The characteristics of the Iberian Peninsula make it a privileged site for bird watching. Not only is it a nesting and transit area for many migratory species, but it is also one of the European regions with the most kilometers of coastline , which makes it easy for a large number of bird species associated with the sea to find abundant refuge areas here. and rest.
The yellow-legged gull is the most common of our coasts. The scientific name is Larus michahellis , it inhabits practically all the coasts of southern, western and central Europe, southeast Great Britain, North Africa, from Egypt to Western Sahara, on the Mediterranean islands and in the Canary and Canary Islands archipelagos. Azores. Some populations enter the interior of the continent, like those that can be seen in the skies of Madrid.
Many groups of Yellow-legged Gulls behave as migratory birds , with autumn trips to wintering grounds and spring returns to nesting grounds. Others, however, have acquired more sedentary habits , have stopped migrating and spend the whole year in the same territory.
Breeding colonies can number up to 8,000 pairs; formed only by members of the same species or sharing environment and resources with other species of gulls.
In a natural way, they feed on fish , invertebrates, reptiles, eggs and chicks of birds and small mammals, which they catch on the coast. However, many populations have transformed their eating habits and also feed on food waste and other rubbish , a consequence of human activity.
The total population of yellow-legged gulls is not quantified, although it is known to be increasing. For this reason, the International Union for Conservation of Nature (IUCN) classifies the yellow-legged gull as a species of least concern , the lowest category of protection that is contemplated.
If the Yellow-legged Gull’s distribution is wide, it is nothing compared to the Common Tern ( Sterna hirundo ) . It is possible to observe the common tern on the coasts of all continents except Antarctica . On the Spanish coast, the most important towns are found in the Ebro delta, at various points on the Levantine coast up to the Mar Menor, in Doñana and on the coast of Asturias, in addition to the Canary archipelago.
The various species of terns are characterized by some of the longest migrations , although the common tern is not as exaggerated as is the case with the arctic tern. However, they make long flights in which they can reach 4000 meters of altitude. They travel to the southern hemisphere in the fall and return to the northern hemisphere in the spring, where they nest and breed during the summer. They reproduce between April and June, in solitary pairs or in colonies of up to several thousand individuals.
Their habitats are mainly coastal. They feed mainly on fish . They usually fish alone or in small groups, although if they find an abundant school of fish, they can group together in large flocks. They frequently take advantage of the waste of large predators or the remains discarded by fishing boats . If they have occasion, they also feed on crustaceans and even insects.
Due to its high abundance, the IUCN also lists the common tern as a species of least concern status .
The Kentish Plover, scientifically named Charadiys alexandrinus, is another bird with an extraordinarily wide distribution. It can be found along the coasts of the northern half of Africa, almost all of Europe and most of Asia, and frequently enters the continent. And it is that, despite being a typical coastal bird, it can also be found in terrestrial wetlands , in grasslands and even in some deserts.
Some populations of Kentish Plover are sedentary or very short-dispersed, but most are long-distance migrants, separating summer breeding and wintering areas.
They normally nest in solitary pairs or loose semi-colonial groups , with no more than 20 pairs per hectare. When not in their reproductive stage, they are solitary or form small flocks of no more than 30 individuals, which frequently mix with groups of other species, forming mixed flocks. Unlike the previous cases, Kentish Plovers feed mainly on larvae and adults of insects , small prawns, shrimps, small crabs and other small crustaceans.
There are few data on its total population and those that exist present wide ranges of error. The Kentish Plover population is currently estimated to be between 300,000 and 500,000 mature individuals . However, it is known that, in general, the population is declining. In spite of everything, due to its wide presence and the large number of specimens, the IUCN also maintains this species in the category of least concern.
Referencias:
IUCN. 2016. Charadrius alexandrinus: BirdLife International: The IUCN Red List of Threatened Species 2019: e.T22727487A155485165 [Data set]. International Union for Conservation of Nature. DOI: 10.2305/IUCN.UK.2019-3.RLTS.T22727487A155485165.en
IUCN. 2018. Sterna hirundo: BirdLife International: The IUCN Red List of Threatened Species 2019: e.T22694623A155537726 [Data set]. International Union for Conservation of Nature. DOI: 10.2305/IUCN.UK.2019-3.RLTS.T22694623A155537726.en
IUCN. 2019. Larus michahellis: BirdLife International: The IUCN Red List of Threatened Species 2019: e.T62030970A154522526 [Data set]. International Union for Conservation of Nature. DOI: 10.2305/IUCN.UK.2019-3.RLTS.T62030970A154522526.en
Redfern, C. P. F. et al. 2020. Overland movement and migration phenology in relation to breeding of Arctic Terns Sterna paradisaea. Ibis, 162(2), 373-380. DOI: 10.1111/ibi.12723
