Naturalised barnacle geese
Whenever we hear the yapping calls of the barnacle geese in the later days of September, we know that autumn has finally arrived. But what if these yaps were heard all year round? In some areas of the UK they can be, you just need to know where to go..
There are three main populations of barnacle geese found in Britain. Two of these are the known migratory populations from eastern Greenland and the Svalbard Islands in Norway. This is where the barnacle population that winters on our reserve comes from. However, there are some of these birds that love their time in the UK so much they’ve decided to stay over here for the summer to start their families, which make up what we call the 'naturalised' population here. These are assumed to have originated from escaped birds and immigrants from the Dutch and German regions. Some barnacle geese that are injured over the winter period can’t make the long return journey back to the Svalbard islands so they set up a home here over the breeding season as well.
The naturalised barnacle goose population was noticed to start and concentrate around the southeast of England. In 1991, a census showed there was 925 estimated barnacle geese to live in the UK. Since then, these birds have become more widely distributed around the country, showing an increase of around 450% to 5800 estimated individuals in 2023. The majority of this population resides in England, with small numbers being present in Wales, Scotland and Northern Ireland.
The Scottish population of barnacle geese has been seen to concentrate in two distinct areas: Perthshire and in the Highlands. In total, estimated numbers are at around 333, roughly 5% of the naturalised birds. Some of the birds that have been raised here have also been witnessed joining those in the Svalbard wintering grounds and on their return journey back to Norway as they fledge the nest.
The reason we have been able to understand these population changes is through colour ringing. This ringing of barnacle geese is mainly undertaken on the migratory birds at their wintering sites and has been done on the Svalbard population since 1973. Cannon ringing was the main method used on these wintering grounds, where a net is shot over a cluster of geese to collect and ring them. Another arguably more effective way of capturing geese is when they are in their annual moult during the summer breeding season, making them easier to collect as they are flightless at this time. Colour ringing is vital in the monitoring of these species as they help us track their movements so we can see where they interact with our naturalised populations. These new populations that emerge in naturalised areas can affect the gene flow between individuals in the species.
This naturalised population is now at a size where they can become self-sustaining within the UK and have the potential to increase in the future. For the population to thrive, and our understanding of their movements and dynamics to continue, adequate monitoring programmes should be put in place to help us predict their future and how they might affect our landscape with growth. The UK has a lot of agricultural land which has seen conflict with the migratory geese populations due to agricultural crop damage. If the population was to increase in the UK, this could be an area of conflict that we may need to work towards to resolve. Needless to say, our annual winter visitors would be welcome here all year round if they so wished to spend more time at Caerlaverock.
Words by Rebekah Allison
Feature image of barnacle goose by Alex Hillier
