Podiceps Cristatus Research Articles

Factors affecting nesting success in the Great-crested Grebe Podiceps cristatus at Lake Tonga, north-east Algeria

The breeding ecology of the Great-crested Grebe Podiceps cristatus was investigated over four consecutive years (2009-2012) at Lake Tonga, north-east Algeria. In all four years, the egg-laying period was relatively short, spanning two months (end of March to end of May), and bimodal. Nests were mainly located in Phragmites australis, over water of substantial depth (178 ± 43 cm, N=209), far from the shore and in habitat with low vegetation cover (12.37 ± 7.67%, N=209). The overall clutch size was 3.73 ± 0.92 eggs (N=127) and it decreased marginally over time. The overall nesting success was 70.4% (N=209), with nest failure caused mainly by predation (65%) and flooding (23%). Breeding outcome was significantly and positively related to nest size, with bigger nests conferring better survival to eggs and young probably through affording better protection during spells of adverse weather. However, the benefits of bigger nests may be confounded by the age or intrinsic quality of birds. The location of nests in P. australis, rather than other vegetation types, increased nesting success marginally but significantly. Two cases of interspecific mixed clutches involving the Great-crested Grebe were recorded.

Host specificity and seasonality of helminth component communities in central European grebes (Podicipediformes) and loons (Gaviiformes)

Structure and pattern of helminth component communities parasitizing grebes and loons are poorly understood. Here we analyze the prevalence, intensity and diversity of helminths in 505 Czech grebes (Podiceps cristatus, Podiceps nigricollis, Tachybaptus ruficollis) and loons (Gavia arctica, Gavia stellata) collected between 1962 and 2014. The species richness of helminth component communities ranged from 31±8 (P. cristatus) to 50±4 (G. stellata) species, with helminth load similar in all five host species, but with strong differences in prevalence and intensity of infection at a helminth species-specific level. The dominance was low, ranging from 0.11 (P. cristatus and G. stellata) to 0.21 (P. nigricollis). Dominant species (>25% prevalence) in P. cristatus were Confluaria sp., Tylodelphys clavata, Echinochasmus coaxatus, Petasiger neocomense and Ligula colymbi; in P. nigricollis and T. ruficollis: Confluaria sp. and Tatria sp.; in G. arctica and G. stellata: Tetrabothrius microcephalus, Stephanoprora denticulata, Cryptocotyle concava, Diplostomum gavium and Ichthyocotylurus erraticus; in G. stellata only: Echinochasmus (Monilifer) spinulosus. Four (12%) of the grebe digenean species were not locally acquired (with non-sympatric intermediate hosts) despite the fact that they represented 25% of digenean individuals found. In loons, five (28%) of digenean species and striking 38% of individuals found used the non-sympatric intermediate host species. Component communities of grebes were similar to each other (Sørensen similarity index 0.47–0.65) but differed strongly from those hosted by loons (0.00–0.20). We present the first systematically collected evidence of intra-annual changes of helminth component communities in grebes, and provide 20 new host records.

Philip Arthur Dominic Hollom (1912-2014)

Philip Arthur Dominic Hollom (1912-2014)

Three echinostome species from wild birds in the Republic of Korea.

Three echinostome species, i.e., Patagifer bilobus, Petasiger neocomense, and Saakotrema metatestis, are newly recorded in the trematode fauna of the Republic of Korea. They were recovered from 3 species of migratory birds (Platalea minor, Podiceps cristatus, and Egretta garzetta), which were donated by the Wildlife Center of Chungbuk (WCC) and the Conservation Genome Resource Bank for Korean Wildlife (CGRB). Only 1 P. bilobus specimen was recovered from the intestine of a black-faced spoonbill (P. minor), and characterized by the bilobed head crown with a deep dorsal incision and 54 collar spines. Twenty P. neocomense were recovered from the intestine of a great crested grebe (P. cristatus), and they had a well-developed head crown with 19 spines and 2 testes obliquely located at the posterior middle of the body. Total 70 S. metatestis were collected from the bursa of Fabricius of 1 little egret (E. garzetta). It is characterized by stout tegumental spines covered in the entire leaf-shaped body, posterior extension of the uterus, presence of the uroproct and a well-developed head crown with 12 pairs of collar spines on each side. By the present study, these 3 echinostome species are newly added to the trematode fauna in Korea.

Fluctuations and trends in the numbers of staging waterbirds in south Sweden in September 1973–2013

Regular September counts of staging waterbirds have been undertaken annually in south Sweden since 1973 as a complement to the International Midwinter Counts undertaken in January each year since 1967. The September counts aim to cover the population development of staging waterbirds, especially relating to species that are not wintering in the country. Between 150 and about 200 sites have been included in the calculation of the September indices, using the TRIM method. September indices were calculated for 18 species. The trends over the entire 41-year period were significantly increasing for all but five species (Anas platyrhynchos, Somateria mollissima and Mergus serrator decreasing, whereas Podiceps cristatus and Fulica atra did not show any clear long-term trend). The September indices were in good agreement with the International Midwinter Counts and the winter counts of the Swedish Bird Survey, but much less well with migration counts at Falsterbo and breeding season counts of the Swedish Bird Survey. For the last ten years of the series, six species showed a significantly increasing trend, whereas four species decreased.

Spatio-temporal dynamics in waterbirds during the non-breeding season: Effects of local movements, migration and weather are monthly, not yearly

Predicting population sizes and dynamics of mobile organisms is important for trend estimation, but this is difficult when the origin of individuals cannot be determined, i.e. residents and migrants are indistinguishable in the field.Here we examine fluctuations in populations during the non-breeding season (autumn to spring) of seven waterbird species, which co-occur on 122 neighbouring water bodies in south-west Germany. We asked whether site-level abundance patterns can be predicted by weather variables, and whether these effects vary over months and years. We used a spatially explicit hidden Markov model to estimate the effects of local and regional movement on population fluctuations.Although the species varied in their dynamics, with different amounts of movement estimated between sites, several patterns were common across species: density effects were highly month-specific, but with little variation in the strength of effects over years. The abundance of most species was positively related to temperature, especially in winter.The common teal Anas crecca and common pochard Aythya ferina were the most site-fidelic species once they were present in the study area, but also exhibited the strongest regional migration. The mallard Anas platyrhynchos, tufted duck Aythya fuligula and great crested grebe Podiceps cristatus each behaved more like a single population, as individuals more frequently moved between sites and abundance fluctuations at sites were not explained by migratory movements alone.Our study shows that the strength of population parameters and environmental forces can be decomposed into monthly and yearly effects. Estimating the unknown origin and movement of individuals may show that commensurate populations of mobile species may have different underlying dynamics, while responding similarly to environmental factors.

Nest and nest site characteristics of the Great Crested Grebe (Podiceps cristatus) on intensively managed fishponds: an example from Bohemia

Selected data of nest biology of the Great Crested Grebe (Podiceps cristatus) (Aves Podicipediformes) in specific fishpond conditions in the Protected Landscape Area and Biosphere Reserve Třeboňsko (Czech Republic) were analysed. An interdependence of dimensions of the nesting dent was found: the wider the dent, the deeper it was. A positive correlation was also found between the total nest height and the nest height above water level. Differences in most measured characteristics in relation to the number of eggs were not found (the positive correlation with the width and depth of the nest dent only). A positive correlation between the distance from the nearest nest and the water depth was found. The results also suggest a relationship between the distance of the nearest nest and the distance from the free water level, as well as between the water depth near the nest and the nest distance from the free water level. Nests near the shore were denser than nests on the free water level. The mutual distance of the nearest nests was linked to the location of vegetation and water depth. In the case of group nesting of more pairs, no inclination to form spatial clusters or regularity in deployment was found. These observations confirmed the ability of Great Crested Grebe to adapt to the specific environmental conditions of intensively managed fishponds including higher nesting density.

Intraspecific kleptoparasitism in flock-fishing Great Crested Grebes (Podiceps cristatus) and Great Cormorants (Phalacrocorax carbo) – a cost to participants?

Abstract Intraspecific kleptoparasitism was studied in flock-fishing Great Crested Grebes Podiceps cristatus during May and June 2011 and in Great Cormorants Phalacrocorax carbo during September 2011 and August 2012 at Lake Krankesjön, South Sweden, for a total of c.11 h for grebes and c.6 h for cormorants. Only attempts to steal large fish (relative to a bird’s gape) were recorded, because small fish mostly did not elicit kleptoparasitic attempts and those seen appeared never to be successful. Attempts to steal large fish were rare, 0.14 h-1 grebe-1 (N = 96) and 0.39 h-1 cormorant-1 (N = 163). In both species, the host lost its fish in about 20% of cases. Based on the observed low parasitism and success rates, it is concluded that kleptoparasitism was a minor cost of participating in flock-fishing

Evolution of displays within the pair bond

Although sexual selection is an important cause of display evolution, in socially monogamous species (e.g. many birds), displays continue after formation of the pair bond. Here, we consider that these displays evolve because they stimulate the partner to increase investment in offspring. Our study is motivated by elaborate mutual displays in species that are largely monomorphic and have long-term pair bonds (e.g. the great crested grebe, Podiceps cristatus) and by many empirical results evidencing that display manipulation affects parental investment. Using population genetic models, we show that a necessary condition for the permanent establishment of mutual displays in the pair bond is that the benefit of investment by the pair is more than twice that resulting from investment by a single individual. Pre-existing biases to respond to displays by increased investment are a necessary component of display evolution. We also consider examples where one sex (e.g. males) stimulates increased investment in offspring by the other sex. Here, display and additional investment cannot evolve permanently, but can increase and linger at high frequency for a long time before loss. We discuss how such transient effects may lead to the evolution of permanent displays as a result of evolution at additional loci.

Further studies on Contracaecum spasskii Mozgovoi, 1950 and C. rudolphii Hartwich, 1964 (sensu lato) (Ascaridida: Anisakidae) from piscivorous birds in China

Contracaecum spasskii Mozgovoi, 1950, collected from the great crested grebe Podiceps cristatus (Linnaeus) (Podicipediformes: Podicipedidae), is redescribed using both light and, for the first time, scanning electron microscopy. Contracaecum spasskii differs from its congeners by having marked transverse cuticular annulations, the length of the oesophagus and spicules, the ratio between the intestinal caecum and the ventricular appendix, the number and arrangement of male caudal papillae, and especially by the particular morphology of the lips and interlabia. Some previously unreported morphological features of C. spasskii are also revealed and others corrected. Contracaecum rudolphii Hartwich, 1964 (sensu lato) is also redescribed based on the specimens collected from the great cormorant Phalacrocorax carbo sinensis (Blumenbach) (Pelecaniformes: Phalacrocoracidae) from China. Based on the geographical perspective, the present Chinese material may represent the species C. rudolphii B.

First detection and genotyping of human-associated microsporidia in wild waterfowl of Slovakia

A total of 47 avian faecal samples of wild waterfowl (great cormorant - Phalacrocorax carbo, great crested grebe - Podiceps cristatus, white stork - Ciconia ciconia) trapped in the eastern Slovakia were screened for the presence of human pathogenic microsporidia by microscopy and real-time SYBR Green PCR method using species primers and sequenced. Microscopic analysis showed presence in 32 samples (29 cormorants, 3 dippers). Microsporidial DNA (Encephalitozoon cuniculi genotype I) was identified in 19 faeces samples (40.4%) namely cormorants in 17 out of 40, one dipper of 5 and a stork out of 2. The present work describes three new host species of the bird population in microsporidium Encephalitozoon cuniculi genotype I which confirms the theory of low specificity of this species.

Sex Determination in 58 Bird Species and Evaluation of CHD Gene as a Universal Molecular Marker in Bird Sexing

The aim of this research was to test the CHD gene (Chromo Helicase DNA-binding gene) as a universal molecular marker for sexing birds of relatively distant species. The CHD gene corresponds to the aim because of its high degree of conservation and different lengths in Z and W chromosomes due to different intron sizes. DNA was isolated from feathers and the amplification of the CHD gene was performed with the following sets of polymerase chain reaction (PCR) primers: 2550F/2718R and P2/P8. Sex determination was attempted in 284 samples of 58 bird species. It was successful in 50 bird species; in 16 of those (Alopochen aegyptiacus, Ara severus, Aratinga acuticaudata, Bucorvus leadbeateri, Cereopsis novaehollandiae, Columba arquatrix, Corvus corax, C. frugilegus, Cyanoliseus patagonus, Guttera plumifera, Lamprotornis superbus, Milvus milvus, Neophron percnopterus, Ocyphaps lophotes, Podiceps cristatus, and Poicephalus senegalus), it was carried out for the first time using molecular markers and PCR. It is reasonable to assume that extensive research is necessary to define the CHD gene as a universal molecular marker for successful sex determination in all bird species (with exception of ratites). The results of this study may largely contribute to the aim.

Numerical and behavioral responses of waterfowl to the invasive American mink: A conservation paradox

A behavioral response is usually the first adaptation of animals to environmental changes such as the introduction of an alien invasive species, and it seems to be the most important factor in reducing the negative impact of new predators on naive prey. This study examined changes in the abundance and behavior of breeding coots (Fulica atra) and great crested grebes (Podiceps cristatus) in response to invasion of the Mazurian Lakeland (NE Poland) by American mink (Neovison vison), first recorded here in 1984. Feral mink densities varied from 1.0 to 14.6 individuals per 10km of shoreline. Mink were responsible for the losses of 17–58% of experimental clutches (artificial nests containing chicken eggs) that were deployed. Mink destroyed more experimental clutches than other predators; the effects of mink predation were similar in reeds and on the bank. Radio-tracking showed that mink avoided lake banks near human settlements. Mink have markedly affected the breeding distribution of both species and caused a greater than 20-fold decline in coot numbers. For coots and grebes breeding distribution and nesting success were positively associated with built-up areas along lake shores and also with whether the birds were breeding in colonies. Increased brood survival of coots and grebes near human settlements is a paradox in the sense that a man-made habitat change has provided refuge from an alien predator.

The Visitation Aspect of Great Crested Grebe (Podiceps cristatus) in the Long Period at Nakdong Estuary, Busan, Republic of Korea

This study was conducted in order to analyze the long-term arrival pattern of the great crested grebe (Podiceps cristatus) in the Nakdong River estuary area, where undergoes rapid environmental changes, by studying the data of early 1990s (between May of 1989 and April of 1993) and the data of mid-2000s (between May of 2002 and April of 2006). The result of data analysis of 8 years showed that, of the total 2,873 members of the family Podicipedidae, there were 908 individuals (31.60%) of the great crested grebe (Podiceps cristatus) observed in the Nakdong River estuary area. The analysis of early 1990s and mid-2000s showed that, in terms of early 1990s, while a small number was observed in October, the number of birds arriving began to increase in November, with the highest number observed in December. In mid-2000s, the smallest number was observed in October, with the number of birds arriving increasing in November and the highest number observed in December. Monthly average number of individuals was approximately 1.7 times higher in 2000s than in 1990s. In terms of the number of individuals per month, there was no significant difference between the time period between November and March of early 1990s and mid-2000s (P<0.343). The average number of individuals per region of the great crested grebe in mid-2000s (between May of 2002 and April of 2006) was 38.53 individuals, and there was no significant regional difference (P<0.075), with 5.00 individuals in Daema-deung (DMD), 6.00 individuals in Jangja, Shinja-do (JJ.SJD), 4.67 individuals in Saja, Doyo-deung (SJ.DY), 6.00 individuals in lower Ulsuk-do (LUD) and 129.50 individuals in Ulsuk-do (USD). Since the great cormorant, a diving bird species which feeds on fish, use lower Ulsuk-do (LUD) and Saja, Doyo-deung (SJ.DY) as foraging and resting ground, it is assessed that the great crested grebe, which is smaller than the great cormorant, use Ulsuk-do, the region right below the estuary dam, as their habitat.

Fishing Flocks of Great Crested GrebesPodiceps cristatusConsist of Breeding Birds

This note corrects a statement made in an earlier note on flock-fishing Great Crested Grebes Podiceps cristatus at the South Swedish Lake Krankesjon, namely that the flocks presumably consisted mainly of non-breeders. This has been proved wrong. The majority come from a loose colony and consist of birds during incubation recesses. Flock-fishing started around 1 May in 2008, 2009 and 2011, but not until the beginning of June in 2010. The reason for the late start in 2010 is unclear. Flocks formed soon after sunrise and dissolved at various times during the day. Only once was a fishing flock seen in early evening.

Waterbirds Wintering on the Crimean Peninsula Coast of the Black Sea

Abstract. As the importance of the Black Sea for wintering waterbirds is poorly known, the species composition and abundance of waterbirds wintering on the Crimean Peninsula coast (Northern Black Sea) was investigated in two habitat types: urban areas and open sea coast. Of 27 waterbird species, 25 were recorded in urban areas, and the dominants were Coot (Fulica atra), Black-headed Gull (Larus ridibundus) and Common Gull (Larus canus). On the open sea coast, fifteen species were recorded, the dominants being Coot, cormorants (Phalacrocorax carbo and Phalacrocorax aristotelis) and Great Crested Grebe (Podiceps cristatus). The species structure of the wintering waterbird community differed significantly between habitats. A trait of the open sea coast community was the high diversity and domination of diving ichthyophagous species. Waterfowl were recorded only in urban areas, which increased species diversity in this habitat. The number of birds wintering on the open sea coast was significantly lower than i...

Variations in Nest-Site Parameters in Breeding Waterbirds at Lake Zarivar, Western Iran

Variations in nest-site parameters were studied at Lake Zarivar, Kurdistan Province, Western Iran in 2007 and 2008. This study was applied for six breeding waterbird species: Great-crested Grebe (Podiceps cristatus), Little Grebe (Tachybaptus ruficollis), Moorhen (Gallinula chloropus), Coot (Fulica atra), Water Rail (Rallus aquaticus) and Whiskered Tern (Chlidonias hybrida). A total of 205 nest-sites were studied in terms of five environmental factors: vegetation density and height, water depth, distance to open water, as well as distance to the nearest nest of the conspecific species were measured. Great-crested Grebes selected areas of deeper waters, possibly to increase feeding efficiency. All species were directly dependent on water for nesting, except for the Water Rail, which established its nest in muddy areas with higher vegetation density and height. Nests were at a higher density for the Whiskered Terns than in other species. Overall, mean water depth at nesting sites was lower in the 2008 breeding season and total breeding population of waterbirds decreased. Evaluating and monitoring of habitat quality of breeding species urges conservation measures with regard to transformations occurring at this freshwater lake ecosystem.

Seasonal Patterns of Aggressiveness in Colonial Great Crested GrebesPodiceps cristatus

Konter A. 2011. Seasonal patterns of aggressiveness in colonial Great Crested Grebes Podiceps cristatus. Ardea 99: 85–92.In birds, coloniality is considered to be evolutionary more advanced than solitary breeding. Territorial Great Crested Grebes Podiceps cristatus may engage in opportunistic colonial breeding. The present study focuses on behavioural aspects associated with clumped nesting. Based on the assumption that different agonistic interactions may trigger different costs, aggressiveness during colony establishment and subsequent nesting in the Great Crested Grebe was measured. Upon platform initiation, focal pairs claimed a territory by performing intense platform courtship. With agonistic behaviour they tried to prevent additional conspecifics from settling in their direct vicinity. As a consequence, early levels of aggression in the entire colony increased with the numbers of settled pairs. Quite quickly however, aggressiveness declined despite additional pairs settling and long before the maximum number of platforms for a particular year was reached. Two main phenomena may have contributed to the decline in aggression. First, colonial Great Crested Grebes could have been conducting behaviour consistent with the ‘dear-enemy-effect’. Second, habituation to or accommodation with new neighbours could have been helped by behavioural adaptations. Focal pairs provided evidence for a relationship between aggression and egg-laying. The aggressive behaviour that was observed after clutch initiation could have been an effort to reduce the risk of intraspecific brood parasitism. Thereafter, fighting was uncommon and aggression was greatly limited to ritualized threatening. Aggression levels were higher in areas of high nesting density prior to and during egg-laying, but no longer so after clutch completion. It is concluded that colony establishment in the Great Crested Grebe is not an index of the species' sociability, but rather expresses its phenotypic plasticity to adapt to close neighbours and to contain its aggressiveness.

Clade 2.3.2 Avian Influenza Virus (H5N1), Qinghai Lake Region, China, 2009–2010

To the Editor: In 2005, a large population of wild migratory birds was infected with highly pathogenic avian influenza (HPAI) virus (H5N1) in the Qinghai Lake region of western People’s Republic of China, resulting in the death of ≈10,000 birds (1,2). On the basis of phylogenetic analysis of the hemagglutinin (HA) gene, the virus was classified as clade 2.2 according to the World Health Organization guidelines. Subsequently, viruses from this clade were found in Mongolia, Russia, Europe, and Africa along the migratory flyways of birds (3,4). This unique distribution of the same clade of HPAI virus (H5N1) through different migratory routes indicates that migratory birds might play a global role in virus dissemination (3,4). In 2006, viruses from the same clade were isolated in the Qinghai Lake region (3). Analysis of viral outbreaks along migratory flyways demonstrated a similar outbreak pattern for the past 4 years (2006–2009) (5). During that period, clade 2.2 avian influenza virus (H5N1) was isolated in China, Mongolia, Russia, Germany, Egypt, and Nigeria; all viruses were closely related to the Qinghai Lake virus. Despite the broad distribution of clade 2.2 viruses in migratory flyways, few isolates of clade 2.2 viruses in local domestic poultry were reported, especially in China (6). Outbreaks of these viruses were reported in poultry in Africa (7). The reason these viruses rarely cause outbreaks in poultry is unknown. During May–June 2009 and 2010, several dead migratory birds were found in the Qinghai Lake region. Nine HPAI viruses (H5N1) were isolated in 2009 and 2 were isolated in 2010 from great cormorants (Phalacrocorax carbo), brown-headed gulls (Chroicocephalus brunnicephalus), great black-headed gulls (Ichthyaetus ichthyaetus), great-crested grebes (Podiceps cristatus), and bar-headed geese (Anser indicus) and serotyped as described (3). HA genes from all 11 isolates were subsequently amplified by using reverse transcription–PCR and sequenced. Phylogenetic analysis of HA sequences and an additional HA gene sequence from the 2009 Qinghai Lake subtype H5N1 virus isolate from a great crested grebe (from the National Avian Influenza Virus Reference Laboratory, Harbin, China) (GenBank accession no. {type:entrez-nucleotide,attrs:{text:CY063318,term_id:301015462,term_text:CY063318}}CY063318) showed that HA genes from all 12 viruses clustered as clade 2.3.2 (Figure); none clustered with clade 2.2 viruses. Additionally, the HA cleavage site in the new isolates is PQRERRRKRG, which is identical to that of clade 2.3.2 viruses. In clade 2.2, the cleavage site is PQRERRRKKRG. Figure Bootstrapped (1,000×) maximum likelihood phylogenetic tree of hemagglutinin genes of avian influenza viruses (H5N1), People’s Republic of China, 2009–2010. Viruses isolated from the plateau pika near Qinghai Lake are indicated ... A bootstrap (1,000×) maximum likelihood tree (8) also demonstrated that Qinghai 2009 and 2010 virus isolates are closely related to those isolated in Mongolia and Uvs Nuur Lake in 2009, as reported by Sharshov et al. (5). Qinghai Lake and Uvs Nuur Lake, which are found along the migratory flyway in central Asia, are major lakes for bird migration and breeding. Many birds fly from Qinghai Lake to Uvs Nuur Lake in the spring. If one considers isolation date and bird species infected, viruses isolated in Mongolia and Russia and our isolates were likely transmitted between the 2 lake regions by bird migration. Moreover, HA sequences are closely related to viruses isolated from wild birds in Hong Kong and Japan during 2007–2008, which are the most recent isolates of clade 2.3.2 viruses before isolation of 2009 Qinghai Lake viruses. These results indicate that viruses in the Qinghai Lake region may be transmitted by wild birds along the migratory flyway in eastern Asia. However, there is no evidence that avian influenza virus (H5N1) is transmitted from eastern Asian (inner China or across the Himalayas) to the Qinghai Lake region. The 2009 and 2010 Qinghai Lake viruses are related to various viruses isolated from plateau pikas near Qinghai Lake (9). In 2007, clade 2.2 and clade 2.3.2 viruses were isolated from plateau pikas, but no clade 2.3.2 viruses were found in aquatic birds. Wild birds, pikas, and other animals near Qinghai Lake share the same environment, and viruses may be transmitted across species. However, surveillance data are limited for wild animals near Qinghai Lake. Therefore, further investigations need to be conducted to clarify relationships among birds, animals, and influenza viruses near Qinghai Lake. Our results and those of Sharshov et al. (5) show that in 2009 HPAI virus (H5N1) began infecting birds along the migratory route near Qinghai Lake and changed from clade 2.2 viruses to clade 2.3 viruses. New outbreaks of HPAI viruses (H5N1) along this migratory flyway should be investigated.

Estimation du nombre total des oiseaux aquatiques hivernant en Tunisie : période 2001/2002 à 2006/2007

Estimating the total number of wintering waterbirds in Tunisia : period 2001/2002 to 2006/2007 Over the past decades, many waterbird populations have undergone rapid changes in numbers as well as in distribution. These continuing changes make it necessary to update population estimates on a regular basis. From this point of view, a regular mid-winter survey of wintering waterbirds was carried out in Tunisian wetlands. The overall objective of this paper is to record wintering population sizes for the period 2001–2002 to 2006-2007 and to identify waterbird indicator species relative to these Tunisian ecosystems. The preliminary analysis of the collected information enabled us to define the size and the actual status of wintering waterbird populations in Tunisia. A total richness of 106 species (3 common, 18 frequent and 85 rare ones), belonging to 23 families and 10 orders, was identified. The most abundant species, which accounted for about 90 % of the total abundance, were : Calidris alpina (18.7 %), Phoenicopterus ruber (13.6 %), Aythya ferina (11.4 %), Fulica atra (10.7 %), Tringa totanus (5.9 %), Larus michahellis (5.2 %), Larus genei (3.9 %), Anas penelope (3.7 %), Calidris minuta (3.5 %), Anas clypeata (2.2 %), Larus ridibundus (2.0 %), Charadrius alexandrinus (1.9 %), Phalacrocorax carbo (1.6 %), Vanellus vanellus (1.4 %), Pluvialis squatarola (1.3 %), Anas platyrhynchos (1.3 %), Anas crecca (1.3 %) and Numenius arquata (1.1 %). With an average of about 427 300 birds per year, Tunisian wetland areas play an important role in waterbird populations conservation due to their large habitats, high productivity and geographical position connecting European and African continents. Considering the Ramsar Criterions, a total of 20 sites appear as internationally important. Indeed, 3 sites individually and regularly held more than 20 000 birds and should be classified as internationally important : Kneiss islands (72 368 birds per year), Ichkeul National Park (91 587 birds per year), and sebkhat Sejoumi (29 276 birds per year). Together, these wetlands host about 45 % of the total national population sizes. Three other sites are also potentially important, recorded as hosting more than 20 000 wintering birds at least once : Kerkennah islands (16 608 birds per year), Jerba island (14 962 birds per year) and sebkhat Ariana (19 122 birds per year). The 1 % threshold for use in Ramsar Convention was met for 14 species (Sterna sandvicensis, Larus genei, Platalea leucorodia, Grus grus, Charadrius alexandrinus, Phoenicopterus ruber roseus, Pluvialis squatarola, Calidris minuta, Calidris alpina, Tringa totanus, Anser anser, Anas penelope, Aythya ferina and Fulica atra) and was exceeded in 10 wetlands. Among all species, 6 are globally threatened (Marmaronetta angustirostris, Aythya nyroca, Oxyura leucocephala, Gallinago media, Limosa lapponica and Larus audouinii) and were regularly observed in 10 sites. Application of the global ANOVA Kurskal-Wallis test to data relative to species richness, mean abundance and Hill (N1 and N2) diversity values reveals highly significant differences between the 8 wetland classes. However, the spatial organization of aquatic birds doesn’t reflect any clear gradient. The ANOSYM test discriminates two major associations : artificial versus natural habitats. The latter are themselves organized into 3 sub-associations according to permanence of water and marine influences. Despite these important carrying capacities of Tunisian wetlands, natural factors and human exploitation have greatly modified many of these ecosystems through habitat loss and fragmentation. Thus, it appears essential to use appropriate strategies, like indicator species method, to enhance the value of these areas for waterbird species, which are very sensitive to habitat changes. In the present case, based on the SIMPER analyses method, 15 species are indicators of the wetland status : Phoenicopterus ruber, Charadrius alexandrinus, Calidris alpina, Larus michahellis, Ardea cinerea, Bubulcus ibis, Ciconia ciconia, Vanellus vanellus, Grus grus, Phalacrocorax carbo, Larus genei, Fulica atra, Tachybaptus ruficollis, Aythya ferina, Podiceps cristatus and Anas platyrhynchos. Besides their fundamental interest and importance, results of the present study can be essential to the application of conservation programs.