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Current distribution and population size of the Barred Warbler Sylvia nisoria in South Tyrol (Italy)


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The Barred Warbler Sylvia nisoria is a critically endangered breeding species in Italy, given the severe decline suffered in the last decades and the reduced population size. South Tyrol, an inner Alpine region, is the northernmost Italian breeding area of this warbler, but we lacked recent information about the distribution and population size. In this study, based on surveys carried out in the year 2019 and other recent observations, we assessed a very restricted current distribution of this warbler, and we estimated a population size of 10-30 pairs. We also observed a singing male at unusually high elevation. A comparison of our results to historical data suggests a strong reduction in distribution compared to the 1980s/1990s. The changes in agricultural practices of the last decades might have contributed to determine such decline. Appropriate conservation measures are urgently needed to try to avoid the local extinction of the species.
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1 Museum of Nature South Tyrol - Via Bottai 1, 39100 Bolzano, Italy
2 Eurac Research, Institute for Alpine Environment, Drususallee 1, 39100 Bozen/Bolzano, Italy
3 Ufficio Valutazione dell’impatto ambientale, Provincia Autonoma di Bolzano, Via Amba Alagi 35, 39100 Bolzano, Italy.
4 Via Rovigo 30/5, 39100 Bolzano, Italy
5 Arbeitsgemeinschaft für Vogelkunde und Vogelschutz Südtirol, Maria-Hilf-Straße 5/3, 39011 Lana (BZ), Italy
6 Ufficio Parchi Naturali, Provincia Autonoma di Bolzano, Via Renon 4, 39100 Bolzano, Italy
* Corresponding author:
Francesco ceresa1,*, Matteo anderle2, leo Hilpold3, roberto Maistri4,
oskar niederFriniger5, renato sascor6, petra kranebitter1
Current distribution and population size of the Barred Warbler
Sylvia nisoria in South Tyrol (Italy) Avocetta 44: 29-31 (2020)
The Barred Warbler Sylvia nisoria is a migratory passer-
ine bird breeding from Central Europe through Mongolia
and Western China. In Italy, this warbler breeds at its west-
ern range limit, mostly at the Alps foothills and valleys
in the North of the country (Brichetti & Grattini 2010).
The Italian breeding population suffered a severe decline
in the last decades, and the population size has been re-
cently estimated in less than 100 pairs (Brichetti & Grattini
2010). For these reasons, the species is currently classied
as ‘Critically Endangered’ at the national level (Peronace
et al. 2012). In such a critical situation, detailed informa-
tion about the distribution and abundance of this species
is urgently needed for conservation. In this study, we pre-
sent recent and detailed information about the Barred War-
bler in South Tyrol, the northernmost Italian breeding ar-
ea. This is an inner Alpine region, where the species was
known to breed mainly on the dry and bushy slopes of the
Venosta valley, and more sparsely in other areas (Nieder-
frininger et al. 1996). However, recent information is very
scarce and exclusively based on occasional observations
(Brichetti & Grattini 2010, AVK 2018), therefore the cur-
rent local distribution and population size of the species
are virtually unknown. In the neighbouring Trento prov-
ince, recent surveys allowed detecting 13-15 breeding
pairs in the Fiemme valley and 5-9 in the Non valley, with
more scattered observations in other areas, and the species
is probably declining (Assandri G. & Pedrini P./MUSE,
unpub. data).
During the year 2019, we surveyed Barred Warblers
(as well as other farmland bird species) across 20 study ar-
eas in South Tyrol, overall covering approximately 1,600
ha (mean study area extension = 80.6 ha, range = 23.5 –
124.8 ha). These areas were located between 700 and 1950
m, and all included bushy areas and/or hedgerows, within
a matrix of open habitats like meadows, pastures or elds.
Each study area was surveyed twice, the rst between 25
May and 19 June and the second between 20 June and 15
July, with at least 10 days elapsing between visits at the
same area. We expected low Barred Warbler breeding den-
sity, hence we used a standardized playback procedure to
Abstract – The Barred Warbler Sylvia nisoria is a critically endangered breeding species in Italy, given the severe decline suffered in the
last decades and the reduced population size. South Tyrol, an inner Alpine region, is the northernmost Italian breeding area of this war-
bler, but we lacked recent information about the distribution and population size. In this study, based on surveys carried out in the year
2019 and other recent observations, we assessed a very restricted current distribution of this warbler, and we estimated a population size
of 10-30 pairs. We also observed a singing male at unusually high elevation. A comparison of our results to historical data suggests a
strong reduction in distribution compared to the 1980s/1990s. The changes in agricultural practices of the last decades might have contrib-
uted to determine such decline. Appropriate conservation measures are urgently needed to try to avoid the local extinction of the species.
Key-words: Alps; farmland birds; montane grasslands; threatened Italian birds.
Short communications
improve detectability (1 minute of stimulation followed
by 1 minute of listening). This procedure was carried out
across the entire study area, in correspondence of potential-
ly suitable nesting habitat (i.e., occurrence of bushes/low
trees, Brichetti & Fracasso 2010), and at a minimum dis-
tance of 200 m between individual playback points. Given
the territory size of the species (0.11 – 2.59 ha, Aymí et al.
2020), such a distance should effectively prevent double
counts, and at the same time, it should provide an adequate
density of playback points. To complement our survey da-
ta, we also considered the very few occasional observa-
tions of Barred Warblers available from the database of
the Museum of Nature South Tyrol (hereafter MNST) for
the last ve years (2015-2019), as well as one observation
from the Biodiversity Monitoring South Tyrol (Eurac Re-
search) in the year 2019. These additional records are re-
ferred to singing males observed in June.
We observed Barred Warblers at 6 out of 20 study ar-
eas, and we mainly detected singing males (overall, 8 dur-
ing the rst survey period and 6 during the second one).
In the study areas where we detected the species, densities
were very low and ranged between 0.1 and 0.4 males/10
ha. In most cases, birds were observed during both survey
sessions and approximately at the same locations, indicat-
ing that they were more likely breeding individuals rather
than late migrants or prospecting males without a territory/
mate. One singing male was observed on 14 June at 1840
m, an unusually high elevation for this species (see Bri-
chetti & Fracasso 2010). This observation occurred near
the main Alpine watershed, on southeast-facing pastures
with scattered bushes and trees (mainly young conifers) in
the municipality of Moso in Passiria. We did not nd any
records at similar or higher elevations for Italy and for the
Alps in the literature, while an observation at 1900 m is
reported in the MNST database (20 June 2000, 3 singing
males; O. Niederfriniger).
Based on our surveys and other aforementioned data,
the Barred Warbler still occurs during the breeding season
in restricted areas of South Tyrol (Fig. 1), i.e., several areas
of the Venosta valley and few scattered sites in the Isarco,
Pusteria and Passiria valleys, with a minimum population
size of 10 breeding pairs. We could not check some other
potentially suitable sites, and especially the high Venosta
valley could host more breeding pairs than we detected.
Even so, in our opinion a population size larger than 30
pairs is highly unlikely because we sampled a large part
of the few areas in South Tyrol that still maintain adequate
habitat characteristics for the species, detecting very low
Comparing our results to the past Barred Warbler dis-
tribution and abundance in South Tyrol is problematic, as
the data available for the past decades almost only consist
in occasional observations, or in episodic surveys of re-
stricted areas (Brichetti & Grattini 2010, AVK 2018). Even
so, a temporally explicit map for the period 1980-2010
(from MNST database) and the current estimated distribu-
tion (Fig. 1) clearly suggest a strong range restriction. In
addition, previously published density data and the number
of individuals recorded per site during some occasional ob-
servations strongly suggest higher abundance than indicat-
ed by our surveys, at least until the 1990s (e.g., 12-15 sing-
ing males/30 ha, Berg-Schlosser 1981; 5 pairs along 0.5
km of hedgerows, Niederfriniger et al. 1996). The assumed
decrease is consistent with the strong decline observed at
a national level. The causes of this decline in Italy are not
completely clear, but could include agriculture intensica-
Figure 1. Past (a) and current (b) distribution of the Barred Warbler in South Tyrol, Italy. The past distribution (1980-2010) has been as-
sessed by conservatively selecting occasional observations, trying to avoid including migratory individuals (we mostly used records from
June and July). The current distribution has been assessed by targeted surveys (year 2019) and few recent occasional observations. Black
squares: 2x2 km occurrence cells; circles: survey areas were the species was not detected.
50 km0
1980 - 1986
1987 - 1993
1994 - 2001
2002 - 2010
Barred Warbler in South Tyrol, Italy
tion (i.e., removal of hedgerows and bushes, pesticide use)
and land abandonment, as well as environmental and cli-
matic changes in the wintering areas (Brichetti & Grattini
2010, Nardelli et al. 2015). Comparably in South Tyrol, the
Barred Warbler population decline is probably related to
a combination of agricultural intensication and land-use
changes, as the traditional heterogeneous and low-inten-
sity farmed landscape has been widely replaced by inten-
sively managed apple orchards, vineyards and hay mead-
ows, while less productive and accessible grasslands were
partly abandoned (Tasser et al. 2007). As an example, the
dry grasslands of Venosta valley, which represented a wide
and continuous suitable area for the Barred Warbler, were
largely abandoned (more than 70%) and replaced by forests
starting from the 1960s (Tasser et al. 2007). Despite its re-
duction, the Barred Warbler population of South Tyrol has
national relevance, given the low number of pairs breeding
in Italy. Therefore, we encourage the local authorities, in
collaboration with the relevant stakeholders, to implement
the appropriate conservation measures to avoid the local
extinction of this species, such as promoting low-intensi-
ty grazing and farming practices and maintaining and cor-
rectly managing the remaining hedgerows and bushy ar-
eas (see, e.g., Brambilla & Pedrini 2014). These measures
would benet also several other bird species with similar
ecological requirements (e.g., Ceresa et al. 2012, Brambil-
la & Pedrini 2014, Assandri et al. 2019 a,b). We strongly
warn against further land-use changes from grasslands to
orchards and berries cultivations, as well as against further
removals of marginal elements such as bushes, hedgerows
and patches of untilled vegetation.
Acknowledgements – The present study has been nanced by the
Research fund of the Museums of South Tyrol, within the project
‘The distribution and conservation status of birds in South Tyrol’,
CUP H53C17000260005. This study was also supported by the
‘Ufcio Valutazione dell’impatto ambientale – Agenzia provinciale
per l’ambiente (Provincia Autonoma di Bolzano)’. We are grate-
ful to Michele Caldonazzi, Sandro Zanghellini, Alessandro Marsilli
and Alberto Bertocchi, who carried out part of the eldwork.
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Received: 02.01.2020
First response: 23.01.2020
Final acceptance: 01.03.2020
Associate editor: Giacomo Assandri
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The sun-exposed open areas of the Brescia hills overlooking the Po Valley (Avanalpica region) were created by man starting from the 11th century. After the Second World War, following agro-pastoral abandonment, these areas have significantly shrunk. The evolution underway is towards the deciduous forest although in some areas the strong presence of quarries is blocking the vegetational succession or delaying it. Local birds are now largely associated with woodland coenosis and more scarcely with open areas, shrublands and wood edges. Seven open areas species have become extinct over the past 30 years: Woodchat Shrike, Barred Warbler, Rufous-tailed Rock-Thrush, Eastern Black-eared Wheatear, Tawny Pipit, Corn Bunting and Ortolan Bunting. Others, like Red-backed Shrike, Common Whitethroat, Cirl Bunting and Wood Lark have declined. Only the generalist Sardinian Warbler and Blue Rock-Thrush, typical of rocky areas with grassy spaces, are still relatively widespread although slightly decreasing. The Cirl Bunting, a species linked to traditional vineyards and orchards, is not expanding in the new intensively cultivated lands. The Eastern Subalpine Warbler is on the rise even though, due to its very low presence and lack of specific surveys, it may not have been detected in the past. The factors determining the presence of these species, i.e. traditional crops, flat open areas, soils with low grass and often with outcropping and/or rocky substrate, are in sharp decline. We can state that this bird community is negatively influenced by the percentage of tree cover and positively influenced by the presence of quarries which, however, represent an ephemeral and strongly impacting environment. In the absence of fires and/or natural disasters as well as human interventions, which are not likely to occur due to their poor economic sustainability, the prognosis for these birds is to be considered poor and a reduction in both bird and general biodiversity is to be expected.
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Semi‐natural grasslands are among the richest European ecosystems in terms of biodiversity. However, they have been severely affected by farming intensification and land abandonment, which have been both exacerbated by the European Union's Common Agricultural Policy ( CAP ). The most recent CAP included a “greening” measure dedicated to grassland conservation, presumed to be beneficial to biodiversity; however, scientific evidence about its effectiveness is still scarce. In the Alps, hay meadows have undergone dramatic management changes in recent decades. We used a comprehensive community ecology approach to highlight how the multi‐scale and interacting effects of such changes impact birds, with the aim of providing knowledge to support improvements to the CAP . Birds were surveyed at 63 landscape units in northeast Italy, equally subdivided into areas dominated by (a) extensive hay meadows, (b) intensive hay meadows, and (c) areas formerly dominated by meadows but partially converted into other agricultural land use. This environmental gradient mirrors in space the temporal gradient of the agricultural changes that have recently occurred in the Alps. Community composition, species richness, and the number of meadow‐specialist species were analysed according to environmental predictors (i.e. landscape, meadow management, and topography), and to spatial factors. We aimed to disentangle the exclusive and joint fraction of variation explained by each of them. Meadow conversion, allowed by the CAP in force, created a shift in community composition towards assemblages dominated by generalist species at the expense of meadow specialists. The cover of intensive meadows was negatively correlated with species richness, whereas the number of meadow specialists was negatively correlated with the cover of early‐mown (i.e. within the third week of June) meadows. Mowing date was, in turn, related to elevation, with meadows at higher elevations mown later in the season, and to meadow intensification (the use of external inputs, in particular liquid manure, leads to earlier and more frequent cuts per year). Policy implications . Our study confirms the concerns about effectiveness of the European Union's Common Agricultural Policy greening grassland measure in conserving biodiversity in those ecosystems. We suggest rethinking the Common Agricultural Policy environmental prescriptions to account for the importance of meadow management in determining bird diversity patterns in Alpine hay meadows. Finally, we highlight market‐based conservation strategies as complementary approaches for preserving grassland biodiversity.
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Distribution abundance and evolution of the populations of Barred Warbler Sylvia nisoria nesting in Italy in the years 1970-2009. In the past decade the breeding range of Barred Warbler Sylvia nisoria in Italy has been very fragmented, including some hills and mountains in the Norhern regions (Lombardy, Venetia and Trentino-Alto Adige), and isolated areas in Western Piedmont. In the previous two decades the range comprised also wide areas in the Po Valley, reaching as far South as Romagna, with unconfirmed breeding records in the hills of Piedmont and in the plains of Venetia and Friuli. The Italian population has progressively decreased in the past two decades, and more conspicuously since the late ‘90s, going from 1000-2000 pairs estimated in the ‘80s, down to fewer than 100 pairs, as estimated in the period 2000-’09, with a 90% decrease. The loss of habitat and the use of chemicals in agriculture appear to be the main limiting factors, although climatic and environmental issues in the African wintering areas may have a significant role.
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The 2011 Red List of Italian breeding birds. The purpose of Red Lists is to assess the short-term risk of extinction in a given taxon, and they are drafted according to guidelines produced by the IUCN. The guidelines make it possible to draft both global and regional or sub-global lists, keeping in mind the relationship between the populations being assessed and neighbouring populations. The present work results from the application of this methodology. It aims to update the previous Red List of breeding birds in Italy and to bridge the methodological and temporal gap that for many years has prevented Italy from availing itself of an important tool for bird conservation and planning. We considered a totol of 270 specie: 51.1% were classified as Least Concern (LC),9.6% as Near-Threatened (NT), while 27.3% are in one of the three threatened categories: 2.2% Critically Endangered (CR), 8.1% Endangered (EN) and 17% Vulnerable (VU). The data for 3.3% of the species assessed was not sufficient to assign them to a threat category, and they were thus classified as Data Deficient (DD). Finally, three species that were classified as Regionally Extinct (RE) in the previous Red List of Breeding Birds in Italy were confirmed as such. A total of six species were classified as Critically Endangered (CR), of which four are raptors (Lammergeier, Egyptian Vulture, Griffon Vulture, Bonelli’s Eagle) and two are passerines (Sedge Warbler, Barred Warbler). At the level of orders, Anseriformes is the taxon with the highest percentage of threatened or near-threatened species (55.6%), followed by Gruiformes (54.6%) and Accipitriformes (53.8%). Unfortunately it was not possible to effectively compare the current Red List with the previous one, as there are significant methodological differences between them. The current work follows IUCN guidelines for regional red lists, which had not yet been drafted when the previous Red List of Breeding Birds in Italy was prepared. Nevertheless, it clearly emerges that the number of threatened passerines increased from 21.7% to 31%. This finding may in part depend on improved knowledge about population trends in widespread species, or it may truly reflect the worsening of the conservation status of many passerine species over the last decade. Current knowledge on breeding birds in Italy has made it possible to classify the vast majority of the species that were assessed, in spite that information is still limited for many species.
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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 high-lighted 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.
In recent decades, upland hay-meadows underwent large transformations due to the modernization of livestock husbandry system. Such changes impacted on biodiversity, but their consequences on the upper levels of the food web (e.g. birds) are largely unknown. Grassland specialists could respond differently to landscape structure and management practices, and such potentially different responses should be integrated into conservation and management strategies. To elucidate the effect of meadow characteristics on avian grassland specialists, we considered three declining bird species regularly found in European meadowlands. We compared their mean densities at 63 landscape plots in the Italian Alps with that reported from other studies and analysed their environmental preferences in relation to landscape (composition and structural elements), management (meadow fertilization and mowing calendar), topographic (slope and elevation), and spatial predictors. Shedding light on their ecological requirements, we identify possible causes of long-term decline as well as conservation strategies for grassland specialists. Mean territory density of ground-nesting species (whinchat, 0.75 territory/10 ha, and tree pipit, 0.42) resulted lower than most other estimates obtained in the Alps; conversely, the density of the shrub-nesting red-backed shrike (1.97) was comparable to that of many other Alpine areas. Meadow conversion into other crops and the modern livestock husbandry (i.e. first mowing performed before the end of the third week of June, made possible by meadow overfertilization) have likely contributed to regional depletion of whinchat and tree pipit populations, especially below 900-1000 m asl. Heterogeneous landscapes dominated by grassland, with large extents of unimproved meadows, close to meadows interspersed with isolated trees, hedgerows and ecotones, could accommodate the ecological preferences of multiple grassland specialists. As such landscapes have become increasingly rarer, the remaining ones must be preserved via integrated plans for sustainable mountain development.
In modern agriculture, only the cultivation of highly productive and easily accessible slopes remains profitable. As a consequence, inaccessible and steep areas are being increasingly abandoned. In this paper, the mechanisms of natural reforestation of abandoned areas are examined on three levels as a prelude to determine natural reforestation rates. The study sites selected on the municipality level (1:25,000) are situated in four agrarian structure regions in the Alps: ‘Innsbruck Land’, ‘Südtiroler Berggebiet’, ‘Unterland/Überetsch’ and ‘Carnia’. For more detailed data, studies on the level of a case study area (1:5000) and plot level (permanent plots) were carried out in the municipality of St. Leonhard in Passeier (‘Südtiroler Berggebiet’, South Tyrol, Italy). Data were collected through analysis of historic photographic material as well as by detailed field work. Significant explanatory variables of natural reforestation were determined using count data models. A zero-inflated negative binomial model was employed as analysing tool. Key findings are: (1) in the past 150 years, areas were abandoned in all analysed agrarian structure regions. Between 8 and 67% of the formerly used areas are now abandoned, and in the majority of these abandoned areas, forest re-growth is observed. (2) Seed dispersal and agricultural use are the most important variables influencing natural reforestation. The nearer an area is situated to old trees, the higher the reforestation rate. Grazing and mowing reduce reforestation. (3) The less intensively the land was formerly used and the longer the area was abandoned, the higher the tree density is. Whereby, the average sapling density is significantly higher in mixture communities than in grasslands or dwarf shrub communities. However, snow gliding and avalanches cause damage to trees that retard or hinder tree growth.
Die Vogelwelt der Steppenhänge oberhalb Vezzan und
  • G Berg-Schlosser
Berg-Schlosser G., 1981. Die Vogelwelt der Steppenhänge oberhalb Vezzan und Tiss im Vinschgau/Südtirol/Italien. Monticola 49: 149-163.
  • P Brichetti
  • G Fracasso
Brichetti P. & Fracasso G., 2010. Ornitologia italiana. Vol. 6 -Sylviidae-Paradoxornithidae. Oasi Alberto Perdisa Editore, Bologna.