Positive Lympstone

Wild About Lympstone: John Goss-Custard

Sep 1, 2022

Wild About Lympstone:  Local resident John Goss-Custard tells us about his passion for estuaries, shorebirds and why he spent 26 years sitting on middle of the Exe estuary.

We’re incredibly fortunate to live alongside the beautiful Exe estuary with its internationally important wildlife and habitats. With thousands of birds feeding here each year, it’s become one of the most highly designated sites in the South West. And it’s the humble mudflats we must thank for this abundant estuary life. Brimming with invertebrates like snails, worms and clams, although they may look empty, they are actually as rich in biodiversity as a rainforest. 1m3 of mud apparently contains the same calories as 14 mars bars! John Goss-Custard has lived in Lympstone for 22 years. Here he chats to us about his fascinating life as a research ecologist on estuaries and shorebirds, his work on the Exe estuary and what he loves about Lympstone.

Where did your passion for nature and estuaries came from John?

I grew up in Stoke-on-Trent which is about as far away from an estuary as you can get! But as a young boy I was hugely inspired by Peter Scott, (son of Robert Falcon Scott of South Pole fame), and his natural history TV series, ‘Look’. I spent my summer holidays volunteering at the Slimbridge Wildfowl and Wetland Trust that Peter founded, learning bird’s names and developing a love of for wild birds, estuaries and sunsets.

After a degree in zoology from Bristol University, I headed to Scotland to do a PhD studying the biology of wading birds. This further fuelled my passion, both learning amazing facts such as how the Redshank needs to eat 30-40,000 food items a day to maintain its biological fitness (not easy in the cold Scottish climate!) and by the beauty of working on the Ythan Estuary with its huge flocks of geese and eider ducks. That, and the perks of visiting the excellent local pub that claims to have invented the sticky toffee pudding!

My research focused on investigating the basic biology of wading birds at a time when international interest was increasing in this area, particularly the Dutch, with their internationally important Waddenzee area for shorebirds (wildfowl and waders). The main aim of my work was to better understand the natural pressures operating on the birds, how these impacted biological fitness, and how the birds dealt with this.  After my PhD, I returned to Bristol University to lecture, but soon discovered I enjoyed research more than teaching. Thus, I accepted a job with the Nature Conservancy at the Coastal Ecology Research Station in Norwich. For 3-4 years, I investigated the potential impact of a proposed reservoir development on the shorebirds of the Wash.

Tell us about your work on the Exe estuary

In conjunction with new emerging thinking around Foraging Theory and Behavioural Ecology, I was started developing an interest and specialism for predicting the effects on shorebirds of any change in the way estuaries are managed and used, and their effect on human interests.  I landed a job with the Centre for Ecology and Hydrology in 1976, looking to further this work. After looking around the whole of the UK for a suitable estuary that was in reasonable distance of a research station, we identified the Exe estuary as a perfect research site and so, I came down to the River Exe for the first time. Thus, began the most significant project of my career.  For 26 years, between 1976 – 2002, I essentially lived in the River Exe estuary. Every day I’d sit on my own in hides on stilts out in the estuary, sometimes up to 10 hours a day collecting data on bird behaviour. This was fed into a model my colleagues and I were developing (an individual based model) which offered a pioneering method for understanding and predicting the impact of human activities in estuaries on the shorebirds that live there. Although I spent many hours alone collecting the data that fed the model, the interest in these migratory shorebirds spanned many countries, and I have been lucky enough to work with many amazing shorebird enthusiasts from all around the world.

Tell us a bit more about this model

The key criteria in determining the health of a bird population, and therefore whether a new or changing activity in the estuary is detrimentally impacting the population, is the number of birds that survive the winter in good biological condition. The model we developed compares data on how much the birds need to eat to survive in good biological condition, and the quantities of food currently available to them. If the model finds any new, or changing, activity in the estuary is not impacting bird survival rates in good biological condition, then it can be surmised that the activity is currently having no detrimental effect on the birds. I know that models can be incomprehensible to some people, whilst being the object of deep and passionate love by the inventor! The most important thing to do with any model is to test it rigorously to ensure that its predictions are validated. This increases the model’s credibility and means the results can be used with some confidence. We spent a significant amount of time testing the model and in my view, an invalidated model is a menace!

How has the model been used to help protect shorebirds?

The model is now with Bournemouth University (that I’m affiliated to as a visiting professor) and it has now been applied to many species of birds, on many issues, in many countries around the world. Here’s a few examples –

Investigating the impact of shellfisheries on oystercatchers and mussels

A hot topic in the 1970s&80s was whether oyster catchers were a serious pest for estuary shellfisheries (cockles and mussels), and vice versa. We first used the model to understand this better. Oyster catchers were a good species to collect data on as they’re large birds and it’s easy to see, and measure, the size of mussels and cockles they eat along with many other important aspects of their foraging and social behaviour. There was a particular interest in the Netherlands on the effect of shell fishing on birds. It had been calculated that to compensate the birds at the end of the shell fishing season, when the birds were returning from breeding grounds, 70% of their gross food requirements should be left for them. But, despite this, birds were dying in large numbers. The model was used to investigate this situation, and the results showed that to maintain survival and body condition, birds required not 0.7 of what they required, but anything up to 7 times what they required. This directly changed Government policy and helped to reduce the numbers of dying birds. The model has been used for the same issue in many other areas, for example in Lincolnshire and the Norfolk Wash on the east coast of England.

Looking at levels of disturbance on shorebirds in the River Exe, and other European estuaries

The concern here was whether levels of disturbance (for example from recreation or collecting shellfish) causes levels of impact for shorebirds that results in the loss of their body condition, or death. Disturbance causes birds to fly away, expending energy in flight that they wouldn’t otherwise have needed to use, and reducing foraging time. Models are useful is this kind of situation as they deal with amounts and can think quantitatively. In this context, the model was able to consider the energetic and time costs of disturbances of various frequency and amounts, and the link between this and the ability of birds to survive winter in good condition to maintain fitness. The model allowed us to know how many disturbances per day (rates of disturbance) it takes before birds are affected in a way that they can’t compensate for, and thus loose biological fitness, or may die.

The good news is that the model tells us that the frequency of disturbance on the Exe estuary is low and that it would have be increased between 29-43 times before birds are adversely effected.

How has your work influenced your views around conservation vs development?

My work has been incredibly intellectual stimulating, not only from a biological perspective but from an estuary management and decision making perspective. I’ve often been asked to inform management decisions that look to balance nature conservation and human activity, and this has provided me with ample opportunity to develop my own thinking around this often contentious issue. Here are a few of my thoughts –

  • Whatever your objective it will be better served if it’s based on well tested, reliable science.
  • As a scientist, I always endeavour to bring scientific integrity and honesty, and consider it my job to make reliable predictions based on thorough and well-tested science, not to provide value judgements, or to produce results to fit desired outcomes.
  • Science helps us understand how we can maintain a balance between enabling valid human activity and ensuring the conservation of environment and wildlife. Science helps us understand how we can marry these two often seemingly conflicting objectives, without personal, non-evidence based, agendas high jacking the process.
  • If there is no scientifically validated evidence to suggest damage to something we value e.g. wildlife, people should be able to carry out their activities unrestrained.
  • All decision making should be evidence-based, and evidence-based conservation management is the best approach. Large amount of conservation money has been wasted, having been poured into policies that are not evidence-based.
  • Solutions will best be found where we balance perspectives and use scientific evidence, rather than be swept up in the latest cause or way of thinking. Science can help identify the real cause of a problem.
  • For example, reduced numbers of migratory birds on the Exe might have nothing to do with the estuary here, but rather events elsewhere. Migratory birds annual cycle involves flights and visits to many estuarine areas, in many countries, and the health and number of these bird will be dependent on the management of all these areas, as well as events that might happen to the birds in migratory flight.
  • For example, egg survival rates (and thus bird numbers) will reduce significantly in any year if ground predators are prevalent. High numbers of Arctic foxes, for example, can significantly impact bird populations that breed in the far north (such as brent geese). Indeed, one of the possible theories for the lower numbers of oystercatchers on the Exe estuary since 1990 could be due to diminishing game keeping in northern breeding grounds, which is leading to an increase in predators that feed on the eggs of ground-nesting birds, such as the oystercatcher.

Why is the River Exe so special to you?

Apart from all the internationally important bird life found here, for me it’s the aesthetics. In Lympstone we’re blessed to be on the east side of the river so looking west, we benefit from the marvellous sunsets, and looking east in the morning, we’re also able to see wonderful sun rises. The most magical time to enjoy the estuary is as the sun sets or rises – watching the shifting colours reflecting on the mudflats and listening to the call of the waders. Some of the most dramatic I’ve seen were out in the boat near the middle of the estuary mouth at Bull Hill – an old mussel bed now a gravel heap – but to be honest it’s hard to beat ‘The Green’ in Lympstone for an ideal spot to watch the sunset, especially with a beer in hand!

What’s your favourite Exe estuary birds?

Autumn and winter is a great time of the year because all the migratory birds are back. Some of my favourite birds at this time is the spotted redshank (quite rare), greenshank (with grey-green legs) and common sandpiper (which bobs up and down). I particularly love the geese – the Canada and brent geese flocks. For me they embody both the wonder of biology and aesthetics. The Exe estuary is the winter home to 1% of the world’s population of brent geese, and numbers are going up. Their migratory cycle takes them from the Exe, along the south coast of England, across to the Netherlands, around the White Sea, and on to the north coast of Russia, in the Arctic, where they breed. Another bird I love looking out for is the whimbrel. This looks like a curlew, only smaller, with its white eye stripe, and spends the winter on the west African coast where it feeds on crabs. It has a 7- note call, and when you hear this, you know it’s May without having to look at the calendar!

A few amazing bird facts …

Natural selection has adapted migrating shorebirds to achieve amazing feats of survival and longevity – way superior to our much-loved garden birds. On Dawlish Warren you’ll see sanderlings, for example, that can double their mass in a fortnight. The bar-tailed godwit migrates 14,000 km without stopping from Alaska to New Zealand & Australia, shrinking parts of their body in the process to have extra space for storing fat and water.

What advice would you give others to get more involved with nature and wildlife?

  • Be inspired – read books, or listen to those who love wildlife and nature. Learn amazing facts about birds, like those above.
  • Get outside – and observe nature up close. The colour and patterns of a bird’s plumage is amazing, as are the colours on the mudflats as the sun sets at the end of the day.
  • Get engaged – take photos, or paint pictures of what you see, join a local wildlife group.
  • Be curious and ask questions – bring out your inner scientist and get excited about how the natural world works.

For example, did you know that the Exe Estuary once had vast mussel beds stretching from Bull Hill at the mouth of the estuary right up to the marine camp, but that these have all but disappeared since 1976? Scientists, including myself, have been looking into what why this is. Baby mussels used to be laid out on intertidal zone in large sheets where they connected to each other and held fast. Today, where these mussel beds used to be you’ll see instead large expanses of pacific oysters. Introduced in France from Japan, 30-40yrs ago, these have spread across Europe, including Exe estuary. Scientists are investigating if there is a causal link between the oysters arriving and the mussels disappearing, and if the reduction in mussels (the main food source for oystercatchers) is partly responsible for the recent reduction in their numbers from approximately 3000 – to close to 1000.

Can you tell us a few interesting things about yourself others might not know?

  • When I retired, I wrote down 25 ‘must-do-things’. One of which was to learn the Bagpipes! I’ve been playing now for 18 years – you might have heard me during the Jubilee celebrations.
  • I love walking and meet each year with my three grown-up children to hike a new trail somewhere in the UK.
  • My passion for geese is the reason we have a glass roof in our This gives me my fix of ‘goose moments’ – watching the flocks on their flight path over our house, to and from the river.

And lastly what do you like most about living in Lympstone?

The community is very friendly and welcoming – it’s the kind of place that’s easy to feel at home and develop a sense of belonging. Of course, there’s also the amazing natural beauty on your doorstep, like the estuary. And lots of good pubs!

For more information –

A couple of inspirational books on nature for youngsters –

  • ‘Diary of a Young Naturalist’ (Dara McAnulty) – awarded the Wainwright prize, this amazing book shares the experience of how an autistic boy experiences, and benefits, from connections to nature.
  • ‘Birdgirl’ (Dr Maya Rose Craig) – a young British-Bangladeshi ornithologist’s story of her passion for birds.

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