Sand and dust

Since the last update on 24 December UV has continued to travel between various coastal and inland day spots. On 28 December he appeared to be perched in the water, not on the sandy shore, near Lac Guembeul.

UV perches around the shoreline

UV perches around the shoreline

The Google Earth image was taken in early July during the wet season so the water levels will be lower now with more sand exposed.

There have been fewer fixes over the past week – some days only every 20 minutes or so at best – because the tracker’s battery voltage level has been relatively low as this graph by Paul shows.

courtesy Paul Wildlifewriter

courtesy Paul Wildlifewriter

The tiny battery in UV’s tracker unit is charged by solar energy and the charging system is only just enough to maintain battery condition under good direct sunlight. High-altitude dust can attenuate the power of the sun by as much as 20% – even when the sun ‘appears’ to be shining.

The reason for the relatively low voltages is the amount of dust in the atmosphere. At this time of year the Harmattan affects West Africa. Paul has created an animation which shows how the dust eventually reached South America.

The Senegalese authorities issued a ‘red alert’ health warning, a relatively rare event. The fine dust reached ground level as you can see in this powerful photograph by ornithologist Frédéric Bacuez.

The Harmattan (c) Frédéric Bacuez/

The Harmattan
(c) Frédéric Bacuez/

There are some Osprey photographs in the most recent post on Frédéric’s blog, click the link under the photograph.

Despite the impact on his battery UV’s behaviour seemed unaffected by the week long Harmattan and he was recorded at altitudes over 300m ASL on several days. In this image he was only at foraging level for a couple of fixes during an offshore flight and he flew inland at over 600m ASL.

Was UV foraging briefly?

Was UV foraging briefly?

Today’s data arrived just as this post was being finalised. UV had a busy morning visiting several inland sites but he was at foraging level just offshore for the last few fixes, perhaps finding some lunch!




This entry was posted in Abroad, Blue UV, Migration and tagged , . Bookmark the permalink.

5 Responses to Sand and dust

  1. JW4926 says:

    Thanks for the update Joanna …. and for the fix and battery explanations…. I never thought about the Harmattan having such an effect ….. Has UV been spotted in Senegal …. did he get his pic in the session lined up for December?

  2. joannadailey says:

    As far as we know UV wasn’t seen during the Census although he was over the main survey area a few times. Usually pretty high so he may be included in the numbers, just not identifiable.

  3. Cirrus says:

    I suppose the dust would affect the wild life too, wouldn’t it – oh dear Would UV be above the dust at 300 m ? Thanks Joanna

  4. thegreatgeraldo says:

    So much sand & dust!! The stuff tends to build up as well. When the UK was down near the equator, we used to have the same problem. As we know, if you don’t deal with dust, it hangs around & accumulates; the red sandstones in Devon & along the Jurassic coast are accumulations of desert dust. Fascinating stuff, dust!! ;-#))

  5. Whether migratory or resident, the wildlife of west Africa has always lived with the dry-season Harmattan winds. They are part of their natural environment, just as thunderstorms and rain are part of it during the wet season. At ground level, incursions of wind-blown desert sand are a nuisance to animals (and to people) but these are local, short-term events and they soon pass.

    Our article refers to this, but also to a much larger-scale and more influential climate phenomenon – known to meteorologists as the “Saharan Aerosol Layer” (SAL for short.) This is a region of the atmosphere between 1500m and 6000m in which very fine particles of dust are transported out over the Atlantic by prevailing west-going winds. The dust plume contains vital nutrients, such as phosphates, which eventually precipitate over the equatorial ocean and (usually washed out by rain) over the Amazon rain forest. The scale of the transport is difficult to imagine on human scales: it’s been estimated that some 28,000,000 tons of Saharan dust material falls on the Amazon basin each year. This cycle of long-distance “fertilizer” transport is thought to be of vital importance to marine life and rainforest ecosystems, and is currently the subject of much scientific research.

Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out /  Change )

Google+ photo

You are commenting using your Google+ account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )


Connecting to %s

This site uses Akismet to reduce spam. Learn how your comment data is processed.