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Seabirds and Waterbirds

Barbara Bacci


I am acquainted with some seabirds and waders I regularly observe on my trips to Ireland. However, for the sake of simplicity and continuity, in this lesson I have chosen to describe those species I see close to home and, given that most of my observations take place in Latium, where I live presently, I’d like to briefly explain the geomorphology of this region.

Latium borders with 6 Italian regions and the Tyrrhenian Sea. Its coast is low-lying and sandy. Behind the coast are former swampy areas, most of which have been reclaimed for repopulation and agricultural exploitation. Further up are cork woods and mixed woods, followed by higher altitude woods. The Latium Preapennines, marked by the Tiber valley and the Liri with the Sacco tributary, include three groups of mountains of volcanic origin, whose principal craters are occupied by lakes. There are more mountains to the South of the Tiber, also of volcanic origin. The highest peak is Gorzano Mount (2458 m.) on the border with Abruzzo.

The major river is the Tiber, 406 km long, the third longest river in Italy. In its course from Mount Fumaiolo, it flows through Rome, takes various tributaries and reaches the Tyrrhenian Sea in two branches. In Latium there are other, smaller and shorter rivers, which flow directly into the sea. The climate is mild throughout the region, but the difference of temperature and humidity between the coasts and the inner areas is remarkable. Due to its climate and geomorphology Latium is characterized by a high biodiversity and is is one of the richest regions of Italy in terms of fauna (58 out of 88 mammals present in Italy, 33 amphibians and reptiles out of 72, 171 nesting birds out of 240) and vegetation (3,185 species of vascular flora out of 5,599 present in Italy).

Every day I walk my dog along a stretch of the river Tiber, right in the heart of the city centre. From there I can observe the whole life cycle of the many mallards that inhabit the area. Mallards are migratory birds, but in most of Europe they are resident. The mallard, Anas platyrrhynchos, is one of the most widespread ducks worldwide. It belongs to the family Anatidae, a group of birds which feed on vegetable matter by upending on the water surface, or grazing, and rarely dive. They can be seen in parks, by canals in towns, on euthrophic lakes, woodland marshes, seashores.

The mallard is a medium sized bird, 50 to 60 cm in length with a wingspan of 81-95 cm. The male in full plumage is very characteristic, due to the metallic green head, narrow white head collar, black rear end and a blue speculum edged with white. The bill of the male is yellow, whereas the female has a yellow-orange bill with blackish culmen. After the breeding season, the male displays an eclipse plumage similar to that of the female, aside from the uniformly green-yellow bill. The juvenile is similar to the adult female.

In this season (autumn) couples are already formed and will be stable until the female will lay eggs. Mallards spend a lot of time in small groups, or in couples, which can be formed by two males as well as male and female. They are very vocal, sometimes using “soft” sounds resembling chicks calls, or a loud “alert” sound to warn the group of possible danger. When they are very scared they repeat a series of “quarr-quak”. During the mating season, in the spring, it’s not uncommon to see two or more males chasing an isolated female duck, then peck at her until she weakens, and then take turns copulating with the female.

I know hens choose a wide variety of nest sites: under bushes, tree-holes, under boats or buildings, but I have never seen one. The clutch comprises 9-13 eggs, and when they hatch, after 26-28 days, the hen leads the ducklings to water and does not return to the nest. Ducklings are precocial and can swim and feed themselves on insects as soon as they hatch, although they stay near the mother for protection. Young ducklings are not naturally waterproof and rely on the mother to provide waterproofing.

Mothers are very careful with the young, and watch over them tirelessly. When startled, the chicks start crying and calling the mother and only stop when they are reunited. While swimming or feeding, the hen calls out to them constantly. Most mallard hens breed as yearlings, but they may not have much success in raising their young. I have seen hens lose all of their young, often to Yellow-legged gulls who prey on them. Once I have seen a drake and hen looking after their two ducklings, and in another case a male alone raised three ducklings to adulthood.

Mallards are very good and fast flyers and can take off from the water surface, without having to run.

Recently, I have been seeing Gadwalls (Anas strepera) mixing with the mallards. Gadwalls are somewhat smaller than Mallards. The male has a brown head, the rest of the body grey and finely vermiculated, the scapulars are grey-buff and the bill dark grey. The female resembles the female mallard, but the belly is whitish, has a small white speculum and the bill has an orange stripe along the cutting edge. Gadwalls too are dabbling ducks.

In the area, there is a couple of Pochards. They are always in the same spot, and I wonder if it is because the water is deeper there: Pochards (Anas ferina) are diving ducks and plunge nimbly in the water when feeding, although do feed on the surface too. It is also clear that although occupying the same niche as the other ducks, they move quite independently. At present, the male is in eclipse plumage: dull rufous head, breast and stern dark brown-grey, flanks pale ash-grey. I think it is probably a hybrid, as the bill is light orange instead of blackish, although it does have a grey band across it. The female is grey-brown, flanks and back greyish with darker breast, crown and neck; dark bill, chestnut eyes.

On the Tiber, there are many moorhens. Moorhens (Gallinula chloropus) belong to the Order of the Gruiformes and the family of the Rallidae. They have a compact body, slate-grey with upperparts tinged with brown, and a white line running across the flanks and white undertail coverts. They have very long greenish-yellow legs with long toes, a red bill with a yellow tip and a red frontal shield, red eyes. They are shy birds and stay close to their hiding spots unless they feel very safe. In many years of watching Mallard ducklings grow up, only once have I seen some moorhens ducklings, and they were rushing to hide.

At the end of the summer, I often see immatures venturing out on their own. Usually moorhens move in pairs, but sometimes – and more so outside the breeding season - they gather in small flocks as they do on the thin stretch of land where the Grey Heron I wrote about likes to fish. There cannot be easily reached on foot. I know they spend a lot of time under the boat houses; it’s much easier to hear them than to see them. While swimming they often jerk their head and look about. Their long toes enable them to walk on floating vegetation, or climb small branches.

Moorhens are omnivorous and feed on plants, grasses, insects, snails and worms. When they are scared and unable to hide somewhere, they either dive or fly away by half flying half running across the surface of the water. However, on the river they hardly ever venture far enough to have to fly.

The only representative of the Charadriiformes I know of which can be seen on the Tiber is the Common Sandpiper, Actitis hypoleucos. It’s a small wader, 18 to 20 cm in length, with greyish-brown upperparts and white underparts. Neck and legs are short and yellowish or greenish, the bill is pale at the base with a darker tip. Sandpipers are summer visitors and do not gather in large flocks. In the spring, their characteristic flight-call (a sort of high pitched whistling) starts echoing along the river. With a little patience it is possible to spot them swooping fast just above the surface of the water. I never saw more than three together, most commonly there are only one or two. In flight, they can be recognized by the white bars on the primaries, on land, by the constantly bobbing tail. They often stand in shallow waters, where they can catch insects, crustaceans and other invertebrates.

The two representatives of the order Gaviiformes in my area are the Yellow-legged Gull, Larus cachinnans michahellis, and the Black-headed Gull, Larus ridibundus. The first is a resident, breeding everywhere in town – along the river, when appropriate safe places are found, on top of houses and buildings, where they build their spartan mound of vegetation -, the second is a winter visitor, arriving approximately in October. Many individuals of both species travel in small flocks to the sea in the early morning and away from it at dusk. Both species spend a lot of time flying in circles, calling out and landing on the water. In general, they spend much time swimming on the water surface. On the whole, Black-headed Gulls tend to fly more often in small groups; when they are not just flying in circle they fly in formations. Gulls don’t perch on trees like, for instance, cormorants, but prefer to sit on the top of light poles, on walls, building cranes or some such things.

The Yellow-legged Gull is sometimes considered a subspecies of the Herring Gull. It’s a common bird in much of Europe, Middle East and North Africa. It’s quite large, measuring 52-58 cm., with a wingspan of up to 140 cm. It’s similar to the Herring Gull, from which it can be distinguished primarily by its bright yellow legs. It is also more white-headed in the winter and has larger black wing tips, the ring around the eye is red rather then yellow, like the Herring Gull. Like other large species of gulls it acquires its adult plumage after the third year of life. Immatures have a brown-mottled mantle which gradually becomes greyer and adult-like with each moult.

It’s a highly social and loud bird, and its calls, sounding like strange laughing, are a common sound in Rome. It is omnivorous and feeds on any kind of refuse or carrion, as well as taking small prey, such as mallard ducklings or other small birds or mammals. It is less afraid of humans than other birds and does not take off readily when approached; it quickly learns to take food, and will learn to visit a window in a building at set times if someone feeds it.

The Black-headed Gull is a small and elegant gull (38-44 cm long with a 94-105 cm wingspan) breeding in much of Europe and Asia. It is not a pelagic species and commonly occurs in fresh water and often inhabits towns, where it can easily find all kinds of food. It is omnivorous. In the summer, the adult has a dark chocolate hood, but when it arrives here in the spring the head is white with dark streaks behind and over the eye. In flight, the white leading edge is quite visible. Legs and bill are reddish in the summer and brown red in the winter; the bill has a dark tip. Young individuals have ginger-brown upperparts and head markings and brownish wing markings; legs and bill are yellowish-pink. It takes two years to acquire full adult plumage.

It is a gregarious bird forming large flocks, it’s noisy and often employs its call, a sort of “kreeeaar”, especially when trying to steal food from its companions. The birds spend a lot of time on top of the boat houses along the river, resting on one leg with the head tucked amongst the back feathers, preening or simply watching.

Of the Pelecaniformes I have the fortune to see cormorants. These magnificent birds arrive at the end of September, beginning of October and remain until spring. The Great Cormorant, Phalacrocorax carbo, is a large bird, with a long, thick neck, a strong hooked-tipped bill, and totipalmate feet. The tail is longish; the plumage is black with bluish and greenish gloss. In winter, the white on the cheeks and the throat becomes dull and is not quite visible. The bare skin at the base of the bill is yellow, the eyes round and emerald green. It’s a widespread bird and feeds on the sea, in estuaries and on freshwater lakes and rivers. It dives from the water surface and catches fish by propelling itself with its feet. It possesses a nictitating membrane protecting the eyes which allows it to see underwater. The plumage is partially wettable in order to decrease buoyancy, but as a result it needs to dry its feathers on land, which it does by spreading its wings.

Cormorants like to sit on trees, often choosing the tallest branches to roost. When resting, preening or drying out they form small groups, but otherwise they fly alone or in twos. They have a powerful flight: Keeping their neck outstretched they fly along the water surface rapidly to then land on the water and shortly afterwards dive. They also fly very high, always in a straight line. I never hear them call out, but I read they are manly vocal at colonies.

My personal experience with penguins is limited to the parade I watched in Australia years ago, when Little Penguins came ashore at sunset during the breeding season; or to books, wildlife parks, documentaries and movies. To describe penguins, I have chosen one such documentary, March of the Emperor. This documentary by Luc Jacquet describes the breeding cycle of the Emperor Penguin, Aptenodytes forsteri.

Standing over 1 m. tall and weighing about 30 kg. the Emperor Penguin is the largest of the all penguin species. It has black wings and head, a white abdomen, a bluish back and a purplish bill. On the side of the neck it has the characteristic yellowish-orange circular stripes. Unlike most other penguins who feed on surface krill, they live on fish, squid and crustaceans they catch by pursuit diving. They can reach depth of 700 feet and remain underwater for up to 18 minutes.

Emperor penguins spend their entire life in Antarctica and are the only Antarctic birds breeding in winter. They start breeding at the age of five. Apparently, they spend the first years of their life in the ocean, until the time comes to undertake the 90 km long journey to the colonial nesting areas. Not quite as agile as they were in the ocean, they cover the distance by wobbling along or sliding over the ice on their belly. Males reach the rookeries before females and start displaying to attract them. Females are more numerous than males and this leads to intense competition amongst males. Males adopt the “ecstatic” display: They stand still, let the head fall onto the chest, then stretch the head and the neck, hold the flippers outstretched and give the courtship call. Calls vary from one individual to another and are used for recognition.

Emperor penguins are seasonally monogamous (although they can choose the same mate the following year) and often adopt a mutual display position: they stand face to face and hold their heads down with bills pointed to the ground while braying. The display takes place throughout the breeding season and might be repeated when they switch places for incubation and chick feeding. In May or June, the female lays one egg which she needs to transfer to the male penguin before she returns immediately to the sea to feed. This is a risky operation and many eggs are lost. For over two months, the male incubates the egg in his brood pouch (also King Penguins have a brooding pouch) surviving by means of his fat reserve alone. He can fast for nine weeks or more.

To survive the extreme temperatures and winds (-80° F with winds reaching 112 miles per hour), penguins huddle together with their back to the wind, taking turns in the middle to preserve heat. Penguins are insulated by a dense network of feathers – about 70 feather per square inch. When the chick hatches the father feeds it by regurgitating a substance produced by a gland in his oesophagus and keeps warm on his feet. At about the same time, the mother returns to the colony and identifies her mate by its call. It is her turn to take care of the chick and feed it by regurgitating the food stored in her stomach, while the male returns to the sea to feed. He will be back and both parents will then raise the chick together. The chicks are initially unable to regulate their own temperature and need to sit on their parents feet for the first two months of life. After this time, they group in crèche while continuing to be cared for by their parents until they all go back to the ocean.

Morphology of feet

Waterfowl and seabirds share similar habitats, but they differ in their feeding techniques and adopt different breeding strategies.

Feet Diversity in Birds - pen and ink

(Feet diversity in birds. Pen and ink)

All Anseriformes have webbed-feet, which are more or less flattened; they are good swimmers and their plumage is excellent for shedding water due to special oils they produce.

Gruiformes, unlike Anseriformes, are morphologically diverse. Most species live in damp habitats near lakes, swamps and rivers. The lobed feet of coots make them good swimmers and enable them to walk on marshes. Moorhens long-toed, unlobed feet enable them to walk on floating vegetation as well as climb. Jacana’s toes are even longer, as they don’t only walk on floating vegetation, but make their nests on floating plants.

Waders (Charadriiformes) tend to have long legs and unwebbed feet, although avocets have partially webbed feet that permit them to swim easily in deeper water.

Seabirds have webbed feet, which they need for swimming.

Pelecaniformes have totipalmate feet, which means all 4 toes are connected and form a large paddle, useful for swimming or propelling themselves under water if they feed by pursuit diving. Some boobies have colourful feet which they display during mating.

Gaviiformes have webbed feet set far back on the body for greater stability in the water at the expense of walking on land. For the same reason, their sleek bodies are wider than they are high. They are adapted to diving; they have solid bones, and propelling themselves with their feet they can dive 240 ft below the surface of the water. Their body cells can store large amounts of oxygen, which they save also by dropping the heart rate and many of their vital organs can function with low levels of oxygen.

Some species have sacrificed the ability to walk on land. Procellariformes have webbed feet with underdeveloped toes, or lack them altogether. Some procellariids have weak legs and can’t walk; on land, they move by pushing themselves forward on their breasts.

Penguins (Order Sphenisciformes) adopt an upright posture because their short feet are set far back on their body. They walk with difficulty and often move by pushing themselves along on their breast with wings and feet.

Bill Morphology

Bill morphology is correlated to foraging behaviour. Marine predators, such as penguins, cormorants or albatrosses, have bills with curved projections that direct fish towards the oesophagus. Waders have bills of different lengths and curvatures to reach different invertebrates by probing into the mud or soft soil (or by upturning stones like the Turnstone, or skimming the water surface like the Avocet). In this way, different species feed in the same habitat without competition for food. Prey is detected by means of the sensitive nerve endings at the end of the bill. Plovers feed on small invertebrates they find on the surface. Redshanks and waders with a similarly medium length bill probe the top 4 cm. of substratum and feed on worms, bivalves, and crustaceans. Curlews, godwits and other long-billed birds can reach lugworms and other such deep burrowing animals. The avocets swings its bill back and forth underwater, looking for aquatic insects, crustaceans and mollusks, but also feeds on plants and seeds it finds on the water surface.

 

Waders bill structure. Adapted from F. Gill. Pen and Ink

All Anseriformes share the same bill structure (Screamers have adopted an alternative feeding strategy, but still retain vestigial lamellae), characterized by a special internal shape of the bill and a modified tongue which sucks in water at the tip of the bill and expels it from the sides and the rear; along the sides of the bill is an array of lamellae (filter plates) meant to trap small particles which are then licked off and swallowed. The nail at the tip of the bill is used for biting off vegetation. They are primarily herbivorous and feed on leaves, stems, flowers, roots, etc. However, aside from the differences in body size and neck length, waterfowl species have developed different bill sizes and shapes. Dabbling ducks have a flat bill, deeper than they are broader at the base. The edges of the bill are soft because these ducks find their food by touch. The nail on the tip of the bill serves to hook or move food. The interior lamellae act like sieves, retaining seeds, bugs and other food. Shovelers have extra-wide bills with well-developed lamellae to skim crustaceans and other invertebrates from the water’s surface. The bills of geese are adapted to uproot grasses to eat roots, rhizomes and bulbs (Snow geese) or shear off short grasses (Canada geese).

Black-footed Albatross, Northern Gannet, White Goose, Atlantic Puffin, Razorbill. Watercolour and coloured pencil

(From the top left, clockwise: Black-footed Albatross, Northern Gannet, White Goose, Atlantic Puffin; in the centre: Razorbill. Watercolour and coloured pencil)

Some rallidae species, such as coots or moorhens, have a frontal shield on the upper mandible which often becomes dullers after the mating season.

Procellariformes are highly pelagic birds with nostrils enclosed in one or two tubes on their straight, deeply grooved bills with hooked tips (hence their name: tubenoses). The tubes allow the birds to have an acute sense of smell and to excrete salt. The beaks are made up from several plates. They all eat fish, squid or other marine prey. The hook on the tip of the bill of albatrosses and petrels is used to snatch fast-moving prey. Prions have specialized bills with lamellae to filter out plankton.

Gannets are specialized in plunge diving and can dive from a height of 30 m. at a speed of 100 km/h., therefore, their external nares are closed, instead they have alternative openings on the inside of the upper mandible of the bill. Other adaptations include the presence of air sacs in the face and chest for protection from the impact with the water. Plus, they have better binocular vision than most birds (see drawing).

Gulls don’t have specialized bills and are often omnivorous.

Puffins (Charadriiformes) have large bills whose colourful outer parts are shed after the breeding season. They have the ability to hold several fishes crosswise in their bill, using the tongue to hold the catch against spines in their palate, leaving the beak free to open and catch more. Skimmers, which are small tern-like birds, feed by flying low over the water surface with their elongated lower mandible submerged. When they catch a fish they double the head back under the body, then swallow the prey in flight or after landing.

Many members of the Pelecaniformes, like pelicans, have developed a gular pouch.

Birds’ bills are multipurposed organs serving a variety of functions – feeding, preening, building nests, etc.) and are also very important in mating and reproduction. In some bird species, bills change colour during breeding, or they develop plates they later shed.

Morphology of Wings

Seabirds have adapted to living and feeding in the sea. Wing morphology is an indicator of feeding behaviour. Longer wings and low wing loading are typical of more pelagic species, whereas diving species have shorter wings.

Albatrosses are amongst the largest flying birds, with a wingspan exceeding 340 cm in the larger species (see drawing). They employ two flying techniques: Dynamic soaring and slope soaring. Dynamic soaring allows the birds to minimise energy expenditure by gliding across wave fronts, gaining energy from the vertical wind gradient. When slope soaring the albatross turns to the wind, gains height and then glides back down to the sea. The glide ratio of an albatross is such that for every metre it drops it can travel forward 22 metres. Albatrosses and giant-petrels are equipped with a special shoulder-lock: A tendon that locks the wing when fully extended so that no muscle effort is required to keep it open. Flying efficiency is further enhanced by the fact that during flight the heart rate of albatrosses is close to the basal heart rate when resting.

Storm-petrels belonging to the family Oceanitinae feed mostly by surface pattering, moving their feet on the water’s surface while remaining stationary by means of rapid fluttering, or by using the wind to anchor themselves in place.

Frigate birds are highly aerial birds: they can barely walk, cannot swim nor can they take off from a flat surface. They have the largest wingspan to body weight ratio of any birds and can fly for a week or more. Like other Pelecaniformes, they have totipalmate feet, but the webbing is reduced.

Some species, like auks and puffins, are not efficient flyers. Auks need to flap their short wings very fast in order to fly. They catch their prey by pursuit diving, propelling themselves with their wings, like penguins. Different subfamilies specialize in catching different fish: murres (guillemots) hunt faster schooling fish, whilst auklets pursue slower moving krill. Puffins too feed on fish and zooplankton by pursuit diving, “flying” underwater thanks to their short wings (see drawing).

Ducks and geese are good flyers too, but do not soar or glide like seabirds such as gulls do; instead, they fly very fast (see drawing).

Penguins’ wings are modified into stiff flippers by their wing bones being flattened and joined so that they are highly efficient for swimming fast under water (up to 30 miles per hour. The webbed feet and the tail are employed as rudders for turning. Penguins have small wings, feet and heads so that the surface area in comparison to the bird’s volume is small and results in efficient heat conservation. In addition, they possess an insulating layer of fat under the skin and dense, waterproof plumage to further help them withstand cold temperatures.

Flight morphology in marine birds and gannet plunge diving technique. Pen and ink

(Flight morphology in marine birds and gannet plunge diving technique. Pen and ink)

Seabirds have waterproof plumage and, compared to land birds, more feathers protecting them. Cormorants are an exception: they have a layer of feathers that retain a smaller layer of air compared to other diving birds, but otherwise soak up water. In this way, they can counterbalance buoyancy without losing excessive heat through contact with water. Generally, the plumage of most seabirds is less colourful than that of land birds and colour occurs mostly in the bills and legs.

Many seabirds feed by surface feeding, which they can accomplish while flying (gadfly-petrels, frigate-birds and storm-petrels), and surface feeding while swimming (fulmars, gulls, shearwaters and gadfly-petrels). Some birds are such good flyers they can snatch morsels from the surface, like some terns and frigate-birds do, or pattern and hover over the surface, like storm-petrels.

Pursuit divers either use wings to propel themselves underwater (penguins, auks, diving petrels and other petrels) or feet (cormorants, grebes, divers and several types of fish-eating ducks). Wing-propelled divers are usually faster. In general, pursuit divers have difficulty walking or cannot walk at all. Many shearwaters are intermediate between the two kinds of birds and can dive to considerable depths while being good long-distance flyers.

Plunge diving is employed by gannets, boobies, tropicbirds, some terns and brown pelicans. The birds use the energy from the momentum of the dive to counteract natural buoyancy, saving energy compared to pursuit divers, and being able to exploit more widely distributed food resources such as in impoverished tropical seas. Brown Pelicans take years to learn the skills of plunge diving and finally learn to dive from a height of 20 m., shifting the body before impact to avoid injury.

Kleptoparasitism is yet another feeding strategy. Frigate-birds and skuas engage in this behaviour, but also gulls and terns will steal food when possible.

Waterfowl differs from seabirds in their breeding strategies. Seabirds live longer than other birds, between 20 and 60 years, and delay breeding for up to 10 years. Most species only have one clutch a year and species like the tubenoses and sulids only have one egg a year, while most albatrosses breed every two years. Care of the young is protracted. This breeding strategy might have evolved in response to the difficulties of feeding at sea, breeding failures due to unfavourable marine conditions and lack of predation. Because raising the young is so energy-consuming, in all seabirds species except the phalaropes both parents participate in caring for them. Almost all seabirds are colonial and seabird colonies are amongst the largest bird colonies in the world.