Ben Green The population biology of Common in Britain T. W. Dougall, P. K. Holland and D. W.Yalden

Abstract The population biology of Common Sandpipers hypoleucos has been studied, especially by colour-ringing breeding adults, at two sites, in the Peak District and in the Scottish Borders. Adults are usually site-faithful, males more so than females, contributing to a good apparent survival rate (72% and 67%, respectively). Some, at least, return to breed at one year old, but usually not to the site where they hatched. The population in Britain seems to be in slow decline, most obviously indicated by a contraction along the edges of its range, which results especially from poor recruitment of young . This does not seem to be due to poorer breeding success, but it is uncertain whether it is caused by a subtle effect of climate change, change in quality of stopover sites on migration, or changes in wintering habitat. Since we don’t know precisely where British birds spend the winter, the last possibility is especially hard to evaluate.

Introduction or Wood Lark Lullula arborea, but not suffi- The Common Actitis hypoleucos is ciently abundant to benefit from mass one of those ‘in between’ birds – not rare studies, like the Blue Tit Cyanistes caeruleus enough to have attracted devoted individual or Robin Erithacus rubecula. Unlike many attention, like the Osprey Pandion haliaetus , it does not flock in large numbers to

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fields, estuaries or the Banc d’Arguin, it is not censused by moorland counts, and when on migration does not Howden get ringed in any great Reservoir numbers. There is a little information from the Water- R. Alport Derwent ways Bird Survey on popula- Reservoir tion trends and the species A57 seems to have been targeted Ladybower Reservoir by only one PhD study (Mee R. Ashop (N arm) 2001). Our own, essentially spare-time, efforts have been an attempt to fill in some of 1234 km the gaps. In reviewing what we have learnt, we inevitably Ladybower also highlight how much Reservoir remains unknown. (W arm) Study sites and Fig. 1. Sketch map of the Ashop–Alport study site and the nearby methods reservoirs in the Upper Derwent Valley, Peak District (areas of woodland shown in green, water features in blue; also shown is the Our efforts started with a A57 between Manchester and Sheffield) (from Dougall et al. 2005). survey of numbers in the Peak District in 1977–79, combined with a colour-ringing study of birds along a 10-km stretch of Blackhope the Rivers Ashop (‘Snake Heriot Water Water Pass’) and Alport (Holland et al. 1982a,b). Of about 200 pairs then breeding in the Dewar Peak District, 20–22 pairs Burn occupied these valleys, with another 45–50 pairs nearby on B709 the Ladybower-Derwent- Lugate Water Howden (LDH) Reservoir chain. The Ashop flows into the western arm of Ladybower Glentress Reservoir, about 2 km down- Water stream of the study site; the whole forms part of the Upper Derwent catchment. Leithen The colour-ringing study con- Water tinues to the present day, giving 32 years of data (PKH, 1234 km then DWY), but has also been extended to the reservoir chain. Thinking that a com- parative study would be R. Tweed revealing, we started a parallel Innerleithen investigation on the rivers Fig. 2. Sketch map of the Borders study site (woodland in green, Leithen Water (8.5 km) and water features in blue; also shown is the B709 road from Heriot Water (6 km) in the Edinburgh to Innerleithen) (from Dougall et al. 2005). Moorfoot Hills, Borders, in

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1993 (TWD), and this also continues returning migrants than the Peak District (Dougall et al. 2005; Pearce-Higgins et al. (hereafter referred to as Ashop) study area. 2009). This study site, and our knowledge of On the other hand, the LDH reservoir chain the species, benefited from an intensive PhD has a shoreline of 30 km. This must also study in 1998–99 (Mee 2001). The two provide a good target for returning sand- stretches of river are about 6 km apart, and pipers, but is too extensive to be studied as together perhaps provide a larger target for intensively as the rivers. The whole shoreline has been surveyed twice (once in May, once in June) each year since 1992, and one or two ex-Ashop birds are invariably present. Adults are usually caught on the rivers in short, single-panel mist-nets set within the territories, usually targeting particular individ- uals, and birds are ringed with 3–4 Darvic colour rings, as well as a BTO metal ring, so that T. W. Dougall W. T. individuals are sub- 29. An upper stretch of Glentress Water, near Blackhopebyres, in the sequently recognis- Borders study area. This shows the meandering river and the wide shingle banks that develop in the bends, producing favoured feeding sites for able in the field. In Common Sandpipers Actitis hypoleucos. the Ashop study area, potential terri- tories are checked weekly through May and June, sometimes into mid July, for the presence of colour- ringed birds. Nests are rarely located, and the adults are secretive during incubation, but once the chicks hatch, their parents become very vocal (‘alarm’), revealing roughly where their chicks are. By backing off, or using a car as a hide, it is sometimes T. W. Dougall W. T. possible to watch 30. A lower stretch of the Borders study site, on Glentress Water near Whitehope. This is good habitat for Common Sandpipers Actitis hypoleucos, adults returning to with wide shingle beds, cover for chicks in the boulders, and with the brood young chicks. advantage of the nearby road, allowing a car to be used as a hide; May 2009. Every effort is made

102 British Birds 103 • February 2010 • 100–114 Common Sandpipers in Britain to ring these, with a single (‘scheme’) colour ring and a BTO metal ring. Ashop birds receive a white ring on the right tibia as the scheme mark, while those around the reservoirs get a light blue ring on the left tibia. The hope was that recruits to the Ashop from the reservoirs would be quickly recognised. In the Borders, chicks as well as adults were formerly fitted with individually recognis-

able combinations, but in W.Yalden D. more recent years both 31. ‘Walk-in’ traps set at the waterline of Ladybower Reservoir, chicks and adults have May 2009. Two traps are set, facing in opposite directions, and with scheme colours applied to boulders or other debris to mask the outline of the trap, and the right leg only: red on mealworms on the bait trays as an added attraction. tibia, orange over BTO on tarsus for adults; quickly (and noisily) pair up, usually in their orange on tibia, red over BTO on tarsus for old territories, and have eggs by mid May. It chicks. So far, neither Peak District nor Moor- seems as though they fly into their territories foot Hills birds have been seen in the recip- very quickly (rather than trickle slowly up rocal study area, but a juvenile ringed on through the country, although there are some autumn passage in Lancashire on 4th August sightings in south and southwest England, 2001 (by PKH) was retrapped as a breeding and in Wales, of colour-ringed Borders bird south of Peebles, just outside the Moor- birds). This impression is heightened by the foots study area, on 29th May 2003. The age fact that they get back to their territories in of the chicks (and hence their hatch date) can the Borders about a week earlier than those be estimated from their bill length, and in the Peak District. Young birds arrive back weight relative to age gives an estimate of 5–10 days later, on average, than the old condition (Holland & Yalden 1991b). Sexing hands. Territories are usually 150–200 m long Common Sandpipers is not easy, though when there are neighbours to constrain females are generally slightly larger (means them, and are generally along stretches of 54 g v. 49 g; Mee 2001). The greater weights of shingle shore with some cover for the chicks females during egg-laying are revealing (they (e.g. undercut shores, boulders, taller vegeta- can weigh up to 82 g), and with colour-ringed tion). Females typically lay a clutch of four birds courtship behaviour can be helpful in eggs (mean 3.65) in a nest on a grassy bank a determining the sex of individuals. However, few metres back from the water, but some- both adults incubate, brood chicks and times on shingle islands or at the top of stony defend their territory against neighbours reservoir shores; occasionally the nest may be (sometimes making the mistake of chal- over 100 m from the waterside. Incubation is lenging their own returning mates!). shared, but males sit mainly overnight and Although the male usually follows behind the females during daylight hours (Mee 2001). female while she is feeding up prior to egg- The eggs hatch from mid May (Borders) laying, and signals to her with ‘wings-up’, dis- or the last few days of May into early June, playing the strongly patterned underwing, the but new recruits are later and pairs will same display is used as a threat by both sexes. produce a replacement clutch if the first is lost, stretching the hatch dates to as late as Breeding biology 7th July. At hatching, chicks weigh around Older Common Sandpipers reappear on 9.5 g and have a bill length of about 10 mm. their breeding grounds in mid to late April, Chicks are encouraged from the nest by their

British Birds 103 • February 2010 • 100–114 103 Dougall et al. D. W.Yalden D.

32. A typical Common Sandpiper Actitis W.Yalden D. hypoleucos nest, with a clutch of four eggs; this 33. A late, replacement nest, in growing one, in a patch of Bracken Pteridium aquilinum in Bracken Pteridium aquilinum, Ashop Valley, the Ashop study area, 15th May 1984, belonged 9th June 1982; another of Red-Red’s successful to the long-lived male ‘Red-Red’. nests. parents, and for their first few days usually this age to fledging: their camouflage, ability frequent damp areas – rushes, streams trick- to run and hide, and to dive and swim if sur- ling over reservoir shores – where small prised near deeper water, gives them an are readily available. Mortality at this ability to dodge most predators (and stage is high, around 25% (Yalden & Dougall ringers!). Detailed observations suggest that 2004), despite both parents being present as they are thermally independent by then, guards. Young chicks need brooding every though older chicks may still be brooded in seven minutes or so, and for about seven rain and at night. From about seven days old, minutes each bout. By seven days, the chicks the chicks may be closely attended by only are mobile, weigh around 16 g and have a bill one parent, the other going off to feed nearby length of 14 mm; most (75%) survive from (though still alert to intruders). By their third week (the chicks usually fledge in 19 days), often only one parent is left guarding the chicks, and usually stays beyond fledging for another week or so. When one parent leaves early, it is usually, but not always, the female. Partial desertion is more likely with later-hatching broods (Mee 2001). Clearly, their territory is very important to Common Sandpipers; both adults defend it against their neighbours. Moreover, it is demon- strably the stretch of D. W.Yalden D. 34. A brood of three young Common Sandpiper Actitis hypoleucos shoreline that they are chicks, about four days old and about 20 m away from their known defending: the four neigh- nest-site; June 2009, Ladybower Reservoir. bours will feed together

104 British Birds 103 • February 2010 • 100–114 Common Sandpipers in Britain comfortably in nearby pasture, but renew ter- ritorial aggression when they return to the river. An analysis of habitat suggests that they need an area of shingle, and the adults spend much time patrolling the water’s edge in search of food. However, their diet contains an even mix of aquatic prey (caddisfly (Tri- choptera), mayfly (Ephemer optera) and stonefly (Plecoptera) larvae) and terrestrial Sean Gray prey (click beetles 35. A young Common Sandpiper Actitis hypoleucos chick, probably only a (Elateridae), carabids day or two old, still with a short (10 mm) bill; Whiteholme Reservoir, Yorkshire, June 2008. (Carabidae) and earth worms (Lumbricidae)) (Yalden 1986), and low recruitment. The Ashop had 20–22 so reliance on the water’s edge to provide a pairs in 1977–80. However, the severe late food supply is not the whole story. The most April (24th–26th) snowfall of 1981 apparently prolonged territorial fight we have observed surprised, and killed, a number of returning (27 minutes) involved two pairs guarding adults; the population dropped to 14 pairs chicks, on 18th June 1989. One pair, dis- that year, and recovered only slowly (by one turbed by an angler, led its chicks into the or two pairs a year) up to 1988 (Holland & neighbouring territory, and to start with all Yalden 1995). Another cold, late spring in four birds were fighting (three of them were 1989 then caused another sharp decline, from colour-ringed) (Yalden 1992a). One male which the population has never properly then led his chicks back, while his mate con- recovered. Although there were 15 pairs in tinued fighting for another 11 minutes. Such 2006, only five pairs were present in 2007 and observations suggest that the most important 2008. Averaged over 28 years, the population roles of the territory are to provide the chicks with a 35 Borders feeding area and good cover. 30 Territorial fights are certainly more prolonged when chicks 25 Ashop are also present than early in the season, when the briefest of 20 challenges is usually sufficient 15 to maintain territorial integrity. 10 Population trends 5 The early years of study in the Peak District, and the early 0 years of the Waterways Bird 1975 1980 1985 1990 1995 2000 2005 2010 Survey (WBS), suggested a Fig. 3. The long-term decline of the Ashop–Alport Common stable population, as might be Sandpiper Actitis hypoleucos population from 1977 to 2009, and expected for a relatively long- the fluctuating population in the Borders study site from 1993 lived species with high survival to 2007.

British Birds 103 • February 2010 • 100–114 105 Dougall et al. has declined by 59%. This matches what has Survival rates, breeding success happened more generally on the streams and recruitment around the Peak District, and the national We have tried hard to understand the basis of trend revealed by WBS and BBS (Breeding the national decline, and the contrast in for- Bird Survey), which suggests a 25% decline tunes between the Peak District and Borders over eight years (www.bto.org/birdtrends/ populations. Originally (1970s and 1980s) wcrcomsa.htm). Over the shorter run of data there was a strong correlation between sur- from the Borders, there seems to have been vival rates and minimum temperatures in no decline, though much variability. Even late April: fewer adults returned in cold more puzzling, the LDH reservoir population springs. Simple apparent survival rates near the Ashop also shows no such decline. (resighting of the previous year’s colour- There were 49 (±8) pairs in the early 1980s ringed adults, on average 72% for males and and 51 (±11) pairs in the 1990s and 2000s; 67% for females) declined between 80% and indeed the highest count ever was as recent as 47% as late April mean minimum tempera- 2007, when 84 pairs were logged. In the ture went down from 5.6 to 1°C (Holland & Moorfoots, along a discontinuous 10.13 km, Yalden 2002a). The variation in population monitored annually between 1993 and 2007, this produced matched changes in the North the number of territories ranged between 14 Atlantic Oscillation (NAO); warm wet in 2000 and 31 in 1993, and the percentage winters (high NAO, perhaps snowier) are bad which hatched at least one chick ranged for sandpipers (Forchammer et al. 1998). between 48% (in 2004) and 82% (in 2003) However, in the 1990s, this relationship no (Dougall et al. 1999; Dougall unpubl.). longer fitted, though survival rates were still While estimating the national population just as variable, as were April temperatures is fraught with difficulties (see below), it is (Dougall et al. 2004). Not only did the easier to map the breeding distribution. Borders population not show the long-term Between the two breeding atlases (1968–72 decline, but the considerable variations in (Sharrock 1976) and 1988–91 (Gibbons et al. populations there from year to year were not 1993)), the breeding range contracted, partic- correlated with those in the Ashop popula- ularly along the fringes of the species’ range. tion (Pearce-Higgins et al. 2009). If anything, An apparent net loss of 14% of its breeding survival rates were slightly higher in the range in Great Britain and a substantial, declining Ashop population than in the though perhaps overestimated, 54% of its Borders population, although the difference Irish range suggests a considerable decline was not significant. (Yalden 1993). It will be fascinating to see Breeding success is hard to evaluate pre- what the third atlas reveals. cisely; because well-grown chicks are so good at running and hiding from any 1.0 threat, whether ringer or pred- 0.8 ator, counts of older young or fledglings are invariably underes- 0.6 timates. One calculation suggests that perhaps 35% of the actual 0.4 fledglings were not recorded 0.2 (Yalden & Dougall 2004), another that 30% were missed (Holland & 0 Yalden 1994). However, the fact -4 -2 0246that their guarding parents are so Winter NAO vocal suggests that at least the Fig. 4. This figure shows the slight negative correlation of success of breeding attempts can annual adult survival for the Ashop birds with winter North be reliably counted: a territory Atlantic Oscillation (NAO) values (yellow circles denote first- that has ‘alarming’ parents over year birds, i.e. new recruits, red circles represent older adults) (from Pearce-Higgins et al. 2009). A higher NAO value three or four weeks has surely got indicates a warmer, wetter winter in western Europe, but at least one chick through to cooler, drier conditions in NW Africa. fledging. On that basis, there is no

106 British Birds 103 • February 2010 • 100–114 Common Sandpipers in Britain evidence that breeding success has been mate at least once (Holland & Yalden 1994). poorer in the Ashop study area than in the The converse pleasure is of discovering Borders study area over the decade or more that individual birds which have failed to that both have been studied. What is clear, return to their territories have moved else- however, is that recruitment of ‘new’ birds, as where (emigrated) rather than died. Obvi- well as returns of fledglings, is very much ously, this does not happen often. One 1980 higher in the Borders than in the Peak Dis- female that had been presumed dead in the trict. Only one of the 99 chicks and fledglings 1981 spring was found in 1982, about 20 km ringed in the Ashop study area over the 1990s away to the southwest in the Goyt Valley, returned to breed there, but 49 of 421 ringed where she returned in 1983 and 1984. In in the Borders did so. Over the same period, 1990–93, ten birds from the supposedly site- while 68 adults were recruited to the Ashop faithful Ashop population contributed population, there were 172 new adults ringed further to the decline there by moving to in the Borders (Dougall et al. 2005). The LDH. One, having bred successfully along the attempt to identify the source of new recruits Ashop in 1992, as a new recruit, returned to the Ashop population did find four birds there briefly in April 1993, but in June 1993 bearing LDH light blue rings, including what was at Derwent Reservoir, guarding a family, has become the record for longevity. A 13- as he was in 1994, 1995, 1996 and 1997. This day-old chick ringed as NV54164 at Lady- example highlights one of the mysteries of bower Reservoir on 21st June 1992 turned up this species. What are returning birds, as a breeding male 7 km away in one of the whether old hands or new recruits, looking upper territories on the Ashop in May 1993, for when they get back? If they were heading with an unringed female. Both were caught for familiar habitat, we might expect riverine and individually colour-ringed, but their birds to return to rivers and reservoir birds to breeding attempt failed that year, and the return to similar shorelines. Obviously, estab- female was never seen again. The male didn’t lished birds return to their familiar territory, return to the Ashop, but in May 1994 was and get back to claim it as quickly as possible. seen three times with an unringed female at Often, they also meet their old mate there, Ladybower, about 3 km south of where he and experienced birds are more likely to hatched. He was seen back in that territory breed successfully together (Mee 2001). every year to 2007, being last recorded on Rarely, females get back before their mate, 19th June 2007; moreover, judging by his and may then pair with an already estab- ‘alarming’ behaviour in June, he bred suc- lished (but different) male. Are birds that cessfully in 11 of his 14 years at Ladybower, move sites ones whose mate fails to return? and at 15 years old was much the oldest Are they looking to set up territories near Common Sandpiper that we or anyone else other, already established, birds or pairs, on has recorded. the basis that their presence signifies a suit- This sort of resighting is one of the able site? If the latter is true, it might explain delights of studying this species. The birds the geographical retreat from peripheral are highly site-faithful (and if they were not, parts of the range, in the Peak District cer- the apparent survival rates would be much tainly, but also in northeast Scotland and in poorer). An early calculation was that 89% of Ireland, as revealed by Gibbons et al. (1993). returning males and 78% of returning It is possible that some of the apparent con- females came back to the same or an adjacent traction in range was actually a consequence territory (Holland & Yalden 2002a). So, in of less thorough surveying of the thinly pop- late April, checking the rivers to see who is ulated periphery of the species’ range in safely back, and with whom they are paired, 1988–91, especially in Ireland, although local is a special pleasure. With an average survival accounts confirm losses in many areas. rate of about 80%, adult life is likely to last three years, so the chances of both members Natal dispersal of a pair returning are only about 50%. Put Given that chicks wear at least a scheme ring, another way, a bird that holds territory for any that return to our study areas are con- three years is statistically ‘bound’ to get a new spicuous, and targeted (albeit not always suc-

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perhaps a large proportion, of them. This is an aspect of our studies where sightings from others would be especially valu- able.

Migration and wintering This section deals with our biggest uncertainties! There are ringing recoveries of British birds moving south in Britain, and from France, Spain, Portugal and Morocco, in July–October. Similarly, there are recoveries of returning birds, through Morocco, Spain and France in March–April. These include recoveries/resightings of D. Priddle D. 36. A well-grown Common Sandpiper Actitis hypoleucos chick, our own birds in southern within about two days of fledging (bill length 19.7 mm, wing England, France, Iberia and length 79 mm, but underweight at 27.5 g), showing remnants Morocco. None of our birds has of chick down on the nape and tail. The red ring above the been seen in November–February, BTO metal ring identifies this as a chick from the Borders and, more surprisingly, there has study site; Leithen Water, June 2005. been just one recovery from West cessfully) for recapture, identification and Africa of the 19,000+ Common Sandpipers full colour-ringing. This gives us a measure ringed in Britain. This was of a bird ringed at of natal dispersal – the distance between Abberton Reservoir, Essex, in July 1964 and hatching and establishment of a breeding ter- recovered in Guinea-Bissau in September ritory in later years – but this is clearly going (though birds ringed at Abberton are mostly to be an underestimate, since we are more Scandinavian birds on passage, as nine other likely to detect a ringed new recruit within recoveries in Scandinavia testify). The nearest our study areas than farther afield. Of 36 thing to a recovery in West Africa of a Borders chicks that returned later to breed, British-bred bird involves an unfortunate they were between 0 and 39 km from where chick ringed at Grassington, Yorkshire, on they hatched, and at a median distance of 6 2nd June 1963. Its remains were recovered on km. It is probably no coincidence that this is 20th November 1963 from the radiator of an roughly the distance between the two parts, aircraft that landed at Moscow airport after a Heriot Water and Leithen Water, of the study journey from Accra (Ghana) via Conakry site. In the Peak District, the 35 returning (Guinea), Bamako (Mali) and Belgrade. The chicks were between 0.7 and 138 km away, likelihood is that this young bird had been with a median of 3.3 km, which is, similarly, caught up in Guinea or Mali; this is roughly roughly the distance between the Ashop and where we would predict British birds to be in the LDH reservoirs (Dougall et al. 2005). winter on the basis of the SSW trend shown How biased are these two figures? We have by recoveries of Common Sandpipers ringed had a few exchanges between the Goyt Valley, elsewhere in Europe (Poland, Germany, 20 km to the southwest, and the Upper Russia) and recovered in West Africa Derwent, and there is a weak correlation, (Holland & Yalden 2002b). with a two-year lag, between population Common Sandpipers move south in changes in the Ashop population and those summer very quickly. Our study sites are in the Goyt. The most distant return, at 138 usually already thinly populated by early July, km, was in north Wales. If our returns are and typically empty before the end of the spread so far, it is obvious that a search con- month. Some have been recovered in Por- centrated within 10 km or so of the sites of tugal and Spain as early as mid July, and we ringing is going to miss a proportion, suspect that failed breeders may leave for

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Africa very quickly. One Peak District bird at St Abbs Head, Borders (Dougall & Yalden was recovered, already back in Morocco, on 2007). These August falls are presumably of 15th June 1979. On the other hand, we also Scandinavian birds on passage, but the July have recoveries (and sightings of colour- flocks are likely to be from more local ringed birds) into August of sandpipers still breeding areas. in Britain, and we suspect that juveniles are A small minority of Common Sandpipers in less of a hurry to reach Africa. remain in Britain overwinter. We know little Over a period of 12 years, PKH succeeded about these, either. On the basis that, in birds in fitting colour rings to 60 full-grown birds generally, those summering farthest north near the mouth of the River Lune. It was winter farthest south, whereas those in the thought that these might be a sample of the middle of the range move relatively little, we 100 pairs or their offspring that breed higher would expect that Scandinavian birds overfly up the Lune catchment. Yet none of these was Britain. Birds wintering in Britain are more ever seen on territory there in later years, nor likely to be part of our summering popula- were any of 38 birds ringed on those tion. The chances of spotting one of our breeding areas ever seen at the mouth. colour-ringed breeding birds still in Britain However, one was seen later breeding in the in winter seem slight, but would be a worth- Borders (see above) and another in while target for those with telescopes or Northumberland. Evidently, the mouth of digiscoping equipment. If some of the the Lune is a feeding-up site for birds from Common Sandpipers overwintering in the Borders. The mean weight of these birds Britain could be caught and colour-ringed, was 66 g, but the six heaviest weighed 80, 80, they are perhaps more likely to yield a 81, 81, 82 and 84 g. Others have also reported resighting in summer. Birds regularly birds fattening up to over 80 g at sites away hunting along reservoir shores can some- from their breeding grounds (e.g. Brown times be caught in walk-in traps or small 1974). spring-traps (Dougall & Yalden 2008). Trap- Relatively large concentrations of ping may also confirm that wintering birds migrating birds sometimes occur in autumn, are site-faithful to their wintering territories, for example 100 at Carron Valley Reservoir, as suggested by one caught on Southampton Upper Forth, on 7th July 1984; 64 at Endrick Water on 6th January 1974 that was caught Mouth, Clyde, on 25th July 1977 and 14th there again on 18th March 1975. The ringing August 1978; and 83 roosting at the River expeditions to Djoudj, Senegal, in the early Annan mouth, Dumfries & Gal- loway, on 25th July 2003. Occasionally there are ‘falls’ in the Northern Isles and along the east coast of Scotland, most recently during 18th–22nd August 2001, when there were 15 on Fair Isle; seven on North Ronaldsay; 50 on the Isle of May; 23, 11, nine and eight at four sites in the East Sean Gray Neuk of Fife; 37. An adult (female?) Common Sandpiper Actitis hypoleucos executing a seven at Skateraw, ‘double wing-up’, showing the striking underwing pattern. This is both a Lothian; and eight threat and a courtship display. Whiteholme Reservoir, Yorkshire, April 2007.

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1990s showed that Common Sandpipers (51%) were recorded (Dougall et al. 2005). ringed there had a higher return rate (9/65 or However, given the median natal dispersal 14% after one year) than any of the other distance of 6 km, and a range up to 39 km, it waders, implying that they were indeed site- is not known if the ‘missing’ 49% were in fact faithful (Sauvage et al. 1998). Limited obser- recruited elsewhere, or if mortality rates are vations suggested that they established higher than we assumed. Moreover, we must territories of about 200 m in length along the expect that first-year survival rates vary banks of the Senegal River, and defended widely, as they do for adults, with weather them against neighbours, but there is scope and other conditions, but we know nothing for considerable work on the species’ winter of this. Colour-ringing studies of wintering ecology. birds, comparing adult and first-year survival We have estimated that around 54% of rates, would be interesting. Although they newly hatched chicks survive to fledging reach adult size by the time they fledge, (Yalden & Dougall 2004), and we have a good juvenile sandpipers have more conspicuous set of estimates for adult survival (more barring on their primary coverts, so they strictly, adult return rates) from resighting would still be recognisable as young birds our colour-ringed birds (see above). Because when they reach Africa. fledglings rarely return to their natal sites, at Returning birds, as we remarked above, least in the Peak District, we have no clear seem to return quickly to their territories. estimate of the survival rate of first-year birds However, this is clearly a stressful time. In over their first winter. When the Ashop pop- addition to the suspected, and recorded, ulation was stable, we could create a balanced mortality in 1981, recoveries in other years life table by assuming that 57% of young are quite frequent in late April/early May. A birds survived their first winter. Using that conspicuous example is NV82841, ringed as a assumed survival rate, we might have chick on 8th June 1996 at Garvald Lodge, expected 96 recruits to the Borders popula- Heriot Water. He was not seen again until tion from the 1993–2002 cohorts; and 49 2002, when he was breeding successfully, at David Hutton 38 & 39. Two splendid portraits of Common Sandpiper Actitis hypoleucos ‘Light blue//BTO, orange/black, photographed on migration at Seaswood Pool, Nuneaton, Warwickshire, on 15th April 2008. It had been ringed as a newly fledged juvenile at Ladybower Reservoir on 10th July 2002. It was seen in its territory at the northeastern end of Derwent Reservoir in June 2004, June 2005, May 2007 and June 2008, and was retrapped there on 28th May 2009.

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Whitehope, 6 km to the south, and he was rivers. A major problem, of course, is to there again in 2003 and bred successfully translate observed linear densities (per km of with the same mate. On 22nd April 2004, river or shoreline) into sensible figures for though, he was found dead at Devizes, Wilt- areas. Among a variety of estimates, we sug- shire. His mate returned safely, took a new gested that 1.6 pairs per monad (1-km mate, was unsuccessful in breeding and was square) was the most plausible (Dougall et never seen again. al. 2004), while the BBS suggested that 2% of the monads in England and Wales but 15% Estimating the size of the British of those in Scotland were occupied; there are population few data for Ireland, but we assumed that Given our interest in the densities of birds in 5% of monads were occupied. The total our study areas, it was a natural progression occupancy for Britain & Ireland is then to attempt to estimate the size of the total 19,500 monads, with a breeding population breeding population of Britain & Ireland. of 30,622 pairs, twice the number estimated In the New Atlas (Gibbons et al. 1993), it was in Gibbons et al. (1993). Moreover, a recal- suggested that the population of a hectad culation of the appropriate figure for the (10-km square) might be 15 pairs, implying 1968–72 breeding atlas (Sharrock 1976) sug- a population of 15,000 pairs in Great Britain gests a population then of 39,600, and thus a and 2,500 pairs in Ireland. This figure was in decline of 23% between the two breeding part suggested by our earlier estimate of the atlases. A decline of 23% is also suggested by Peak District population (11 pairs per hectad the WBS, albeit between 1989 and 1999 averaged over 18 hectads), tempered by (Dougall et al. 2004). Using the same some acknowledgment of the fact that the methodology, we estimated the nationally species was clearly most abundant in Scot- important Scottish population to be in the land. Since the 1980s, many more surveys range of 17,000–24,000 pairs, most probably have been published, including both local around 19,000 pairs (Dougall & Yalden tetrad atlases and particular surveys of 2007). David Hutton

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Causes of the decline tering birds) and near our two study sites in Our attempts to explain the decline of the Britain, produced evidence of some effect of national and Ashop populations by studying climatic variation (NAO) on adult survival the population dynamics of the Ashop birds rates, and declining adult survival rates and contrasting these with patterns in the explained the overall population decline; Borders have not been especially fruitful. however, there was no evidence that any Adult survival rates and breeding success long-term trend in climate was responsible seem comparable between the two areas for the decline of the Ashop population (Dougall et al. 2005). There is clearly a major (Pearce-Higgins et al. 2009). Increased agri- discrepancy in recruitment rates between the cultural use of the wintering grounds or the two areas, but we are not clear what underlies stopover sites on migration might be this. Possibilities include the poorer survival affecting return rates. In Britain, it is evident of first-winter birds in West Africa and that the decline is most marked on smaller poorer survival on migration. If there is streams and rivers. Moreover, this retreat poorer survival of young birds, is this a con- from small streams has been proceeding for a sequence of climatic changes? Alternatively, century or more (Holloway 1996). Are these are new recruits put off by finding poorer sites more affected by agricultural change breeding habitat on the rivers when they get than larger sites? The species is certainly sus- back so that, perhaps, they take territories on ceptible to recreational disturbance, from reservoirs instead? These ideas merit some both anglers and picnickers (Yalden 1992a), elaboration. and this is regularly cited as a harmful factor. A recent attempt to correlate changes in The pair described earlier that led their population size from year to year with chicks into their neighbours’ territory, climatic variation, both in Africa (for win- inducing a prolonged fight, did so because an angler was standing in the middle of their own territory. Conversely, the species responds quickly to the provision of secure sites (islands, fenced areas). However, in the Peak District, reservoir shores suffer more human intrusion than the streams, so the cause-effect correla- tion is weak. One interesting possibility is that climate change might be affecting the populations of some freshwater prey. Many of the common stream larvae prefer colder water (Durance & Ormerod 2007). Stream temperatures would be much more sensitive to fluctu- ating weather than reservoir waters, which are buffered by their large volume. Stream are also more exposed to changes in management regimes on neigh- bouring farmland. A regular hazard of mist-netting at dusk used to be getting dor-beetles Geotrupes caught in the nets; it was quite Sean Gray 40. An adult Common Sandpiper Actitis hypoleucos carrying usual to get three or four in an just a BTO metal ring – against the grey legs, these are easily evening whereas now there are not missed; Whiteholme Reservoir,Yorkshire, June 2008. that many in a season. Are the cow-

112 British Birds 103 • February 2010 • 100–114 Common Sandpipers in Britain pats now inhospitable to beetle larvae sandpipers do migrate in long hops, it might because of the use of ivermectin vermifuges explain why relatively few are seen in July in on cattle? Many smaller invertebrates also southern England as they migrate south emerge from dung, and are eaten by sand- (although more are seen in August, these are pipers. Reduced sheep numbers mean that probably Scandinavian birds). There are vegetation is now longer along some stretches major uncertainties with this scenario. Some of Heriot Water; chicks are harder to locate, evidence from elsewhere in Europe suggests but they might also be less able to feed freely. that Common Sandpipers accumulate little In places, the shingle is becoming overgrown, or no weight at stopovers (e.g. Meissner so that too is less suitable feeding habitat. 1997, Arcas 2001). Is this a strategy that An entirely different scenario is suggested varies among populations, or age groups? for the wintering habitat by recent survey work in West Africa. In some places at least, Summary wintering Common Sandpipers frequent We have learnt much about our favourite mangrove swamps and roost communally, bird in over 30 years of study. What began as though it is not certain whether they also a very local concern (how many Common defend territories while feeding. Trolliet & Sandpipers are there in the Peak District and Fouquet (2004) suggested that 15,000 feed in how is the population balanced?) has mangrove areas and another 8,000 on the expanded to a second study (do Borders mudflats of Guinea; this could be a substan- birds vary the same way?), and to national tial proportion of the British population, if concerns (how many breed, how is the popu- Guinea is where they winter. Mangroves are lation changing?). Now we are faced with highly productive, but also subject to intense problems on a flyway scale. We suspect that it pressure from coastal development, for fish is this wider population that is declining, not farming, timber, and agriculture. Apparently, just the Ashop or British ones (Sanderson et Common Sandpipers exploit the abundance al. (2006) suggested a 49% decline across the of fiddler crabs Uca in this habitat. Therefore, Western Palearctic). Greater understanding this habitat is highly susceptible to human of the species will require a co-ordinated intervention and could be that in which most international effort. We urgently need to of our birds overwinter. However, it is locate the wintering areas and habitats of the unlikely to be affected by winter rainfall or bulk of our birds. If there are routine temperature, as would be expected if the stopover points during migration, these too Sahel region (as at Djoudj) is their main win- need to be established. The attachment of tering area. Thus our failure to detect any satellite or radio tags would be one, albeit obvious relationship between year-on-year expensive, way to do this (cf. the studies of population change and weather variation in White-rumped Sandpiper fuscicollis; West Africa (Pearce-Higgins et al. 2009) Harrington 1999). An alternative would might fit with such a wintering habitat. involve routine studies on the wintering Migration remains an area of major areas, similar to ours on the breeding sites. uncertainty and concern. Fat-free mass seems Given the numbers of ringers and other to be about 40 g (Baccetti et al. 1992). If our ornithologists visiting exotic locations, as birds regularly accumulate 40 g of fat (as well as dedicated expeditions and collabora- implied by birds weighing over 80 g in July), tive studies with local birdwatchers in West and have an average wingspan of 350 mm, we Africa, we hope that someone will take up can calculate that they should have a flight this challenge. range of 6,000 km in still air (Pennycuick 1989). This would easily take them to the Acknowledgments Senegal River mouth in one hop, farther if We must thank the estates and farms on whose land they exploit tailwinds. If this is optimistic, we have worked for their permission to do so, and two major refuelling stops in, say, Morocco those who have helped with our fieldwork (as detailed and Senegal would enable an easier migra- in, for example, Dougall et al. 2005). We also thank the photographers for the accompanying images. Sightings tion; if such sites exist, they need to be identi- of colour-ringed birds away from our study sites can fied so that they can be protected. If be reported to [email protected]

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References — & — 2002b. Common Sandpiper Actitis hypoleucos. Arcas, J. 2001. Body weight variation and fat deposition In: Wernham, C. V., Toms, M. P., Marchant, J. H., Clark, in Common Sandpipers during their autumn J. A, Siriwardena, G. M., & Baillie, S. R. (eds.), migration in the Ria de Vigo, Galicia, north-west The Migration Atlas. movements of the birds of Britain Spain. Ringing & Migration 20: 216–220. and Ireland. Poyser, London. Baccetti, N., de Faveri, A., & Serra, L. 1992. Spring —, Robson, J. E., & Yalden, D. W. 1982a. The status and migration and body condition of Common distribution of the Common Sandpiper (Actitis Sandpipers Actitis hypoleucos on a small hypoleucos) in the Peak District. Naturalist 107: Mediterranean island. Ringing & Migration 13: 90–94. 77–86. Brown, S. C. 1974. Common Sandpiper biometrics. —, — & — 1982b. The breeding biology of the Study Group Bull. 11: 18–22. Common Sandpiper (Actitis hypoleucos) in the Peak Dougall, T. W., & Yalden, D. W. 2007. Common District. Bird Study 29: 99–110. Sandpiper Actitis hypoleucos. In: Forrester, R. W., Holloway, S. 1996. The Historical Atlas of Breeding Birds Andrews, I. J., McInerny, C. J., Murray, R. D., in Britain and Ireland: 1875–1900. Poyser, London. McGowan, R. Y., Zonfrillo, B., Betts, M. W., Jardine, Mee, A. 2001. Reproductive strategies in the Common D. C., & Grundy, D. S. (eds.), The Birds of Scotland, Sandpiper Actitis hypoleucos. Unpubl. PhD thesis, pp. 679–681. SOC, Aberlady. University of Sheffield. — & — 2008. Catching Common Sandpipers. Meissner, W. 1997. Autumn migration and biometrics of Ringers’ Bull. 12(4): 56–57. the Common Sandpiper Actitis hypoleucos caught in —, Holland, P. K., & Yalden, D. W. 2004. A revised the Gulf of Gdansk. Ornis Fennica 74: 131–139. estimate of the breeding population of Common Pearce-Higgins, J. W., Yalden, D. W., Dougall, T. W., & Sandpipers Actitis hypoleucos in Great Britain and Beale, C. 2009. Does climate change explain the Ireland. Wader Study Group Bull. 105: 42–49. decline of a trans-Saharan Afro-Palaearctic migrant? —, Mee, A., & Yalden, D. W. 1999. Recent fluctuations Oecologia 159: 649–659. in a Common Sandpiper breeding population. Pennycuick, C. J. 1989. Bird Flight Performance. A practical Scott. Birds 20: 44–45. calculation manual. OUP, Oxford. —, Holland, P. K., Mee, A., & Yalden, D. W. 2005. Sanderson, F. J., Donald, P. F., Burfield, I. J., & van Bommel, Comparative population dynamics of Common F. P. J. 2006. Long-term population declines in Afro- Sandpipers Actitis hypoleucos: living at the edge. Palearctic birds. Biol. Conserv. 131: 93–105. Bird Study 52: 80–87. Sauvage, A., Rumsey, S., & Rodwell, S. 1998. Recurrence Durance, I., & Ormerod, S. J. 2007. Climate change of Palaearctic birds in the lower Senegal river valley. effects on upland stream macroinvertebrates over Malimbus 20: 33–53. a 25-year period. Global Change Biology 13: 942–957. Sharrock, J. T. R. 1976. The Atlas of Breeding Birds in Gibbons, D. W., Reid, J. B., & Chapman, R. A. 1993. Britain and Ireland. Poyser, Calton. The New Atlas of Breeding Birds in Britain and Ireland: Trolliet, B., & Fouquet, M. 2004. Wintering waders in 1988–1991. Poyser, London. coastal Guinea. Wader Study Group Bull. 103: 56–62. Forchammer, M. C., Post, E., & Stenseth, N. C. 1998. Yalden, D. W. 1986. Diet, food availability and habitat Breeding phenology and climate... Nature 391: selection of breeding Common Sandpipers Actitis 29–30. hypoleucos. Ibis 128: 23–36. Harrington, B. A. 1999. The hemispheric globetrotting —1992a. The influence of recreational disturbance on of the White-rumped Sandpiper. In: Able, K. (ed.), Common Sandpipers Actitis hypoleucos breeding by Gathering Angels: migrating birds and their ecology, an upland reservoir. Biol. Conserv. 61: 41–50. pp. 119–133. Cornell University Press. —1992b. The Common Sandpiper population of the Holland, P. K., & Yalden, D. W. 1991. Growth of Ladybower reservoir complex – a re-evaluation. Common Sandpiper chicks. Wader Study Group Bull. Naturalist 117: 63–68. 62: 13–15. —1993. Common Sandpiper Actitis hypoleucos. In: — & — 1994. An estimate of lifetime reproductive Gibbons, D. W., Reid, J. B., & Chapman, R. A. (eds.), success for the Common Sandpiper Actitis The New Atlas of Breeding Birds in Britain and Ireland: hypoleucos. Bird Study 41: 110–119. 1988–1991, pp. 192–193. Poyser, London. — & — 1995. Who lives and who dies? The impact of — & Dougall, T. W. 1994. Habitat, weather and the severe April weather on breeding Common growth rates of Common Sandpiper Actitis Sandpipers Actitis hypoleucos. Ringing & Migration 16: hypoleucos chicks. Wader Study Group Bull. 73: 33–35. 121–123. — & — 2004. Production, survival and catchability of — & — 2002a. Population dynamics of Common chicks of Common Sandpipers Actitis hypoleucos. Sandpipers Actitis hypoleucos in the Peak District of Wader Study Group Bull. 104: 82–84. Derbyshire – a different decade. Bird Study 49: 131–138.

T. W. Dougall, 38 Leamington Terrace, Edinburgh EH10 4JL P. K. Holland, 32 Southlands, East Grinstead, West Sussex RH19 4BZ D. W. Yalden, High View, Tom Lane, Chapel-en-le-Frith, High Peak SK23 9UN e-mail [email protected]

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