Friday, 10 February 2017

The Curse of the Curlews

If you had to choose which family of waders you could be born into surely being a curlew of any kind is not what you'd pick!

These wonderful and charismatic birds are in trouble, and not just our familiar Eurasian Curlew Numenius arquata, all curlews across the planet are struggling and two of them, the Eskimo Curlew N. borealis and Slender-billed Curlew N. tenuirostris, although officially still Critically Endangered have given up the fight and disappeared; they are now probably Extinct.

Eskimo Curlew. Specimen in Tring Bird Collection. BNHM.
Much has been written and published lately about the Near Threatened Eurasian Curlew and its almost complete disappearance from Ireland with 97% of the breeding population now gone and the rest of the British Isles faring nearly as badly with a decline of 80% in Wales and 50% across England and Scotland.

Eurasian Curlew. Titchwell Marsh RSPB reserve, Norfolk, England; July 2015

At a recent Southern Curlew Workshop it was shown that the key to this drastic reduction was the lack of breeding success, very few young curlews are fledging to replace the adults which are dying off. In Shropshire, of the eggs that survived to hatching, the chicks were only around for a day or two at most. Predation, chiefly by Red Foxes Vulpes vulpes it seems, was seen as the dominant factor in this decline.

Delegates at the Southern Curlew Workshop, Slimbridge WWT, Glocestershire, England: February 2017.
But what can be done about fox numbers and why are they so high? If foxes depended on waders for a living then they'd be in steep decline too, there are fewer rabbits and wildlife in general in the countryside is sparse, so how are foxes surviving in such large numbers? One suggestion is that they are being fed by the 35 million pheasants that are released into the British Countryside each year which maintain an abnormally high number of predators of all kinds.

Released Common Pheasant at large in the countryside. Newport Pagnell, Bucks. England: February 2013.

This may or may not be the case, but whatever the reason for their existence, getting rid of foxes is no easy task either, at least not by simply shooting them. In a personal conversation with one person responsible for predator control in an area where there are three shooters who kill one hundred foxes each a year, we learned that the numbers in the area don't seem to fall. The foxes are a bit like a gas, they will flow into any vacuum that is left vacant very quickly.

Red Fox. Newport Pagnell, Bucks. England: August 2014.

Other curlews, all of which are to be found on the Pacific shores and are also in decline, are the Far Eastern Curlew N. madagascariensis (Endangered), Bristle-thighed Curlew N. tahitiensis (Vulnerable),  and Long-billed Curlew N. americanus (Least Concern).

The Far Eastern Curlew uses the East Asian-Australasian Flyway which famously includes the Yellow Sea region, which is being destroyed at a devastating rate, resulting in this species' rapid decline and thus, it has little hope of a recovery any time soon. 

Far Eastern Curlew. Cairns Esplanade, Queensland, Australia: September 2013

The Bristle-thighed Curlew only has a population of around 7,000 and is thought to be declining mainly due to predation and hunting on the wintering grounds on the South Pacific islands where, unusually among waders, during their moult around half of the adults are rendered flightless for a time. 

Bristle-thighed Curlew. Specimen in Tring Bird Collection. BNHM.

Although considered of Least Concern, the Long-billed Curlew is also in decline, so if you had to choose to be a curlew species, would this be the one? It has a large range, there are good numbers still and the decline is not rapid nor dramatic enough to cause concern... yet.

Long-billed Curlew. Border Park, California, USA: 13/12/2012
But wait! What is that diminutive creature in the corner, almost unnoticed among the large and imposing curlews of which we have spoken? It is the Little Curlew N. minutus (Least Concern). Also to be found in the Pacific region, this remarkable bird has a stable population and so, despite sometimes being called a Little Whimbrel (which are curlews by another name it is true), this surely must be the curlew of choice for those with a view to survival.

Little Curlews. Broome, Western Australia, Australia: Photo Ric Else

Sunday, 22 January 2017

How are waders being affected by warming tundra?

You might imagine that a warmer tundra may result in an increase in the abundance of insects which would provide a good source of food for young waders. It almost certainly increases the season for flying insects such as blood sucking mosquitoes which is bad news for caribou, but it does not necessarily mean the same for the important flightless insects that wader chicks depend upon.

White-rumped Sandpiper Calidris fuscicollis: Photo © Elis Simpson - Wader Quest

When it comes to raising your young in the Arctic, it is all about timing. Several insect species emerge one after the other over a three or four week period providing a super abundance of insects in a pulse. If this window of opportunity shifts and the timing of the egg laying does not, then this will lead to the chicks missing this vitally important window of opportunity.

Dunlins Calidris alpina and Semipalmated Sandpiper Calidris pusilla.

The emergence of insects is triggered by thawing. The hatching of the birds has been synchronised with plant growth and the emergence of insects but with temperature changes the development of plants and insects may not follow the same timetable as the birds' needs. 

Semipalmated Plover Charadrius semipalmatus.

This may well disadvantage shorebirds in more than one way as it may well benefit geese meaning an increase in goose populations on wader breeding grounds. In the USA the Snow Goose Chen caerulescens population has increased hugely. This increase in the number of geese will further add to the negative impact on the breeding success of waders. Greater numbers of geese will damage the vegetation, increase disturbance of brooding birds as they have to defend their nest site leaving it unattended, there is the potential for egg trampling by the geese and there may well be an increased number of predators attracted by the presence of the geese.

Snow Geese Chen caerulescens

In especially warm springs the size of the chicks that survive to migrate south are on average smaller. This is thought to be because the birds are under-nourished as they have missed the super abundance of insects. 

Bar-tailed Godwit Limosa lapponica.

Does it matter that birds are slightly smaller? Sadly, yes, it does.

Among the Red Knots Calidris canutus being studied in Russia by Jan van Gils the smaller birds have, by default, shorter bills. Whilst this does not necessarily impact on their survival in the arctic it seems to have a negative impact further south on the wintering grounds. 

Red Knot Calidris canutus and Sanderling Calidris alba.

There are two main types of food that the Red Knots eat on the tropical intertidal mud, one is abundant and nutritious and lives at 35mm or deeper in the substrate the other is less abundant and less nutritious and lives at a shallower depth. The average bill size for a Red Knot normally is around 40mm so they can easily reach the nutritious and abundant prey. The smaller birds may have a bill as short as 30mm and this will mean they cannot reach this rich resource having to rely instead on the less abundant and less nutritious prey nearer the surface.

Grey Plover Pluvialis squatarola.

The result of this is that the smaller birds are less well nourished on their wintering grounds than those with longer bills. For long distance migrants being well-fed is essential to their very survival, it is not surprising then that van Gils has found that smaller birds have a shorter life expectancy than normal sized birds. 

Hudsonian Godwit Limosa haemastica.

Reference Van Gils, J.A. et al. 2016. ‘Body shrinkage due to Arctic warming reduces red knot fitness in tropical wintering range.’ Science 352: 819‒821

Wednesday, 28 December 2016

New Southern African Wader book: quick review by Rick and Elis Simpson.

Our friends at Wader Quest South Africa Owen and Sue Oertli and Peter and Jenny Sharland and their respective families have sent us the new CHAMBERLAIN'S WADERS The Definitive Guide to Southern Africa's Shorebirds written and illustrated by Faansie Peacock! And what a book it is!

Tremendous new addition to our collection of wader books.

Not yet available in the UK (we believe it'll be out here in January and available from the nhbs) we have, what is probably, one of the first copies yet to make it to the UK and, to make this even more special, it has been signed by Faansie himself.

Signed by Faansie Peacock.

What is it like? 

'Fantastic' springs to mind as an immediate reaction. The illustrations are first rate (which will not surprise anyone familiar with Faansie's previous work) and the amount of information that is included about the 80 species of wader (which includes three buttonquails for the more modern waderologists out there), in an simple to understand and sometimes humorous manner, is extensive and easy to read.

There is a lot of detail about the life and biology of waders and some really helpful hints on how to identify them in all their plumages. This you would expect from a guide of this sort but, because it is about a specific region, Faansie has been able to helpfully included wader hotspots for anyone planning a trip to look for these wonderful birds. As not everyone will haveas we did, the advantage of help from the Wader Quest South Africa  team this will prove to be an essential bonus at the planning stage.

An example of the amazing plates

Obviously we haven't had a chance to read it cover to cover yet as it only arrived today (incredibly posted on the 23rd of December in Johannesburg) but we have seen enough to know we like it very much indeed and will be delving into it every opportunity we get in the next few days and weeks to come and, after that, it will form a useful part of our reference library filling a gap about the southern African waders that has existed for too long.

It is a fantastic achievement for one person to produce such an excellent piece of work creating both the brilliant illustrations and writing the comprehensive and authoritative text, we take our hats off the Faansie and offer him our congratulations on the publication of this beautiful book.

A huge thank you to the good folks of Wader Quest South Africa who have typically once more gone above and beyond the call of duty with their generosity and also to Faansie Peacock and Chamberlain for producing the newest stunning addition to our collection of wader books.

Best Christmas present ever!