Ocells aquàtics, Aiguamolls, Nord d'Àfrica, Refugi hivernal, Riquesa específica, Fenologia
Data de recepció: 21/04/2021 | Data d'acceptció: 09/06/2021 | Data de publicació: 01/07/2021
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Ecology, phenology and wintering behavior of Anatidae in the wetlands of Souk–Ahras (north–eastern Algeria)
Ecology, phenology and wintering behavior of Anatidae in the wetlands of Souk–Ahras (north–eastern Algeria)
Understanding the spatial and temporal niche of waterfowl is essential for effective management and conservation. To determine the ecology and phenology of Anatidae in North Africa, we carried out a 12–month study (2019–2020) in three wetlands that constitute a winter refuge for waterbirds in the Souk–Ahras region in north–east Algeria. We surveyed species richness, the seasonal pattern of the number of Anatidae, and their wintering diurnal behavior using regular counts and scans. We recorded thirteen species: six wintering species (Anas clypeata, Anas penelope, Anas strepera, Tadorna tadorna, Aythya ferina, and Anas crecca crecca) and three sedentary nesting species (Anas platyrhynchos, Oxyura leucocephala, and Aythya nyroca), the latter two having national and international protection status. The survey showed that the wintering behavior of all these species is dominated by sleep, which on average accounts for almost half of the total time (48.91 %). Our results indicate that the three wetlands host a complex waterfowl community that includes species of conservation concern and that these sites likely play an essential role in providing the essential resources for wintering.
Key words: Waterfowl, Wetlands, North Africa, Winter refuge, Specific richness, Phenology
Ecología, fenología y comportamiento de Anatidae durante la invernada en los humedales de Souk–Ahras (noreste de Argelia)
Comprender el nicho espacial y temporal de las aves acuáticas es esencial para una eficaz gestión y conservación de las mismas. Para determinar la ecología y fenología de Anatidae en el norte de África realizamos un estudio durante todo un año (2019–2020) en tres humedales de la región de Souk–Ahras (noreste de Argelia) que constituyen un refugio invernal para muchas aves acuáticas. Estudiamos la riqueza específica, el patrón estacional del número de Anatidae así como su comportamiento diurno durante la invernada mediante recuentos periódicos y escaneos. Registramos trece especies, incluyendo seis especies invernantes (Anas clypeata, Anas penelope, Anas strepera, Tadorna tadorna, Aythya ferina y Anas crecca crecca) y tres especies nidificantes sedentarias (Anas platyrhynchos, Oxyura leucocephala y Aythya nyroca), las dos últimas de las cuales tienen estatus de protección nacional e internacional. El estudio mostró que el comportamiento de todas las especies durante la invernada está regido por el sueño, que de promedio representa casi la mitad del tiempo total (48,91 %). Nuestros resultados indican que los tres emplazamientos albergan una compleja comunidad de aves acuáticas (entre las que se cuentan especies cuya conservación es motivo de preocupación) y que probablemente desempeñan un papel determinante en la oferta de recursos esenciales para la invernada.
Palabras clave: Aves acuáticas, Humedales, Norte de África, Refugio invernal, Riqueza específica, Fenología
Ecologia, fenologia i comportament d’Anatidae durant la hivernada als aiguamolls de Souk–Ahras (nord–est d’Algèria)
Entendre el nínxol espacial i temporal dels ocells aquàtics és essencial per a una gestió i una conservació eficaces. Per determinar l’ecologia i la fenologia d’Anatidae al nord d’Àfrica vam portar a terme un estudi durant tot un any (2019–2020) en tres aiguamolls de la regió de Souk–Ahras (nord–est d’Algèria) que constitueixen un refugi hivernal per a molts ocells aquàtics. Vam estudiar la riquesa específica, el patró estacional del nombre d’Anatidae i també el comportament diürn dels ocells durant la hivernada mitjançant recomptes periòdics i escanejos. Vam registrar tretze espècies, incloent–hi sis espècies hivernants (Anas clypeata, Anas penelope, Anas strepera, Tadorna tadorna, Aythya ferina i Anas crecca crecca) i tres espècies nidificants sedentàries (Anas platyrhynchos, Oxyura leucocephala i Aythya nyrocaa), les dues ultimes de les quals tenen estatus de protecció nacional i internacional. L’estudi va mostrar que el comportament de totes les espècies durant la hivernada està regit pel son, que de mitjana representa gairebé la meitat del temps total (48,91 %). Els nostres resultats indiquen que els tres emplaçaments acullen una comunitat d’ocells aquàtics complexa (que inclou espècies la conservació de les quals és motiu de preocupació) i que probablement tenen un paper determinant en l’oferta de recursos essencials per a la hivernada.
Paraules clau: Ocells aquàtics, Aiguamolls, Nord d’Àfrica, Refugi hivernal, Riquesa específica, Fenologia
The wetlands of north–eastern Algeria are characterized by great biodiversity of fauna and flora (Samraoui and De Belair, 1998; Samraoui and Samraoui, 2008; Khelifa et al., 2016). One of the key taxonomic groups that characterizes their ecological importance is waterbirds, not only because of their crucial role in ecosystem functioning (Temple and Wiens, 1989; Carignan and Villard, 2002) but also because they reflect the environmental health of these areas (Maazi, 2005; Houhamdi et al., 2009). Additionally, Algeria has a strategic geographic position in the Western Palaearctic, and it has more than 1,200 wetlands, 52 of which are internationally classified (Samraoui and Samraoui, 2008). These geographic and environmental attributes make local wetlands a high–quality refuge for waterbirds.
Algerian waterbirds have attracted a lot of attention over the last two decades, highlighting their great importance for biological conservation (Houhamdi et al., 2008; Saheb, 2009; Khelifa, 2012; Chettibi et al., 2013; Bara et al., 2014). These studies have focused on a wide range of waterbirds, including the common scaup (Aythya nyroca), the flamingo (Phoenicopterus roseus), the elegant avocet (Recurvirostra avosetta), white stilt (Himantopus himantopus), white–headed duck (Oxyura leucocephala), common cranes (Grus grus), teal (Anas crecca crecca), shelduck (Tadorna tadorna), Eurasian coot (Fulica atra) and souchet duck (Anas clypeata) (Boulkhssaim et al., 2006; Baaziz and Samraoui, 2008; Houhamdi et al., 2008; Mayache et al., 2005; Aissaoui et al., 2009; Metallaoui et al., 2009; Saheb et al., 2009; Maazi et al., 2010; Metallaoui et al., 2014). Among these birds, the Anatidae constitute the most dominant group in view of both species richness and abundance (Metallaoui and Houhamdi, 2008; Maazi, 2009; Houhamdi et al., 2009; Boukrouma et al., 2011; Baaziz et al., 2011; Merzoug et al., 2014; Guergueb et al., 2014; Amor Abda et al., 2015; Halassi et al., 2016; Atoussi et al., 2017). Given that the most threatened waterbirds also belong to Anatidae, studies on their ecology, behavior, and demography should be regularly conducted to build up a long–term database and support their management and conservation.
Our aim was to assess the abundance, species composition, and wintering diurnal behavior of Anatidae in three wetlands in the Souk–Ahras region in north east Algeria. The study was conducted from September 2019 to August 2020, thus covering both the wintering season and the breeding season. We determined species composition and abundance by means of bi–monthly visits, allowing us to monitor seasonal patterns. The wintering behavior was categorized into seven different behaviors. The time allocated to each behavior was then calculated using the scan method.
Material and methods
The wilaya of Souk–Ahras (4,365.59 km2) is located in north–eastern Algeria, at the limit of the Tunisian border on a strip of 88 km. It is bound to the northeast by the wilaya of El–Taref, Guelma in the northwest, Oum El–Bouaghi in the southwest, Tébessa in the south, and Tunisia in the east (fig. 1). The region has a Mediterranean climate; it is subhumid in the north and semi–arid in the south with cold winters and scorching summers in the south. Most wetlands in the region depend on the climatic conditions for their water supply, mainly rainfall. Our work covered three natural wetlands: Tiffech and El–Kaf hill reservoirs and the marsh of Madjen Djedj (table 1).
The phenology and structure of the Anatidae population was monitored bi–monthly over 12 months, from September 2019 to August 2020. Our counts allowed an individual count when the flock of waterbirds was close to the point. When the number of individuals was less than 200, we counted them individually. When the number of individuals was greater than 200 or at a greater distance, we made a visual estimate (Lamotte and Bourlière, 1969; Blondel, 1975; Houhamdi, 2002). The counts were carried out by direct observation using a KONUSPOT 20–60 x 80 telescope. The estimated total number represents the sum of all flock snumbers (Houhamdi and Samraoui, 2001, 2002, 2008; Aissaoui et al., 2011). This method often has an estimated margin of error among professionals of 5–10 %. It also depends on the observers’ experience and the quality of the optical equipment used (Legendre and Legendre, 1979; Tamisier and Dehorter, 1999). To characterize the waterbird community, a few ecological indices were calculated, namely the total abundance, species richness, the Shannon and Weaver diversity index (H’) and the index of fairness (E) (Chessel et al., 2004).
The second part of our study consisted of monitoring the rhythm of the daily activities of Anatidae. We used the the SCAN method, carried out every hour, from 9 a.m. to 4 p.m. (Baldassare et al., 1988; Losito et al., 1989; Tamisier and Dehorter, 1999; Boulkhssaim et al., 2006). The activities monitored were feeding, sleeping, swimming, grooming, flight, courtship, and antagonism (Houhamdi and Samraoui, 2001, 2002, 2008; Metallaoui et al., 2009).
We used R 3.5.2 (R Development Core Team, 2019) provided with the FactoMineR package. Data were expressed as mean ± SD for analysis. The Shannon and Weaver diversity index (H’) and equitability index (E) were calculated using ADE software (Chessel et al., 2004). Species are presented in the systematic order of Sibley and Monroe (1990). To conduct comparisons of diversity indices across the three sites, we applied the Kruskal–Wallis test (nonparametric alternative to ANOVA), first because our data did not meet the normality and homoscedasticity assumptions, and second to assess the difference in abundance across sites.
Phenology of species
During the wintering season, the three natural wetlands were visited by a total of 13 species showing different phenological status. Six species (46 %) were overwintering (Anas clypeata,
Anas penelope, Anas strepera, Tadorna tadorna, Aythya ferina, and Anas crecca crecca), three species (23 %) were sedentary nesting species (Anas platyrhynchos, Oxyura leucocephala and Aythya nyroca) and four (31 %) were occasional visitor species (passing visitors) (Anas crecca crecca, Marmaronetta angustirostris, and Anas querquedula) (table 2, fig. 2, dataset published through GBIF, Doi: 10.15470/fozdot).
Seasonal pattern of abundance
Throughout our regular counts between September 2019 and August 2020, we recorded considerable fluctuations in the population size of the Anatidae. The highest numbers were noted during January and February at all three sites. Tiffech hillside reservoir showed the largest populations, with a maximum of 1,002 individuals (fig. 3). The other two sites, El–kaf hillside reservoir and Madjen Djedj marsh, had lower numbers, hosting a maximum in January of 264 and 172 individuals, respectively. In this regard,we found a highly significant difference in abundance between sites (Kruskal–Wallis test, X2 = 90.151, P < 0.001) (fig. 4).
Variations of species richness
The difference in species richness between sites was significant (Kruskal Wallis test, X2 = 48.427, P < 0.01) (fig. 4). Highest richness was recorded at Tiffech hillside reservoir with a maximum of thirteen species, including twelve in January and February 2020. The lowest richness was recorded at Madjen Djedj marsh (10 species), with a maximum of nine in February.
Study of the rhythm of daytime activities
Monitoring the rhythm of the diurnal activities of Anatidae was dominated by sleeping, which represented almost half the time allocated to all behaviors (48.91 %). This activity was followed by swimming (18.82 %), then, respectively, grooming (13.91 %) and feeding activity (12.09 %). A small proportion of time was allocated to activities such as flight, courtship, and antagonism (fig. 5).
Analysis of the settlement structure
Throughout the study period calculation of the Shannon and Weaver diversity index (H’) indicated that Madjen Djedj marsh had the highest values, exceeding 2 bits, with a maximum of 2.67 bits in February. This maximum corresponds to a species richness of nine species for 155 individuals (fig. 6). Tiffech hillside reservoir presented low values of H’, which resulted in an imbalance in species abundance in the community where two species dominated the total abundance, namely the mallard (Anas platyrhynchos) and the common pochard (Aythya ferina). At most sites, equitability was recorded at the beginning of the wintering period and during the breeding period when the total numbers were represented by the mallard and the common or greater scaup.
The wetlands of the wilaya of Souk–Ahras retain are of high ecological value, particularly for the population of Anatidae, which they harbor year round. The richness of wintering and nesting waterbird species demonstrates the the crucial role of these sites in ecosystem functioning.
The Anatidae family is the third largest group in number of species in Algeria after the Rallidae and Podicipidae family. During our study, we identified thirteen species of birds; three regularly reproduce in these water bodies (Anas platyrhynchos, Oxyura leucocephala, and Aythya nyroca), and represent about half of the population of breeding Anatidae at the national scale, which is seven in Algeria (De Balsac and Mayaud, 1962; Isenmann and Moali, 2000). The presence of large numbers of the two endangered species, the black scaup (Aythya nyroca) and the white–headed duck (Oxyura leucocephala), which nest in very few areas at the national level (Boumezbeur, 1993; Houhamdi and Samraoui, 2002; Houhamdi et al., 2009; Metallaoui and Houhamdi, 2008, 2010; Aissaoui, 2009; Lazli et al., 2011a, 2011b; Chettibi et al., 2013) make these areas important sites for their conservation. Of particular note, we point out that most Algerian wetland complexes are frequented by 15 species of Anatidae (Chalabi and Belhadj, 1995; Mettallaoui and Houhamdi, 2010; Baaziz et al., 2011; Seddik et al., 2012; Boudraa et al., 2014; Elafri et al., 2017), which is similar to the number of species recorded at our sites. Besides the species richness, the studied sites harbored a large number of waterfowls, reaching a maximum number of 1,002 winter individuals.
Analysis of the phenological status of aquatic avifauna in this region showed that 46 % of the recorded species in these environments have a wintering status, giving the region the role of a favorable wintering area for aquatic avifauna, particularly for species that were observed at such time in large numbers, such as the mallard (Anas platyrhynchos), the white–headed duck (Oxyura leucocephala) and the common scaup (Aythya ferina). The availability and diversity of food resources and the variety of microhabitats in these three study sites provide not only the physical space but also the trophic niche and nesting site for 23 % of species that are considered sedentary nesters. These birds seem to prefer large open areas where they often present particular aggregation, probably seeking low disturbance conditions (Nilsson, 1970; Houhamdi and Samraoui, 2008).
The perennial water and the large size of the Tiffech hillside reservoir site probably explain the greater abundance of waterfowl therein. This was particularly the case for the mallard which is known as a generalist that feeds on emergent vegetation in reed beds and flooded grasslands (Krapu et al., 2006; Steen et al., 2006). Furthermore, the site receives a high rainfall, which is a pivotal environmental feature of wetlands to receive the largest and most diverse populations (Tamisier and Dehorter, 1999; Broyer, 2007; Cherkaoui et al., 2015).
The diurnal time budget monitoring showed a predominance of sleeping behavior, the most common behavior of waterfowl in wintering grounds during the day and a crucial phase to gain mass, reduce energy expenditure, and prepare for reproduction (for sedentary species) or migration (for migratory species) (Green, 1998; Costa and Bondi, 2002; Tucakov, 2005; Boumezbeur et al., 2005). Sleeping also allows these birds to minimize loss of body heat (Tamisier, 1972) in order to withstand the region’s occasional cold temperatures during a subhumid bioclimatic stage in a cold winter. The dominance of the sleeping behavior at our study sites indicates the fulfillment of the ecological conditions needed for the waterfowl to winter. Our results concerning the diurnal behavior confirm those previously recorded by Houhamdi and Samraoui (2008) and Metallaoui et al. (2014).
This study, carried out during an annual cycle in three wetlands of the wilaya of Souk–Ahras, helped us to collect important information on the community structure, phenology, and diurnal behavior of Anatidae so as to understand the ecological needs of local waterfowl and better manage these. The different phenological status among the thirteen recorded species highlights the role of these wetlands in welcoming a diverse community of waterbirds in the wintering, stopover, and breeding seasons. Daytime budgets are dominated by sleeping activity, indicating that these wetlands constitute an ideal refuge for the reception of these birds and, like all Algerian wetlands, play an important role in the transit of migratory birds (Houhamdi and Samraoui, 2001, 2002, 2008; Metallaoui et al., 2014; Merzoug et al., 2014; Amor Abda et al., 2015). The presence of two nesting species, Oxyura leucocephala and Aythya nyroca, protected by Algerian or international legislation, is also an indicator that these sites are of biodiversity importance and should be protected and managed. To this end, it is necessary to establish a management plan based on effective strategies involving law enforcement, surveillance, regular monitoring, and public awareness–raising for the protection of these threatened species.
We thank the reviewers for their comments and suggestions, Dr. Rassim Khelifa and Pr. Kerfouf Ahmed for their comments and suggestions on the manuscript, and the MERS and the DGRSDT for supporting and funding this work.