Tuesday, 21 July 2015


I must have been living in a cave for a while as I had never heard of 'Biofilm' until reading the journal of Bird Studies Canada (BSC) Birdwatch Canada Summer 2015 - Number 72 and an article entitled 'When Important Bird Areas are Urban Areas'. BSC is the Canadain equivalent of the BTO.

This article was about the importance of particular estuarine systems on the Pacific Flyway, and in this case the Fraser River Estuary IBA, and it went on to say that shorebirds were previously thought to stop over in the estuary and feed on intertidal invertebrates (my understanding too). However, it was recently discovered that they are also feeding on 'biofilm' (also known as 'magic mud'), which is a thin layer of sugars and microbes that grows on the surface of mudflats!

Microscopic analysis of the tongues of Western Sandpipers has revealed minuscule bristle structures, described as being like toothbrushes, that are used to slurp up large quantities of this rich, slimy food source. Amazing!

 Western Sandpiper (courtesy of the Cornell Lab of Ornithology)

Apparently Biofilm sugars are easily digestible, and are thought to be a very efficient energy source to fuel completion of the final major leg of the spring journey from south Central America to the Arctic tundra to breed. The author's of the article, Catherine Jardine and Peter Davidson, posed the important question of how might human activities impact the health and productivity of biofilm in the Fraser River Estuary IBA, and indeed in estuarine environments around the world? It made me wonder whether any research into this has been carried out on biofilm on estuarine habitats over here.

This spring, BSC in collaboration with other leading experts in the field published a study investigating the diet composition of migratory waders. They wanted to determine how much biofilm they consumed within the Fraser River Estuary IBA. The study used an analysis of nitrogen and carbon, which come in different forms called isotopes. By looking at the ratios in each of the waders' prey items compared to the ratios in their droppings, it is possible to determine how much of each prey type the birds are eating. 

Remarkably the study found that Western Sandpipers consume biofilm throughout the stopover site, and biofilm made up a conservative estimate of between one quarter and one half of Western Sandpiper droppings, depending on where the birds were feeding. These results confirm that biofilm is an important component of their diet and again it got me thinking about some of the wader species on estuaries over here.

I knew nothing about biofilm until reading this article and it is quite possible that I have missed something and all of you know about it and are shouting out "where have you been these past few years!". It just goes to show that we are all still learning and how important this kind of research is.

Fingers crossed I'll have some ringing news for you tomorrow!

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