Our post this morning comes from Ron Macdonald, who is becoming well known on social media these days for his fantastic bird photographs. Today he talks about one of his favourite waders…
This morning I’m off to photograph purple sandpipers on Forvie’s wild eastern shore, where the North Sea pounds against the high cliffs. Here on the rocky shore below the cliffs I find 16 purple sandpipers foraging among the rock pools, gradually being pushed higher and higher as the tide comes in. Soon they’ll call it a day and head for their high tide roost on a nearby islet.
I’ve always been drawn to Purple sandpipers. Compared to other waders they’re much more confiding, usually allowing me to get within 3-4 metres before they edge away keeping that minimum distance between us. They are slightly larger and dumpier than a dunlin with an overall grey looking plumage with yellowish legs and beak. On the face of it you would think their grey plumage might make them, err, grey and uninteresting but the grey set against the yellow orange bill and legs results in one smart looking bird. This morning I’m lucky enough to come across a bird with the last vestige of its purple summer plumage, which adds to its beauty.
The Purple sandpipers that winter on Forvie probably breed in Canada. Research on birds trapped and ringed in Eastern Britain (Kincardineshire to Yorkshire) are mainly short-billed and come from the Norway breeding population. North of this and on Scotland’s west coast, long-billed (almost certainly Canadian breeders) dominate. Northeast Scotland has populations of both and there appears to be no clear boundary line between the two populations – rather the percentage of small billed birds decreases as you go north.
Purple Sandpipers have fared badly in the last while. Research* in the Moray Firth found that from from the mid 1980’s, the total population fell from 400-600 birds to 200-300 in the late 90’s, which represents over half the population. The decline in the Moray Firth has been replicated elsewhere in Britain with a similar 50% drop in the purple sandpiper population. In the Lothians the decline has even been greater. Nowadays the UK wintering population is around 10000 birds.
What has caused the decline? Research* has shown that the recruitment of young birds has been insufficient to maintain the numbers. Exactly why this should be the case is open to question but climate change has been put forward as a possible reason with birds preferring a colder winter climate. Increasingly, young birds are choosing to remain in Iceland, rather than migrate as far as UK. Adults are very site faithful so they keep coming to traditional wintering areas. As they die off numbers will drop – hence the decline.
Another reason responsible for the decline is the improvement in sewage treatment and the relocation of outfalls into deeper water which in turn reduces the amount of invertebrates found in rocky pools close to settlements.
It’s now nearing high tide and the birds have stopped feeding. The occasional squabbling between feeding birds stops and most tuck their heads under their wings. Suddenly, as if on cue, a large wave breaks on the shore and they flit across to their high tide roost.
My thanks to Bob Swann, Robert Rae and Raymond Duncan for providing information and advice on the origin of wintering Purple sandpipers in the North East of Scotland.
* Local and global influences on population declines of coastal waders: Purple Sandpiper Calidris maritima numbers in the Moray Firth, Scotland by Ron W. Summers, Simon Foster, Bob Swann & Brian Etheridge in Estuarine, Coastal and Shelf Science 102-103 (2012).
You can follow Ron’s amazing photography on Twitter – @ronpon_ron