Saturday, 18 January 2014

Macro-demography and conservation of the world’s wildfowl

Posted by Beth Roberts

Beth is two years into a part-time PhD, funded by The Wildfowl and Wetlands Trust (WWT) examining demographic patterns in the world's wildfowl. She is supervised by Stu, along with Dr Ed Harris (MMU) and Dr Geoff Hilton (WWT). Here, she introduces her study and some of her initial findings about the biases in our knowledge of the world's wildfowl.
Drawing: Iris Aspinall Priest, @Iris_Priest

Anseriformes, often called wildfowl, is a large order that consists of 166 extant species. They are found in all major regions of the world and have a wide range of life-history traits. Due to the importance of wildfowl for hunting, domestication and aviculture they are one of the best-studied bird orders. Wildfowl species are relatively large and conspicuous, and many migrate and aggregate in large groups on their wintering grounds. 

Barnacle Geese Branta leucopsis: Least Concern. Photo: Richard Taylor-Jones
Wildfowl species depend on wetlands throughout various parts of their life cycle; this dependency is a major issue, as many wetlands are under serious threat. With nearly 20% of wildfowl species threatened with extinction and many declining wildfowl populations found in Asia and Africa, the most threatened wildfowl species may have severely limited knowledge. The trajectory of wildfowl populations is determined by demographics: productivity, survival, immigration and emigration. Combining demographic data with population assessments in the field is key to improving our understanding of wildfowl population trajectories.

Blue Duck Hymenolaimus malacorhynchos: 
Endangered. Photo: Richard Taylor-Jones
The endemic Hawaiian Goose or Nene  
Branta sandvicensis: Vulnerable is 
recovering through management 
interventions. Photo: Richard Taylor-Jones

The aim of my research is to identify demographic rates for poorly-studied species; to understand how demographic variation contributes to population change and extinction risk; and ultimately, to inform management strategies for wildfowl species.

There have been no confirmed records of the Crested Shelduck Tadorna cristata since 1964. 
The species is listed as Critically Endangered and just may still occur in the wild. Painting: Joseph Smit.

The first stage of the research has investigated the distribution of wildfowl demographic research outputs. Over 2000 published papers have been collated and the demographic information extracted. Strong taxonomic, geographic and demographic biases are apparent in published wildfowl demographic research, with consequent substantial knowledge gaps, despite wildfowl being one of the better-studied groups. 

The endemic Philippine Duck Anas luzonica is listed as Vulnerable. Although the species is undergoing a rapid population decline due to hunting and habitat loss, there is no published demographic information on this species. Photo: Arman Asilo.

Over 80% of wildfowl species had at least one demographic research output and North America and Europe contributed to more than 80% of the research output. However, a high proportion of wildfowl species had very little information: over 50% of taxa had 10 or fewer demographic outputs. Productivity measures were the most well studied of the demographic traits. Nearly half of the published research has involved just 10 species from 7 genera - Mallard Anas platyryhnchos, Northern Pintail Anas acuta, Canada Goose Branta canadensis, Common Eider Somateria mollissima, Common Teal Anas crecca, Snow Goose Anser caerulescens, Wood Duck, Aix sponsa, Brent Goose Branta bernicla,  Mute Swan Cygnus olor, and Tufted Duck Aythya fuligula. All species found in North America and Europe have been studied (75 species).

Common Eider Somateria mollissima: Least Concern. Photo: Richard Taylor Jones

The next stage of my research asks whether we can use this large body of information on North American and European species to make inferences about the demography of poorly-studied species. The life histories of birds have been widely studied to develop theories to explain patterns in life history traits. This has led to a large body of research to explain and understand how avian traits covary. Can we exploit these relationships to predict traits for poorly-studied taxa? The next stage of my research will use intrinsic and extrinsic factors to examine trait covariation, and develop a predictive demographic model to produce surrogate rates. More on this will follow soon. 

If you have any demographic information on any wildfowl species, please email or follow on twitter @duckgirl73.

Beth's PhD is sponsored by the Wildfowl and Wetlands Trust 


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