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A method for defining the value of
breeding birds |
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Abstract.
A synthetic methodology is proposed in order to define the
intrinsic specific Value (Vs) of the regularly breeding birds species in Italy,
also required for the studies of environmental impact assessment, landscape
planning and recovery. INTRODUCTION The necessity to attribute a value as objective as possible
to animai species, and to birds in particular, was initially originated in
England and in United States, especially for the defìnition of models of
management and conservation of protected areas, or for the establishment of
intervention priorities in the preservation of rare species. METHODS In order to define the specifìc value, we have used an
algorithm of the kind Vs = Ki.Ei (where Vs = synthetic value of the ith species),
including 15 different parameters, relative to geographic distribution,
population status and dynamics, presumed level of vulnerabiity, present
scientifìc interest, availability for human activities. Each one of these
parameters has been built through a Paired Comparison Procedure, in matrices,
according to a partial adaptation of the U.S. Habitat Evaluation Procedure
(1980) for enviromental impact studies. Scores, which are proportional among
themselves, are not the same ones for each parameter; generally speaking,
parameters of biological type (Ta, Tp, C, etc.) have received much higher values
than the "anthropic" ones (Vs, Vv, Vall., etc.). Specifying the parameters used and their relative scores we bave: Biogeographic value (Vb): obtained using the recent corological classification proposed by Boano and Brichetti (1989) and Boano et al. (1990), with endemic species reaching the highest value, and the cosmopolitan species reaching the lowest one. Value of national distribution (Vd): is the result of the combination of two additional parameters (N. of occupied Italian Regions = Vdr, and % I.G.M. maps 1:50.000 occupied = Vdp). Trend of distribution area (Ta): express the present tendency (if known) to extend or contract the distribution area. Highest scores bave been given to decreasing species. Species established recently (e.g. Spoonbill) are included in the class of fluctuating species. Level ofterritoriality (St): expresses the link degree with the sorrounding territory, as regards: strict sedentariness, same environments used for feeding and breeding, frequented habitat at the maximum level of naturality (p = 1 high; p = 0,5 medium; p = 0). Ecological rarity (R): is connected with the availability, within the national territory, of those environments which are considered as preferential for breeding. The lowest scores bave been assigned to the man-used environments; in case of several preferential environments we have calculated an average with possible rounding to the higher half-mark. Consistence (C): expressed as number of breeding pairs, divided into 5 classes, with the highest scores assigned to those species breeding with less than 50 pairs. Population trend (Tp): is evaluated upon a period of 10-15 years (on the basis of available data); in this case too decreasing species are favoured. Naturalistic-aesthetic value (Vn): is the first of the "anthropic-cultural" parameters and expresses the interest which unspecialized, but stimulated people shows for the species in question. The parameter has been calculated on the basis of the frequency of articles devoted to the species and published in the magazines "Oasis" and "Airone". Scientjtìc value (Vs): similar to the previous parameter, but is an expression of the interest shown by the technical and scientific community; it is expressed by the frequency of articles published in the specialized periodicals and congress proceedings within the last 15 years. Value of availability (Vf): obtained from the addition of Venatorial Value (Vv) to the Value of possible rearing (Valla), fot which Vv has been calculated on the basis of frequency of articles published in the periodical "Diana" (number of references divided into 3 classes with corresponding scores from 1-0; 5-0; 25-0, from most abundant to not mentioned; for the species of hunting interest the minimum score is 0.25, even though not recorded by the venatorial literature). Vall has been calculated on the basis of those species at present available for rearing, used for reintroduction or repopulation schemes, or for aesthetic reasons. Value of vulnerabilìty (Vvul): obtained on the basis the inclusion of the various species in the "Red list" of threatened birds, as well as in the EEC and national legislations. In case of species included in more than one class, the one with highest score is taken into account. Endangered and threatened species are favoured. Importance of the population and of the distribution area (Ipa): is perhaps the most subjective parameter but, so far, also the least considered one, even for the scarcity of available data. As a matter of fact we consider the importance of the distribution area in Italy in connection with range in the Palearctic (position, degree of dispersal/concentration of the range in the Palearctic consistence of the Italian population in connection with the western palearctic population), regularity of nesting the presence of ascertained subspecies or endemisms. Endemic populations and those the range of which in Italy is placed centrally in comparison with the Palearctic are favoured, as well as the populations which in our Country number more than one third of the total population estimated for the Western Palearctic region. Trophic level (Lt): expresses the prevailing composition of the diet and the position of the species within the food web (division in 4 class). Degree of anthropophily (Ga): indicates the sensitivity of the species to the presence and to the interventions of man, as well as its adaptativeness to nest in modifìed and man-inhabited environments (4 classes). Table I - Value (Vs) of Italian breeding avifauna: list of the first 20 species.
Griffon Vulture (Gyps fulvus) 90.7 RESULTS AND DISCUSSION The detailed examination of the 237 species regularly nesting in Italy has allowed us to prepare a "classification" of the Italian Avifauna. At the highest positions we find almost exclusively non-Passeriformes species (Table I), with the notable exception of the Sedge Warbler (Vs = 73); on the contrary, most Passeriformes appear at the lowest levels (Table II). Such a difference in "weight" is reflected by a greater value of non-Passeriformes, approximately +31% than Passeriformes. Very eterogeneous species, such as the Tawny Owl (Vs = 42.6), the Coot and the Sparrow Hawk (Vs = 42.9), the Grey Woodpecker (Vs = 47.3) or Grey Heron (Vs = 47.5), are situated around average values. Quite predictable, however, is the presence of stenotopic species at the top of the list, while those more generalist are placed at bottom. Among the first 20 species, only one, the Ferruginous Duck, is legally hunted. Table II - Value (Vs) of Italian breeding avifauna: list of the last 20 species.
Robin (Erithacus rubecula) 32.3
The analisys of three species grouped into families stresses
how those including one or two taxa are placed at the top (Haematopodidae,
Hydrobatidae, Otididae) and at the bottom (Troglodytidae, Oriolidae) of the
scale: therefore their significance concerning more numerous families, such as
Sternidae, Laridae, Anatidae, Accipitridae and Ardeidae, notable, their global
value, is more obvious. On the contrary Turdidae, Corvidae and Fringillidae are
the families with less specific value. REFERENCES
ADAMUS P.R.. & CLOUGH G.C., 1978. Evaluating species for
protection in natural areas. Biol. Conserv. 13: 165-178. |
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