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WHITE-WINGED BLACK TERN occurrences at Wilstone Reservoir, Tring, on 30 August 2008
Ian Williams very kindly provided the images above - the top two relate to the first juvenile, whilst the lower three the second bird. There are subtle differences in head pattern and upperwing pattern.
Following a call from Dave Bilcock shortly after 0655 hours (Roy Hargreaves had just discovered an adult Sandwich Tern on Wilstone), I arrived at Wilstone Reservoir, Tring, shortly after 0715 hours. Knowing the forecast was for freshening SE winds, I had already been making my way towards the reservoir beforehand. As soon as I reached the top of the car park steps, I knew we were going to be in for an exciting and eventful morning, and as soon as I raised my binoculars, a quick scan revealed the presence of a large flock of 27 BLACK TERNS. I quickly transferred to the 'scope and checked through each one, attempting to age them individually (the large proportion were juveniles).
As Dave Bilcock approached me from the direction of the hide, all 27 suddenly gained height and flew away strongly due west at 0735 hours (the adult Sandwich Tern had done that earlier at 0655 !). After discussing the morning's birds with Dave, I wished him luck as he set off for Ivinghoe Hills CP and quipped ''with these tern flocks coming in like this, any moment it's going to hit off''. Off he went. I sat down and started to 'scope around as usual and as I scanned the skies towards the Wendover Forest ridge (mainly for an early rising overnight roosting Osprey), I picked up a very white tern coming in high from the west. In fact, within seconds it was over Stuart Wilson's Drayton Beauchamp house (in Bucks) and then over the Drayton Bank Hide (where both SW and RH were sat). Within seconds, I realised that is was a juvenile WHITE-WINGED BLACK TERN and as it dropped down over the Poplars and on to the reservoir adjacent to the new outflow, the white rump, dark 'saddle' and silvery-grey upperwings soon confirmed this. It flew right past me by the car park steps affording excellent views at 0748 hours and within seconds, I contacted Chris Batty (of Rare Bird Alert) to inform him of my find. By 0749, this news was consequently broadcast to the nation's birders. I then contacted Dave Bilcock (who had by now reached Startopsend Reservoir bank) and other local observers (DB placed it on the Tring SMS text ring).
The bird then flew towards the jetty where it was almost immediately joined by 7 'new' juvenile BLACK TERNS, the eight birds then careering around the reservoir in one urgent mass. After a short while, the flock settled down and began a routine of feeding over the eastern quarter of the reservoir. DB was first to join me and within a few seconds, I put him on to it. Af Nasir, sat on the East Bank, also soon independently located it, shortly followed by SW and RH. Over the next half hour, it performed admirably from the jetty and adjacent bank, allowing the next 15 or so birders to connect (including IW, JT, SR, RDA, MW, MCo & CJ), before suddenly thermalling with the 7 Black Terns at 0832. It continued to gain height (always keeping slightly aloof and below the Black Tern flock) and continued disappearing to the west towards Aylesbury, until I eventually lost it from view (perhaps by now over Aston Clinton and well into Buckinghamshire) at 0835.
Whilst I and others were watching this bird disappear into the clouds, DB attempted to call me by phone at 0834. I thought he had left Wilstone but on his second attempt, his successful line informed me of ANOTHER White-winged Black Tern - a few hundred yards in front of me. Again, this bird had arrived alone, and was sortying in the eastern quarter. Apparently Roy, Mike Wallen and others had also got on to this second bird, and within seconds, the 9 or so observers still standing by me also quickly got onto it as I shouted out directions. This second bird was a much more contrasting individual and therefore a lot easier to locate; furthermore it was more advanced in covert moult and had a much more striking white rump. Like my initial bird, this individual also took to resting on the raft for a brief period, allowing IW, DB and MW to obtain photographs. Again, it was very active, and flew around alone until 0902 hours, when it too decided to leave, and once again departed high to the WNW (and well into Buckinghamshire - the 2nd record !!).
DESCRIPTIONS
Critically, both individuals had bright red (rather than dark or very dull red) legs and feet, and contrasting dark chocolate-brown 'saddles'. The inner wing panel was clearly paler grey and both birds had unmarked pure white rumps (not concolorous grey with the upperparts as with juvenile Black Tern). Both birds were also gleaming white below, and lacking the dark breast patch that protrudes on juvenile Black Tern.
There appeared little difference in size between the Black and first WWBT and the bill was entirely black and perhaps slightly shorter.
The two White-winged Black Terns were only subtly different in plumage, the second individual being more contrasting between the silvery-grey upperwings and darker mantle, a cleaner and more obvious white rump and more obviously plain feathered on the tertials and rear scapulars.
PREVIOUS STATUS: 8 previous individuals, including two together in 1970 and two at Wilstone Reservoir in autumn 1994, of which LGRE has connected with four..
These records represent the eighth occurrence for Tring Reservoirs, following a winter-plumaged adult and first-winter on Wilstone Reservoir on 7 October 1929, a moulting adult on 31 July 1999 (RH, MC, B Pegrum) and further juveniles on 24-27 August 1994 (GJ White et al), 15 September 1994 (Bill Pegrum) and 31 August 2005 (RH, DB, SW, MC, LGRE, et al).
Elsewhere in Hertfordshire, two juveniles were identified at Hilfield Park Reservoir on 19-22 September 1970 (British Birds 64: 354).
Rather surprisingly (and considering the fact that Milton Keynes regularly attracts large numbers of passage Black Terns and has hosted several vagrant Whiskered Terns in the past), there are no previous records for Buckinghamshire.
Following a call from Dave Bilcock shortly after 0655 hours (Roy Hargreaves had just discovered an adult Sandwich Tern on Wilstone), I arrived at Wilstone Reservoir, Tring, shortly after 0715 hours. Knowing the forecast was for freshening SE winds, I had already been making my way towards the reservoir beforehand. As soon as I reached the top of the car park steps, I knew we were going to be in for an exciting and eventful morning, and as soon as I raised my binoculars, a quick scan revealed the presence of a large flock of 27 BLACK TERNS. I quickly transferred to the 'scope and checked through each one, attempting to age them individually (the large proportion were juveniles).
As Dave Bilcock approached me from the direction of the hide, all 27 suddenly gained height and flew away strongly due west at 0735 hours (the adult Sandwich Tern had done that earlier at 0655 !). After discussing the morning's birds with Dave, I wished him luck as he set off for Ivinghoe Hills CP and quipped ''with these tern flocks coming in like this, any moment it's going to hit off''. Off he went. I sat down and started to 'scope around as usual and as I scanned the skies towards the Wendover Forest ridge (mainly for an early rising overnight roosting Osprey), I picked up a very white tern coming in high from the west. In fact, within seconds it was over Stuart Wilson's Drayton Beauchamp house (in Bucks) and then over the Drayton Bank Hide (where both SW and RH were sat). Within seconds, I realised that is was a juvenile WHITE-WINGED BLACK TERN and as it dropped down over the Poplars and on to the reservoir adjacent to the new outflow, the white rump, dark 'saddle' and silvery-grey upperwings soon confirmed this. It flew right past me by the car park steps affording excellent views at 0748 hours and within seconds, I contacted Chris Batty (of Rare Bird Alert) to inform him of my find. By 0749, this news was consequently broadcast to the nation's birders. I then contacted Dave Bilcock (who had by now reached Startopsend Reservoir bank) and other local observers (DB placed it on the Tring SMS text ring).
The bird then flew towards the jetty where it was almost immediately joined by 7 'new' juvenile BLACK TERNS, the eight birds then careering around the reservoir in one urgent mass. After a short while, the flock settled down and began a routine of feeding over the eastern quarter of the reservoir. DB was first to join me and within a few seconds, I put him on to it. Af Nasir, sat on the East Bank, also soon independently located it, shortly followed by SW and RH. Over the next half hour, it performed admirably from the jetty and adjacent bank, allowing the next 15 or so birders to connect (including IW, JT, SR, RDA, MW, MCo & CJ), before suddenly thermalling with the 7 Black Terns at 0832. It continued to gain height (always keeping slightly aloof and below the Black Tern flock) and continued disappearing to the west towards Aylesbury, until I eventually lost it from view (perhaps by now over Aston Clinton and well into Buckinghamshire) at 0835.
Whilst I and others were watching this bird disappear into the clouds, DB attempted to call me by phone at 0834. I thought he had left Wilstone but on his second attempt, his successful line informed me of ANOTHER White-winged Black Tern - a few hundred yards in front of me. Again, this bird had arrived alone, and was sortying in the eastern quarter. Apparently Roy, Mike Wallen and others had also got on to this second bird, and within seconds, the 9 or so observers still standing by me also quickly got onto it as I shouted out directions. This second bird was a much more contrasting individual and therefore a lot easier to locate; furthermore it was more advanced in covert moult and had a much more striking white rump. Like my initial bird, this individual also took to resting on the raft for a brief period, allowing IW, DB and MW to obtain photographs. Again, it was very active, and flew around alone until 0902 hours, when it too decided to leave, and once again departed high to the WNW (and well into Buckinghamshire - the 2nd record !!).
DESCRIPTIONS
Critically, both individuals had bright red (rather than dark or very dull red) legs and feet, and contrasting dark chocolate-brown 'saddles'. The inner wing panel was clearly paler grey and both birds had unmarked pure white rumps (not concolorous grey with the upperparts as with juvenile Black Tern). Both birds were also gleaming white below, and lacking the dark breast patch that protrudes on juvenile Black Tern.
There appeared little difference in size between the Black and first WWBT and the bill was entirely black and perhaps slightly shorter.
The two White-winged Black Terns were only subtly different in plumage, the second individual being more contrasting between the silvery-grey upperwings and darker mantle, a cleaner and more obvious white rump and more obviously plain feathered on the tertials and rear scapulars.
PREVIOUS STATUS: 8 previous individuals, including two together in 1970 and two at Wilstone Reservoir in autumn 1994, of which LGRE has connected with four..
These records represent the eighth occurrence for Tring Reservoirs, following a winter-plumaged adult and first-winter on Wilstone Reservoir on 7 October 1929, a moulting adult on 31 July 1999 (RH, MC, B Pegrum) and further juveniles on 24-27 August 1994 (GJ White et al), 15 September 1994 (Bill Pegrum) and 31 August 2005 (RH, DB, SW, MC, LGRE, et al).
Elsewhere in Hertfordshire, two juveniles were identified at Hilfield Park Reservoir on 19-22 September 1970 (British Birds 64: 354).
Rather surprisingly (and considering the fact that Milton Keynes regularly attracts large numbers of passage Black Terns and has hosted several vagrant Whiskered Terns in the past), there are no previous records for Buckinghamshire.
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