The probable breeding of Ferruginous Ducks in Avon A. H. Davis and K. E. Vinicombe

Abstract The probable breeding of Ferruginous Ducks nyroca at Chew Valley Lake, Avon, is documented. In 2003 and 2004, nesting attempts probably took place, although no nest or young were observed and it is assumed that any attempts failed. In 2006, a juvenile male appeared in October. Although it could not be established that this had hatched at Chew, events suggest that it may well have done so, and perhaps was raised by a foster parent (probably A. ferina).

Introduction some time, sets out the full story. Holling et al. (2010) published a summary of On 16th November 1998, Dave Chown the suspected breeding of Ferruginous Ducks discovered a female Ferruginous Duck at the Aythya nyroca at Chew Valley Lake, Avon, in RSPB’s Ham Wall reserve on the Somerset 2004. That account was, however, based on Levels; it remained there until 19th March incomplete information presented to the 1999 (Rogers et al. 2000). It was a fairly Rare Breeding Panel. The following typical record in terms of the dates of occur- article, which has been in preparation for rence, since the species is predominantly a Gareth Gareth Jones 35. Male Ferruginous Duck Aythya nyroca, Chew Valley Lake, Avon, March 2009.

© British Birds 104 • February 2011 • 77–83 77 Davis & Vinicombe rare winter visitor to Britain (Vinicombe from Herriott’s Pool at the north end of the 2000). That bird returned to Ham Wall in the ‘Main Reeds’, Chew Valley Lake’s largest following three winters and, on 22nd March reedbed. In previous years, Wick Green Point 2000, what is considered to have been the had been a favoured feeding site for the same individual was located by Richard female, which regularly flew there from Her- Andrews, 20 km to the northeast at Chew riott’s Pool. Late in the evening of 23rd June, Valley Lake, where it remained until 15th the pair again flew from the back of Her- April. More surprisingly, however, it re - riott’s Pool onto the main lake, presumably to appeared at Chew from 23rd June to 10th feed. However, at dusk, the male was alone on July 2000. It was rediscovered at Chew in Herriott’s Pool, although he then once again 2001, but on the later date of 19th May, flew back onto the main lake. Between 26th remaining to 28th June; it returned yet again June and 7th July, we saw the male on four in 2002, but it was seen only on 22nd August further occasions, either alone on Herriott’s and 14th September. It was, however, Pool or flying towards Wick Green Point to extremely elusive in the extensive reedbeds at feed, usually in the evening. On two occa- the south end of the lake and was undoubt- sions, he was seen displaying, with a peculiar edly overlooked for long periods. In March backwards ‘neck jerk’. 2002, what is likely to have been the same BWP suggests that, as with many species bird was seen on the South Lake at Slim- of duck, the male Ferruginous ‘stands guard’ bridge, Gloucestershire (Rogers et al. 2003). over the female and the nest-site during the Although summer records of Ferruginous early stages of incubation, accompanying the Duck in Britain are not unprecedented (Vini- female when she leaves the nest to feed. The combe 2000), these repeated summer appear- behaviour of the male and the erratic appear- ances were surprising, given that the species ances and protracted absences of the female is essentially a winter visitor. Inevitably, there throughout June and early July 2003 suggest were suggestions that the bird could have that she was incubating. That idea gained been an escape from captivity, but never at credibility on 13th July, when KEV saw the any point did its behaviour suggest this. female again as she swam very quickly from the southeast corner of Herriott’s Pool to a Summary of events at Chew, small island at the back of the pool where she 2003–10 bathed and then behaved very aggressively Summer 2003 towards some female Tufted Ducks A. Surprising as these records may have been, fuligula that had approached the island. events took a remarkable turn in the spring of However, there was no sign of any young, 2003. The female made her, by now expected, either then or subsequently. reappearance on 10th April, on Herriott’s From 3rd August to 2nd September, the Pool at the south end of Chew Valley Lake. male was to be seen loafing with moulting This is a shallow, reed-fringed, 8-ha pool, sep- Tufted Ducks and Common Pochards A. arated from the main lake by a causeway; in ferina (hereafter simply ‘Pochard’) in Strat- contrast to the main lake, the water levels are ford Bay in the southwest corner of the main relatively constant. All seemed set for a repeat lake. KEV saw the female again on 3rd Sep- of the previous three summers but then, on tember, when she was feeding alone in her 18th April, she was joined by an adult male. favoured spot off Wick Green Point, now in Since the female had appeared alone eight fresh plumage, having clearly moulted. days earlier, it is not only remarkable that a male also turned up but that the two birds Summer 2004 located one another and paired up so quickly. The female reappeared at Chew on the early Although the pair was then reported date of 20th February, the male three days throughout late April and May, the male was later, but they were not seen again until 23rd seen alone on 10th June, asleep, at the back of March. Events in 2004 mirrored those of the Herriott’s Pool. On the evening of 16th June, previous summer with the birds becoming the pair was together again, feeding on the attached to the same small island at the back main lake at Wick Green Point, about 1.2 km of Herriott’s Pool (hereafter referred to as the

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‘nesting island’). Again, they often flew to feeding behind the nesting island and, after 15 Wick Green Point to feed, particularly in the minutes, they came out of the water beneath evenings, where the male tended to keep a large willow Salix at the back of the pool, guard over the female, remaining alert and where they were watched preening. diving less frequently as she fed. 24th June At 13.00 hrs, the pair appeared at On 26th May, the pair was watched by the back of the pool but then flew onto the KEV at a range of about 25 m from the hide main lake and disappeared towards Wick at Wick Green Point, often picking flies off Green Point. the water. After a while, the male was seen to raise his head and also his crown feathers and The pair was last seen on 30th June, although the two birds briefly swam around each other the female reappeared from 15th August to with their heads raised. The male then copu- 15th September. The birds’ behaviour in 2004 lated with the female and both birds then again suggested that nesting was attempted bathed. No vocalisations were heard. on the same island, as evidenced by the pair’s displays and general behaviour, copulation AHD made the following observations in (observed five times between 26th May and 2004: 8th June), their prospecting of the island, the 28th May At 15.00 hrs, copulation took place male chasing off Tufted Ducks from the on Herriott’s Pool, again followed immediately vicinity of the island and apparently keeping by both birds bathing. They then came out of guard during the early stages of incubation. the water and preened on the edge of a small island. Both then swam around, as if searching Summer 2005 for nest-sites. Two islands were investigated Disappointingly, the only sightings were of before they were lost to view behind them. the male on 25th March and the pair on 3rd 30th May The male, on his own at the back of July. As in 2004, the female then returned the pool, was seen to display, kinking his neck later in the year, during 6th–27th September. and then tossing back his head. The female then appeared at the back of the pool. Later, Summer 2006 the pair was seen prospecting the previous There was no sign of the birds until 11th year’s nesting island, at one point going ashore June, when KEV saw the pair apparently at the eastern end. On returning to the water, prospecting along the southwest side of Her- they circumnavigated the island several times, riott’s Pool; they flew onto the main lake the male sometimes alone, before flying onto when chased by a pair of Common Shelducks the main lake at 16.45 hrs. Tadorna tadorna. The pair was seen again, on 2nd June Copulation was observed at 12.00 the west side of Herriott’s Pool, on 12th June hrs on Herriott’s Pool. by AHD. The male was seen throwing back 4th June At 14.30 hrs, the pair was again at his head at the female and copulation was the back of the pool. They then flew to the observed twice in an hour. The male vigor- main lake but they returned 30 minutes later ously chased off nearby male Tufted Ducks and vanished onto the nesting island. that appeared interested in the female. 8th June At 14.00 hrs, copulation was again On 2nd July, KEV watched them feeding noted on Herriott’s Pool, followed by bathing in the late evening at Wick Green Point, only (female only), then neck-stretching by both 15–20 m from the hide. As in 2004, the birds. Copulation occurred again before both female was feeding more intently than the vanished. male, which remained much more alert the 10th June At 16.00 hrs, the male appeared on whole time. Eventually, the male ‘pumped up’ Herriott’s Pool and was followed by the and raised his head, and then started calling: female, which seemed to have come off the a soft, quiet ‘zree zree zree’. The female then nesting island. Both then started diving. had a short bathe and the male performed a 13th June The male was seen alone on the few pre-flight intention signals before both eastern end of the nesting island, chasing off birds flew a short distance, the female calling Tufted Ducks from the vicinity. ‘kurr kurr’. They swam into the north end of 19th June At 14.00 hrs, the pair was watched the Main Reeds and vanished. It was hoped

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that they were nesting somewhere in the Ferruginous Ducks in juvenile plumage are Main Reeds but this proved to be the last sign incredibly rare in Britain. Having analysed of them until the evening of 20th July, when occurrences of the species in preparation for the female was seen feeding with two Tufted his 2000 paper, KEV had no recollection of Ducks in Stratford Bay. any in full juvenile plumage, although it is The female reappeared from 13th August not easy to obtain a comprehensive list of all to 4th November, and the male was also seen the records. However, there is a record of a again, between 24th August and 16th juvenile at Hornsea Mere, Yorkshire, on 24th November; the female was also seen at August 2007 (present from 23rd August to nearby Blagdon Lake on 15th October. 6th September; Brit. Birds 100: 633, see also Although 2005 proved to be a disappoint- photo on www.surfbirds.com). ment, the birds’ behaviour in 2006 again sug- Considering the possibilities, it occurred gested nesting activity, albeit in a different to KEV that there was perhaps another expla- area from the 2003 and 2004 attempts. nation for the juvenile’s appearance: that it The most intriguing event of 2006, was the result of nest parasitism. In other however, took place in the autumn of that words, the female Ferruginous had laid an year. On 18th October, a male Ferruginous egg in another duck’s nest and the resulting Duck in full juvenile plumage was discovered youngster had been raised incognito, by in the channel in front of Herriott’s Bridge, either a female or a female immediately adjacent to the Main Reeds, and Pochard. remained until 5th November (plate 36). Yom-Tov (2001) stated that a high rate of Although wild immigrants start to appear in intraspecific nest parasitism (when birds lay earnest in October, peaking in November eggs in nests of the same species) is expected (Vinicombe 2000) – and, of course, some when host nests are available for extended Ferruginous Ducks escape from captivity – periods of time or in a limited space. It occurs the coincidence of the juvenile’s appearance mainly in precocial species (those in which the was intriguing: could it have been the young are active immediately after hatching) product of that summer’s activities? because they lay larger clutches than do simi- Given that only 18 days after the last larly sized altricial species (those in which the sighting of the pair together, on 2nd July, the young are helpless when hatched) and they female had been seen alone and with no start incubating mostly after the last or penul- brood in tow, it seemed likely that the later timate egg is laid, thus leaving the nest without presence of a juvenile was nothing more than protection for most of the laying period; and a strange coincidence. On the other hand, also because parasitic eggs and young among precocial birds require a smaller increase in parental care from hosts than in altricial species. He listed 234 species of birds where this behaviour has been recorded, the biggest family being the , where it has so far been recorded in 74 out of 161 species (46%). It is well known that some Aythya species, such as the A. americana, are inveterate egg-dumpers (Weller 1959). KEV had previously noted interspecific nest Simon Mackie 36. Juvenile male Ferruginous Duck Aythya nyroca, Chew Valley Lake, parasitism at Chew in 1980 Avon, October 2006. and 2003 when Pochard

80 British Birds 104 • February 2011 • 77–83 The probable breeding of Ferruginous Ducks in Avon ducklings were attached to Tufted Duck is more similar to a Pochard than to a Tufted broods (one and two ducklings respectively), Duck (i.e. brown and yellow rather than and in 1980 and 1991 when single Ruddy completely dark blackish-brown) so it seems Duck Oxyura jamaicensis chicks were most likely that, if our juvenile was the result attached to Pochard and Tufted Duck broods. of egg-dumping, it was hidden among one of However, those were the only four instances the Pochard broods on Herriott’s Pool. When of such parasitism recorded between 1967 discussing the possibilities of nest parasitism and 2010, in a total of 733 observed broods at the end of the 2006 season, KEV predicted of these three species (115 Pochards, 521 that, if the Ferruginous juvenile really had Tufted Ducks and 97 Ruddy Ducks); in other hatched at Chew then it (a) would return the words, it affected just 0.9% of Pochard and following summer and (b) display to either 0.6% of Tufted broods. These low levels of Tufted Ducks or Pochards, having become recorded (interspecific) nest parasitism may imprinted on its surrogate mother. reflect the low breeding density of both Pochards and Tufted Ducks at Chew, particu- Summer 2007 larly since the mid 1990s, after which there The male and female reappeared together on was a large decline in the numbers of Herriott’s Pool on the early date of 8th Feb- breeding Tufted Ducks. Interestingly, Yom- ruary; this turned out to be the last time that Tov listed Ferruginous Duck as one of the the male was ever seen. The female was seen species in which nest parasitism has been again on 20th June and 19th–20th August, recorded. which proved to be the last occasion that she There were three broods of Pochards seen was ever seen. By 2007, she would have been at at Chew in summer 2006 and seven broods of least nine years old and the male at least five. Tufted Ducks. The Pochard broods were first In line with KEV’s predictions, a first- seen on Herriott’s Pool on 29th June and 13th summer male appeared at Chew on 6th June, July (two), while seven Tufted Duck broods remaining until 10th November (and visiting appeared between 20th July and 17th August nearby Blagdon Lake on 16th June). On (one on Herriott’s Pool and six on the main arrival it was readily separable from the adult lake). The description and illustration of a male by remnants of juvenile plumage, with Ferruginous duckling in BWP suggests that it some quite prominent dark marks on the Rich Andrews Rich 37. Male Ferruginous Duck Aythya nyroca, Chew Valley Lake, Avon, May 2009. This photograph shows the bird’s peculiar ‘backward neck-jerk’ display.

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belly; it also showed more gingery flanks. nearby sites (Barrow Gurney Reservoirs, Moreover, almost as soon as it arrived, the Weston-Super-Mare Sewage Treatment young male started to pursue female Tufted Works, Blagdon Lake and Cheddar Reser- Ducks, something that the adult male had voir) and then on the other side of the Bristol never done (although, of course, that bird Channel at Cosmeston Lakes, East Glam- had found a mate of its own species). The organ. In winter 2009/10 it was recorded young male, now in adult plumage, returned again at Cheddar Reservoir and also on in the summer of 2008 and continued to Westhay Moor on the Somerset Levels. show an unhealthy interest in female Tufted At Chew, there were further records of a Ducks. Bizarrely, at the same time, several female Ferruginous Duck on 3rd November male Tufted Ducks developed a similar 2008 and an additional male on 17th May interest in the male Ferruginous, seemingly 2009. In September–November 2010, four under the illusion that it was some kind of were present in total (the returning adult female Aythya ready for the taking! Several male, two first-winter males and an adult times this resulted in a rather amusing female) with a large gathering of up to 3,240 ‘ménage-a-trois’ taking to the air, the female Aythya ducks (820 Pochards and 2,420 Tufted Tufteds trying to shake off the male Ferrugi- Ducks). The three new birds in autumn 2010 nous, which in turn was trying to avoid the brought the total number of Ferruginous male Tufteds! By the summer of 2009 that Ducks recorded at Chew since 2002 to eight activity had waned although, on 27th Sep- (and there had been three previous records: tember, the male Ferruginous was seen dis- in 1955, 1968 and 1976). playing persistently to a female Pochard. Previous possible breeding 2008–10 attempts in Britain The male Ferruginous reappeared each Although breeding has been recorded occa- summer from 2008 to 2010 (plates 35, 37 & sionally in western Europe (see below), there 38). Each year it disappeared after a summer are no such records for Britain. However, an sojourn at Chew although, in the autumn unusual series of summer records at and winter of 2008/09, it was seen at several Holkham, Norfolk, was documented in Taylor Gareth Gareth Jones 38. Male Ferruginous Duck Aythya nyroca, Chew Valley Lake, Avon, March 2009. This shows the bird in its ‘neck stretch’ display, in which it raises the feathers of the crown, side of head and chin and shows off its darker neck ring (BWP). This photo, and also plates 35 & 37, illustrate the same individual shown as a juvenile in plate 36.

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(1999). An approachable pair on 27th April changes have probably also been influential). 1992 was joined by a second pair on 12th June Despite breeding records since 1975 in and two pairs remained until mid July; the France, Belgium, the Netherlands, Germany original female subsequently reappeared on and Switzerland (Hagemeijer & Blair 1997), 26th September. The following year there were the species has never become established in erratic sightings of singles from 12th March to western Europe, unlike Pochard and Tufted 2nd August, followed by a wary pair seen in Duck, both of which have spread west since Holkham Park on 20th August. It is possible the nineteenth century (BWP). that breeding may have been attempted in this Although owned by Bristol Water, the case, at a site where the habitat is suitable for south end of Chew Valley Lake is a nature this species. Subsequently, another pair was reserve managed by the Avon Wildlife Trust. seen in Norfolk, at Syderstone Common on It was disappointing that, in this era of acute 21st–22nd May 1995. interest in rare-bird conservation, local Taylor et al. (1999) also described a birders found themselves surprisingly iso- remarkable influx of Ferruginous Ducks in lated in having to deal with the protection of Norfolk on 15th April 1903, when a flock of what were probably, at that time, Britain’s ten drakes was recorded on Hickling Broad, rarest breeding birds. For this reason, news of most of which were shot, and an additional their presence was restricted, as far as it was ten birds on Rollesby Broad. This large spring possible to do so. influx may suggest some kind of drought- induced irruption, and its similarity in timing Acknowledgments with the appearance of the Chew birds is We are grateful to John Aldridge, Richard Andrews, Rupert Higgins, Richard Mielcarek, Nigel Milbourne, interesting. Similarly, it is also worth noting a Mark Ponsford and Tim Twiggs for their help in record of two males at Kenfig Pool, East Glam- obtaining records, and to the various bird information organ, on 28th April 1999 (Rogers et al. 2000). services for their full co-operation in restricting news of the presence in the breeding season of these rare and vulnerable birds. Summary and conclusions Although there is no proof that Ferruginous References Ducks bred or even nested at Chew during BirdLife International. 2004. Birds in Europe: population 2003–06, we believe that the above observa- estimates, trends and . BirdLife International, Cambridge. tions suggest that nesting took place in 2003 Hagemeijer, W. J. M., & Blair, M. J. (eds.). 1997. The EBCC and 2004 and that a youngster may have been Atlas of European Breeding Birds. Poyser, London. raised in 2006, perhaps by a foster parent. Holling, M., and the Rare Breeding Birds Panel. 2010. The birds’ behaviour certainly fulfills the cri- Rare breeding birds in the United Kingdom in 2008. Brit. Birds 103: 482–538. terion for ‘probable breeding’ (Hagemeijer & Rogers, M. J., and the Rarities Committee. 2000. Blair 1997; Rare Breeding Birds Panel). Report on Rare Birds in Great Britain in 1999. The Ferruginous Duck was listed as ‘Vul- Brit. Birds 93: 512–567. nerable’ in a European context by BirdLife — 2003. Report on Rare Birds in Great Britain in 2002. Brit. Birds 96: 542–609. International (2004) so it is disappointing Taylor, M., Seago, M., Allard, P., & Dorling, D. 1999. that the birds were not more successful at The Birds of Norfolk. Pica Press, Robertsbridge. Chew. However, their failure to establish is Vinicombe, K. E. 2000. Identification of Ferruginous Duck and its status in Britain and Ireland. perhaps not surprising, given the low success Brit. Birds 93: 4–21. rates of breeding wildfowl at the lake in Weller, M. W. 1959. Parasitic egg laying in the Redhead recent years (KEV pers. obs.), perhaps a con- (Aythya americana) and other North American sequence of low chick survival rates after the . Ecological Monographs 29: 333–365. Yom-Tov, Y. 2001. An updated list and some comments introduction of pike Esox lucius in the mid on the occurrence of intraspecific nest parasitism in 1990s (although more subtle ecological birds. Ibis 143: 133–143.

A. H. Davis and K. E. Vinicombe, Bristol

Andy Davis is a retired teacher who was editor of the award-winning Avon Bird Report from 1991 to 2002. Keith Vinicombe is a civil servant who has previously written about Ferruginous Ducks in this journal, having become concerned that this rare and beautiful duck was being given inadequate attention as a British bird. Both Andy and Keith made their first visits to Chew in 1963 and are still patch regulars there.

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