Plan of

Management of Gaviota Cocinera

Cooking Seagull

Larus dominicanus

Scope of the project

Currently, in Argentina, the Black-headed Gull is considered a non-threatened species and its population is expanding due to the availability of food and its plasticity in adapting to new territories.

habitat and behavior

It inhabits seashores, rivers and mountain lakes, suburban areas, garbage dumps, occasionally it is found in lagoons and steppe rivers. Individuals can also be seen far away from aquatic environments, if resources are available. Individuals can be seen solitary or in small groups but also form large concentrations, even with other species of gulls. It has the ability to glide long distances. It has an aggressive behavior.

feeding

Their varied diet is made up of fish, mollusks, echinoderms, crustaceans and other animals, but also includes garbage, fishing discards, carrion, etc.

reproduction

Forms breeding colonies of dozens or hundreds of pairs. It nests on islands, cliffs, beaches, lava fields or even urban areas. The usual clutch consists of three eggs.

curiosity

Due to the expansion of its territory, associated with human activities, it is described as a "neonnative" species. The Kittiwake is the most important native predator found at Hooded Grebe.

context

Management Plan for the Lesser Black-backed Gull

The Kittiwake Gull frequents both marine and freshwater environments, and it is estimated that in marine environments of Patagonia its breeding population is more than 100,000 pairs distributed in 140 colonies. It is a generalist and opportunist that uses during its reproductive season a wide diversity of prey such as marine invertebrates, fish, insects, including resources of anthropic origin (e.g. urban and industrial garbage dumps and fishing discards), carrion, etc. Their colonies can be on islands, beaches, lakes, areas with or without vegetation cover, even on cliffs. It breeds from September to January, depending on the area, and the incubation period is approximately 26-27 days. In Patagonia, the Lesser Black-backed Gull has had a population increase, probably related to a greater availability of anthropogenic resources (e.g. garbage, carrion). Some researchers suggested that the population increase could negatively affect the reproductive success of other bird species, due to their territorial and predatory behavior of chicks and eggs. For this reason, the Black-headed Gull has been mentioned since the late 1970s as one of the main threats to Hooded Grebe. There are even reports of individual gulls preying on colonies and even on chicks that are only a few weeks old.

patagonia in action program

Lines of research

Management Plan for the Lesser Black-backed Gull

Responsible

Technical Team

State

Active

Target

The work to control the impact of the Black-headed Gull on the populations of Hooded Grebe had three different stages. On the one hand, we started working with the "Colony Guardians" in the 2011-2012 season, which are currently in force, with the idea of fulfilling the first urgent objective of direct protection of the colonies to prevent the loss of nests and chicks by predation of problem individuals. The main objective of this strategy is to stop the reduction of the reproductive success of Hooded Grebe by preventing direct interaction with this neonative species, but it also has the goal of directly identifying problem individuals and removing them from the system, thus minimizing the risk in the long term.
As a second objective we proposed in 2013 to start reducing the local populations of the Lesser Black-backed Gull, focusing on the plateau area of Lake Buenos Aires. This plan seeks to reduce the population in the region, minimizing the probability of interaction between the gull and the Hooded Grebe. Finally, the third major objective is to work with local authorities to minimize the availability of resources that encourage the increase in the populations of the Lesser Black-backed Gulls, mainly by working on the management of urban solid waste.

methodology

Each of the objectives is approached from different working methods. The "Colony Guardians" are trained technicians who remain throughout the reproductive cycle of Hooded Grebe (i.e. from the time of the beginning of laying until migration) directly protecting all detected colonies. The work includes shifts of surveillance and monitoring throughout the day in the colonies. When a problem individual is detected, it is chased away and, if possible, removed from the system. The team is minimally two people per colony and with rotating shifts of two weeks, to avoid extreme fatigue of each technician.
For the second objective, we worked in the colony of the Lesser Black-backed Gull found in the "El Gaviotero" lagoon (E74) located on the plateau of Lake Buenos Aires. This colony is established on three rocky islets, located at a distance of approximately 200 m from the coast. To control the populations, the method consists of interrupting the embryonic development of the eggs by "beating" them. This process is repeated every 15 days to minimize the hatching of new eggs. To carry out the method, the islets are accessed with a dry suit and a "marker" (flour) to mark the nests. All the islets are visited to count the number of eggs and nests, and the nests are marked with the "marker". To prevent the gulls from replacing the eggs and continuing with the incubation process, the eggs are left in the place and position where they were found to prevent them from breaking. We complement these actions by carrying out censuses of the lagoon to keep track of the number of individuals of Kittiwakes and other bird species.

Scope area

The management work on the Lesser Black-backed Gull is directly related to the reproductive distribution of Hooded Grebe, which covers mostly the west of the province of Santa Cruz.

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