The dubious accolade of being the biggest threat to wader populations, of multiple species, goes to habitat loss, be it by destruction or degradation. This scourge manifests itself in a variety of devastating, human initiated, actions; intertidal reclamation, changes in agricultural practices, drainage, pollution, disturbance, afforestation, dredging, river management and ploughing up of grasslands are some of the more obvious actions that are seriously affecting waders, of all kinds, everywhere. Add to this the background threat of the effect of climate change altering the environment, a rather more chronic problem, which is never far away and you’ll discover that every habitat in which waders exist is under threat in one way or another.
Historically many areas across the world have been drained to provide fertile soil for agriculture as well as for development, road construction, mining and mosquito control, among many others. One of the grandest examples of this is the Fenlands of England which once stretched from Lincolnshire and Norfolk south to Cambridge and which rendered Ely an island when flood waters inundated the land. This area has changed so much that it would now be unrecognisable to anyone who lived in the days before it was drained, the land now comprising flat and fertile fields criss-crossed by drainage ditches to maintain the lower water table. The population of many wader species would have been seriously compromised by the loss of this extensive marshland. Among them the Black-tailed Godwit which was once a relatively common species in the region became extinct as a British breeding bird. As their numbers dwindled their new rarity made them more valuable to the trophy hunters and collectors.
In the 1800’s projects were initiated to drain the massive Everglades swamp in Florida with a view to converting the land to agriculture and development for towns and tourism. Today it receives less than one-third of its historic water flow and the wildlife-rich wetlands are half the size they were even in the 1920s. Greater access to the everglades led to unrestricted hunting when waders and other water birds suffered greatly, especially egrets, which were killed for their glorious plumes. The piecemeal drainage and conversion to agriculture and urbanisation has increased pollution from run off and fertilisers in the water that remains.
Haarlemmermeer (The lake of Haarlem) is one of the biggest, if not the biggest, drainage project ever accomplished. Situated in the Netherlands it once covered over 150 square kilometres and was drained by successive projects finally being dry in 1852. It is thought that around one thousand billion litres of water were removed to drain the lake.
Mangroves are another habitat that waders find of great value for foraging and roosting, and they are under threat across the globe particularly in Asia where they are being converted into agricultural land, aquacultural areas and removed for building development, particularly in the tourism sector. On the other hand, mangroves have been spreading across saltmarshes and tidal mudflats removing vital feeding areas of open mudflats and marsh from the waders’ choice of feeding area. Mangroves are restricted in their range by temperature requirements, as the planet warms they are able to access new areas and invade new coastal marshes and mudflats that are critical to the survival of migrating and wintering waders.
Peat bogs naturally hold a lot of water, and carbon. In order to extract the peat the area needs to be drained and then the peat extracted. The draining of the peat causes greater run off and that water is altered containing augmented suspended material and dissolved organic matter and increases in nutrient and metal content, colour and pH are to be found. Small scale hand dug peat extraction may not have caused too much harm, but the mechanised wholesale destruction of entire habitats in the last thirty years has had a devastating effect, particularly in Ireland where it has been instrumental in the decline in Curlew numbers.
River and coastal management
Degradation of habitat can also occur by the altering of water flowing from a river or along a coastline. Many estuarine mudflats exist because for millions of years the rivers have been depositing sediment at their final destination, the sea. But naturally that sediment is also washed away so needs constant replenishment. If a river is dammed or dredged to control the flow, altering its speed and volume, it will inevitably affect the amount of sediment deposited. Damming can reduce the flow to such an extent that the mud flats will simply disappear or at least change their character. Sediments may settle further upstream in slower moving water or be trapped by the dam itself and existing mudflat may erode, the sediment being transported and deposited elsewhere changing the physical form of the flats.
Dredging has the opposite effect where fast flowing water carries larger, heavier sediment which washes away smaller particles preventing them from settling. From a waders point of view deeper faster moving water is far less suitable for feeding than shallow slow-moving or still water.
If the flow of the water is changed it will therefore alter the deposition of the sediment and can change mud flats into sandy flats if the flow increases and vice versa if it is reduced. In addition a change of water level and velocity can render some islands in the middle of rivers, which were hitherto unreachable to land mammals, accessible if water levels drop or they can be washed away if the speed and level increases.
At the mouth of a river, where it meets the sea, the fresh water mixes with the salty sea water and salinity levels are increased. There are creatures in that environment that require the diluted salinity to thrive, so, if river flows are reduced the salinity increases and some life forms will not be able to survive. These victims may well be those that the waders are feeding upon again reducing the suitability of the habitat for waders.
River flow will also impact upon floodplains where periodic inundation is the main driver of habitat survival. Many waders rely on floodplains and their existence is under threat where the flooding has been reduced or halted altogether.
Changes in the physical aspects of a coastline caused by large projects, such as the development of a port, or smaller objects, like groins or barriers, can dramatically change the drift of sediments along the shoreline. This can impact on the formation and evolution of flats and spits which are often extensively used by foraging waders. In one instance in New Zealand a new port development changed the currents to such an extent that silt deposits to one side of the port all but ceased, this led to the erosion of that portion of the coast. Some important coastal lagoons which existed there, which had been separated from the sea by the sediment were lost and swallowed by the sea as the barrier diminished thus eradicating not one, but two vital wader habitats.
If predicted warnings are correct, the impact of climate change would be devastating to coastal environments as previously intertidal areas would remain permanently under water and with human structures along much of the coast, which we would obviously protect, there is no natural place for the intertidal area to advance into and mud flats would become an endangered environment.
Existing ports are being developed and expanded, often meaning that large areas of mud are removed to allow ships to enter the area. The same thing happens in small bays, which are often shallow and ideal feeding grounds for waders where marinas are constructed for privately owned boats and yachts.
We all love a beach, and being by the sea is the preferred place to live for many of us. In addition it is where many of us choose to spend our holidays. The result is that all those people wanting to be beside the sea need places to live, or stay temporarily, and the entire infrastructure that goes with that.
Coastal towns tend to spread along the coast rather than inland increasing the area of beach front that is compromised from the point of view of the natural world.
A secluded bay that becomes a promenade is no longer secluded. Either the birds that nested there before are forced to move on or stay and live in substandard conditions with increased disturbance and predator numbers, both the dogs and cats that the people bring with them deliberately and the rats, foxes and gulls that they attract inadvertently. Litter and pollution soon follow any development, at night light spills from the town alter the environment and provide light for predators to hunt by.
Coastal saltmarsh erosion
Saltmarshes provide a sponge to soak up tidal surges and storm floods. They naturally erode as the sea pounds them and as they retreat so the land behind them retreats changing the landscape in form if not structure. However sea walls and urbanisation prevent the saltmarsh from moving back into the land the result of that is the loss of saltmarsh and the sea reaching these unnatural barriers causing them damage.
Grasslands turned over to agriculture
Away from the acute crisis in the intertidal zone the change of land use for agriculture has, over the last few hundred years, had a more chronic effect; more like a death by a thousand cuts. The pace of this change has been accelerating at an alarming rate as nations become more developed, what were once pristine grassland habitats have been ploughed and converted to farmland and previously suitable wader habitats within farmed areas have been altered to allow greater yields.
Grasslands, such as the prairies and the Great Plains in North America, and the Pampas of South America were once important areas sustaining the huge flocks of Eskimo Curlews. The prairies also held healthy breeding populations of Mountain Plovers, which have been much depleted, and Long-billed Curlews which are retreating westwards. At least half of the Prairies are now under the plough and that which remains is seriously degraded by the lack of the great grazing herds of American Bison and the eradication of Prairie Dog towns. Likewise the Eurasian Steppes may have been crucial to the breeding success of the Slender-billed Curlew which too may well be extinct and the breeding Sociable Lapwings which are now Critically Endangered. The effects of their conversion to farmland have been devastating as it is breeding success that maintains a population, lack of success is the road to extinction.
Changes in agricultural practices
Where traditional agriculture had already existed, largely in harmony with wildlife, the great advances that technology and science has brought to the industry have caused great and often overwhelming changes.
Northern Lapwings have declined by eighty per cent across the UK in the last fifty years, particularly in southern England and Wales. This is not due to some horrific single piece of environmental vandalism like the Saemangeum project, nor over harvesting of their food supply as in the Delaware Bay Horseshoe Crab situation, no, the blame for the huge reduction in Northern Lapwing numbers in the UK recently can be placed firmly at the door of habitat loss due to changes in agricultural practices.
It is the lack of breeding success due to a paucity of suitable places and despoilment of those that remain, rendering them unsuitable and unsafe, that is undoubtedly driving the numbers down. The species needs a variety of habitats in which to rear its young. Among these are open ground for nesting and incubation and longer vegetation for hiding the young when they have hatched. These habitats were lost at an alarming rate due to cessation of rotation of crops and mixed farming practices.
It’s all about the maths, and logic will tell you that a stable population relies on each adult being able to replace itself in its lifetime. If a pair can bring off two fledglings a year and survive for the average four and a half years, and if just two of those nine chicks can outlive their parents, which doesn’t seem like too much of an ask even in the harsh natural world then, as a species, they have cracked it. Sadly of late, it seems that this is not possible, especially in arable land, in the modern world of mega farming.
A trip to warmer places for birders is never complete without a visit to rice fields, they provide both food and shelter for many bird species and in particular waders. However once again the changes in the patterns of flooding are compromising their suitability for waders. Some rice strains can now be grown in relatively dry fields much reducing their suitability for waders and those that are still wet are advancing harvesting times. Conversely higher temperatures due to climate change are also affecting the flooding of rice fields. An example of this can be seen in Japan where the higher summer temperatures are bad for the rice harvest. In this case the farmers are delaying the flooding so that the harvest can be done in more suitable temperatures. The main use of the fields by waders is in the spring as they migrate north, and increasingly they find the rice fields dry and of little value for feeding.
In some places the rice fields are being abandoned altogether when they quickly become covered with tall vegetation making them of little use to waders. However, all is not lost for waders who frequent rice fields, particularly in the USA where the rice fields in South Carolina are managed wetlands and many areas are managed with waders in mind. Water levels are controlled to benefit them making areas always available to them, an idea that can be exported around the world and indeed has been with students at Gifu University in Japan involved in a project to persuade rice farmers to do just that.
Over grazing and under grazing by livestock
Grazing has been a friend to waders in the past, keeping vegetation relatively short can be an advantage along with the promotion of plant rich environments in which many invertebrates can dwell. However, over grazing turns the tables very quickly due to the increased threat to the eggs and young from trampling and also the reduction of any sort of cover for the birds. Under grazing on the other hand can result in the vegetation growing so much that it is rendered unsuitable for ground nesting birds due to its composition changing and scrub conditions prevailing.
Hay meadows replaced by silage
Another example of a species falling foul of farming changes is waders that breed in hay meadows such as the Black-tailed Godwit in the Netherlands. There are vast areas of lush Dutch meadows in which Black-tailed Godwits have found a home for many years. Hay meadows are wonderful places. Full of native plants and flowers upon which butterflies and other invertebrates can feed and breed attracting their predators. Among those predators are waders. In these meadows waders find a safe haven to breed, concealed by the growing grasses and other plants, the young are protected from prying eyes and also find plenty to eat and soon they fledge and fly to other habitats to continue their development before the hay meadows are cut in late June.
Well that is how it used to be, but these meadows are few and far between these days, they have been replaced by silage, a fast growing monoculture plant that can have several yields a year. The consequence for the natural world is that it is a much more sterile environment, no flowers grow and few other plants flourish which means there is nothing for the invertebrates and by dint, those that prey on them, to eat. Worse still, if the waders choose to breed in them they will seldom be able to bring off their young. Cutting can take place in early June before the chicks are fledged; they are defenceless against the mowing machines. If the cutting is earlier still, the chicks may be lost or the nest with eggs destroyed, earlier still and the birds find nowhere to nest at all. Either way, an entire population of birds is no longer able to reproduce and declines are inevitable as youngsters are not replacing the older birds that don’t survive each year.
In Brazil for example, there was much trumpeting about how they had reforested vast swathes of land, and therefore they were the defenders of the environment. However what was emerging was a forestry industry that planted exotic Eucalyptus trees and not native rain forest trees rendering them almost useless for all but the most adaptable of local fauna. Those areas grew quickly but then of course inevitably they too were clear felled. Whilst this did not, with the possible exception of Southern Lapwing, cause a great problem for waders, it shows that afforestation needs to be viewed with some scepticism when it comes to environmental improvement.
Worse still are the schemes where exotic forests are cultivated to the detriment of natural habitats. In the North York Moors of England for example the scars of dark green plantations stood out like acne on the face of a fresh young teenager, somehow menacing in their march across the more open landscapes desired and required by the moorland birds. The ribbons of dry stone walls and heather being engulfed by the advancing army.
In Iceland too forests have replaced heathland. These Icelandic heathlands are a veritable goldmine for those in search of breeding waders. Eurasian Golden Plovers, Eurasian Whimbrel and Common Snipe are dominant and in the more humid areas they will be joined or replaced by Black-tailed Godwits, Dunlins and Common Redshanks. The common thread that links all these birds is of course that they are not forest birds so replacing their natural habitat with trees has a devastating effect on their local population eventually wiping it out completely.
In the same way afforestation occurs in Africa where large areas of scrub and savannah are covered with trees. These trees have an entirely negative impact on grassland bird diversity even in relatively small projects. Studies have shown that if you compare the diversity of bird species that benefit or otherwise from afforestation, grassland communities possess more species and are richer in both endemics and threatened species than those to be found in plantations. The species that depend on these grasslands in terms of waders are many Lapwings particularly Blacksmith and Crowned, and Coursers such as Temminck’s, Burchell’s and Double-banded.
‘Ah! Those Autumn mornings and evenings! How I love them! What stirring scenes among the birds I can recall; what stores of notes I made! How vividly some of them return; incidents of twenty years ago, among what were peaceful fields and wooded valleys then, but now, alas, the busy centre of a score industries. All those mighty trees, where the Rooks and Ring Doves bred, have bowed their noble heads before the axe; all the brushwood and the thickets and the close-set hedgerows, where the Warblers and Finches nested, are gone; all the tangled ditches and hollows, sacred to the Grasshopper Lark, and the Jack Snipe, Levelled away! … No longer does the air resound with song at morn and even; all the feathered hosts are gone; the trout-stream is little more than an open drain; and one of the fairest sylvan scenes that ever eye of man gazed upon is now a desolation of bricks and mortar, and a wilderness of tall chimney shafts, factories and workshops! My ruined Aviary!’
This passage was written by Charles Dixon in his book The Annals of Bird life – a year book of British Ornithology in 1890 and it just goes to show that nothing changes. It could have been written by any one of a countless number of people who can remember places that they frequented, as a younger person, full of birds and song that now are gone; replaced by urban sprawl.
Human Population Expansion
Stand on any motorway bridge at rush hour, spend an hour or so in any international airport lounge, or take a look at one of those live population counters on the internet, and you will soon realise there is an awful lot of people in the world and that the number is getting bigger every minute.
This seemingly unstoppable growth is probably the single biggest problem the world faces as it generates a need for ever growing, ever stronger, and ever more stable economies to support all those people. In addition these economies become an ever greater consumer of resources and water. These factors mean more pressure is put on every inch of available land to be used for the purposes of food production and the provision of safe drinking water supplies, usually to the exclusion of all else. In addition, the energy required to service all these economies is rapidly increasing and, despite good intentions of renewable energy, this seems to be leading to the change in the climate that we are experiencing.
Conversely, across the world, study after study is recording declines in wader populations. Some flyways are losing as much as eighty-six per cent of their waders, others may be losing just thirty-three per cent, but the average loss across the board shows that nearly half of our waders have already disappeared! Across North America seventy per cent of waders have been lost, especially Arctic breeding species. In the UK alone Northern Lapwings have declined by eighty per cent over the last fifty years. Eurasian Curlews have undergone a similar decline in England, Wales and Scotland, while Ireland has lost a staggering ninety-seven per cent of its breeding Eurasian Curlew population.
All waders are preyed upon in one way or another but there are two main categories of predator, natural and unnatural. Natural threats come from the air in the form of aerial predators such as falcons and hawks preying on adults and also other raptors and crows when eggs and chicks are involved. To give you some idea of the level of threat and levels of intelligence a clutch of eggs faces there was an example of an Australian Kestrel visiting the nest of a Hooded Plover. It visited the nest several times while the eggs were in place. It was clear the bird was inspecting to see if the eggs had hatched and thus provide a suitable meal for it. Finally the Kestrel was thwarted after all its patience when the eggs were plundered by a crow before actually hatching.
Although less of a threat to fit adult birds terrestrial animals such as foxes, badgers, stoats, weasels and even hedgehogs and reptiles can pose a significant threat to eggs and chicks alike.
Recently it was discovered that surprisingly, some herbivores also predate nests. There are examples of sheep eating Curlew eggs in the UK and in New Zealand deer have been found to be a threat to the Critically Endangered Southern Red-breasted Plover.
Feral and introduced species have posed a threat to ground nesting birds since the days of discovery when cats, dogs and rats were transported around the world, deliberately or inadvertently to places where the birds had not developed a means by which they could cope with the new threat. Many of the extinctions that have occurred, especially among ground nesting birds, have been as a result of these introductions. Well-meaning people will often feed these feral populations, especially cats, whilst not appreciating the dreadful toll these animals take on their wild neighbours.
The hunting of waders used to be widespread, but in recent, more enlightened times most wader species are off the quarry list. Those that remain on the list are legally sought such as Woodcocks, Snipes and some Plovers. The rules on what is legitimate quarry vary depending on where you happen to be. A bird may be protected on one side of a national border, but not on the other once it has crossed. It is however unlikely that this legal sport hunting is having a drastic impact on populations although common sense would suggest that if a species is in decline it seems to be an unnecessary pressure to keep shooting them for pure sport.
Illegal sport hunting is also a threat in some areas. The Mediterranean region is a dangerous place for migrants, especially those passing through Malta, Cyprus and Lebanon. Traditional and cultural reasons are usually cited as an excuse for this destruction. Although legislation is in place to stop this, monitoring and prosecuting are both difficult and costly to achieve.
Rather more difficult to deal with is subsistence hunting, where people are hunting birds for the pot. The alternative is not a Big Mac and fries or a trip to the supermarket, the alternative is hunger. It is in these situations that conservation needs to deal with the underlying poverty before it can address the hunting issue. This has been done with some success in Bangladesh and Myanmar where hunting was a threat to the Spoon-billed Sandpiper.
The primary pollutants are sediment, fertilisers, pesticides, plastics, salinity, heavy metals, weeds, poorly oxygenated water and altered pH levels.
Even if the flow of a river is not altered in some unnatural way, causing pollution by sediments, direct pollution and changes to the chemical make-up of the water can occur. This happens especially where the water course receives water run-off from urban areas, run off from farmland (which includes grazing stock), or direct use of the water for flushing or cooling chemical treatment and sewage. This change in the water can be obvious with a reduction of the clarity of the water but much of it is unseen and undetected.
Although not an obvious source of pollution deforestation can affect the component parts of the water with increased sediment due to erosion and loss of water clarity. These higher deposits can increase saltmarsh build up, but the quality of the water, often poorly oxygenisated, may affect wader prey species or reduce the nitrogen uptake by microorganisms in the water and mud.
Recently it has become apparent that our over use of plastic, combined with careless and irresponsible disposal and a lack of recycling is causing one of the biggest pollution problems ever faced worldwide, especially in our seas and along our coasts.
Further pollution risks come from accidental spillages at sea and into water courses, illegal dumping and tank flushing and mining activities.
Much of the disturbance caused to waders is as a result of people partaking in recreational activities. Beaches are much favoured as playgrounds where quad bikes and other vehicles are driven and parked. Other activities such as dog walking (especially if dogs are off the lead), jet skiing, boating, kayaking, surfing, windsurfing, kite surfing, low flying aircraft, sunbathing, fishing, shellfish collecting, horse-riding, birdwatching and photography can keep birds from resting or feeding for periods of time. Away from the beach other activities can be detrimental to birds in their breeding grounds such as hill walking and off road vehicles.
Uncontrolled domestic animals such as dogs and cats can cause great loss or distress to ground nesting and roosting birds. Recently horse training on beaches has become a problem in some parts of Australia.
Loss of food supply
The principle cause of food shortage is habitat loss, and also climate change is having a greater effect but our direct actions can cause problems too. Shellfish, in uncultured populations, can become over harvested; this is one of the probable causes of the demise of the Canarian Black Oystercatcher.
Another excessive use of the fruits de mer was in the over exploitation of Horseshoe crabs in the Delaware Bay in North America for fishing bait. Stocks of these bizarre creatures fell drastically depriving migrant waders, which were heading for their breeding grounds, of vital feeding opportunities.
The destruction of fisheries also has a knock on effect on the balance of nutrients in the sea which can result in ecosystems collapsing.
With thanks to the following photographers:
Where stated, images are subject to CC license