Structure of waterbird assemblages in fragmented coastal wetlands of Northeastern Algeria

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Como citar

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Bouldjedri, M., Mayache, B., 2020. Structure of waterbird assemblages in fragmented coastal wetlands of Northeastern Algeria. Museu de Ciències Naturals de Barcelona. Dataset/Occurrence: https://doi.org/10.15470/oud0fp

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O editor e o detentor dos direitos deste trabalho é Museu de Ciències Naturals de Barcelona. This work is licensed under a Creative Commons Attribution (CC-BY 4.0) License.

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Este recurso foi registrado no GBIF e atribuído ao seguinte GBIF UUID: 04bcb0c1-be72-4e7f-8170-c73ccf4cb4d0.  Museu de Ciències Naturals de Barcelona publica este recurso, e está registrado no GBIF como um publicador de dados aprovado por GBIF Spain.

Palavras-chave

Breeding; Eco-complex; Habitat; Waterbirds; Wetlands; Wintering; Occurrence; Occurrence

Contatos

Cobertura Geográfica

Fieldwork was conducted in Jijel eco-complex wetlands located in north-eastern of Algeria (36° 34'-36° 52'N, 5° 33'-6° 19' E), which are approximately 60 km2 in size. This natural wetland reserve comprises two major aquatic habitats that may vary in vegetation composition and structure, namely: (i) Beni-Belaid Lake (B-B.Lake) and (ii) El-Kennar Marsh (E-K.Marsh) (see map in fig. 1). This latter freshwater swamp is dominated by herbaceous rather than woody plant species. These mosaic hydrosystems are characterized by several types, mainly lakes, marshes, reservoirs, ponds, estuarine waters, and shallow seawater. Together, they form a complex ecosystem of wetlands.

Cobertura Taxonômica

Nenhuma descrição disponível

Cobertura Temporal

Dados Sobre o Projeto

Wetland habitats are used by waterbird species for nesting, breeding, feeding, sheltering, migration stopovers, and wintering in various stages of their annual life cycle. These ecosystems have high biodiversity and are sites of conservation concern due to the extensive food chain (Saygili et al., 2011). The great diversity of wetlands in North Africa has long been recognized (Gauthier-Lièvre, 1931), but despite concerns for their conservation, they continue to be disturbed, drained and polluted (Bouldjedri et al., 2011; Daoud-Bouattour et al., 2011; Rhazi et al., 2012). According to the General Directorate of Forestry, Algeria has 2,375 wetlands. They are composed of 2,056 natural areas and 319 human-made wetlands. Although most of these freshwater hydrosystems (lakes, lagoons, marshes, wet meadows, peat lands and alder swamps) are concentrated in the northeastern part of the country, several shallow lakes, with varying salinity are found in the High Tell and the Algerian arid and Saharan zones (“Chotts”, “Sebkhas”, “Gueltas” and Oases). These ecosystems are part of a large Mediterranean eco-complex which is strongly exploited by many waterbird populations, often structured as metapopulations (Boulkhssaim et al., 2006; Samraoui et al., 2011). Several studies show that these zones meet one or more of the criteria required for an Important Bird Area “IBA” (Samraoui and Samraoui, 2008; Baaziz et al., 2011; Benradia et al., 2018; Nouidjem et al., 2019) and constitute a valuable network of sites used each year by thousands of birds migrating between their breeding grounds in the Arctic and their wintering sites in southern Europe and North Africa. The Jijel region in Northeast Algeria occupies a privileged location for waterbird migration because of its eco-complex of coastal wetlands and geographical situation in the Mediterranean flyway. It therefore plays a vital role as a migratory stopover for aquatic avifauna when they cross the Mediterranean Sea. The few preliminary studies (De Bélair and Samraoui, 2000; Mayache, 2008) performed to date for the area have illustrated the ornithological and ecological value of these wetlands; the areas host notably endangered and vulnerable species registered in the IUCN Red List of threatened species (IUCN, 2019), such as the ferruginous duck (Aythya nyroca), thewhite-headed duck (Oxyura leucocephala) and the common pochard (Aythya ferina). Despite their ecological interest, this wetland eco-complex is under strong anthropogenic disturbances, including agriculture, grazing, hunting and fishing (Bouldjedri et al., 2011). This worrying situation motivated the present study, which was carried out over ten years. It describes for the first time the communities of waterbirds that use this area of the Mediterranean flyway and discusses the potential utility of this area as a staging, resting and wintering place. The objectives of the study were to: a) characterize the waterbird communities that visit these coastal wetlands; b) analyze their temporal evolution; c) assess the diversity of both communities and establish comparisons between them; d) assess the importance of these wetlands to propose, where appropriate, protective measures; and e) to complete data on distribution and breeding aquatic birds so as to develop action plans for species threatened by human pressure on Algerian wetlands.

O pessoal envolvido no projeto:

Métodos de Amostragem

To investigate the spatial and temporal variations of waterbird communities, we carried out monthly surveys over ten years, from October 2007 to December 2017, at the two main sites and their related areas. Surveys were carried out during the migration season (in autumn, from September to November), the wintering period (from December to February), the breeding season (from March to July), and the post-nuptial period (from June to August). The species and the peak in total number recorded over a month were all used for analysis. Birds were identified and counted using either: 7 × 50 binoculars or 20 × 60 Meopta telescope, and field guidebooks; we selected waterbirds from the avian fauna that are obligate users of the wetland. Other species were all excluded from the analysis. At each site, all birds were counted, so that the time effort was proportional to the size of the wetland. For each main site, we simultaneously counted its related sites to avoid errors due to bird movements between adjacent areas, the observation points were always the same. Methods of bird observation are numerous and dependent on the studied species and the purpose of the study. Depending on the circumstances, we combined two main methods in our field survey, the absolute method and the relative method. In the case of the absolute method the census is called exhaustive because the population was estimated directly on its absolute value and all the individuals were counted (point counts). An individual bird count was carried out when the group contained less than 200 birds and when it was at a distance of less than 200 m. This is because the area of the related sites was small enough for us to observe the whole site from one location with no optical obstacle, and one point counting was used (Gregory et al, 2004). Concerning the relative method, the population was estimated using sampling that includes only a part of the population. We estimated a sample of average size, then divided the field of vision into several transects (i.e. the flock size was divided into small equal blocks) and counted the number of blocks. This method is commonly used in winter counts of waterfowl when the individual number exceeds 200 birds or when estimating at a distance of more than 200m, as described by the "Scan Sampling Method" (Lamotte and Bourlière, 1969; Blondel, 1975).

Descrição dos passos do método:

1. The study of the avifauna ecology was approached by determining ecological indexes directly linked to the balance of populations (Shannon–Weaver, Frequency and Uniformity). The monthly mean number for species richness and the total number of individuals was calculated for the whole period. These values were then used to calculate the diversity of species for the two main sites, expressed by the alpha diversity (Hα) of Shannon–Weaver index (H′). This index was computed using the following mathematical formula (Shannon–Weaver, 1949): H’ = -∑ pi ln pi where pi = (ni / N), N is the total population (individuals of all species), ni is the size of the population of species and S denotes the total number of species composing a population (specific richness). Frequency index: Relative abundance (RA %)is computed by using the formula: RA (%) = ni / N × 100, where: ni is the number of individuals of species taken into account and N is the total number of individuals of all species.. Species relative abundance status (table 1) was estimated from the frequencies of sightings over 12 months and the categories were assigned according to the Pettingill (1969) scale: abundant (90-100 %), common (65-89 %), moderately common (31-64 %), uncommon (10-30 %) and rare (1-9 %). Uniformity Index (Pielou index): this index measures the degree of numerical balance between species represented by the Equitability index (Evenness index). ‘E’ is calculated as the ratio: E = H′obs / H′max between observed diversity H′obs and maximum diversity H′max = log2(S), S being the total number of species recorded during each month (Pielou, 1966). The equitability index ‘E’ makes it possible to assess the imbalances that the diversity index cannot detect; it varies from 0 to 1. When E < 0.5, this means that the individuals mostly tend to belong to a single species. When E > 0.5, it means that species have similar or balanced abundance, the same abundance occurs when the value is exactly one (Okpiliya, 2012). For the entire study region, the mean (± standard deviation) was calculated for each ecological index (Shannon–Weaver diversity (H′), Equitability index (E), Abundance, Specific richness and Monthly population dynamics) based on all observations. The results were compared using analysis of variance (ANOVA), the choice of a parametric test analysis (two ways ANOVA) is supported by the Shapiro-Wilk test on the ANOVA residuals for the previous ecological index comparison which finds no indication that normality is violated. After this analysis, we used a Bartlett test on the ANOVA residual because the normality and homoscedasticity conditions were met: as the p-value was largely greater than 0.05, the assumption of homogeneity of the residual variances was therefore accepted. However, ANOVA led to the conclusion that there were differences between the means in some groups. Tukey’s (HSD) multiple comparison tests were used to compare the difference between each pair of monthly means. The choice of a non-parametric test (Friedman rank-sum test) analysis in the monthly abundance of shorebirds population is referred to that the condition of residual normality is violated (p= 0.001). These tests were performed using the statistical software R version 3•2•2 (R Core Team, 2015). Correspondence analysis (CA) was applied (bi-plot species and dates) to the data collected from the entire e eco-complex. CA is a two-dimensional solution that is well-suited to describe the spatial and temporal gradients in composition occurrence, status and assembly of waterfowl found at this ecological site. This last statistical analysis was carried out using the ADE-4 software package.

Citações bibliográficas

1. Bouldjedri, M., Mayache, B., 2020. Structure of waterbird assemblages in fragmented coastal wetlands of Northeastern Algeria. Arxius de Miscel·lània Zoològica, 18: 123-140, Doi: https://doi.org/10.32800/ amz.2020.18.0123 https://doi.org/10.32800/ amz.2020.18.0123

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