From sandeels to seabirds
Changes to North Sea sandeel populations are having a devastating impact on seabirds
Atlantic Puffins with their colourful bill and inquisitive nature are quite the charismatic seabird. They are also site faithful, returning to their burrows year after year. In recent years I’ve had the pleasure of visiting islands such as the Shiants and the Farnes where it’s fantastic to watch the seabird spectacle including Puffins returning with fish, dodging opportunistic gulls, and diving into the burrows to feed their young Puffins.
Young pruffins are fed by both parents and fledge between 34 and 60 days depending on the area and year. During this time, they’re at their most vulnerable and chick survival can be greatly affected in times of food shortages. An important fish species for Puffins are sandeels, particularly Ammodytes marinus. This small eel-like fish is easy to ingest by small seabird chicks, and protein packed for a high nutritional value. However, in the last few decades, the abundance of sandeels has decreased in northern waters which has had cascading effects on their predators.
Scientists have been investigating the trophic links of sandeels and there is compelling evidence that they are becoming severely depleted, and that rising sea temperatures are to blame. Since the mid-1980s, the abundance of sandeels’ own food source, a cold-water copepod Calanus finmarchicus has declined in certain areas of the North Sea. A different copepod, Calanus helgolandicus, has increased during the same period, but this species’ spawning time does not overlap with the early life stage of sandeels, so these tiny crustaceans are not suitable as an alternative prey source for the sandeels.
Sandeels have strict habitat and environmental preferences, favouring shallow inshore waters, which means that despite the diminishing food resources they are unlikely to shift their distribution. Changes in habitat are having a detrimental impact to their own body condition. This means that not only are there fewer sandeels available to seabirds, but the size and nutritional value of the individual sandeels are also reducing.
Other birds are also affected; Arctic Terns and Black-legged Kittiwakes can’t dive as deep as Puffins and so have access to an even less diverse range of prey. All three species of sandeel-dependent seabirds have now been red or amber-listed under the UK’s Birds of Conservation Concern, and Puffin and Kittiwake are listed as globally vulnerable to extinction by IUCN.
As a result, the adults are having to travel further to find suitable food in order to feed their starving chicks. On Shetland, we found that some Puffins had to make round trips of 250km, ten times further than normal, and even then, were often bringing back much smaller sandeels compared with those on main¬land colonies further south.
Through provisioning monitoring, scientists record the changes in seabird diet and how they are faring with climate change and the associated sea warming. There are different methods of monitoring these seabirds and their diet and with the help of the public via the RSPB’s ‘Puffarazzi’ project, RSPB scientist are able to get a better insight.
Seabirds are a great indicator of the ocean’s health and we can use your photographs to identify the different types of fish that puffins are eating including, whether they are nutritional in value. So, if you want to get involved, please send through any photograph that you’ve taken of Puffins with food in their bills (be it from any year and any colony).
About the author
Chantal Macleod-Nolan has been working for the RSPB for the last five years on both the Roseate Tern and Little Tern LIFE Recovery Projects. Her role as Project Officer involves making sure the Little Tern project transitions from LIFE funding to a business as usual model. This includes setting up a national coordination group, supporting the regional tern groups and completing outstanding LIFE project commitments. Previously, she spent time monitoring Echo Parakeets in Mauritius and was a Tern Ranger for the National Trust. She’s also a C permit ringer who enjoys participating with the Wash Wader Ringing Group.
All photos © Chantal Macleod-Nolan/RSPB
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