Studies analyzing changes in this species’ diet over the last two decades have shown that the diet of Caspian gulls in the Medes Islands (Girona, Spain) has changed significantly over the last few decades. For seagulls that eat marine resources severely, the region’s abundant landfills and meat industry now make up about 50% of their diet.
Population growth study Aside from the abundance and availability of organic waste in landfills, the region describes the current feeding patterns of seagulls that are capable of adapting to habitats altered by human activity. In parallel, food high availability has caused seagull populations. This is a situation with some problems related to direct and indirect interactions between seabirds and people.
Studies published in the journal Ecological indicatorIs led by members of the Seabird Ecology Group of the Faculty of Biology and the Institute of Biodiversity (IRBio) at the University of Barcelona. Among the participants are the Marine Science Institute (ICM-CSIC) and the Animal Health Research Center (CReSA) of the Agricultural Food Research and Technology Institute (IRTA).
Find food resources
Human activity has changed the characteristics of the environment since ancient times.With the ecosystem Wild animals Is the introduction of food subsidies into the natural environment. In other words, it is the leftover food that humans do not eat and that other species eat. Over the last few decades, human consumption models have led to increased production of food subsidies. It has become an essential food source for many wildlife populations, including the wild boar, which is often found in towns and streets. Throw away the seabirds that eat fishing. In many cases, increased availability of anthropogenic resources is strongly associated with increased populations of species that know how to ingest and eat them. Therefore, such species can become excessive and cause some problems such as urban obstruction, disease transmission, road and airport accidents.
Caspian gull: Bait from landfill waste
Larusmichahellis Caspian gull Seagull Is a species that is perfectly suited for the use of human-derived food subsidies. Originally a seabird, the bird now lives in populated areas, from the coast to the inland.
“This species has excellent feeding and behavioral plasticity, which allows it to feed on sandwiches in school courtyards, food debris from the meat industry, fishing waste and landfill waste. You can, “says researcher Jazel Ouled-Cheikh. Articles and members of the Department of Evolutionary Biology, Ecology and Environmental Sciences of UB, IRBio and ICM-CSIC. “These dietary habits add to the expert, but apart from facilitating a demographic outburst, they turn it into a potential disease vector. Therefore, they manage the population and potentially. Species need to be studied and understood to prevent conflicts. “
In this study, a group on seabird ecology details how the diet of Caspian gulls in the Medes Islands (Girona) has changed over the last two decades. Through stable isotopic analysis, studies determine the basic compounds of seagull feathers to estimate and quantify their diet.The sample analyzed is from a sample of chicks performed there In the Medes Islands during the breeding season of the species during the period 2004-2018. The temporary perspective of the study has been extended thanks to the analysis of dissected model feather samples from the Banyoles Dadder Museum and the Barcelona Natural History Museum. A first-year seagull that died in 1916 and three more seagulls that died in the 90s were captured near the Medes Islands.
The findings reveal some important changes in the diet of Caspian gulls during the study period. “Specifically, the food for seagulls is about 30% from the 70% marine contribution (mainly fish) in 1916,” says expert Jazel Ouled-Cheikh. “However, the contribution of elements (meat products and other leftovers) from landfills was relatively low in 1916. The contribution of this resource to seagull food increased in the 1990s and is now about 50% stable. bottom.”
The study also assesses the contribution of terrestrial invertebrates to this seabird diet. This intake also gradually increases throughout the study period, reaching its current value of 30%.
“The change over time in the tenure population of the Medes Islands can be explained by two oscillating and closely related factors. The population of research colonies and the availability of various food subsidies in the environment. “Tenure Track 2 instructor Raül Ramos (UB-IRBio) says.
The availability of various food subsidies varies significantly both in time and space. Caspian gulls, like many other opportunistic species, can adapt to these fluctuations by changing their feeding strategies. Therefore, individuals from different locations may have very different diets depending on the local availability of these resources. “Therefore, individuals can adapt their schedules and diets to the temporal patterns presented by the human activities that generate these grants. For example, they can change their schedules. diet Francisco Ramírez, a member of IRBio and ICM-CSIC, said: “On weekends when there is no fishing and therefore no waste of fishing, this plasticity is another more specialized and often affected competing species. . “
New scenario for seabirds
The situation for this change will be exacerbated by European Union-led policies that reduce access to food subsidies for seagulls. In this regard, it is important to emphasize community guidelines such as the Landfill Directive. This will significantly reduce the waste available at the landfill. Similarly, the current and future application of the European Landing Mandatory Policy to ban the dumping of waste, which is the main food source for many seabirds today, could end the image of seabirds following the route that fishing vessels eat from seabirds. there is.
“we food Seagull availability (at least two of the three sources described in the study: landfills and fishery waste), the difficulty of covering the energy needs of these birds solely with terrestrial invertebrate consumption In addition, everything shows that the presence of seagulls in urban areas in the not too distant future does not forget the problems associated with this situation, “the researchers warn.
“Therefore, it is imperative to continue to monitor the gull colonies of the most important Medes Islands in the Mediterranean. This monitoring should take into account both the dietary habits of this gull population and the movement of specimens (GPS device). Use), for example), and study their role as a reservoir of pathogenic microorganisms that they can transmit, “says Marta Selda, a researcher at IRTA-CReSA. “Only this way can we obtain quality scientific data to find out why this species encourages it to interact more and more closely with human society and all the associated risks it poses.”
Jazel Ouled-Cheikh et al, Anthropocene Foraging: Opportunistic Predator Eating Plasticity Revealed by Long-Term Monitoring, Ecological indicator (2021). DOI: 10.1016 / j.ecolind.2021.107943
University of Barcelona
Quote: Landfill and Meat Industry: New food source for yellow-footed seagulls in the Medes Islands (September 10, 2021) from https: //phys.org/news/2021-09-landfills-meat-industry-food- Obtained on September 10, 2021 sources.html
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A new source of food for the Caspian gull in the Medes Islands
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