Acrocephalus 28 (133): 61-68, 2007 Habitat, vegetation and land management of Corncrake Crex crex breeding sites in Carnia (Friuli-Venezia Giulia, NE Italy) Habitat, vegetacija in kmetijska raba na gnezdi{~ih kosca Crex crex v Karnijskih Alpah (Furlanija Julijska krajina, SV Italija) Gianluca Rassati1 & Paolo Rodaro2 1 Via Udine 9, I-33028 Tolmezzo (UD), Italy, e-mail: itassar@tiscali.it 2 Via Huber 1, I-39055 Laives (BZ), Italy During the study, the scope of which was to provide some information on breeding habitat choice of Corncrakes Crex crex at one of the most important Italian sites for the species, 21 sites were chosen ranging in altitude from 201-1400 m a.s.l. where the species was present annually from 1991 to 2000. The study was carried out in Carnia (NE Italy). The sites were compared with the same number where the species was not recorded in the same period. In the meadows, some physical factors were measured (slope, aspect, pH, carbonate content, humidity and soil structure), management (number of cuts, timing of frst cut, type, frequency and level of fertiliser application, reseeding, grazing animal species present, cutting equipment used, the use of herbicides or pesticides) as well as the type of meadow and complexity of vegetational structure. From the results it was possible to conclude that in Carnia Corncrakes prefer meadows with slight slopes and damp soils with late cuts where spring grazing does not take place. The type of meadow most favoured is that dominated by False Oat-grass Arrhenatherum elatius because of its structure (high grass with plenty of space at ground level) that guarantees a great deal of cover and is favourite by good local fertility and a limited number of annual cuts. Key words: Corncrake, Crex crex, habitat choice, vegetation, management, site characteristics, Carnia, Friuli-Venezia Giulia, Italy Klju~ne besede: kosec, Crex crex, izbor habitata, vegetacija, kmetijska raba, zna~ilnosti zemlji{~a, Karnijske Alpe, Furlanija Julijska krajina, Italija 1. Introduction The sites at which a species establishes itself during the breeding season are very important for a species’ survival. So it is important to study these for the most threatened species. The Corncrake Crex crex is listed as vulnerable in the IUCN Red List of Threatened Animals (Baillie & Goombridge 2000), and considered as “depleted” in Europe (BirdLife International 2004), whilst in Italy the species is considered “endangered” (Calvario et al. 1999). The aim of the study is to provide information on breeding habitat choice in one of the most important areas in Italy for the species. A partial summary of data has already been published (Rassati & Rodaro 2003). 2. Methods 2.1. Study area The study area was in Carnia, in the central-western part of northern Friuli-Venezia Giulia (Figure 1), dominated by mountains (altitude range: 195-2780 m a.s.l.) and characterised by a broad valley (Val Tagliamento) running west-east occupying the 61 G. Rassati & P. Rodaro: Habitat, vegetation and land management of Corncrake Crex crex breeding sites in Carnia (Friuli-Venezia Giulia, NE Italy) southern part and joining with secondary valleys (Val Lumiei, Val Degano and Val But), which run largely north-south and occupy the central and northern parts. As in other mountain areas, there are a wide variety of geological substrates, soils, aspects and slopes. The climate overall can be considered temperate but with high rainfall (1400-2400 mm/year). The grassland plant communities, once widely distributed, have been greatly reduced following the depopulation of the mountain areas and the subsequent abandonment of agricultural activities, particularly grazing and haymaking that has allowed scrub and secondary woodland, particularly of Hazel Corylus avellana, Maple Acer sp., Ash Fraxinus sp. and Pines Pinus sp. at low and medium altitudes and Spruce Picea abies and Larch Larix decidua to grow on medium and higher ground. At present, grassland communities are represented by hay-meadows that are widespread in the valley bottoms, in fat areas and near settlements and open grazing lands at higher altitude where summer grazing is still practiced or has only recently been abandoned. Figure 1: Study area of the Corncrake Crex crex habitat choice in NE Italy Slika 1: Obmo~je raziskave izbora habitata kosca Crex crex v SV Italiji 2.2. Data collection In an initial phase, based on data collected between 1991 and 2000 by one of the authors (G. Rassati), between 201 metres and 1100 m a.s.l. two areas where the species was present annually and two areas where the species was never recorded were identifed. Single 62 areas with birds present every year between 1991 and 2000 and areas with birds never recorded were identifed for the altitudinal range of 1101 through to 1400 m a.s.l. These subdivisions were made following the percentage presence of Corncrakes at different altitudes in Carnia (Rassati & Tout 2002). The areas not holding Corncrakes were identifed from those adjacent to areas holding calling birds (Rassati & Tout 2002) and apparently similar to the human eye. In this way the 42 (21+21) sites examined were believed to be a representative cross sample of the grassland in the study area. A long time period (10 years) was chosen to identify and distinguish between the 'best' (and 'worst') areas where the Corncrake was present (or absent) since the species can be present at a site for a year or two with many individuals but rare or even absent before and after this (Rassati & Tout 2002). The average number (calculated from 10 years: 1991-2000) of Corncrakes for the sites with annual presence is 1.82, while the average number (calculated from 10 years: 1991-2000) of Corncrakes for the whole Carnia is 85. Following this, standardised data was entered on printed forms covering physical aspects (altitude, slope, aspect, pH, carbonate content, soil classifcation, soil moisture) and management (number of cuts, timing of the frst cut, type of fertiliser application, frequency of fertiliser application, level of fertiliser applied, reseeding, grazing animal used, grazing pressure if any, use of herbicides and pesticides in the felds). The timing of the frst cut was classifed as šnormal’, šslightly late’ or šlate’, refecting the quali-quantitative characteristics of the meadow and its altitude. To each meadow, a probable level of fertilizer application was assigned according to the foristic and physical characteristics observed. Samples of soil were collected so that their characteristics could be examined. The reaction of the frst 10 cm of soil using the colormetric method was measured, as well as carbonate content (Sanesi 1977), the structure following the indications of McRae (1991) and soil humidity, estimated by touch was assessed several times during the course of the season. Any use of herbicides and pesticides in the felds was also assessed, as well as the frequency of fertiliser application by interviewing the farmers. Shortly before frst cut, an overview of the vegetation was made by censusing the most representative species on the basis of their presence and their abundance. To establish the sites to be surveyed, the points where calling males were censused during the study period (1991-2000) (Rassati & Tout 2002, Rassati unpubl.), were georeferenced. In this way, clusters of singing males were identifed and the sampling carried Acrocephalus 28 (133): él-68, 2OO7 Table 1: Site characteristics of the two groups of sites in Carnia studied (21 each); Corncrakes Crex crex were either present or absent. Averages of slope, soil pH and carbonate content are given with one standard deviation. Tabela 1: Zna~ilnosti lokacije za dva tipa lokacij v Karnijskih Alpah, s kosci Crex crex in brez (21 enih in drugih). Naklon, vsebnost karbonatov in pH prsti so podani z eno standardno deviacijo. Group / Skupina Presence of Corncrakes / Prisotnost koscev Average slope / Povpre~en naklon (%) minimum slope / minimalni naklon (%) maximum slope / maksimalni naklon (%) Main aspect / Prevladujo~a ekspozicija Average pH / Povpre~ni pH min. max. Average carbonate content / Povpre~na vsebnost karbonatov min. max. Main soil classification / Glavni tip prsti L-S S-L L-C S L Main soil moisture classification / Glavni tip vla`nosti prsti RD D DW Remarks / Opombe: Carbonate content / Vsenost karbonatov: 0 = non-calcareous / ni (< 0.5-1%) 1 = very low carbonate content / zelo nizka (0.5-1%) 2 = low carbonate content / nizka (1-5%) 3 = calcareous / karbonatna (5-10%) 4 = very calcareous / zelo karbonatna (> 10%) Soil classification / Tip prsti: 5 = sand / pesek L = loam / ilovica C = clay / glina Soil moisture / vlažnost prsti: RD = rather dry / prete`no suho D = damp / vla`no DW = damp with waterlogging / vla`no, prepojeno z vodo I 2 present / p risotni absent / odsotni 6.28 ± 6.7 16.28 ± 23.7 0 0 20 100 SW / SE SW / SE 5.96 ± 0.63 5.98 ± 0.57 4.5 5 6.5 6.5 2.24 ± 1.70 1.99 ± 1.84 0 0 4 4 L-S L-S n 10 7 7 2 2 1 0 0 2 D RD-D 2 8 16 11 3 2 out from the central point of the cluster with the most contacts and identifying a suffcient homogenous square of c. 100 m2 (10 x 10 m) considered suffciently large to establish the nature of the plant communities present (Westhoff & Van der Maarel 1978). In the sites where the Corncrake was not found the survey was made from the central point of the site under examination. On the basis of the data collected, the plant communities were assigned to those proposed in the most up-to-date studies (Roumet et al. 1999, Scotton et al. 2000, Scotton & Rodaro 2001). The vegetational structure’s complexity - that is to say in terms of the stratifcation of the above ground plant biomass and the effect of this on visibility was estimated by eye and classifed as “low”, “medium” or “high”. “Low” was deemed to be the height of the vegetation reduced almost to ground level with ground cover almost complete and a high level of visibility of the ground from above (the animal being easily visible in the meadow). “High” was represented by tall vegetation with limited cover present at ground level and little visibility of the ground from above (the animal being hidden in the meadow). The value “medium” indicates a state of affairs intermediate between the two indicated above. 63 G. Rassati & P. Rodaro: Habitat, vegetation and land management of Corncrake Crex crex breeding sites in Carnia (Friuli-Venezia Giulia, NE Italy) 3. Results 3.1. Site characteristics The results of the site characteristics assessment are presented in Table 1. The sites at which the species was found were fat (9 sites out of 21) or gently sloping, ranging from 0 to 20% with an average slope of 6.28% and main aspect lying between south-west and southeast. Where, on the other hand, the species was not found, the slopes were steeper varying between 0% and 100%, with an average slope of 16.28% and main ~.18 iü S" u 112 £io |8 * 6 i: 0-10 10-20 20-30 30-40 40-50 50-60 60-70 70-80 80-90 90-100 Slope class / Razred naklona (%) Figure 2: Slope (%) of the two groups of sites in Carnia studied (21 each); Corncrakes Crex crex were either present (black) or absent (white) Slika 2: Naklon (%) za dva tipa obmo~ij v Karnijskih Alpah, s kosci Crex crex (~rni stolpci) in brez (beli stolpci; 21 enih in drugih) aspect lying between south-west and south-east. In addition, only 2 out of 21 of the sites could be termed šfat’ (Figure 2). The pH in the frst 10 cm ranged from 4.5 to 6.5 in all the sites examined. Carbonate levels ranged from very low carbonate content through to calcareous, whilst the soil types ranged from sandy loam to loamy sand. The sites holding Corncrakes tended overall to be more humid compared to those where the species was absent (Figure 3). 3.2. Management characteristics The results of the management characteristics assessment are presented in Table 2. On average, the felds are cut twice a year. The timing of the frst cut at the sites where Corncrake is present is slightly later than those sites in which the species is absent. Fertiliser applications take place, on average, once a year using organic material (manure and slurry); the level of fertiliser application overall appears to be medium. None of the felds used by the birds appear ever to have been re-seeded and even in the control group (Corncrakes absent) the practice appears rare. Autumn grazing is rarely practised and where it occurs the principle grazing animals used are cattle. To complete the study, other factors were assessed, such as the equipment employed to do the cut and any use of herbicides and pesticides in the felds. As far as the frst element is concerned, cuts are made using rotary cutters where the lay of the land allows, whereas in steeper areas, the cuts are made with slower machines, such as Allen Scythes (motor scythes with horizontal knife) or even hand-held scythes. Finally, no use of herbicides or pesticides was noted. 3.3. Vegetational characteristics The results of the vegetational characteristics assessment are presented in Table 3. Five types of vegetation were identifed: 1) Upright Brome Bromus erectus dominated, 2) False Oat-grass Arrhenatherum elatius dominated – sparse, 3) False Oat-grass dominated – typical, 4) False Oat-grass with umbellifers, 5) Yellow Oat-grass Trisetum favescens dominated. Corncrakes were found at the sites dominated by False Oat-grass (containing mostly Arrhenatherum elatius, particularly in those classifed as štypical’ together with |18 316 n »14 » ž 12 £ ilio- » 8 £ c «> 6 » 2 li RD D DW Soil moisture category / Kategorija vlažnosti zemlje Figure 3: Soil moisture of the two groups of sites in Carnia studied (21 each); Corncrakes Crex crex were either present (black) or absent (white). RD = rather dry, D = damp, DW = damp with waterlogging Slika 3: Vla`nost prsti za dva tipa obmo~ij v Karnijskih Alpah, s kosci Crex crex (~rni stolpci) in brez (beli stolpci; 21 enih in drugih). RD = prete`no suho, D = vla`no, DW = vla`no, prepojeno z vodo 64 Acrocephalus 28 (133): él-68, 2OO7 Table 2: Management characteristics of the two groups of sites in Carnia studied (21 each); Corncrakes Crex crex were either present or absent Tabela 2: Zna~ilnosti kmetijske rabe za dva tipa lokacij v Karnijskih Alpah, s kosci Crex crex in brez (21 enih in drugih) Group / Skupina Presence of Corncrakes / Prisotnost koscev Average number of cuts / Povpre~no {tevilo ko{enj min. Timing of first cut / ^as prve ko{nje normal / obi~ajen slightly late / rahlo kasnej{i late / pozen Fertilisation regime / Re`im gnojenja manure / gnoj slurry / gnojnica manure and slurry / gnoj in gnojnica no fertiliser / brez gnojila Frequency of fertiliser application / Pogostost gnojenja no fertiliser / ni gnojenja annual fertiliser application / letno biennial fertiliser application / na dve leti Prevalent level of fertiliser applied / Intenzivnost gnojenja low / nizka medium / srednja high / visoka Reseeding / Vnovi~no sejanje no / ne yes / da Most frequent grazing animal used / Prete`ni tip `ivine cattle / govedo sheep and goats / ovce in koze horses / konji horses and cattle / konji in govedo sheep and cattle / ovce in govedo sheep and horses / ovce in konji ungrazed meadows / ni pa{e Use of herbicides or pesticides / Uporaba herbicidov in pesticidov 1 2 present / prisotni absent / odsotni 2 2 0 0 3 3 sl. late - late/ sl. late (late)/ rahlo kasnej{i - pozen rahlo kasnej{i (pozen) 3 6 5 4 13 11 manure manure - slurry/ gnoj - gnojnica 10 5 4 4 3 8 4 4 annual / letno annual / letno 4 4 16 17 1 0 medium / srednja medium / srednja 3 5 13 11 5 5 no / ne rare / redko 21 18 0 3 cattle / govedo cattle / govedo 3 4 0 2 0 0 1 1 1 1 0 0 16 13 no / ne no / ne Cocksfoot Dactylis glomerata, Meadow Fescue Festuca pratensis and White Bedstraw Galium album, whilst in those with umbellifers the latter largely consisted of Cow Parsley Anthriscus sylvestris and Hogweed Heracleum sphondylium) as well as in the Trisetum favescens meadows, whilst it was absent from the sparse felds of Bromus erectus. The complexity of the vegetation structure shows a slight difference between the two groups of sites: that in which Corncrakes are found was shown to be slightly more complex. 4. Discussion The results obtained allow the identifcation of certain physical, management and vegetational aspects of sites where Corncrakes were recorded annually when compared with the sites where the species was never recorded. We refer to the comparisons obtained with descriptive statistics presented in Tables 1, 2 & 3. max. 65 G. Rassati & P. Rodaro: Habitat, vegetation and land management of Corncrake Crex crex breeding sites in Carnia (Friuli-Venezia Giulia, NE Italy) Table 3: Vegetational characteristics of the two groups of sites in Carnia studied (21 each); Corncrakes Crex crex were either present or absent Tabela 3: Zna~ilnosti vegetacije za dva tipa lokacij v Karnijskih Alpah, s kosci Crex crex in brez (21 enih in drugih) Group / Skupina Presence of Corncrakes / Prisotnost koscev Types of vegetation / Tipi vegetacije Bromus erectus dominated / dominira Arrhenatherum elatius dominated – sparse / ponekod dominira Arrhenatherum elatius dominated – typical / ve~inoma dominira Arrhenatherum elatius with Umbellifers Trisetum flavescens dominated / dominira Complexity of vegetational structure / Kompleksnost vegetacijske strukture low / nizka medium / srednja high / visoka 1 2 present / prisotni absent / odsotni 3 (4) 3-4 0 1 3 5 9 7 7 7 2 1 high / visoka high (medium)/ visoka (srednja) 3 4 3 5 15 12 The difference between grasslands occurring on the Broyer 1996, Schäffer & Weisser 1996, Green et al. two groups of sites are not very evident for various 1997a, Green et al. 1997b, Broyer & Renaud 1998, parameters, as already noted, but the sites without Tyler et al. 1998, Broyer 2003, Rassati 2004). The Corncrakes chosen tended to be in marginal areas new element met with in Carnia is represented by the but close to the main sites holding birds with a view fact that the use in different times (or non-use) of sites to establishing the parameters used by the birds in seems dependent upon the lay of the land and not a choosing breeding sites. As far as site characteristics choice in favour of “Corncrake-friendly mowing”. are concerned, the species appears to be infuenced Slope and humidity are also connected inasmuch as in its choice of reproductive habitat principally by where the slope is greater, waterlogging is usually less. slope and humidity that, at the sites that consistently In addition, where humidity is linked to a favourable held birds, were respectively lower and higher than in type of soil (deep and moisture-retaining) it favours those without. Slope was the parameter that showed the development of the sort of vegetation (False Oat-the greatest difference. To further confrm this, in grass or False Oat-grass with umbellifers), which seem sites with variable slope the singing males tend to best suited to the species’ requirements. Humidity has position themselves in the fatter areas and these are been found to be important in other studies on the also chosen for nesting (Rassati unpubl.). It was also choice of breeding habitat (Cadbury 1980, Broyer noted that where Corncrakes do occupy slopes they 1987, Green et al. 1997a, Green et al. 1997b, Trontelj tend to choose those where fat areas tend to alternate 1997, Broyer & Renaud 1998). with (usually small) steeply sloping areas where hand- As far as agricultural management and vegetational or Allen scythes (motor scythes with horizontal knife) characteristics is concerned, one parameter that are used and rotary cutters cannot be employed. In certainly affects the presence of Corncrakes is the timing many cases, these sites remain uncut or are cut only of the frst cut, which, if it occurs early and intensively, occasionally allowing adults and young to fnd refuge certainly compromises the chances of birds choosing during mowing operations, given the lower speed a site and breeding successfully (Cadbury 1980, of the tools employed (Rassati unpubl.). Cadbury Broyer 1987 & 1994, Green & Stowe 1993, Green (1980), Green (1995), Niemann (1995), Schäffer 1995, Niemann 1995, Green et al. 1997a, Green et & Weisser (1996), Green et al. (1997a), Tyler et al. al. 1997b, Broyer & Renaud 1998, Rassati 2001 & (1998) all indicated that slower mowing gave greater 2004). Early or frequent cutting was not recorded in chances of a successful outcome of breeding and the the meadows studied. Overall in the sites where the presence of unmowed or mowed in different times animals were located the date of the frst cut was slightly areas close by was generally considered important for later that in those meadows in which animals were not the survival of broods and adults (Green & Stowe recorded. As far as fertiliser application is concerned, 1993, Schäffer & Münch 1993, Niemann 1995, the amount of nitrogen distributed during the process 66 Acrocephalus 28 (133): 61-68, 2007 seems important regardless of its source (organic or inorganic) as it tends to infuence the species present in the meadow and therefore the type of vegetational community found there. On average, the level of fertiliser applied was slightly higher in the meadows where birds were recorded. Grazing does not take place during the breeding season of Corncrakes and this is a positive element in that intensive grazing can cause the death of individuals or the abandonment of a site (Stowe & Hudson 1991, Trontelj 1997). It has been shown on more than one occasion in montane areas of the region when the passage of large herds of sheep has caused the (at least temporary) abandonment of important Corncrake breeding sites as well as those of Rock Partridge Alectoris graeca and Black Grouse Tetrao tetrix (Rassati unpubl.). Only a single example is known, late on in the breeding season, of a calling male at a site a few days before a fock of sheep had arrived (Rassati unpubl.). The reason that Corncrakes prefer meadows of False Oat-grass (especially the štypical’ variety and those containing umbellifers) as well as those of Yellow Oat-grass when compared to those of Upright Brome can be put down to their structure. The former are usually tall but with a low density of vegetation at ground level that permits free movement. These are characteristic of good local fertility but nevertheless with just a small number of annual cuts (Rassati & Rodaro 2003). In the meadows of False Oat-grass, in addition, the ground is hardly visible from above. The felds dominated by Upright Brome, on the other hand, although extensively managed and therefore less disturbed, do not offer good habitat because they are usually low, denser at soil level and, therefore, with a structure not much liked by the Corncrakes. To add weight to the above, the height of the vegetation is a parameter held to be important by other authors together with an overall favourable structure (Cadbury 1980, Broyer 1987, Schäffer & Münch 1993, Niemann 1995, Green et al. 1997a, Green et al. 1997b, Trontelj 1997). To end with, it is hoped that the information obtained in this study might be used to direct appropriate safeguard measures for the species at a regional level that foresee the modifcation of management of areas suitable for Corncrakes and compensatory measures should these changes lead to lower or inexistent revenues as a result of these changes, already recommended in Rassati & Tout (2002) and in Rassati (2004) but currently still lacking in Friuli-Venezia Giulia. Acknowledgements: We would like to thank Giancarlo Rassati, father of one of the authors, for the help in collecting the data, and Paul Tout for translating part of the paper into English. 5. Povzetek Raziskava primerja obmo~ja, stalno naseljena s kosci v obdobju 10 let (1991-2000), z obmo~ji brez koscev v Karnijskih Alpah, SV Italija. V primerjavi je bilo zajetih 21 obmo~ij s kosci in 21 obmo~ij brez njih, obmo~ja pa so bila v razponu nadmorske vi{ine 201-1400 m. Avtorja sta primerjala naslednje spremenljivke: naklon, ekspozicija, pH prsti, vsebnost karbonatov v prsti, vla`nost in strukturo prsti, {tevilo ko{enj, ~as prve ko{nje, na~in gnojenja, vrsto `ivali na pa{i in {e nekatere druge spremenljivke. Primerjala sta tudi vegetacijo. Iz rezultatov sta zaklju~ila, da imajo kosci v Karnijskih Alpah raje travnike z manj{im naklonom in vla`no zemljo, raje pa imajo tudi kasnej{o ko{njo in obmo~ja brez pomladanske pa{e. Najraje imajo travnike z dominantno travo visoko pahovko Arrhenatherum elatius, ker ima primerno strukturo; zaradi vi{ine pticam zagotavlja primerno skrivali{~e, a tudi dovolj prostora za premikanje po tleh. 6. References Baillie, J. & Goombridge, B. (eds.) (2000): IUCN Red List of Threatened Animals. - IUCN, Gland & Cambridge. BirdLife International (2004): Birds in Europe. Populations estimates, trends and conservation status. BirdLife Conservation Series No. 12. - BirdLife, Cambridge. Broyer, J. 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