Mattia Brambilla

Song perception among incipient species as a mechanism for reproductive isolation.

Many functions in behavioural processes of small passerines are regulated via vocal messages. Song plays an important role in the development of reproductive barriers and thus playback experiments can often be used for investigating the potential for reproductive isolation through behavioural mechanisms. Moltoni’s warbler Sylvia (cantillans) moltonii is characterized by diagnostic vocalizations and a peculiar pattern of distribution, being parapatric and partly sympatric with the nominate Sylvia c. cantillans. With this work, we test whether these two closely related taxa react equally to their own song and to the song of the other taxon, shedding light on whether they perceive each other’s songs as coming from the same species. We carried out 184 playback experiments within the mainland range of the two forms. We judged the response of the bird on a scale of scores. Each taxon responded more strongly to playback when faced with the song of its own taxon. This held true when applied only to males or females. Additionally, birds tested for both songs showed a stronger response to the song of their own taxon. The distributional context (sympatry vs. allopatry) did not affect bird response. Results indicate that a certain degree of reproductive isolation between the two taxa (because of diverged mate recognition systems) already exists; consistently with genetic data and with the peculiar pattern of distribution; this suggests that the two taxa have reached species status.

Rainfall and landscape features affect productivity in an alpine population of Eagle Owl Bubo bubo

We investigated the effects of habitat structure and composition, rainfall and nest spacing on the productivity of an Eagle Owl Bubo bubo population in Piedmont, northern Italy, at 10 sites from 1996 to 2007. We modeled the effects of the above factors on the productivity of 85 breeding attempts through a mixed model procedure. The number of fledged young per pair was affected positively by wetland interspersion index (a potential estimate of prey abundance) and negatively by rainfall during chick-rearing and by cover of urbanized land in the nest surroundings. Our results demonstrated that productivity can be affected by a variety of factors of different kinds, which should be considered together in studies on habitat quality.ZusammenfassungWir haben die Effekte von Habitatstruktur und -zusammensetzung, Niederschlag und Nestabstand auf die Produktivität einer Population des Uhus Bubo bubo in Piedmont, Norditalien, an zehn Standorten zwischen 1996 und 2007 untersucht. Wir haben die Effekte der obengenannten Faktoren auf die Produktivität von 85 Brutversuchen mit Hilfe einer gemischten Modell-Prozedur modelliert. Die Anzahl ausgeflogener Jungvögel pro Paar wurde positiv vom Feuchtgebiets-Interspersion-Index (einem potenziellen Maß der Beuteabundanz) und negativ vom Niederschlag während der Kükenaufzucht sowie von der Bedeckung mit urbanisiertem Land in der Nestumgebung beeinflusst. Unsere Ergebnisse zeigten, dass die Produktivität von einer Vielfalt unterschiedlicher Faktoren beeinflusst werden kann, die in Studien über Habitatqualität berücksichtigt werden sollten.

The importance of key marginal habitat features for birds in farmland: an assessment of habitat preferences of Red-backed Shrikes Lanius collurio in the Italian Alps

Capsule Key marginal habitat features maintain their importance even when they occur at very low density. Aims To assess the importance for breeding birds of key habitat elements, such as isolated shrubs, hedgerows and untilled vegetation patches. Methods We investigated the habitat preferences of Red-backed Shrikes Lanius collurio in an agricultural environment where key habitat elements have been dramatically reduced. Based upon data from territorial maps, a fine-scale model of habitat preference was developed and the results of three different analytical approaches (binary logistic regression, multimodel inference and hierarchical partitioning) were compared. Results The occurrence of Red-backed Shrikes was positively influenced by the extent of non-grazed/mown grassland, isolated bushes and hedgerows, and negatively influenced by woodland cover. The model highlighted the importance of bushes/hedgerows despite their very scarce occurrence in the study areas (overall, average cover only 7.94%). Breeding densities were rather low, but mean densities were slightly higher in pasture zones in which bushes/hedgerows availability was higher than elsewhere. Conclusion These results confirm the crucial importance of these key marginal elements even in depauperated farmland landscapes. Maintaining and increasing their availability is a key management option for the encouragement of breeding Red-backed Shrikes, and potentially for other species which are also declining in these farmland habitats.

Intra-seasonal changes in local pattern of Corncrake Crex crex occurrence require adaptive conservation strategies in Alpine meadows

Summary As a double-brooded species inhabiting grassland habitats subject to mowing and located at different elevations, the Corncrake Crex crex in the Alps is potentially affected by changes in its breeding habitat within a season, thus leading to shifts in occurrence and habitat association, with potentially relevant consequences for conservation. We investigated Corncrake abundance in four sites in Trento province (N Italy); two sites were defined as ‘low elevation’ (mean elevation 975 m and 976 m a.s.l., respectively) and two as ‘high elevation’ (mean elevation 1,173 m and 1,177 m). The number of calling males showed a clear variation in relative abundance between early and late periods of the breeding season; in particular, at low elevation sites, abundance decreased from the early to late periods, while the opposite was recorded at high elevation sites. A mixed model suggested that the number of males decreased in the second half of the breeding season and at high elevations, and changed according to mid-season altitudinal shifts. Conservation strategies for this species should take into account the mid-season territory shift.

Modelling distribution and potential overlap between Boreal Owl Aegolius funereus and Black Woodpecker Dryocopus martius: implications for management and monitoring plans

Correlative species distribution models (SDMs) are increasingly widespread in the conservation literature. They can be used for a variety of purposes, including addressing practical conservation tasks on the basis of a spatially explicit assessment of environmental suitability for target taxa, which in turn allows for a transparent evaluation of needs and opportunities. Here we used the maximum entropy method (by means of the software MaxEnt) to model distribution of the rare Boreal Owl Aegolius funereus and the Black Woodpecker Dryocopus martius , which excavates the nest-holes used by the owl for breeding. We believe that monitoring surveys for Boreal Owl should consider areas suitable for both species as priority sites, whereas the provision of nest-boxes for the owl may be particularly desirable in habitat patches that are suitable for that species but not for the keystone species whose nest-holes represent the usual nest site for the owl. Finally, areas suitable for both species can represent priority areas for the conservation of forest birds in the Alps, as both species have been reported as umbrella and/or keystone species. Our example provides a possible framework to model management and monitoring opportunities in other species or species pairs, but such an approach can be used to infer the need for particular management options when both limiting factors and species distribution can be spatially modelled, and also to model the areas where different target species are more likely to overlap and interact. The use of distribution models as tools to address practical conservation tasks should also be encouraged in order to accomplish practical tasks according to sound knowledge and transparent methods.

Alpine bird distributions along elevation gradients: the consistency of climate and habitat effects across geographic regions

Many species have shown recent shifts in their distributions in response to climate change. Patterns in species occurrence or abundance along altitudinal gradients often serve as the basis for detecting such changes and assessing future sensitivity. Quantifying the distribution of species along altitudinal gradients acts as a fundamental basis for future studies on environmental change impacts, but in order for models of altitudinal distribution to have wide applicability, it is necessary to know the extent to which altitudinal trends in occurrence are consistent across geographically separated areas. This was assessed by fitting models of bird species occurrence across altitudinal gradients in relation to habitat and climate variables in two geographically separated alpine regions, Piedmont and Trentino. The ten species studied showed non-random altitudinal distributions which in most cases were consistent across regions in terms of pattern. Trends in relation to altitude and differences between regions could be explained mostly by habitat or a combination of habitat and climate variables. Variation partitioning showed that most variation explained by the models was attributable to habitat, or habitat and climate together, rather than climate alone or geographic region. The shape and position of the altitudinal distribution curve is important as it can be related to vulnerability where the available space is limited, i.e. where mountains are not of sufficient altitude for expansion. This study therefore suggests that incorporating habitat and climate variables should be sufficient to construct models with high transferability for many alpine species.

Identifying key conservation threats to Alpine birds through expert knowledge

Alpine biodiversity is subject to a range of increasing threats, but the scarcity of data for many taxa means that it is difficult to assess the level and likely future impact of a given threat. Expert opinion can be a useful tool to address knowledge gaps in the absence of adequate data. Experts with experience in Alpine ecology were approached to rank threat levels for 69 Alpine bird species over the next 50 years for the whole European Alps in relation to ten categories: land abandonment, climate change, renewable energy, fire, forestry practices, grazing practices, hunting, leisure, mining and urbanization. There was a high degree of concordance in ranking of perceived threats among experts for most threat categories. The major overall perceived threats to Alpine birds identified through expert knowledge were land abandonment, urbanization, leisure and forestry, although other perceived threats were ranked highly for particular species groups (renewable energy and hunting for raptors, hunting for gamebirds). For groups of species defined according to their breeding habitat, open habitat species and treeline species were perceived as the most threatened. A spatial risk assessment tool based on summed scores for the whole community showed threat levels were highest for bird communities of the northern and western Alps. Development of the approaches given in this paper, including addressing biases in the selection of experts and adopting a more detailed ranking procedure, could prove useful in the future in identifying future threats, and in carrying out risk assessments based on levels of threat to the whole bird community.

Assessing common birds' ecological requirements to address nature conservation in permanent crops: Lessons from Italian vineyards

Viticulture has contributed to shaping cultural landscapes in several regions across all continents. Recent farming intensification is causing landscape homogenization and biodiversity loss in several of those areas, but knowledge about the impacts on biodiversity in vineyards is still scarce. Simplified agro-ecosystems resulting from intensification host mainly generalist and common species, which still play a key role in the regulation of ecosystems and in the provision of ecosystem services. We assessed the abundance of 11 common bird species at 47 linear transects in a vineyard-dominated landscape in Trentino (NE Italy), in both spring and winter, and analysed abundance variation in relation to three independent groups of predictors: landscape, management, and topographic-climatic variables. In the majority of species (7), abundance was primarily or considerably affected by landscape attributes. However, an additional 5 species were largely affected by management practices, often with conspicuous seasonal differences. Overall, landscape and management heterogeneity positively affected the abundance of 6 species. Vineyard cover (and in particular the new spalliera trellising system) was negatively related with the abundance of 6 species, with the strongest impacts occurring in winter. On the contrary, the cover of marginal habitats had major positive effects over 8 species. Hedgerows, tree rows, and dry stone walls, as well as traditional pergola vineyards and landscape and management heterogeneity should be conserved or restored in viticultural landscapes to promote the abundance of common bird species. This strategy would ensure the maintenance of the ecosystem services they provide, while promoting the general sustainability of the agroecosystem.

Defining favourable reference values for bird populations in Italy: setting long-term conservation targets for priority species

Summary Setting favourable reference values (FRV) for conservation targets may help in assessing the conservation status of species and habitats. FRVs should be expressed through population size or demographic parameters that are likely to ensure the long-term persistence of a species across its range. We developed a conceptual framework for defining FRVs for Italian birds included in Annex I of the European Union’s Wild Birds Directive 79/409/CEE. The approach was based on demographic trends, current population size and the minimum viable population concept. We subdivided bird species according to abundance at the national scale, spatial distribution in discrete isolated populations and/or biogeographic categories. FRVs based on population viability analysis (PVA) were provided for populations of less than 2,500 pairs. For species with more than 2,500 pairs and a wide, more or less continuous range, the FRV was expressed in terms of breeding density at different spatial scales for non-colonial species. Out of the 88 species considered, we were able to formulate FRVs based on PVA for 47 populations belonging to 21 species, and breeding density for 15 further species; lack of adequate data prevented us from defining FRVs for the remaining species. Further work should focus on the translation of FRV density values into population size and on the definition of reference values for range and habitat.

The park-view effect: Residential development is higher at the boundaries of protected areas.

Land-use changes in the surrounding of protected areas might compromise their conservation efficacy, and thus the potential attractive effect that protected areas may exert on urban development is particularly concerning. We investigated whether the proximity to protected areas in a region (Lombardy, Italy) with a high density of urban areas and parks may increase the likelihood of residential development. The main change around protected areas was the loss of open areas (mostly due to development processes at the expense of arable land), which was higher in proximity of parks. Changes in residential discontinuous development were significantly and negatively related to proximity to parks, whereas changes in productive developments were unrelated to park proximity. The higher likelihood of residential development in proximity to parks is likely due to the attraction exerted by parks. The severe loss of open areas and increase of residential development around parks heavily impacted on habitat availability for a declining bird species (Alauda arvensis). Conservation policies considering also what happens around protected areas are urgently needed.