An Oystercatcher's tale
November 2003
The Story of YBY
Background
As part of the Dibden Bay Environmental Impact Assessment the Farlington Ringing Group has marked hundreds of oystercatchers, grey plovers, turnstones, dunlin, brent geese, curlews, redshanks and wigeon. These birds were caught at several sites in Southampton Water and have since been sighted throughout the Greater Solent and further afield. This article tells the story of one bird of the hundreds ringed - YBY, or to give it its full designation - Left Above BTO; Left Below Yellow; Right Above Yellow; Right Below Blue, Yellow.
History of YBY Oystercatcher
YBY was caught in a cannon net at Hamble Point on 13th December 1999. It was already an adult and as oystercatchers achieve adult plumage in their third calendar year it was at least three years old. He (there is no basis for this assumption of masculinity) was not seen again until February 2000 when Pete Potts (FRG) received a sighting report from the Starrevaart, Leidschendam, Netherlands, 5206N, 0426E (just outside the Hague). Inevitably, most sightings of these marked birds are from Southampton Water so this foreign sighting made YBY something special.
A year later, on 7th February 2001, he was seen feeding at Hamble Point. On 25th he was again reported to be at the Starrevaart. And after that - nothing. PP thought that YBY had changed wintering area - itself an unusual event.
Dutch report
On 16th February 2003 PP was emailed by Adri de Groot who told him that YBY was back at the Starrevaart, where he had been seen every year since 2000, and attached a picture so that there could be no doubt. Pete circulated Adri's email to ten Southampton Water observers, speculating that the bird might winter at Solent Breezes which is rather neglected by observers.
Adri emailed again with all the Starrevaart sightings, most by himself but including four by other Dutch birders. YBY had been seen in February 2000, February 2001, February-April 2002, July 2002 and February 2003.
Discovery and Doubts
On receiving Pete's email on 16th I immediately thought "I've just seen that bird!". My notebook confirmed it - Y+YBY, Hamble Point, 14:00-17:10 (at least), 15th February 2003. But if he was in the Netherlands on the 10th how and why would he have come back here? I thought I'd better relocate him and confirm that I'd read the colours correctly. The next day saw Sue and I on the beach at Hamble Point as the tide went out. We were in luck. At 15:20 YBY flew in from the direction of Fawley.
The sun was low and we were looking directly into it. We walked down the beach to get a better angle and then had doubts about the ring colours. Could this be WBY rather than YBY? Three official-looking people arrived, dressed in oilskins and strode onto the beach; the bird decided they were dangerous and flew off north towards the oil terminal jetty. We slogged after it and found it just beyond the jetty. With the light failing our doubts increased, was it WBW with discoloured rings?
Deciding we needed better telescopes we emailed PP that we had probably seen either Y+YBY or Y+WBY and suggested he go and look for it.
Pete first replied that Y+WBY had not been used but that W+WBY had. He followed up with "I am sure that the OC Y+YBY would not return to the UK after making it back to the Netherlands - only possible reason would be severe weather which we have not had. (in fact we had very cold weather with ice on the tideline at Hook Spit) .not sure what to make of your record at Hamble Point". BWP supports this contention, the Habitat section for Oystercatcher begins "Little affected by climate, apart from avoidance of freezing conditions...".
Then a report came in which tipped the balance. Ruth Croger, equipped with a more expensive telescope and being a member of FRG, saw YBY at Hamble Point on 25th Feb 2003.
A converted PP promptly emailed the Netherlands querying their sightings! "...has anyone photographed this bird this Spring? The reason I ask is that an Oystercatcher with this combination was seen..........by three regular and very reliable observers. (does he mean me?!)............. Was the weather exceptionally cold in Holland in early-mid-February - I just wondered if it didn't like the cold weather and returned to the southern UK and has now returned back again to the Netherlands?! I suppose this is possible but seems unlikely?!"
Dutch explanation
Adri replied "February 12 was the first day of a period with frost, day and night, not strong but continuously with minimum till -10 degrees. Though there was less wind and a lot of sun it was very pleasant birding weather. The Starrevaart, shallow, was frozen in a few days. There were even skaters on it! The most birds had gone, all the oystercatchers too, there were only ducks and geese in a few holes. Accidentally I made a picture of the Starrevaart on February 21. There were also very less birds at the frozen grazings. The period of frost ended on Sunday February 23. A few days later the birds and the oystercatchers returned. Y+YBY too. I think it is very reasonably that oystercatchers preferred to stay in a country with a temperate climate, the observations prove it. Very interesting for the rest!" (Adri de Groot 13/2/2003)
YBY was next seen on 1st March at the Starrevaart.
Conclusion
YBY moved from Starrevaart (latitude 52 06N, longitude 04 26E) to Hamble Point (latitude 50 51N, longitude 01 19W) between 11 and 15 Feb 2003, a direct distance of 265 miles in 4 days, probably further as the oystercatcher flies and possibly in a shorter time.
YBY moved back from Hamble Point to Starrevaart between 25 Feb and 1 March 2003. The same distance in the same time - is this standard oystercatcher speed?
Hamble Point is where YBY feeds at low tide, it was seen flying in from the direction of Fawley where it probably roosts at high tide. Hamble Point is a large area of intertidal shingle and mud which attracts up to 200 oystercatchers plus large numbers of dunlin, grey plover, brent geese and black-headed gulls and smaller numbers of redshank, turnstone, ringed plover and curlew. Starrevaart is a shallow, freshwater lake near the Hague.
Breeding
YBY presumably breeds in the Netherlands where oystercatcher is a very common breeding species throughout the country.
He has only been recorded at Hamble Point in the period December-February and at Starrevaart in February, March, April and July.
Oystercatchers take at least three months to breed successfully and don't start before April or after July. Presumably he doesn't breed at Starrevaart otherwise Adri would say so.
If you?re visiting the Netherlands this summer look closely at every Oystercatcher - you might just find YBY!
Questions
Might YBY breed further north than Netherlands, perhaps Norway, and just be stopping off at the Starrevaart? No, oystercatchers are short-distance migrants with the median distance around 250 miles (The Migration Atlas).
Where is YBY in May-June and between July and December. Breeding in the Spring certainly and perhaps back in Southampton Water afterwards. There are no regular observations at Hamble Point until November.
Would it stop in between Starrevaart and Southampton Water - say Dungeness, North Kent, Essex marshes? Who knows - more research is needed such as satellite tracking.
Would it follow the coast or fly direct? BWP suggests oystercatchers dislike swimming and keep to coasts but do they ever fly across country?
For those who read Dutch the website www.vogeldagboek.nl describes the Starrevaart and its birds, including YBY.