Seals and seabirds: A guest blog post by Kevin Sene, author of Spectacular Britain: A spotter's guide to the UK’s most amazing natural phenomena

Spectacular Britain, published by Bloomsbury in 2024, features Nature’s Calendar in three chapters and describes when and where to see seal pups, nesting seabirds and other natural phenomena around the UK. Below, author Kevin Sene shares some fascinating insights into the impacts of climate change on seals and seabirds. Kevin also publishes a free fortnightly Substack newsletter called Nature’s tidings on natural phenomena such as the Northern Lights, seabird cities, wildflowers and bird migration. His author website is www.meteowriter.com

Seabirds and seals are some of the most familiar yet spectacular sights around our shores. Some have iconic status, such as the comical puffin and fluffy white Atlantic grey seal pups.

Sightings follow the seasons, with many seabird species arriving to mate in spring, having spent the winter roaming the oceans in search of prey. Most nest on vertiginous cliffs but some, such as the puffin, choose burrows on remote islands. Typically, most are gone by late summer, with just a few species lingering into autumn.

Grey seals reside all year but have favoured breeding grounds, typically on remote rocky shores or sandy beaches hidden away behind sand dunes. The seal pupping season begins in August in southwest Wales but doesn't really get going until October in east Scotland and November or December in Lincolnshire and Norfolk.

Common or harbour seals are the other main species of seal found around British shores. Like grey seals, they are classed as true seals (phocidae), since they have no ear flaps, unlike a sea lion say, which is classed as an eared seal. There are 18 species of true seal worldwide. Perhaps 40,000 to 50,000 common seals live around the British Isles, which is less than half the population of grey seals. Outside the breeding season, the two species are often found together on haul out sites with no obvious rivalry. From Spectacular Britain, Bloomsbury

However, the survival of each species depends on a complex and interconnected set of factors, and as is often the case in the natural world it doesn’t take much to disrupt their behaviour, including the influences of climate change.

Long term monitoring at Skomer Island

Long term monitoring of populations is one way to better understand the risks and one of the longest running seabird studies has been into guillemots at Skomer Island off the coast of Pembrokeshire.

Here, monitoring over the past fifty years led by the University of Sheffield has shown that the median date of egg laying has advanced roughly two weeks in that time. A recent article in British Birds¹ suggests that this has been linked to changes in the distribution and abundance of fish prey, with the added complications of storm events and avian flu affecting numbers in recent years.

Grey seal populations are also monitored at Skomer in a joint initiative between the Wildlife Trust of South & West Wales and scientists of the Skomer Marine Conservation Zone. A recent analysis of nearly thirty years of data led by the University of Swansea² found that the pupping season advances in periods with higher sea temperatures and that this is associated with an older average age of mothers, affecting the population age structure.

Citizen Science and puffins

Contributors to Nature’s Calendar will be pleased that citizen science also plays a role, and in 2017 Project Puffin shed light on puffin numbers around the UK. This was led by the RSPB and volunteers – dubbed the ‘Puffarazzi’ - submitted photographs that they had taken of the classic sight of birds with a beak full of fish, ready to feed to their chicks, which are known as pufflings.  

Analyses of more than a thousand photographs from 27 colonies³ showed that adults at sites with declining populations tended to bring back larger numbers of smaller, lower biomass fish, particularly post larval or juvenile versions of their favourite prey, a small eel-like fish called the sandeel. This less nutritious diet poses a risk to the survival of chicks and was found to be a particular problem in Shetland.

Climate risks to the UK’s seabirds

Reviews and modelling studies also play a useful role and one of the findings from a study by the Marine Climate Change Impacts Partnership⁴ was that ‘Many UK and Irish seabird populations are at or near the southern limit of their breeding range and/or are highly sensitive to changes in prey availability, limiting their resilience to climate change. Some species may struggle to shift their breeding locations northwards due to low natal and breeding dispersal rates.’

Potential climate factors that can affect food availability include changes in sea temperatures and ocean currents, while other dangers include those from fisheries and pollution.

Seals and climate change

Grey seals face similar risks, but as opportunistic feeders are possibly better able to respond to variations in climate. However, with only one pup per mother per year, they are particularly vulnerable to increased sea levels and wave action during the breeding season, as shown by high pup mortality during storms at several sites in recent years. Further north in the Arctic, the risks are clearer cut for seals that rely on sea ice for shelter, such as harp seals and hooded seals.

References

¹ Birkhead T (2023) British Birds. https://britishbirds.co.uk/. ² Bull et al. (2021) Proceedings of the Royal Society. https://doi.org/10.1098/rspb.2021.2284. ³ Owen et al. (2024) Avian Conservation & Ecology. https://doi.org/10.5751/ACE-02619-190117. ⁴ Burton et al. (2023) CCIP Science Review 2023. https://doi.org/10.14465/2023.reu14.saw

Thumbnail image credit: John Bridges / WTML