23/01/13 - Icy blast & an Icelandic visitor

Last week the cold weather that had been predicted hit the country, leaving most places blanketed by a covering of snow. Two inches fell at our reserve base, Bank Island, and temperatures in the valley did not get above freezing for several days. The birds that had been making the most of the large expanse of water in the (still) flooded LDV suddenly became concentrated to the small areas of open water that they had kept free from ice.

Bank Island - 22/01/13

The rest of the water has frozen over and is now resembling a large ice rink, with the majority of the birds staying in the small pools of open water. However some of them have been standing out in the open, braving the icy blast and the Russian chill that would make most huddle together for warmth. This has resulted in the collection of some data - their shiny metal and brightly coloured rings have been standing out well against the snow - last week (18th) Tim Jones had two colour-ringed Mallards standing out on the ice at Bank Island, both birds were ringed as ducklings by us on 15/07/12 (no previous sightings). Yesterday down on Wheldrake we had a number of birds with metal rings (mainly Canada Geese & Mallards) however amongst them one lone bird stood out with its orange and red rings - another Mallard ringed as a duckling on 15/07/12. As we scanned the ice a group of Greylags started to wake up and slowly make their way down the thin strip of vegetation, as we counted them we came across '7HP' - a bird ringed by us on 15/06/11 on Wheldrake - again another first sighting.

Mallard duckling - summer 2012

We were pleased with the data from the local Mallards but then we stepped it up a notch and found some darvic'd Whooper Swans at North Duffield on the 21st. Despite the continued snow fall several of us managed to make our way into work on Monday, once in the valley the roads weren't too bad and so we headed out for the day - on passing North Duffield we came across a large flock of Whoopers feeding on the arable. With them were the two Bewicks that have been around the valley since the start of January (including the darvic'd bird - 702). Careful scanning, lots of patience and a good scope was needed, an hour later and fingers were definitely feeling the cold but we had managed to read off 4 darvics from the Whoopers. The flock was 85 on arrival, with an extra 6 birds dropping in whilst we were there, making it 91 birds (plus another 18 were then counted from the Geoff Smith Hide). 

Whooper Swans - North Duffield - 21/01/13

Details are listed below for the 4 darvic'd Whoopers and the Bewick - many thanks to Kane at the WWT for his prompt reply in sending us the history of these birds - 2 were completely new ones for the valley!

Whooper Swans:

Yellow 'C3S' - initially ringed as an adult in November 2007 at North Duffield Carrs, the following winter it made a single appearance at North Cave Wetlands, then moved north to Scotland before making a quick return (possibly weather related) to the valley for the remainder of the winter. It wintered again in the valley during 09/10 and once again during the winter of 10/11.

Red '499' - initially ringed as an adult female in November 2007 at North Duffield Carrs, since then she's been seen back in the valley during the winter of 08/09 and 09/10.

Yellow 'Z5T' - initially ringed as an adult female in February 2011 at the WWT catch in Caerlaverock, Dumfries. The following winter (11/12) saw her frequent various sites within Ross-shire & Dumfries, she was last seen at Caerlaverock on 29/02/12 before appearing in the valley this week. 

Red 'AUZ' - initially ringed as a male cygnet in August 2011 in Skagafjordur, Iceland, since then he must have been keeping a low profile as there have been no other sightings until Monday when we came across his red ring amongst the flock of birds at Duffield.

Bewick Swan:

Yellow '702' - initially ringed as a female cygnet in November 2007 in the Netherlands, a month later and she had made her way to the UK and was residing at Slimbridge WWT, Gloucestershire. The following winter (08/09) she made her first apperance in the LDV, spending most of January with us. The winter of 09/10 her whereabouts went unknown, but pleasingly during the winter of 11/12 she was sighted in Denmark, and was last seen there until we came across her on the 3rd January in a field near Aughton.

It's always fascinating to get the life stories of individual birds and wonder what made the Bewicks return to Denmark for a winter and then come back to us again. It's nice that colour-rings don't tell us everything and that we still get to wonder!

Whooper & Bewick Swans - North Duffield - 21/01/13

The number of Whooper Swans in the resident herd appears to remain remarkably consistent from one winter to the next (although numbers have increased from 60-70 during the 1980's to 100-120 since the late 2000's), it is clear from colour-ringing (both in the valley and marked birds from elsewhere), that site fidelity is very low - i.e most birds have not wintered in the valley before. It appears that most birds only return to the valley for two or three winters at the most. Without colour-ringing one may assume that the same birds returned year after year - with recruitment and losses in the population keeping the numbers stable. This is clearly not the case!

Furthermore, with colour-ringing, we also know that whilst numbers in the herd remain fairly stable throughout the winter, there is actually regular comings and goings and an interchange of birds - some moving through in autumn, a more stable mid-winter herd and then some returning birds in spring. Using this colour-ringing data, along with the number of first winters in the herd and numbers of passage flocks (particularly in spring) we now know that despite the herd averaging 100-120 during the winter period, as many as 300-500 different Whoopers may use or pass through the Lower Derwent Valley during the same period - making it much more important for the UK wintering population than originally thought.

Whooper catch - 2008

Along with the sightings of colour-ringed birds the cold weather has also seen an influx of Skylarks and Corn Buntings to the LDV. From the start of the year Skylarks had been virtually absent in the valley, however snow fall from the 18th brought an expected influx of birds into the valley from higher ground on the Wolds. A huge influx on the 20th saw an impressive 670 at Bubwith, 144 near Ellerton, 200 at East Cottingwith and 150-200 at Loftsome Bridge. 168 were present on the arable fields in North Duffield on the 21st, plus 320 at Sutton-on-Derwent, and then 230 at Thornton on the 22nd, meaning that in the region of 1500-2000 birds had been moving through the valley, and possibly a great deal more. 

Not only have we seen an arrival of Skylarks but we've also noticed an increase in their close relative - the Corn Bunting. Some encouraging counts for this red listed species have been had lately - 50 were present in the usual winter roost at Church Bridge, Melbourne on the 3rd, whilst feeding flocks of 120 at South Duffield and 20 at North Duffield on the 5th were welcome finds. 30 were also present at East Cottingwith on the 9th and then the heavy snow fall that hit Yorkshire brought a substantial influx into the valley with 30 at Bubwith on the 20th and 210 at Sutton on the 21st.

The last week or so has also seen an influx of thrushes, with a number of Fieldfares & Redwings reported, again presumably looking for easier feeding in the 'lowlands'. One or two incoming Woodcock, five new Water Rail and several thousand Woodpigeons were also presumably cold weather movers.

Fieldfare - Bank Island - 22/01/13

Despite the harsh weather and freezing temperatures there are many birds to be seen throughout the Lower Derwent Valley - if you're out and about do send in your records or post them on our facebook site - just search for Lower Derwent Valley/Skipwith Common NNR - give us a 'like' and you'll receive regular updates from the valley. Also, many thanks to Andy Walker, Tim Jones, Andrew Kisby & Chris Harris for their contributions so far this month.

Robin - North Duffield Carrs - 21/01/13