Monday, September 14, 2009

How waders get enough water to drink

My query about the water drops on the ends of some waders' beaks in my 5th September post brought the following interesting response from Ed Keeble:

"I think the way it works is that waders take in salt water (where no fresh is available) and then excrete the salt via faeces and bill- like tubenoses but without the tubes. So that's what the drop might be- shedding salt, plus cooling by evaporation/excretion.

There's some interesting stuff calculating whether in some situations the ability to deal (or not deal) with salt limits the ability of some wader species to exploit some habitats, latitudes. So for example, Red Knots might not take what otherwise seems suitable prey- if they did, they would take in more salt than they could handle.

There are also some references to thin-billed species like phalaropes, stints which feed by capillary action and so can take in prey without also taking in lots of salt water."

When I took a closer look at some of my pics, I could actually see what look like salt deposits around the nostrils.

Thanks Ed!

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