A huge thank you to our wonderful volunteer Phil for his sightings report from Friday 12 May
Lowering clouds bring perpetual motion
On Friday 12 May I arrived at Pulborough Brooks in bright sunshine but the forecast suggested deteriorating weather in the morning with some light rain by lunchtime.
I spent the morning gradually working my way round to a rather quiet North Brooks and by the time I left Nettley’s Hide at lunchtime the clouds had come down considerably, a fresh Northerly wind had sprung up and the rain had started. I hurried round to Winpenny to escape the wind and rain for lunch and on approaching the hide noticed my first Swift of the year passing overhead along with a Swallow and a Sand Martin.
Swallow (above), Sand Martin (below)
Earlier in brighter weather the only hirundine I’d spotted on the North Brooks was a solitary House Martin. (Hirundines is the collective name given to Swallows and Martins). However from Winpenny Hide there was a scene of perpetual motion as many Swallows and Sand Martins, with a few House Martins mixed in, were whizzing over the flood water feeding on insects too small to see. After lunch I spent quite some time attempting to photograph this scene with mixed results.
Swallow (above), House Martins and Swallows (below)
I have noticed over the years that Swallows and Martins always seem to be more visible when the weather is not so good. My hypothesis to explain this effect is that in sunny weather the birds have plenty of feeding opportunities higher in the sky but when the clouds are down this tends to drive the insects and birds to a level where they become much more visible. And I have come across some evidence to support this in the form of some old folklore which goes “When the Swallows fly high, the weather will be dry” as quoted in an old Weatherwatch article in The Guardian. This article also points out that the warmer air created in sunny weather rises, lifting the flying insects with it.
This means that on poor days in late spring and summer there is a chance of seeing one of these perpetual motion spectacles which can be mesmerising and are well worth looking out for.