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Breeding birds in agricultural landscapes have declined considerably since the 1950s and the beginning of agricultural intensification in Europe. Given the increasing pressure on agricultural land, it is necessary to identify conservation measures that consume little productive land. We tested the hypothesis that field margins represent substitute habitats for bird species in agricultural wetlands. We monitored bird species in 86 crop fields in rice paddy landscapes of Camargue (southern France), a wetland of international importance for birds. We investigated whether the area of three types of field margins (grass strips, hedgerows and reed strips) within a 500 m buffer around each studied crop field had an effect on the abundance of three groups of birds defined based on their primary habitat (reedbeds, grasslands, and forest edge species). We controlled for the area of each semi-natural habitat (wetlands, grasslands, and woodlands), crop diversity and mean crop field size. Our study confirms that bird guilds are favored by the cover of their primary habitat but are also influenced by the cover of field margins. Reedbed birds are favored by the cover of wetlands and reed strips, grassland birds are favored by the cover of grasslands and wetlands and negatively impacted by the cover of woodlands and hedgerows, while forest edge birds are favored by the cover of hedgerows and negatively impacted by the cover of reed strips. These results suggest that field margins may represent substitute habitats for reedbed and forest edge bird species and highlight their importance for biodiversity conservation in wetland agricultural landscapes. However, our results also suggest that increasing the area of hedgerows and reed strips may have a negative effect on grassland birds and forest edge birds, respectively. Recommendations for field margin management in agricultural wetlands should therefore be tailored to local conservation priorities.

International audience; Functional dispersal (between-site movement, with or without subsequent reproduction) is a key trait acting on the ecological and evolutionary trajectories of a species, with potential cascading effects on other members of the local community. It is often difficult to quantify, and particularly so for small organisms such as parasites. Understanding this life history trait can help us identify the drivers of population dynamics and, in the case of vectors, the circulation of associated infectious agents. In the present study, functional dispersal of the soft tick Ornithodoros maritimus was studied at small scale, within a colony of yellow-legged-gulls (Larus michahellis). Previous work showed a random distribution of infectious agents in this tick at the within-colony scale, suggesting frequent tick movement among nests. This observation contrasts with the presumed strong endophilic nature described for this tick group. By combining an experimental field study, where both nest success and tick origin were manipulated, with Capture-Mark-Recapture modeling, dispersal rates between nests were estimated taking into account both tick capture probability and survival, and considering an effect of tick sex. As expected, tick survival probability was higher in successful nests, where hosts were readily available for the blood meal, than in unsuccessful nests, but capture probability was lower. Dispersal was low overall, regardless of nest state or tick sex, and there was no evidence for tick homing behavior; ticks from foreign nests did not disperse more than ticks in their nest of origin. These results confirm the strong endophilic nature of this tick species, highlighting the importance of life cycle plasticity for adjusting to changes in host availability. However, results also raise questions with respect to the previously described within-colony distribution of infectious agents in ticks, suggesting that tick dispersal either occurs over longer temporal scales and/or that transient host movements outside the breeding period result in vector exposure to a diverse range of infectious agents.

International audience

International audience; Three nestlings of Spoonbill ringed in spring 2016 in the Camargue were resighted on 30 November 2016 in the Bahr El Ghazal province in South Sudan located at some 4 500 km to the south-east of their birthplace. This wintering site is rather unexpected. Although Sudan (at least its northern part) is known since a long time to be reached by a few birds breeding in southeastern Europe (Hungary), the southernmost part (now belonging to South Sudan) may also belong to the species’ wintering area.

The epidemiology of vector-borne zoonoses depends on the movement of both hosts and vectors, which can differ greatly in intensity across spatial scales. Because of their life history traits and small size, vector dispersal may be frequent, but limited in distance. However, little information is available on vector movement patterns at local spatial scales, and particularly for ticks, transmitting the greatest diversity of recognized infectious agents. To test the degree to which ticks can disperse and disseminate pathogens at local scales, we investigated the temporal dynamics and population structure of the soft tick Ornithodoros maritimus within a colony of its seabird host, the Yellow-legged gull Larus michahellis. Ticks were repeatedly sampled at a series of nests during the host breeding season. In half of the nests, ticks were collected (removal sampling), in the other half, ticks were counted and returned to the nest. A subsample of ticks was screened for known bacteria, viruses and parasites using a high throughput real-time PCR system to examine their distribution within the colony. The results indicate a temporal dynamic in the presence of tick life stages over the season, with the simultaneous appearance of juvenile ticks and hatched chicks, but no among-nest spatial structure in tick abundance. Removal sampling significantly reduced tick numbers, but only from the fourth visit onward. Seven bacterial isolates, one parasite species and one viral isolate were detected but no spatial structure in their presence within the colony was found. These results suggest weak isolation among nests and that tick dispersal is likely frequent enough to quickly recolonize locally-emptied patches and disseminate pathogens across the colony. Vector-mediated movements at local scales may therefore play a key role in pathogen emergence and needs to be considered in conjunction with host movements for predicting pathogen circulation and for establishing effective control strategies.

National audience; Emerging infectious diseases are actually of major concern worldwide. Most of them are zoonotic and their epidemiology must consequently be studied conjointly in humans and animals. We present here a long-term research program led in the Camargue. This area situated in the Rhone delta, crossroads of many birds‘ migration routes is a biodiversity hotspot. It appears vulnerable to disease emergence due to its key location and to the common use of wetlands by wild and domestic animals as well as humans. Since 2004, a health ecology program is led in the Camargue mainly focusing on Influenza A viruses. First, pathogen dynamics are studied in their wild reservoir. For example, a seasonal pattern of avian influenza A virus circulation in waterfowl was highlighted, an infection peak being generally observed in early fall, probably due to the massive arrival of young and possibly immunologically naive birds. Seasonality of avian Influenza viruses is currently studied in gulls. Second, pathogen transmission between wild and domestic birds is investigated. Interestingly, no highly pathogenic avian influenza virus was detected in wild birds of the region from 2006 to 2009 suggesting that migrating birds do not play an important role in the transmission of these viruses. On the other hand, the potential impact of domestic duck releases for shooting on avian influenza A viruses dynamics in wild waterfowl is currently studied. Finally, researches are led on pathogen exchanges between wildlife and humans. Antibio-resistant bacteria, similar to those circulating in humans in France, have been detected in gulls showing that they could be contaminated by human pathogens. This multidisciplinary program already proved that animal health, human health and ecology issues can be fruitfully linked to gain insight in the epidemiology of emerging pathogens. Besides, it highlights that long-term studies are needed to be able to face emerging health issues, rather than short-term studies limited to crisis periods that are necessarily insufficient.