Yves Kayser

Are ricefields a good alternative to natural marshes for waterbird communities in the Camargue, southern France?

Abstract Rice cultivation has frequently been suggested to provide an important wetland habitat for waterbirds. However, in contrast to most other regions of the Mediterranean, the Camargue still has a substantial amount of surface area of natural marshes. Thus, we compared the abundance, species richness, and community composition of waterbirds in ricefields and natural marshes of the Camargue, during a one-year study. Based on surveys conducted at 4–7 day intervals in 1997–1998, our results suggest that natural marshes had substantially greater abundance of waterbirds, with ca. 99% of the individuals having been observed in natural marshes. Estimates of species richness and associated parameters further indicated that ricefields were clearly less rich than natural marshes. Although our results were rather striking for the Camargue, they may not be applicable to other regions because of the relatively high availability of natural marshes and differences in management of ricefields.

Influenza A Virus in Birds during Spring Migration in the Camargue, France

Wild aquatic birds are considered to be the natural reservoir for influenza A viruses, and previous studies have focused mainly on species in the orders Anseriformes and Charadriiformes. In this study, we surveyed a larger spectrum of potential hosts belonging to 10 avian orders. Cloacal swabs (n=1,044) from 72 free-living bird species, were analysed by reverse transcription-polymerase chain reaction for the presence of avian influenza virus. Only two Mediterranean Gulls (Larus melanocephalus) tested positive; one of these viruses was identified as an H9N2 subtype. The absence of infection among passerine birds supports the idea that the prevalence of avian influenza virus infection in terrestrial species is low.

INFLUENCE OF ENVIRONMENTAL AND DENSITY-DEPENDENT FACTORS ON REPRODUCTION OF LITTLE EGRETS

Abstract We evaluated the influence of environmental and density-dependent factors (intraspecific and interspecific) on clutch size, brood size, and nesting success of Little Egrets (Egretta garzetta) in the Camargue of southern France. We recorded these reproductive parameters in most years from 1970 to 1998. We used a generalized linear modeling approach (model selection based on AIC) to examine the environmental effects of spring rainfall, winter temperature, and wind on these parameters. We also examined density dependence of these parameters based on the total number of Little Egrets and the total number of tree-nesting herons nesting in these mixed-species colonies. Clutch size was positively associated with rainfall and negatively associated with the number of Little Egret nests in the Camargue. Brood size was negatively associated with the number of Little Egret nests, although rainfall was only significant as an interaction effect with these two effects. Nesting success was negatively associated with the number of tree-nesting herons, the proportion of each colony consisting of Cattle Egrets (Bubulcus ibis), wind speed, and several interactions among these variables. Virtually all of the reproductive parameters that we evaluated were negatively associated with the number of Little Egret nests or the number of tree-nesting herons. Anecdotal evidence suggests that Cattle Egrets displace Little Egrets at some centrally located nest sites. Such sites are better protected from strong winds, which are a common cause of nesting failure.

Prevalence of West Nile virus neutralizing antibodies in wild birds from the Camargue area, southern France.

The Camargue area of southern France experienced the re-emergence of West Nile Virus (WNV) in the late summer of 2000 and 2004. Immediately preceding the 2004 outbreak, samples were collected from 432 birds of 32 different species captured in mist nets and from 201 Cattle Egret (Bubulcus ibis) nestlings sampled in their nests between 1 April and 12 June 2004. West Nile virus neutralizing titers of ≥40 were detected in 4.8% (95% confidence limit, 2.9–7.5%) of the adult birds and in 1.6% (0.3–4.6%) of the egret nestlings. Migratory passerines had a higher prevalence of WNV neutralizing antibodies (7.0%) than did resident and short-distance migratory passerines (0.8%), suggesting exposure to WNV or a related flavivirus during overwintering in Africa.

Avian Influenza Circulation in the Camargue (South of France) During the 2006–07 Season

Abstract Situated at the crossroads of numerous migratory routes of Palaearctic birds, the Camargue is considered a high-risk area for the introduction and transmission of numerous avian-borne pathogens. We investigated the epidemiologic cycles of avian influenza viruses (AIVs) in the local bird community by performing regular sampling on a large variety of bird species during 11 consecutive months in 2006–07. To detect the presence of AIV, SYBR green reverse transcriptase–PCR targeting the M gene was performed on 2901 samples from 66 bird species. A clear seasonal pattern of AIV circulation in ducks was observed during autumn and winter, with higher prevalence rates in early fall. Our results also support an absence of circulation of AIV in passerine birds during spring and the wintering periods. Finally, even if the prevalence of infection was very low, AIVs were found in gulls in breeding colonies, indicating a possible specific circulation in spring in these birds.

Nestling size rank in the little egret (Egretta garzetta) influences subsequent breeding success of offspring

Abstract Few studies have investigated the long-term fitness consequences of nestling size hierarchies in altricial birds. In this study, we investigated whether or not the size rank order of siblings influences subsequent breeding success in the little egret, Egretta garzetta. From a marking program allowing individual recognition of wild birds, we obtained data on the breeding success of 56 pairs comprising individuals for which the size rank order was known. The breeding success in these pairs was positively influenced by the age of the marked bird but negatively affected by the laying date of the pair and the size rank order of the marked individual. There was also a significant difference between breeding colonies. We suggest two main hypotheses for a link between size rank order of individuals and their breeding success and we discuss our results in relation to current hypotheses on the adaptive value of hatching asynchrony.

Variability in breeding parameters of the Squacco Heron Ardeola ralloides

Capsule Breeding parameters and body condition of chicks varied with colony sites. Aims To investigate variations of breeding parameters and chick body condition. Methods In 2000, marked nests (n = 86) were surveyed weekly at four colonies and each nestling was measured and weighed. Nest survival probabilities during the egg and nestling periods were estimated, and the number of fledglings per breeding attempt were estimated and compared between colonies. Results The mean clutch size of all colonies combined was four eggs but varied significantly (Kruskall–Wallis = 10.4, P = 0.01) between colonies. Daily nest survival probabilities during the egg and nestling periods were constant across colonies and were 0.983 (± 0.005 se) and 0.999 (± 0.009 se), respectively. Nest survival during the entire breeding period was 0.7. The number of fledglings per breeding attempt was 1.8 (± 0.02 se) and varied between colonies. The body condition of chicks varied with colony site and size rank of chicks in the brood hierarchy, i.e. the first hatched having a better condition. Conclusions The differences between colonies were mostly in laying date, clutch size, number of fledglings per breeding attempt and chick condition. We conclude that breeding parameters need to be monitored over several breeding colonies in order to obtain reliable estimates.

Detection probability of nests of Squacco Herons in southern France

Abstract The double observer approach with marked nests was used in southern France for estimating the detection probability of nests of the Squacco Heron (Ardeola ralloides), a cryptic species in its breeding behavior. Results indicate that the detection probability varied from 0.518 to 0.700 between observers. The overall detection probability, i.e., the probability that a nest was detected by at least one observer, was 0.856. Given a total of 66 nests found by both observers during the surveys, the breeding population was estimated at 77 nests. Since previous estimates of the Squacco Heron breeding population size did not take into account detection probability, we suggest that the breeding population is larger than previously thought in the Camargue and in other European breeding localities.

Satellite-Tracking Migrating Juvenile Purple Herons Ardea purpurea from the Camargue Area, France

Migratory movements of juvenile Purple Herons from the Camargue area in France were studied by satellite-tracking. Six juvenile birds were fitted with transmitters in early July 2004. Of these six, four successfully started migration in September. Tracked birds followed a western migratory route, heading out south-south-west, towards Spain, the Balearic Islands and then Algeria. They pursed their flight either south-west to the Moroccan Atlantic coast or straight to Mauritania, flying over the Sahara desert. Flight speed could be estimated for one of the birds and was about 40 kilometres per hour. The results of this study are consistent with previous ring recovery data and provide additional knowledge on the speed and departure date of juvenile Purple Herons during autumn migration.

Fluctuations in chick diet of the Squacco Heron Ardeola ralloides in southern France: changes over the last 30 years

Capsule The composition varied between colony site, month and year. Aims To determine the diet composition of chicks and its variations in 2000 and 2001. To look for any changes over the last 30 years. Methods Chick regurgitates were analysed to determine which Order contributed most to the diet, by frequency and by biomass. Results During 2000 and 2001 chick diet was dominated by insects (92% and 70% by biomass, respectively), mainly Coleoptera (60% and 41%) and Orthoptera (27% in both years). The dry mass of Orthoptera, Coleoptera adults, Odonata and amphibians differed significantly between breeding sites, months and years.The proportion of invertebrates (in biomass) increased from 36.5% in 1970 and 31% in 1971 to 95% in 2000 and 90% in 2001 whereas the proportion of amphibians decreased in the same time from 49% and 33% in 1970 and 1971 to 5.0% and 9.5% in 2000 and 2001, respectively. Conclusion The proportion of prey types differed bewteen colony sites and months. Major changes were found in the diet composition between the early 1970s and 2000s. The possible hypotheses for the observed differences are discussed.