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The numbers of juvenile brent geese arriving in the Solent can tell us how the lemmings in the arctic are doing.

The brent geese numbers around the Solent coast are starting to build up from the hundreds into the thousands as more birds continue to arrive. These birds are often accompanied by a few odd looking individuals, with a smaller neck collar and pale barring across their backs… these are the juvenile brent geese. They are just starting to arrive now from arctic Siberia. The number of juveniles arriving on the Solent indicates how successful the breeding season has been.

The breeding success of dark-bellied brent geese has been shown to follow a three-year cycle of ‘good’, ‘variable’ and ‘poor’ breeding success. This variability in their success depends largely on lemmings. Yes you did read that right, lemmings!

Lemmings are small rodents that live in or near to the Arctic Circle. They have a cyclic population going from boom to bust over a 3 to 4 year cycle dependent upon locality. This happens because lemmings feed upon moss. Moss regrows slowly, and so a horde of hungry lemmings can empty the larder very quickly and the lemming populations then crash due to shortage of food. This gives the moss a chance to regrow and the lemming populations begin to rise steadily. When the lemming population is booming the number of predators the following year will increase due to a successful breeding year. This cyclical boom to bust of the population could be in part what has fuelled the long standing myth that lemmings commit mass suicide!

What have lemmings got to do with brent geese though? Brent geese and lemmings are both vegetarian so its’ not to do with predation of each other. It is however due to predation from other animals…

In top lemming years, predators such as Arctic foxes concentrate on lemmings, leaving large numbers of young brent geese to survive to fledging. However, once the lemming populations have dropped the predators switch their diet to ground nesting birds, which can sometimes result in an almost complete breeding failure for brent geese.

In recent years, this cyclic event has not been observed with a large degree in breeding success for the brent geese, which indicates that there are other factors such as climate change that are effecting the breeding season in the Siberian Arctic.

Each juvenile brent goose you see this winter has undergone an amazing survival with high numbers of predators, then a 2500 mile migration to the Solent coast. Give these birds a wide berth and let them winter in peace.