorded breeding in Cyprus. Since then, survey results from Paphos District suggest that the endemic Cyprus Warbler population has declined, while the Sardinian Warbler breeding population has increased and expanded in Paphos District. Colour-ringed Cyprus and Sardinian Warblers were observed during 2003 to 2005 breeding seasons on seven scrub study plots located across Paphos District. Both species appeared to establish home-ranges without reference to the other species, resulting in considerable interspecific home-range overlap. A playback experiment indicated that Cyprus Warblers reacted equally strongly to conspecific and congeneric song in areas where the two species coexist, but less strongly to congeneric than conspecific song in areas where Sardinian Warblers did not yet breed. The vegetation composition of Cyprus and Sardinian Warbler home-ranges was very similar. There was no indication that the species competed for nest sites. Cyprus and Sardinian Warbler have similar breeding biology; they laid similar sized first clutches and had similar chick output per pair for first nesting attempts. However Sardinian Warblers had a higher frequency of second nesting attempts and this resulted in a higher chick output per pair per year than was achieved by Cyprus Warblers. In both species total chick output per year was higher for pairs that nested early. Nest survival was similar for the two species. Cyprus and Sardinian Warbler diets were very similar. Body condition of both species’ chicks was higher earlier in the breeding season. Cyprus Warblers had higher productivity but lower chick body condition in the zone where their population has declined than in the zone with fewest breeding Sardinian Warblers. Productivity was positively related to arthropod biomass available on different plots for Sardinian Warbler, but not for Cyprus Warbler. There was no evidence of a negative impact of either species on the number or condition of nestlings produced by the congener.

Birds can behave aggressively towards conspecifics to defend a territory and to compete for access to food and mates. The effects of phenotypes, such as sex and age, in aggressive behaviour have not yet been fully understood. Moreover, differences in aggression levels can reflect alternative behavioural strategies (i.e. proactive–reactive axis). We aimed to understand the relation between aggressive behaviour and different phenotypes (i.e. age, sex, body size) and between behaviours present in the proactive–reactive axis (i.e. aggression, exploration and fear). We studied the behaviour of a highly territorial species that shows sexual dimorphism, the Sardinian warbler (Sylvia melanocephala), using four behavioural tests: mirror, exploration, predation and tonic immobility. The tests measured respectively aggression, exploration and fear (the last two). Our results showed that the studied behaviours were not related to each other, suggesting an absence of the proactive–reactive axis. Only body size was found to predict aggressive behaviour, which might signal fighting ability in this species. Males and females did not differ in their aggression levels, suggesting that both sexes might play a role in territory defence. These results may reflect the importance of territorial defence in both sexes for species evolution.

SummaryThe recent classification of the endemic Cyprus Warbler to a Species of European Conservation Concern by BirdLife International has renewed interest in its interaction with the Sardinian Warbler, a widespread Sylvia that was first confirmed as breeding in Cyprus in the 1990s and has since expanded in numbers and range. In areas where the Sardinian Warbler has become established, there has been a reduction in the abundance of the Cyprus Warbler, leading some researchers to suggest the recently arrived species is outcompeting its endemic congener. However, clear evidence of competition between the two species has not been found, and more recent research has suggested the closely related warbler species show preferences for subtly different scrub habitats, which might be influenced by the extent of grazing. We carried out line transect surveys during the breeding season at 48 scrub and open woodland sites across Cyprus in 2012, 2014 and 2016, recording Cyprus Warblers and Sardinian Warblers in order to estimate their densities. In addition, we recorded vegetation characteristics and estimated grazing pressure at these 48 sites. Our analysis showed that the Sardinian Warbler continues to increase in abundance over time and its higher abundances were associated with lower Cyprus Warbler abundances. Sardinian Warbler however was negatively associated with all but very low grazing pressure, whereas the Cyprus Warbler was more tolerant of grazing. Our findings suggest continued grazing of scrub sites is important for the maintenance of suitable habitat for the endemic warbler, which will help improve its conservation status.

The primary hazard for open-cup nesting birds is nest predation. Vegetation structure and coverage may affect nest predation through various mechanisms such as the ability of a predator to locate the nests, which may vary between breeding habitats. We examined the association between vegetation structure and nest predation in three different types of pine plantations using artificial nests of the Sardinian warbler, Sylvia melanocephala, which were located 30 cm above ground in low bushes. We also assessed the relationship between bird abundance and nest predation in each type of forest. Finally, we identified predators through their bite marks on 3D-printed plaster eggs that were placed in the nests. The percentage of nests predated in pine forests with high understory coverage was significantly higher than in pine forests with only sparse understory. We also found that the nest predation rate positively correlated with total bird abundance and the abundance of S. melanocephala. The species of nest predators varied between different forest types, although rodents and birds were the most and second-most abundant predators, respectively, in each forest type. These results show that patches with only sparse understory vegetation within the forests generate nesting sites for birds with less risk of predation. But because bird abundance in this habitat type was relatively low, the net effect of preserving such habitat on the number of hatched birds should be further studied.

Background In recent decades, a decrease of passerine densities was documented in Mediterranean shrublands. At the same time, a widespread encroachment of Aleppo pines (Pinus halepensis) to Mediterranean shrubland occurred. Such changes in vegetation structure may affect passerine predator assemblage and densities, and in turn impact passerine densities. Depredation during the nesting season is an important factor to influence passerine population size. Understanding the effects of changes in vegetation structure (pine encroachment) on passerine nesting success is the main objective of this study. We do so by assessing the effects of Aleppo pine encroachment on Sardinian warbler (Sylvia melanocephala) nest depredation in Mediterranean shrublands. We examined direct and indirect predation pressures through a gradients of pine density, using four methods: (1) placing dummy nests; (2) acoustic monitoring of mobbing events; (3) direct observations on nest predation using cameras; and (4) observation of Eurasian jay (Garrulus glandarius) behaviour as indirect evidence of predation risk. Results We found that Aleppo pine encroachment to Mediterranean shrublands increased nest predation by Eurasian jays. Nest predation was highest in mixed shrubland and pines. These areas are suitable for warblers but had high occurrence rate of Eurasian jays. Conclusions Encroaching pines directly increase activity of Eurasian jays in shrubland habitats, which reduced the nesting success of Sardinian warblers. These findings are supported by multiple methodologies, illustrating different predation pressures along a gradient of pine densities in natural shrublands. Management of Aleppo pine seedlings and removal of unwanted trees in natural shrubland might mitigate arrival and expansion of predators and decrease the predation pressure on passerine nests.

The name of the Sardinian Warbler Sylvia melanocephala is usually attributed to Gmelin (1789), but it dates from Piesch (1784). The correct name of the Sardinian Warbler is thus Sylvia melanocephala (Piesch, 1784). Comments are added on other bird species described by Piesch (1784) from Sardinia.

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.

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.

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.

Juvenile animals generally disperse from their birthplace to their future breeding territories. In fragmented landscapes, habitat-specialist species must disperse through the anthropogenic matrix where remnant habitats are embedded. Here, we test the hypothesis that dispersing juvenile frugivores leave a footprint in the form of seed deposition through the matrix of fragmented landscapes. We focused on the Sardinian warbler ( Sylvia melanocephala), a resident frugivorous passerine. We used data from field sampling of bird-dispersed seeds in the forest and matrix of a fragmented landscape, subsequent disperser identification through DNA-barcoding analysis, and data from a national bird-ringing programme. Seed dispersal by Sardinian warblers was confined to the forest most of the year, but warblers contributed a peak of seed-dispersal events in the matrix between July and October, mainly attributable to dispersing juveniles. Our study uniquely connects animal and plant dispersal, demonstrating that juveniles of habitat-specialist frugivores can provide mobile-link functions transiently, but in a seasonally predictable way., Spanish MINECO (CGL2017-82847-P) and Junta de Andalucía Excellence Projects (RNM–5731) awarded to P.J., Severo Ochoa Award for Centres of Excellence in R + D + I (SEV-2012-0262) and a postdoctoral fellowship from the Severo Ochoa Program awarded to J.P.G.-V. (SEV-2012-0262). While writing this paper, J.P.G.-V. was funded by a Spanish ‘Ramon y Cajal’ fellowship (RYC-2017-22095).

Invasive alien species, once introduced, may affect local biodiversity, both directly (e.g. by predation) and indirectly (e.g. by reducing the vegetation cover). Among those, rats (Rodentia, Muridae) are listed among the most invasive species, exerting strong impacts particularly when introduced to island ecosystems. Accordingly, black rats Rattus rattus have been eradicated from a number of islands in the Mediterranean basin to protect breeding seabirds. Where the larger Norway rat Rattus norvegicus is present, extent of damage may be even higher. In our work, we present the results of the first eradication program dealing with Norway rats in a small Mediterranean island (Isola delle Femmine, Sicily, Southern Italy). The eradication took place in 2007-2008 and, since then, no rat has been observed on the island, thus proving the success of the management action. Vegetal cover increased on the island after rat eradication. Furthermore, the Sardinian warbler and the blackbird started to breed on the island.

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 Warblers Sylvia melanocephala has raised concerns that it might be displacing the closely related and endemic Cyprus Warbler Sylvia 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.

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.

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.

J. L. Telleri´a (telleria@bio.ucm.es), A. Ramirez and J. Pe´rez-Tris, Dept of Zoology, Faculty of Biology, Univ. Complutense, ES-28040 Madrid,Spain.Knowledge of the ability of birds to track spatiotemporal variation in fruit distribution is essential for understandingplant-frugivore interactions. Arguably, although total fruit availability sets an upper limit to the number of birds that canexploit a habitat patch, not all species can equally distribute abundance according to variation in fruit resources. Toexplore this, we studied bird and fruit abundance in 1999 2005 in Mediterranean scrublands and woodlands of southernSpain. We analysed whether changes of fruit abundance in eight different sites during six winters could predict numericalchanges of a set of frugivorous passerines of the area (blackcap Sylvia atricapilla, Sardinian warbler S. melanocephala, robinErithacus rubecula, song thrush Turdus philomelos and blackbird T. merula). We also investigated if all frugivores togethertracked 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 despitestrong differences in the use of space (vagrant and territorial, respectively). This suggests plastic behaviour of territorialrobins, with individuals changing from strictly territorial to wandering, a flexibility that would favour between-sitenumerical arrangements according to food resources. Annual changes in bird numbers were independent of theavailability 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 offrugivorous birds, inconsistent with the idea that these species track together the changing availability of fruit resources.

Cluster N is a cluster of forebrain regions found in night-migratory songbirds that shows high activation of activity-dependent gene expression during night-time vision. We have suggested that Cluster N may function as a specialized night-vision area in night-migratory birds and that it may be involved in processing light-mediated magnetic compass information. Here, we investigated these ideas. We found a significant lateralized dominance of Cluster N activation in the right hemisphere of European robins (Erithacus rubecula). Activation predominantly originated from the contralateral (left) eye. Garden warblers (Sylvia borin) tested under different magnetic field conditions and under monochromatic red light did not show significant differences in Cluster N activation. In the fairly sedentary Sardinian warbler (Sylvia melanocephala), which belongs to the same phyolgenetic clade, Cluster N showed prominent activation levels, similar to that observed in garden warblers and European robins. Thus, it seems that Cluster N activation occurs at night in all species within predominantly migratory groups of birds, probably because such birds have the capability of switching between migratory and sedentary life styles. The activation studies suggest that although Cluster N is lateralized, as is the dependence on magnetic compass orientation, either Cluster N is not involved in magnetic processing or the magnetic modulations of the primary visual signal, forming the basis for the currently supported light-dependent magnetic compass mechanism, are relatively small such that activity-dependent gene expression changes are not sensitive enough to pick them up.

This paper presents and analyses autumn migration data on phenology and biometrics for 12 species of birds trapped at the Capri Bird Observatory, south-western Italy. The material has been collected over 15 years, mainly in two periods, 1959—1963 and 1994—2004. The passage of trans-Saharan migrants (like the Garden Warbler Sylvia borin) peaks in late September and these birds generally carry moderate to large fat stores, some probably large enough for the full journey to just south of the desert. The short-distance migrants that are mainly due to winter in the Mediterranean region (like the Robin Erithacus rubecula) arrive later, around the beginning of October, and carry less fuel deposits. Mainly resident birds (like the Sardinian Warbler Sylvia melanocephala) do not build up any substantial fat reserves and their phenologies do not indicate much migratory movement.

Undergrowth clearing is a widespread forest management technique used in many Mediterranean regions to reduce dense vegetation in order to prevent fire or to facilitate other forest exploitation activities. Here, we analyze the effects of undergrowth clearing on biodiversity by focusing on the variations in bird diversity in Holm oak forests in Catalonia (north-east Iberian Peninsula) under different forest management regimes: (1) coppice Holm oak forests where the undergrowth layer has been completely cleared, (2) partially cleared forests and (3) cleared and tree thinned forests and finally, (4) undisturbed forests. The synchronic comparison approach was used in conjunction with a before–after control impact (BACI) experiment in which the effects of undergrowth clearing were explicitly measured. Complete undergrowth clearing resulted in the almost complete disappearance of three Warbler species (Subalpine Warbler, Sardinian Warbler and Garden Warbler). Partial clearing also led to a marked reduction in the numbers of these three species, but the presence of Sardinian and Garden Warblers was maintained in the treated forests. Complete undergrowth clearing accompanied by tree thinning also led to a decrease in amount of undergrowth species and involved additional negative effects for species such as Wren, Robin, Blackbird and Blackcap. Only one species, the Nightjar, appeared to benefit from undergrowth clearing, while many others increased their numbers only when clearing was applied together with tree thinning: Turtle dove, Mistle thrush and Cirl bunting. Undergrowth clearing brought about a significant simplification in the vertical structure of the forest, which probably reduced foraging opportunities and breeding resources for most undergrowth species. These effects became more pronounced when tree thinning was applied together with undergrowth clearing. To reconcile forest management and bird diversity, undergrowth clearing should be applied selectively to ensure that a certain number of undergrowth patches, preferably corresponding to different shrub species, are not affected by management treatments.

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 m 2 and the mean home range was 22 321 m 2 . 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.

Migratory birds stay in a particular area for only short periods and must rapidly acquire appropriate information about stopover sites. In contrast, resident birds can update their knowledge whenever necessary. In a novel environment migrants are thus predicted to assess relevant information faster than nonmigrants. We tested this prediction with two closely related species, the migratory garden warbler, Sylvia borin, and the resident Sardinian warbler, S. melanocephala momus. Each bird was allowed to explore two unfamiliar boxes, one of which contained food. Garden warblers found food significantly faster than Sardinian warblers. Garden warblers may have a wide-area exploration strategy to assess a novel room and Sardinian warblers may have a local-area exploration strategy. We conclude that a wide-area exploration strategy might be required for migrants to assess environmental information as rapidly as possible.

Wing feather mite burdens on seven species of passerine birds (Carduelis carduelis ‐ goldfinch; C. chloris ‐ greenfinch; Serinus serinus ‐ serin; Sylvia atricapilla ‐ blackcap; Sylvia melanocephala ‐ Sardinian warbler; Turdus merula ‐ blackbird; Passer domesticus ‐ house sparrow) from Portugal were assessed by the subjective semi-quantitative scoring system of Behnke et al. (1995) in order to evaluate more fully the accuracy and reliability of the technique. Our analysis indicated that in all species, scores allocated to flight feathers showed a significant positive relationship with mite counts as assessed through microscopical examination of the same feathers. However, there were differences between species of birds. Of the species examined, goldfinches and greenfinches showed the weakest relationships between assigned mite scores and actual mite numbers indicating that the technique was less accurate when applied to these species compared with the remaining five. No evidence was found that anything more was to be gained from scoring both wings, rather than just one. Feather mites (Proctophyllodes spp., Trouessartia incisa) were also detected on tail feathers, but the assessment of these feathers presented additional problems and it was concluded that in the interests of minimizing handling time of birds, tail scores had little more to offer. We conclude that scoring all the flight feathers (including all primary, secondary, and tertiary feathers) on one entire wing, but alternating between left and right wings of birds within a species, represents an acceptable compromise between sufficiently detailed examination and minimization of bird handling time in the field.

The relationships between a series of environmental variables and the abundance of individual species of forest birds were examined in 58 large woodlands along a band crossing the Iberian Peninsula from north to south. The variables were mean annual rainfall, mean annual temperature, density of trees 30 cm in diameter, floristic composition (conifer or broadleaved trees) and geographical situation (distance from northern extreme of study band). The variable most highly correlated with bird density was mean annual rainfall (40% of the species had significant partial correlations with this parameter). The northern species (Chiffchaff, Goldcrest, Robin, Song Thrush, Bullfinch, etc.) generally correlated positively with mean annual rainfall, while the Mediterranean species (Sardinian Warbler, Bonelli's Warbler, Black-eared Wheatear, Rock Sparrow, Spotless Starling, Azurewinged Magpie, etc.) exhibited an inverse pattern. Mean annual temperature (36%) was also closely assoc...

The ability of many species of tiny, relatively short-lived birds to carry out migrations over thousands of kilometres has fascinated many researchers. This apparent ability is the more extraordinary because it is widely distributed amongst bird genera but migratory species often have close relatives that do not budge from home.New work by Claudia Mettke-Hofmann and Eberhard Gwinner at the Max Planck Research Centre for Ornithology in Andechs, Germany, (Proceedings of the National Academy of Sciences, published online) has looked at the cognitive abilities of two closely related species of warbler. The garden warbler migrates from Europe to sub-Saharan Africa each autumn and returns each spring whereas the Sardinian warbler is resident in the Mediterranean region. It might be an advantage, the researchers believe, if migratory species were able to remember places of food, shelter and other needs on their journeys. Previous neuroanatomic studies suggest that the size of the hippocampus, important for processing spatial information, in garden warblers that have undergone migration is larger than in pre-migration juvenile birds. No such difference was found in young and older Sardinian warblers.So the team captures young adults of both species and kept them in large aviaries. For the experiment they placed them in cages containing ‘rooms’ that contained one of two particular types of artificial vegetation with feeding bowls that did or did not contain food. After the tests the birds were returned to the aviaries. The researchers then re-exposed the birds to the different rooms over a period of days and months. They found a significant ability of the garden warblers to remember the rooms that contained food initially for up to 12 months in contrast to the Sardinian warbler, whose memory seemed to lapse after two weeks.Sedentary birds may be able constantly to update knowledge of their environment and do not need months-old memories to help them on their way. A migratory lifestyle, the researchers suggest, may have shaped the garden warbler's extended cognitive abilities.View Large Image | View Hi-Res Image | Download PowerPoint Slide

Global warming may affect the physiology, distributions, phenology and adaptations of plants and animals. In Israel, minimum summer temperatures increased by an average of 0.26 degrees C per decade during the second half of the 20th century. Bergmann's rule predicts that, in warm-blooded animals, races from warm regions are smaller than races from cold regions. Numerous studies have reported general correlations between body mass in fossil animals and independently established palaeoclimatic changes from various parts of the world in accordance with this rule. Using museum specimens, I tested the prediction that the body mass and tarsus length of five resident passerine species in Israel declined between 1950 and 1999. The body mass of four species (the graceful warbler Prinia gracilis, the house sparrow Passer domesticus, the yellow-vented bulbul Pycnonotus xanthopygos and the Sardinian warbler Sylvia melanocephala, but not of the crested lark Galerida cristata) declined significantly during this period. Tarsus length also declined significantly during this period for two species (the graceful warbler and the house sparrow). Body condition (body mass-to-tarsus length ratio) decreased in the Sardinian warbler, the yellow-vented bulbul and the crested lark. It is suggested that the above declines in body mass and tarsus length are due to global warming and also in accordance with Bergmann's rule. The above explanation does not exclude the possibility that other factors, such as a decrease in food availability, contributed to the decline in body mass. These declines may have serious implications for community structure and competition among bird species and may affect the survival of small passerines.

We tested the hypothesis that experience of migration from Europe to tropical Africa by Garden Warblers is associated with changes in the relative volume of the hippocampus, a brain region thought to be involved in processing spatial information, including that used in navigation. Relative hippocampal volume was larger in birds at least one year old that had migrated to and from Africa, than in naive birds approx. 3 months old. Further comparisons between groups of differing age and experience of migration suggested that both experience and age during the first year have an effect of relative hippocampal volume. The increase in relative hippocampal volume was mainly due to a decrease in the size of the telencephalon; however, the comparison between young, naive birds and older, experienced birds also suggests a possible increase in absolute hippocampal volume. The latter is associated with an increase in number and density of neurons, whilst the former is associated with an increase in density but no change in total number of neurons. In a non-migratory close relative of the garden warbler, the Sardinian warbler, older birds had a smaller telencephalon but there was no change in hippocampal volume, which supports the view that changes in the hippocampus may be associated with migratory experience, whilst changes in the telencephalon are not.

The occurrence of sectoral postjuvenile primary moult is confirmed for Sardinian Warbler, Greenfinch, Goldfinch and Red Crossbill and is newly described for White Wagtail, Siskin and Cirl Bunting. A characteristic feature for this type of moult seems to be that the primary coverts belonging to the renewed primaries are not at all or irregularly moulted. It is supposed that sectoral primary moult is provided in the moult programme of many passerines but is only manifested under special conditions. One of these is an early hatching date.