At Forvie National Nature Reserve (NNR) the breeding season for the terns is coming to an end. It has been another mixed year for one of Scotland’s biggest colonies of terns and a time when the NNR staff and volunteers can breathe a sigh of relief. After much hard work, most of the species have delivered another cohort of youngsters into the wide world to swell the tern population. Read on to find out more about the Forvie terns from Reserve Manager, David Pickett.
Terns are just amazing birds. They are the greatest of travellers despite some only weighing the same as a blackbird. Many terns winter off the coast of Africa but the arctic tern heads to Antarctica, forever chasing summer. At the colony, terns are so noisy, frenetic and stressed that you could imagine them burning themselves out quickly. But, at Forvie, we have recorded the two oldest known arctic terns in the UK. At 31 and 32 years old they have survived long enough to have a million miles on the clock, despite their frantic life.
The success of breeding terns can be affected by many different factors so no year is ever the same. At Forvie we put up an electric fence around a four hectare area to protect these ground nesting birds from foxes. We also keep visitors out of the ternery during the breeding season to avoid nests from getting trodden on and birds disturbed. But crows, kestrels, gulls and even oystercatchers can still take eggs and chicks. Heavy rain and cold weather can also decimate young chicks and, crucially, the fish that the terns need to grow strong chicks need to be present and healthy.
This year at Forvie the terns have mostly found these requirements to their liking. To work out how well the terns are doing each year we count the number of nests, the clutch size and, most importantly, the fledged youngsters that have left the nest. This number gives us an idea of how successful breeding has been. We have four species of terns breeding here. The highest number is of sandwich terns, 1100 pairs of them and they have a peak fledged chick count of nearly 700 – one of the best years yet. The arctic terns and the common terns look very similar to each other so for monitoring purposes we combine their totals. This year, 1600 pairs bred but we have a peak fledged chick count of only 350 chicks. This indicates that either predation of some sort was higher than normal or the fish weren’t as plentiful. Our rarest tern is the little tern; there are only about 2000 pairs across the UK. At Forvie, 27 pairs attempted to breed but it appears that they have all failed. Awful weather in June didn’t help them but we have also evidence from trail cameras that black-headed gulls and oystercatchers have been eating eggs and chicks.
Besides nearly 3000 pairs of terns at Forvie, other birds have been taking advantage of the excellent nesting conditions provided. We have some 2000 pairs of black-headed gulls, 100 eiders, a few pairs of ringed plovers and oystercatchers and, remarkably, one pair of hole-in-the-ground nesting jackdaws! This all makes the seabird breeding colony at Forvie exceptionally important.
The success of here is down to a partnership. Scottish Natural Heritage (SNH) staff work tremendously hard to perfect the protection system and then monitor the birds afterwards. The fence has to be checked every single day of the breeding season and our fantastic team of local volunteers play a really important part in this, as well as doing the grunt work of putting up and taking down of the fence and clearing the site in the winter.
A key part of the Forvie tern project is gaining an understanding of the importance of Forvie in the context of the North Sea. For many years the Grampian ringing group, led by Ewan Weston and Raymond Duncan, have been ringing young and adult terns and, by monitoring returning ringed birds, a better picture is emerging. Some terns have darvic rings put on which have an obvious and unique colour and letter combination that enables the rings to be read as the birds go about their lives. From these, the ringers have found where some Forvie birds winter – for example, yellow ECB has been seen twice off the coast of Namibia. And there are indications that Forvie exports birds to other colonies that may be doing less well while still supporting the strong colony here. Also, birds from across the North Sea head to the Ythan estuary and Forvie after they have finished breeding to fuel up before starting on their seasonal ocean wanderings. So it appears that Forvie is important on a much wider European scale. The Forvie colony continues to thrive thanks to the partnership of SNH, volunteers and the bird ringers but also thanks to the visitors who follow the signs and leave the birds in peace.
However, we can only help the terns from egg to first flight. After that, they are on their own until they return three to four years later to breed again. For tern populations to survive they need more than just a safe place to breed, they also need healthy oceans with good fish populations to feed chicks and feed themselves. At a time of climate emergency with changing oceans and more extreme weather this is something that everyone has to play a part in.