HOW DID THE PROJECT START?

Derek Gow and Coral Edgcumbe of the Derek Gow Consultancy undertook extensive research on the history of White Storks in the UK which was published in British Wildlife. They subsequently produced a feasibility report with considerable input from Dr Roisin Campbell-Palmer and further commented on by various experts. Derek and colleagues approached Natural England, DEFRA and other interests in order to start the project. This initial work was funded by the Lund Fund.

Who is running the project?

The project is a joint venture between a number of private landowners in Sussex and surrounding counties in partnership with Cotswold Wildlife Park and Roy Dennis Wildlife Foundation. Birds for release are provided by Warsaw Zoo as well as other sites in Europe. To find out more about the project team click here.

who is funding the project?

The construction of pens and the husbandry and feeding of storks is funded entirely by landowners themselves. The import and technical support costs were funded by the Lund Fund, the grants programme launched by Peter Baldwin and Lisbet Rausing in 2016. All captive breeding and quarantine costs are funded by Cotswold Wildlife Park.

what is the longterm aim of the project?

The long term aim of the project is to restore a population of at least 50 breeding pairs of White Storks in southern England. Central to this is the establishment of a breeding population in Sussex and surrounding counties that by 2030 is capable of producing sufficient juveniles to a level which is self-sustaining without the need for any further releases. We also hope the storks will ignite the public’s passion for wildlife and also provide social-economic benefits for local communities.

Why reintroduce white storks?

There is evidence that the White Stork bred throughout the UK (Edgcumbe & Gow, 2015). Archaeological records date back at least 360,000 years to the Pleistocene and more recently, nesting White Storks were recorded on the roof of St Giles Cathedral in Edinburgh in 1416. Other literature sources suggest that later breeding attempts could have occurred elsewhere (Edgcumbe & Gow 2015). It is likely that a combination of habitat loss, over hunting and targeted persecution all contributed to their decline. Despite the regular occurrence of vagrants from Europe, and the presence of extensive areas of suitable habitat, the breeding ecology of the species, in particular strong natal philopatry, conspecific attraction and associated colonial nesting, indicates that natural re-colonisation is unlikely. This same barrier has been encountered in other European countries with a recent history of extinction. For example, in Sweden between the years 1955-1988 ~540 individuals were observed, but no breeding attempts were recorded (Jonsson, 1989). A reintroduction project has subsequently restored a breeding population. The UK is now one of the last range states along with Denmark and Albania (NABU, 2013) where the species formerly bred which no longer hosts a stable breeding population. White Storks are charismatic birds. Their large size, colourful plumage, colonial nesting behaviours and well established folklore already ensures their popularity throughout their European range. Tourism based on White Storks is popular with the public, and their economic value to local communities has been demonstrated in Poland and various other locations around Europe (Czajkowski et al., 2014). The association of White Storks as symbols for conservation is well established across Europe and the species is regularly used to promote conservation awareness. In Sweden it has been used as a flagship species for restoration of wetlands.

where have other reintroduction projects taken place?

Over recent decades White Stork reintroductions have taken place in a number of European countries, including Switzerland (1948), Belgium (1957), the Netherlands (1969), France (1970s), Germany (1970s), Italy (1985), Sweden (1989) and Spain (2003). The techniques for the rearing and release of storks devised during these projects are well understood and thus provide a valuable working model for the Sussex project.

WHY UNDERTAKE THE PROJECT IN SUSSEX?

Sussex has extensive areas of suitable habitat, including:

• a ‘frequently flooded’ floodplain of around 39,000 ha and naturally wet soil areas covering 160,000 ha;

• 14,610 ha of coastal and floodplain grassland and ~5,136 ha lowland calcareous grassland;

• In the Arun and Rother catchment there are over 3,200 ha of floodplain grassland and associated habitat and in the neighboring Adur and Ouse catchment over 2,500ha.

  There is evidence that White Storks were widespread in this part of the UK. In 1185, the Sussex town of Storrington (in the Arun Catchment), was called Storketon which has been explained in Old English as Storca-tun being "homestead with storks". In addition, a small farm called ‘Storwood’ once abutted the east end of Oreham Common near Henfield. The Place Names of Sussex (Mawer and Stenton) additionally mentions a 15th century Storgelond in Wartling, on the edge of the Pevensey Levels. White Storks are now regularly seen in Sussex, with 34 recorded in the period between 1995 to 2011 (Birds of Sussex). The presence of reintroduced population is thus likely to attract wandering birds from the continent, which may join the breeding population. Strong conspecific attraction in the species means that unless they encounter other storks, these wandering birds are unlikely to stay.

  
  

WHAT LICENCE IS REQUIRED?

The IUCN Guidelines for Reintroductions set out procedures to ensure that reintroductions and translocations of species for conservation purposes are carried out to high standards. The species is a regular visitor to the UK and the project fulfils all relevant criteria and Natural England and DEFRA confirmed that no licence is required under the Wildlife & Countryside Act (1981) to restore the White Stork in England as a breeding species. This project concurs with Article 22 of the European Habitats Directive and Article 11.2 of the Bern Convention.

WHAT METHODOLOGY IS BEING USED?

More than 50 years of work with White Storks in Europe demonstrates that the best means of establishing a free-living breeding population is to hold juvenile birds for three years until they reach sexual maturity. This technique was first developed in Switzerland beginning in 1948 and has since been replicated across Europe, including in Alsace in northern France where a population of 800 breeding pairs is now established. This removes the urge to migrate, and therefore significantly reduces mortality among released birds. However, the establishment of a sedentary population in Scania in southern Sweden resulted in the need for supplementary feeding during cold Swedish winters when storks are unable to forage sufficiently for themselves. A breeding population of over 70 pairs is now established in Sweden, and with the population secure, migration is actively encouraged in order to reduce the need for winter feeding and to try to replicate a truly wild living population. This is achieved through a range of different release techniques, including releases of first year birds. A large proportion of the older breeding birds remain sedentary but the alternative release techniques have resulted in greater numbers of juvenile birds migrating each autumn. The Swedish experience is particularly relevant because, like southern England, Scania lies at the northern edge of the White Stork’s current breeding range.

We have used the extensive Europe-wide experience to inform our release strategy which involves retaining rehabilitated White Storks imported from Warsaw Zoo, and a smaller number of birds from northern France, in large 6 acre predator-proof pens for two winters before allowing them to disperse into the surrounding landscape where they are likely to settle and breed. In addition, captive-bred first year birds, raised at Cotswold Wildlife Park, will be released in late summer each year in order to boost the establishing population and to encourage migratory behaviour.

HOW MANY BIRDS WILL BE RELEASED?

It is likely that at least 250 White Storks will be released at the various release sites in Sussex and surrounding counties. A total of 166 rehabilitated birds from Poland, along with 12 from France, have been imported to the three pen sites to date. Further releases will involve captive-bred first year birds from Cotswold Wildlife Park in late summer each year.

WHAT WILL THE STORKS EAT?

White Storks are opportunistic feeders and will readily feed on a broad range of small mammals (voles, shrews and moles), insects (beetles, grasshoppers, and crickets), reptiles (snakes and lizards), amphibians (frogs and newts), bird’s eggs, fish, molluscs and earthworms (which can form up to 30% of their diet). Earthworms are likely to be a very important food source in southern England. On occasion they will take the chicks of ground nesting birds and will readily consume carrion. Introduced Louisiana red swamp crayfish have become an important food source in Western Europe. A key aspect of the project will be to work with surrounding landowners to incorporate appropriate habitat management practices to encourage the production of stork food items. Habitat management practices that will be encouraged include maintaining field margins for rodents, retaining areas of wetland to encourage amphibian and aquatic invertebrate populations, and creating pastures which are earthworm rich. This will also benefit a range of other species.  

CAN WHITE STORKS WINTER IN SUSSEX?

The establishment of a sedentary population in Scania in southern Sweden resulted in the need for supplementary feeding during cold Swedish winters when storks are unable to forage sufficiently for themselves. It is expected that a Sussex population would not require supplementary feeding, particularly given that mean winter temperatures are several degrees warmer in Sussex than both Scania and Alsace. Some supplementary feeding is undertaken in Alsace during winter but this is largely confined to sites such as the stork centre at Hunawihr for public engagement, and the majority of the population is not dependent on this additional food. 

WHERE WILL BIRDS BE SOURCED FROM?

In the initial phase of the project the majority of storks have been sourced from Warsaw Zoo in Poland. These are all wild birds that have been rehabilitated after injury. A smaller number of captive-bred storks were also imported from the Asace region of France. After transportation from Poland the birds undergo a period of quarantine at Cotswold Wildlife Park in order to comply with DEFRA regulations.  In addition a captive breeding programme is underway at Cotswold Wildlife Park which, in time, will be capable of supplying up to 50 individuals per year. Swedish experience shows that captive bred birds will migrate. A captive bred juvenile released in its first autumn in Sweden migrated along the eastern flyway through Europe, the Middle East and East Africa before wintering in South Africa.  

Bird flu and What to do if you find a dead stork

Sadly, avian influenza (AI) is now spreading across the UK and there have been some devastating outbreaks in 2022, particularly at seabird colonies in the north of England and Scotland. Whilst we haven’t yet recorded AI at Knepp or among our White Stork Project birds, we remain vigilant and are stepping up our biosecurity measures accordingly.

If you find a dead White Stork anywhere, regardless of the apparent circumstances of death, please do not touch it or pick it up. If you can, please note the specific location at which you found the bird (ideally grid reference, What3Words reference or nearest postcode), as well as the time and date. A photo of the bird in situ would also be useful.

Please email this information as soon as possible to whitestorksgb@gmail.com so that we can deal with collecting the bird and undertaking necessary testing in compliance with the guidance given to us by DEFRA.  

WHY DO WE RING THE STORKS?

We need to have each of our storks individually identifiable, because we want to be able to find out lots of information about each bird. This means every stork has its own metal BTO ring with a unique number on it.  Please look at the BTO’s website to understand more about the reasons behind ringing and the sorts of very useful data that can be obtained as a result.

In addition to the metal ring, our storks have also been given specially designed blue coloured plastic rings, which each have a unique white code on them. This allows us, and members of the public, to be able to identify birds out in the wild, without having to catch them. With these rings we will be able to map the movement of these birds from recorded sightings reported to us via the website sighting form, and our email and twitter accounts.  If you are interested in seeing what information is produced from this type of work, then please click here.

WILL THE ORIGIN OF REINTRODUCED BIRDS AFFECT THEIR MIGRATION?

The European population of White Storks has long been considered to diverge into eastern and western migration pools. This notional divide, occurring in the vicinity of the Elbe River in Germany, is based on observed migration behaviour, with western individuals migrating across the Strait of Gibraltar to overwintering areas in the Sahel region in West Africa and eastern birds following a path through Istanbul to overwintering areas in East and South Africa. However, some birds close to this divide are known to migrate along either flyway.

Reintroduced stork populations have been sourced opportunistically from eastern and western populations, and this has led to artificial mixing between the two flyways. Nevertheless, this appears to have had little effect on migratory behaviour due to strong conspecific attraction during migration, with juveniles usually choosing to migrate in flocks containing experienced adults. The close proximity of breeding populations in continental Europe means that once Sussex juveniles cross the English Channel it is highly likely that they will soon encounter migratory flocks. Having been seen at various locations in southern England one of the rehabilitated storks from Warsaw Zoo, crossed the English Channel to Brittany before eventually returning to the pen at Knepp. This shows that the flight across the English Channel is not a barrier to migration and that the released storks now regard southern England as home. The release of first year birds in late summer is a key requirement in encouraging migration within the population.

WHY ARE SOME OF THE JUVENILE STORKS TAGGED?

Whilst the ringing data on White Storks can tell us a huge amount, there are some aspects to their behaviours and ecology which we need alternative solutions to be able to understand. One of these is to understand if they do decide to migrate south for the winter, where will they go?

We have chosen to use specially designed trackers (called flyway 50 transmitters), which have been proven to work well elsewhere in Europe on this species. The tracking devices we are using collect high spatial and temporal resolution GPS and accelerometer data enabling us to determine home ranges, habitat choice, foraging strategies, distance moved per day, flight efficiency, energy expenditure and body acceleration index. This means that we can track migration success and routes of the juveniles we release and monitor the success of the reintroduction programme and understand migration behaviours. Click here to find out more about how the same tags have been used in Portugal.

The aims of the tagging project are:

(1) to determine the influence of heritable, social and environmental variables on the movement/migratory behaviour of the reintroduced birds;

(2) to investigate the foraging and movement behaviour of the reintroduced storks;

(3) to quantify causes of mortality and identify management measures that may enhance the success of the reintroduction programme.

DO THE TAGS AFFECT THE BIRDS?

The tags are worn by the storks like a backpack, so they don’t get in their way, regardless of what they do. They are also very light, so less than 3% of a stork’s body weight. The backpack harness is fitted in such a way that the biodegradable stitching holding it together will degrade over time and the GPS will fall off. We expect the tags to remain on the birds for 2-3 years before they fall off. This prevents lifelong placement. We are fortunate to have the best team in place to deploy these tags. The team have developed these specially designed tags and have a huge amount of experience in using them on hundreds of storks in Portugal.  The research carried out by the team has provided data to support that tagging these birds is low risk and that fatality or injured as a result of the tags is highly unlikely.   To find out more visit: https://www.bto.org/our-science/topics/tracking/tracking-studies/stork-tracking/about

With any tag fitting we want to know that it won’t affect the birds’ survival. When we examine the survival rates for the breeding/post-fledging period and for adults monitored with the same GPS tracking device in Portugal, the rates are similar to survival rates obtained from published long-term studies done elsewhere. This means we can be confident that the tags themselves are not having a significant negative effect on the birds.

Birds are monitored closely on a near daily basis while they remain at the Knepp Estate study site by the Project Officer and a team of trained volunteers, allowing any issues with the deployed tags to be picked up. The project also has a ‘Report a sighting’ form on the project website and we reach out to birding groups and other members of the public to request any field observations. If we hear about any issues with the tagged birds, then we follow up on any reports.

WHAT HAPPENS TO TAGGED STORKS THAT DON’T SURVIVE?

We’ve given our juvenile storks the best possible start in life. At Cotswold Wildlife Park where they are raised by their parents they receive the very best food to ensure they have a great diet. Once at Knepp, where they are released, they continue to be given supplementary food for as long as they want. In addition, the young storks are given a full health check before they are released and only healthy birds are released. However, for this species the survival rates of the fledglings in the wild are low, which is to be expected for this life stage. This means that unfortunately not all of our juvenile released storks will make it to next summer.

If a GPS tag shows that a bird is no longer moving, then we will make every effort to locate it and find out either the cause of tag failure or if a bird is found dead then we will collect data on them, including sending birds for post-mortems if the cause of death is not clear.

More generally across the project, if members of the public find and report to the project team about a dead bird then we will follow this up with email communication to understand more details. If appropriate, we will collect the bird and it will be sent for post-mortem to ascertain the cause of death.

WHAT WILL HAPPEN TO THE DATA PRODUCED FROM THE TAGGING?

We will have a section on our website as soon as we start to receive data from the trackers. This will allow the public to follow the local movements of the storks and, if they migrate, their journey to Southern Europe or Africa.

The data will be analysed by researchers and written up as a scientific peer-reviewed publication. We will endeavour to ensure the work is published as Open Access and will provide copies of the paper to anyone requesting it. We will also produce a summary of the work for non-technical audiences.

Under the BTO Special Methods licence giving permission for the tagging, the project will supply data on the fates of all tagged birds. The process and all methods involved will be reviewed by the project team to understand the success, before any further tagging of birds is undertaken in future years.