Lake Bant tern colony

For the Flussseeschwalbenkolonie there is a long-term research project of the Institute of Avian Research " Ornithological Helgoland" on the biology of the Common Tern (Sterna hirundo ), a small long-lived seabird. Since 1984, Common Terns breed on the north side of the lake Banter and have since been intensively observed and studied.

Location

The site consists of six, each surrounded by a concrete wall, concrete artificial islands that were present as components of the former U- boat harbor in the Banter See. The hatchery is reported as a natural monument of the city of Wilhelmshaven. Originally the colony bred in the northern harbor, but had to be relocated because of changes. This was achieved by attracting the birds with sound dummies.

Colony

Of the original 90 breeding pairs, the colony grew to 530 breeding pairs in 2005, but declined due to reduced breeding success, lower fledgling survival rates and delayed first brood up to 430 pairs in 2011, due to poor food conditions. The breeding success is highly variable and highly dependent on the food situation in the Wadden Sea, where the Common Terns are looking for young fish of herring, sprat and smelt. The predation rate is low by protective measures against rats and other terrestrial predators. Some years ago, however, there were heavy losses by owls. The colony is also protected against flooding.

Methods

Since 1980, all chicks were ringed in order to determine the breeding success. Since 1992, now has more than 5,000 young birds plus some adult birds were marked with transponders. In each season, the transponder marked animals are recorded automatically with an antenna system, without having to be caught. This is done to seats on the walls ( non-breeding and breeding birds ) and on the nests ( breeding birds ). Many seats also scales are built where the birds can be weighed automatically. This system can be year after year, arrival dates, body weights, pair partners and breeding success documenting hundreds of birds. So the life stories of sedentary Common Terns can be tracked and draw important information for the population ecology of long-lived birds are recovered.

Many features change with the age of the Common Terns, which are getting better in their lives. So they move the arrival and laying dates and increase the breeding success until the age of about 15 years before they show in old age senescence. The highest life breeding success have the Common Terns, which reach a very old age.

For studies of the physiology of animals and blood samples are taken without the capture of adult birds. The blood collection without trapping prevents the stress in the animals, the blood levels eg could change due to increased stress hormones. This is achieved through the use of Mexican assassin bugs ( Dipetalogaster maxima), the hungry, set in a hollow artificial egg and the breeding birds are placed into the nest. Through holes in the eggshell of the bug can suck from the breeding bird blood, which is then used for studies on hormones, other blood parameters and genetics.