Sandwich terns
size:
length: 36-41 centimeters
wingspan: 98-105 centimeters
weight:
250 grams
color:
light gray back, black head cap with a large crest in the summer, black beak with a yellow tip and black legs
age:
maximum 30 years
food:
vis, particularly herring, sprat, lesser and greater sandeel
reproduction:
maturity: 3 years
number of eggs per nest: 1-2
- Dut: Grote Stern
- Eng: Sandwich Tern (Cabot's tern)
- Fren: Sterne caugek
- Ger: Brandseeschwalbe
- Dan: Splitterne
- Nor: Splitterne
- Fries: Klikstirns
- Ital: Beccapesci
- Lat: Sterna sandvicensis
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- Sandwich tern (Cabot's tern), www.fotofitis.nl
Drawing: Erik van Ommen
Sandwich tern
Sandwich terns are easy to recognize by their funny black crest. Their body is built for living along the coast. With their long slender wings, they can hover perfectly above the waves as they hunt for fish. Sandwich terns are very social birds. They like to nest together in large groups. They even like having other tern species and gulls around. The more birds, the better the protection from predators. Common terns and black-headed gulls are much more aggressive than the gentle sandwich tern. In the winter, most sandwich terns migrate to Africa or southern Europe. Only a few birds, which nest further north, overwinter in the Netherlands.
On Texel
Sandwich terns on Texel are called 'kaugek'. The name probably comes from the sound the birds make. Large colonies can produce deafening noise. On Texel, such a colony can be found on the Petten near Den Hoorn. In 2011, 1200 pairs and 1340 chicks were counted.
- Menu
Sandwich terns live off of a diet of lesser sandeel, herring, sprat and greater sandeel. They catch these fish by hovering above the water surface. When they see a potential prey, they dive straight down from great heights. It's not so strange that they catch herring and sprat in this way. These fish live in the upper water layer and can be readily fished from the air. However, lesser and greater sandeel live near the bottom of the sea. Terns can only catch these fish when they swim in areas with a stronge current, which carries them to the surface.
- Close and cozy
- Sandwich terns and Black-headed gulls, foto fitis, sytske dijksen
Just like other kinds of terns and gulls, sandwich terns nest in colonies. The nests are not very substantial, no more than shallow hollows. They lie so close together that the nesting birds can barely turn around without hitting a neighbor. To assure safety, they choose to nest in places such as small islands, where land predators are lacking.
- Threats
- Sandwich tern, foto fitis, sytske dijksen
In the 20th century, the population of sandwich terns in the Netherlands crashed three times. In the beginning of the century, hunting the bird was so popular that the number of nesting pairs was almost annihilated. They were hunted in particular for their feathers, which was fashionable on ladies hoods in those days. The population recovered, growing to around 46,000 pairs, until the Second World War arrived and the eggs became popular as a source of protein for people. The third crash was caused by poisoning from pesticides. The Dutch population crashed from 30,000 to 875 brooding pairs. Since then, the population has not fully recovered. A good year can produce an extra 400 pairs.
There are two reasons why the population is taking so long to recover. First of all, a sandwich tern is only sexually mature at age 3 and it only lays two eggs per year. The second reason is a lack of food. When the herring stand crashed around 1990, it was had a tremendous influence on the birds.
The nesting areas of the sandwich terns are of international importance. Therefore, the sandwich tern is protected by the European Bird Directive. This means that the Netherlands must establish extra protective areas for the species. The conditions for suitable nesting grounds include scarcely grown places along the coast where sufficient food can be found. Nor can the area be disrupted too often (people and land predators). There aren't many such suitable places in the Netherlands for colonies.
- Colonies in the Netherlands
- Sandwich terns on Texel, foto fitis, adriaan dijksen
There are a number of large colonies in the Netherlands. The three largest areas are: Griend, the Hompelvoet (Grevelingen) and the Hooge Platen (Zeeland). Furthermore, new colonies have formed on Schiermonnikoog, Rottumerplaat and Texel. The eastern part of Terschelling (the Boschplaat) is also a popular nesting area. The numbers in the various colonies fluctuate strongly from year to year.
- Drowned nests
- Sandwich tern, Jan Andries van Franeker
Areas located on the seaside of dikes and dunes, such as salt marshes, beaches and scarcely vegetated islands, are important nesting areas for sandwich terns. The disadvantage to these breeding areas is that they flood every once in a while due to storms and extra high tides. If this happens during the breeding season, then the eggs are lost or the chicks that can't get to safety on time drown. In such years, it is possible that hardly any chicks are raised. This is a disaster, but as long as it doesn't happen too often, then it isn't a big problem for the species. They make up for their losses the following year.
However, scientists have now seen that the seawater in the past decades is continually so high that these areas flood more often, particularly during the breeding season. The flooding risks due to climate change are expected to increase in the coming years. Therefore, nature managers would like to make more areas inland of the dikes more suitable for sandwich terns. On Texel, you can find such places by the Petten near Den Hoorn and Ottersaat near Oudeschild.
- Distribution of sandwich terns in the North Sea region
- Distribution of sandwich terns, Ecomare
Source: important bird areas for seabirds in the North Sea
Sandwich terns nest along the West-European coasts and several places along the Mediterranean Sea and Black Sea region. They are even found in North and Central America. The sandwich tern overwinters in Africa where it stays the first three years of its life. Many sandwich terns are caught and eaten in Africa.
