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Monitoring seabirds: new health challenges

With the increase in human activity along the coasts, the monitoring of seabird colonies has become an important health issue, the latter being in fact perfect reservoirs and potential vectors of pathogenic agents. It is with this objective that new CNRS research projects are anchored, the results of which will improve our general knowledge of seabird populations, the dispersion of infectious agents and the impact of human pollution.

Seabirds can carry a variety of parasites/pathogens, some of which are of particular public health concern. It is therefore essential to understand the mechanisms governing the health, survival and movements of these birds if we are to establish effective conservation programs and reliably assess the risks of disease emergence.
For several decades, bird populations have been increasingly affected by various stress factors (pollutants, habitat destruction, changes in food availability) increasing with human activities and the global changes associated with them. . These upheavals can affect their health, with impacts on their reproduction and their movements. Seabirds that live in close association with humans – such as large gulls – are particularly affected by these types of interactions.

Young gull chicks in their nest with waste (P. Landemann 2019)

The great seagull: a little-known reservoir of pathogens

Large gulls, such as the yellow-legged gull (larus michahellis), have easily adapted to human presence and now feed largely on waste. Due to the increasing human presence, these birds seem to be increasingly settling in cities where food sources are abundant and where they are more difficult to track and control.
These gulls are highly exposed to different types of pollutants (plastics, metals, antibiotics, etc.), both in their diet and directly in their breeding grounds, which may include industrial wastelands. Today we know little about the impact of different sources of stress on the ecology and reproductive behavior of these large common gulls. Although they are ubiquitous along Mediterranean coasts, we also know very little about the spatial extent of their movements, both over the course of a year and over their lifetime. Understanding these movements is essential, as these gulls can carry a variety of human pathogens (influenza virus, toxoplasmosis, antibiotic resistant enterobacteriaceae, etc.), as well as a variety of infectious agents of unknown pathogenicity. Finally, their colonies also frequently harbor ectoparasites, vehicles of infectious agents, such as ticks, which can bite humans if the nests are close to dwellings. (tick picture)
The yellow-legged gull is now used as a study model to better understand the impact of different environmental stressors on the reproductive success and behavior of seabirds. This work combines various approaches, including field sampling, monitoring of natural populations, eco-toxicological and chemical analyzes as well as molecular biology with the aim of identifying and tracing the different pollutants and following the movement birds and carried pathogens.
This work is carried out at different spatial scales, from the level of the colony to the scale of the western Mediterranean, and beyond. The interactions between specialists in various research fields and wildlife managers are a key element in making this research program feasible and relevant.

Gulls feeding in an open landfill (P. Landemann 2019)Gulls feeding in an open landfill (P. Landemann 2019)

Two research projects to study and monitor

This research is being conducted through two ongoing projects. The first is the project MITI CIPPE[1] which focuses on the interaction between exposure to plastic pollutants and parasites for the health of birds in the Camargue. The second is the project ANR EcoDIS[2] which addresses this interaction on the scale of the western Mediterranean, and integrates pollutants of different natures as well as modern techniques of bio logging. This is a technique consisting of attaching an electronic device to an animal which will record in its memory different parameters as a function of time so that scientists can reconstruct the activity of the animal, the characteristics of the environment in which it lies and the interactions between the two.
These projects are accompanied by banding programs, where individually marked birds can be identified remotely at different locations and over time. All this data is then centralized and analyzed using statistical models that allow us to estimate the survival probabilities of birds from different colonies at different stages of their lives, as well as the probability that these birds will move to different geographical areas. .
The results of this research program will provide us with general information that can directly contribute to our knowledge of the current state of the Mediterranean ecosystem: the distribution of pollutants in the region (and their potential sources), the diversity and distribution of parasites and pathogens associated with gulls, and in particular those that may represent a problem in terms of public health, and more detailed information on the ecology of a common and abundant Mediterranean vertebrate species. Indeed, although we see this species regularly, we lack key information on its ecology to model its population dynamics. With this information in hand, managers and local actors will be able to make more appropriate decisions regarding this wild species living at the interface between natural and anthropogenic ecosystems.

Ornithodoros maritimus ticks that live around gull nests and feed on gulls during reproduction (P. Landemann 2019)
ticks Ornithodoros maritimus which live around the nests of gulls and which feed on the gulls during reproduction (P. Landemann 2019)

[1] Combined Impact of Plastics and Parasites on seabird population dynamics and disease Emergence

[2] Disease ecology in a modified world: Linking combined environmental stressors, population dynamics and movement ecology to understand the circulation of infectious agents

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