Salinas Research Papers - Academia.edu (original) (raw)

Goal of this study was a detailed description of waterbirds of Tarquinia Salinas National Natural Reserve that covers about 170 ha, including a wetland of about 120 ha, and their ecology, both with a long-term view by historical data analysis, and comparing specie’s presence and environmental variables. The work was strongly addressed to define management prescriptions for this important wetland located in Maremma Laziale (Tarquinia Municipality), in the framework of a wider ICZM (Integrated Coastal Zone Management) project, covering Latium’s coastal area.
Study issues were: waterbird long term historical temporal data series analysis, using data from IWRB (International Waterfowl Research Bureau, now Wetlands International) midwinter counts; circum-annual cycle of waterbird species; study of correlations between environmental variables (salinity, water deep, pH, Oxygen) and bird guilds with similar ecological preferences; development of management prescriptions, following the experience developed in the framework of a LIFE project. More in deep, study goals have been the following: 1) developing a species check-list for the site by original and bibliographical data; 2) keeping field data to define annual cycle of species, to determine main external factors influencing the presence of different waterbird species; 3) gathering and analysing a long-term data set (mid-winter census data) to evaluate long-term trends; 4) gathering and analising a data set on wintering birds (October-February) to use it for correlation analysis with environmental data. To reach these goals, a original data set was taken, made by: a) Historical series: presence data for 26 years for all observed species in mid-winter IWC data (36.881 records); b) Annual cycle: 44 observations for any species (every 10 days) for nov 2004- June 2006; Wintering: 90 observations for any species 2000-2008 period (September-April, bibliographical and original data for 2000-2004 – n. 20 visits, and original data for 2005-2008 period 2005-2008, n. 70 visits); amounting 46.409 records. Method used was total count, assumed correct for this kind of open habitat and strongly-visible species. For last three winters environmental variables data were taken: for the whole data set classes of deep of water and environmental unit (pond number) were registered. For 2006-2007 winter data from a separate study concerning salinity, Oxygen, pH, water deep and plankton (diversity, biomass) are available. For October-December 2007 only data on benthos (diversity, biomass) are available, too.
During this study a detailed analysis of functionality of a small Mediterranean artificial wetland (salt works) for waterbirds, based on a relevant field data set, have been developed. Evaluations on different temporal and spatial scales have been made., trying to understand what kind of factors are determining waterbirds presence and abundance in the site. At local scale, data were tested to understand which environmental factors are relevant do determine waterbirds diversity in the specific study area. Because the huge amount of data, difficult to analyse, waterbird species have been divided in different guilds with similar ecological and feeding behaviour, evaluated on the basis of literature information. Analysis were developed for each specie’s guild (herbivores, filtrating eaters, fish-eaters, omnivores ducks, shorebirds, gulls). Statistical analysis was developed using multivariate techniques commons in ecology like correlation analysis, discriminant analysis and GLM (General Linear Models). Main study results are:
- description of historical presence of different species in the area;
- hypothesis about main factors that at large geographical scale are determining specie’s presence in the area (area-abundance correlation and migration cycling);
- demonstration of spatial segregation of different species and species’ guilds inside spatial units (ponds) in the Salinas;
- to define correlations between some species’ guilds and some environmental factor (especially salinity and water deep);
- to elaborate first considerations about correlations between species’ guilds and food availability (benthos) in the site, to be developed in more detailed experimental designs in the future.
In general, insular model and migration drive probably total waterbird abundance; at local scale salinity, water deep and probably benthos biomass (especially Chironomidae) are correlated with observed spatial segregation of species.
Tarquinia Salinas are one of few nesting sites, sometimes the only one, for rare at regional scale and environmentally demanding species like Avoset, Stilt, Shelduck, Egret, Cattle heron. For these species reproduction is frequently irregular, probably for the high disturbance level on the site. Wintering seems to be more regular; Salines are one of the main wintering sites in the Latium Region. Concerning general historical trends for waterbird wintering, this wetland shows a clear significant trend to increase abundances in the long-term. Historical maximum have been recorded turing the study period (2005-2005 winter, with more then 2.700 wintering birds, between them 692 Flamingoes – Phoenicopterus ruber -, historical maximum for this species at Salinas), after LIFE project intervention. In the last two winter presences decreased, probably for external factors dues to migration waves. On the basis of ecological analysis the study developed a series of management prescriptions, widely described and articulated. Main indications are concerning disturbance control and decreasing, creation of islands for bird roost and possibly nesting, water level management. Possible development of present study will be specific experimental design to define correlations between benthos – especially Chironomidae - and bird species abundance.