8 minute read
Gulls
Gulls
Yelling and rebellious
Text and photos: Wojciech Jarosz
In the vicinity of large breeding colonies, the noise is really hellish. There are other aspects of the life of seagulls to overlook (or sometimes omit) which is not possible. So how is it really: is it that we have entered the areas always belonging to these white aviators, or have the birds themselves decided to try luck between people?
Formerly it was believed that the gulls suspended over the vessels are souls of the sailors who passed away to keep the eternal guard. Even in the most difficult weather conditions, the birds did not fail to guard the boats, protecting of them in a way. However romantic it sounds, the true motivation of the gulls to follow the ship is the desire to catch the waste from the fishing nets and not to guard the sailors. Not without reason, the seagulls are more likely to follow the fish cutters than the tankers, warships or barges. Well, unless the latter transport waste to a landfill site… And here we find the answer to the question previously posed. The seagulls appear wherever they can find something to eat. And as
nature does not like to unnecessarily waste energy, these birds choose places where it is the easiest to get food. What is the food of the gulls? My less than the five-year daughter answers to such a question without hesitation that it is fish. And this is of course true, but not the whole. It would probably be easier to mention what seagulls do not eat, because in fact their menu can be extremely diverse. Of course, in this regard, there are some differences between the various species of seagulls, but most of them basically chase animal food in every form (also the one not really fresh). Not only fish, but also mammals, birds, reptiles and amphibians of the proper size, when it comes to vertebrates. In addition, the entire spectrum of invertebrates, including not only organisms considered to be 'seafood' by us, but also for example, molluscs, earthworms and insects, which they are willing to catch in the fields, often accompanying even working tractors. In the diets of the gulls may also be included plant products. There are known cases of gulls eating the brewery waste left from beer production ending in… drunkenness.
The behaviors associated with obtaining food by these birds do not add to their charm in the eyes of those more sensitive and less immune to, let's call it, the dark side of the gulls' nature. The gulls can even resort to cannibalism. What may seem quite scary is that they can steal the chicks of their neighbors from the cologne and it was observed that they could even eat their own chicks. Sometimes, they do not wait for the hatchling of their own chicks, but they steal eggs from one another for culinary purposes. It happens, especially among representatives of larger species of seagulls that they hunt for adult, in no way small, birds. Sometimes they do it in the very light of the spotlights! This was the case at St. Peter's Square in Vatican, when from the windows of the Apostolic Palace the Pope released the "dove of peace", and not quite a peaceful seagull decided to hunt for it in the company of crows (it happened many times and also happened to the birds released and by both Benedict XVI and by Francis). As we have already referred to the Popes and their relations with the seagulls, it is worth mentioning that the only ship under the Polish flag, where John Paul II was staying, was the minesweeper (after a later reconstruction – a minedostroyer) ORP Seagull – this took place during the Pope's pilgrimage to Poland in 1987.
Getting back to the subject of acquisition of food it should be mentioned that gulls often resort to truly bandit practices. Demonstrating no scruples, they attack other birds that managed to get something to eat, forcing them to abandon their prey. This happens often to the diving birds (e.g. cormorants, coots), which are unable to get rid of the attacker and give the gull whatever was the subject of the attack. Not only the birds are exposed to the pirate practices of the gulls – also those whose freshly served fish was unceremoniously stolen from the plate on the terrace of the seaside restaurant are not really fond of them – a moment of carelessness was enough! In these situations, we can observe a considerable quickness of the
seagulls. They learn quickly what is profitable and modify their behaviour to gain food more effectively. They can, for example, smash the shells of molluscs by dropping them from height to hard ground. Effective attempts to attract fish by spreading food crumbs on the surface of the water have also been described. Interestingly, the acquired knowledge can be passed on, usually by watching and imitating, and it happens also that the gulls cooperate in a group. One of the most interesting examples of this is the collective stamping on the ground to mimic the sound of falling rain, which effectively attracts the earthworms directly under the legs (and beaks!) of lurking birds. The seagulls have long since learned that a lot of food can be found in the vicinity of human habitation. They regularly patrol the waste areas where they feed not only on trash, but also e.g. on rodents, which are common in landfills. But is there anything that eats the gulls (the question applies to adult birds,
as for the eggs and chicks there is always a long queue of takers)? In fact, only the birds of prey may threaten them. You can see the white-tailed eagles attacking seagulls and also in the menu of larger falcons these birds may appear. The gulls often show an astonishing lack of understanding of the seriousness of the situation, and when they spot a large bird of prey they attempt to chase it. A surprised bird looking for peace and quiet often tucks its tail and gives way to gulls. Such scenes can be observed most often close to the gulls' colonies.
The disturbed birds jointly defend their chicks and together chase away the intruder.
Seagulls include just over 50 species, taxonomically grouped in the gulls subfamily (Larinae) belonging together with terns and skimmers to the gull family (Sternidae) in a Charadriiformes order. They are mostly birds with white and gray plumage. The coloration of young birds differs from that of adult birds, making their identification, which is not always easy even for adult birds, difficult, especially for closely related species. In the nesting and brooding season the pattern of colouring is also different from the one beyond the season. A clear sexual dimorphism (differences in the structure and coloration between females and males) in these birds does not occur. Among some of the species during the mating season can be observed a distinctive 'dark hood' on their heads, as this type of colouring is sometimes called. An example would be the most common seagull in Poland (Eurasia) – a black-headed gull, but also other species of the genus Chroicocephalus (from the Greek 'coloured head'). Seagulls can be small or large. The largest one, inhabiting also the Polish coast, is the great black-headed seagull the wingspan of which reaches 1.7 m. At the other extreme is a small seagull with a wingspan of around 0.7 m. And this species can be observed on the Baltic coast. Regardless of the size of the wings, their length and shape make the seagulls very efficient aviators. They can easily sense and use ascending currents drifting in the air for a long time without the slightest movement of their wings.
Seagulls are a cosmopolitan group – they can be found on all continents, even on the Antarctic coasts, as well as in the Arctic. Some species are only present in specific locations, such as the lava seagull (interesting for many reasons, e.g. it is a territorial species and does not form a dense colony), but many species have a wide range of prevalence. Most often they are found near sea coasts or over inland reservoirs – they basically always accompany divers (unless someone dives only in caves), as well as lovers of all other water sports and aquatic activities. A unique in terms of habitat is the grey seagull (not to be confused with common gull), which nests
in an exceptionally dry place, that is in the Atacama Desert in South America. Apart from the nesting and brooding season, it behaves as befits a gull and arrives at the Pacific coast, for many species change their habitat after nesting and brooding is completed. Most of the birds travel not very long distances, although there are exceptions – the Franklin's gull travels from Canada to the south of Latin America. Some species, after nesting and brooding, become typical pelagic birds, that is, living in the open sea. Due to the presence of the interdigital webbing they are great swimmers so the rest on the water surface does not pose any difficulty for them. In addition, gulls can drink sea water because they
have salt glands that allow them to remove excess salt from their body. The swallow-tailed seagull after nesting and brooding on the Galapagos Islands heads towards the high seas. This species is characterised by its unprecedented night life. It hunts for fish and squids in the moonlight, for which it is perfectly adapted. Seagulls have excellent eyesight, but the swallow-tailed gull has the best eyes among gulls equipped with a well-formed nictitating membrane. Its task is to reflect the light in the direction of photoreceptors and thus improve the quality of vision (the presence of a nictitating membrane in animals with good vision in low light or no light causes eyes to shine when a beam of light, e.g. from a torch, reaches them). When in the following season the time to return to the nest comes, the seagulls recreate the same pairs – they are usually monogamous and tend to use the same places where the previous nesting and brooding took place. Such returns can take place several times as some gulls live up to dozens years!
Next time, while watching the aviation skills of the gulls, keep an eye on your sandwiches. And your dog, if you have a Yorkie!
