315

SPRING MIGRATION OF SANDERLINGS Calidris alba THROUGH SW ICELAND: WHEREFROM AND WHERETO?

GUDMUNDUR A. GUDMUNDSSON & AKE LINDSTROM

ABSTRACT The spring migration of Sanderlings Calidris alba through southwest Iceland was studied in 1989-1990. Additional information was collected during the spring seasons of1985-88 and 1991. Ringing recoveries and controls, togetherwith a large number ofsightings ofcolour-ringed birds, revealed that many Sanderlings staging in Iceland in spring spend the winter on the British Isles. Recoveries in winter as far south as Ghana (3 observa­ tions) indicate an extensive wintering range. Most Sanderlings arrive in Iceland after 10 May and the main departure period is 25 May - 4 June. Sight­ ings ofindividually colour-ringed Sanderlings revealed stopover times ofup to 15 days in one season. Many Sanderlings showed a high stopover site fi­ 0 delity between years. The average departure direction was 355 , suggesting breeding grounds in northeast Greenland. There were no indications that Sanderlings in SW Iceland participate in the migration across the Greenland icecap towards breeding grounds in northwest Greenland or northernmost Canada, as has been shown for Knots Calidris canutus and Turnstones Arenaria interpres. Our data suggest a substantial turnover of individuals, especially in the last week ofMay. At least a quarter ofthe northeast Green­ land breeding population of Sanderlings stage in Iceland in spring. Department of Ecology, University of Lund, Ecology Building, S-223 62 Lund, Sweden.

INTRODUCTION the Old World, ringing recoveries have demon­ strated a Siberian breeding origin for Sanderlings Sanderlings Calidris alba have a High Arctic wintering in southern Africa. A fairly good picture breeding distribution. Three regions have been ofthe migration routes between S Africa and Sibe­ pointed out as centers for breeding: the Canadian ria has emerged (Summers et al. 1987). For most Arctic archipelago, northeast Greenland, and Tay­ other winter and migration sites no firm patterns myr in Siberia (Cramp & Simmons 1983, Meltofte have beenreported. The appearance ofSanderlings 1985, Godfrey 1986, Summersetal. 1987). In winter on the British Isles seem to be particularly com­ they are found scattered along most temperate and plex, probably due to considerable mixing ofbirds tropical coasts of the world (Cramp & Simmons from widely different breeding areas (Prater & Da­ 1983, Morrison 1984, Smit & Piersma 1989). The vies 1978, Prater 1981, Cramp & Simmons 1983). migration system of Sanderlings is complex and Sanderlings neither breed nor winter in Iceland, poorlyunderstood. A majorproblemis that Sander­ but occur regularly both on spring and autumn mi­ lings are monomorph, i.e. that no races have been gration (Timmermann 1938-49, Gardarsson 1975, described and only a slight geographic variation Wilson 1981, Gudmundsson & Gardarsson 1993). has been identified (Prater et al. 1977, Cramp & Compared to the numbers of other wader species Simmons 1983, Wymenga et al. 1990). passing Iceland on migration, for example Knot The migration system of Sanderlings within Calidris canutus and Turnstone Arenaria interp­ and between South and NorthAmericais relatively res, they are relatively scarce (Wilson 1981). How­ well known, due to an extensive colour-marking ever, at least 8000 Sanderlings have been seen in scheme (Myers et al. 1990). These birds most cer­ W Iceland in late May (Gudmundsson & Gardars­ tainly breed in the Canadian Arctic archipelago. In son 1993). Itis reasonable to assume that the Sand-

Received 7 May 1992, accepted 26 June 1992. ARDEA 80: 315-326 316 ARDEA 80 (3), 1992 erlings migrating via Iceland, breed in east Green­ Sanderlings breeding in the northeastern Canadian land and/or in northernmost Canada. No ringing archipelago wintered in the Old World. As far as recoveries have beenreported for Sanderlings con­ the population in east Greenland is concerned, it necting the Palearctic region and N Canada, but a has been suggested that they reach their breeding few between NE Greenland and W Europe (Green grounds by a direct flight from the British Isles, & Greenwood 1978, Cramp & Simmons 1983). mainly overflying Iceland (Ferns 1980, Wilson Departure directions of Knot and Turnstone 1981, Clark et al. 1982). flocks leaving west Iceland in spring indicatedthat We have studied phenology, numbers, behav­ a greatmajority cross the Greenland icecap ontheir iour and departure directions of Sanderlings stag­ way to breeding areas inNWGreenland and north­ ing in SW Iceland in spring. In combination with ern Canada (Alerstam et al. 1990). The relative many new ringing recoveries, the information amount offat deposited by Sanderlings in Iceland gathered sheds new lightonthe Nearctic-Palearctic in spring was similar to that of Knots and Turn­ migration link ofSanderlings, andonthemigration stones (Gudmundsson et al. 1991). These reserves through Iceland in particular. should be sufficientfor a direct flight from Iceland to northern Canada. There are a few observations from SE Greenland during the spring migration STUDY SITES AND METHODS period, indicating that Sanderlings may take part in the spring migration over the Greenland icecap Daily field work was carried out 18 May - 4 June towards breeding areas in northern Canada (Aler­ 1989 and 23 May - 3 June 1990 at two nearby sites, starn etal. 1986). Myers etal. (1990) suggested that Gardskagi (64°05'N22°42'W) andnearthevillage Sandgerdi (64°03'N 22°43'W), on the western­ mostpartoftheReykjanespeninsulain SWIceland (Fig. 1). In addition, the two sites were visited by us on a few occasions in May and early June each year 1985-1988. Additional information was re­ ceived from other observers who counted Sander­ lings and checked for colour-markings at Sand­ gerdi in early May 1989-1991. Almost all Sanderlings in the main study area (Sandgerdi) foraged and roosted along a 2 km long strip ofshore (mixture ofsandy beaches and mud­ flats) around the village. Ringing operations and observations offeeding flocks were carriedoutthe­ \ re. On each visit we counted all Sanderlings in the vicinity ofSandgerdi and searchedfor colour-ring­ ed birds. Allbirds caughtbyus weremarkedwith a metal ring on the right leg and two plastic colour-rings (yellow over red) on the left leg. A temporary col­ our-flag was used to distinguish different catches. For all individuals, body mass (to the nearest Fig.t. LocationofIcelandintheNorthAtlantic inrela­ gram), wing andbill lengths (to the nearestmmand tion to the potential breeding areas (black) ofthe Sand­ tenth of mm, respectively) were registered. erlings migrating through Iceland. On the inset the two Most of the observations of departing flocks study sites in SW Iceland are marked with circles. were made at Gardskagi. Departing flocks were Gudmundsson & Lindstrom: SANDERLING MIGRATION 317 followed visually, for as long as possible, with tele­ 1400 scopes or with an optical range-finder equipped with azimuth and elevation scales to determine 1200 their flight directions and flight paths. The actual 1000 migration direction was calculated by adding the angle ofparallax compensation to the measured di­ "E 800 Ql rection (for description ofcalculation see Alerstam (/) et at. 1990). For all departing flocks observed, the ~600 species involved, flock size and the time of day were registered. 400 All directions given are geographical (thededi­ 200 nation in SW Iceland is approximately 23°W). Cir­ cular statistics were used to calculate mean angles, mean vector lengths (r) and angular deviations according to Batschelet (1981). The Watson-Wil­ liams test was used to evaluate differences between mean directions (Batsche!et 19~1). Time given in . this paper is Icelandic local time (=GMT).

RESULTS Fig. 2. Number of Sanderlings present at Sandgerdi, SWIceland in May 1989 (dots) and 1990 (circles; upper Phenology, numbers, stopoverdurationandsite panel). The estimated median staging time is indicated fidelity in days. Number of individuals seen departing from The number of Sanderlings present at Sand­ Sandgerdi and Gardskagi each day (data from different gerdi during the two best covered spring seasons years combined; lower panel). are presented in figure 2. Only small numbers, less than 100, werepresentbefore 10 May. The majority respectively (Fig. 2), and is in a good agreement arrived between 12 and 20 May. Since we believe with the maximum staging times recorded for col­ there was a high turnover rate towards the end of our-marked birds (see below). May, the intensity of arrivals may have continued We caught 208 Sanderlings whereof 196 were undetected. On four occasions in the last week of colour-marked with the same combination. Only May, more birds were seen departing from the area four were later retrapped by us in the same season than suggested by the change in daily numbers. (with a maximum delay of4 days). None ofthe 75 This indicates that some arrivals took place even ringed in 1989 was retrapped in 1990, but several during the lastdays ofMay, and/orthat some flocks (a minimum number of 6 individuals, on the same just pass over the area. Furthermore, most of the occasion) were sighted inthe area in 1990 (the total birds that we caught and colour-marked soon dis­ number is unknown as they were not individually appeared from the area, suggesting a high turnover colour-marked). Furthermore, two of the Sander­ rate. The highest number counted was 1374 on 25 lings colour-ringed in Sandgerdi in 1989 were May 1989, and 1176 on 17 May 1990. It is difficult sighted in May 1990 at Akrar on Myrar (64°40'N to get an estimate of the median staging time of 22°2TW), 70 km away from the ringing site. individuals, buta roughmeasure is the time interval Since a large number of individually colour­ between the dates when 50% ofthe seasonal maxi­ marked Sanderlings, ringed elsewhere (see below) mumhave arriveduntil 50% haveleft. This interval were present on the beaches, information about was very similar in 1989 and 1990, 13 and 14 days stopover duration and between-year site fidelity 318 ARDEA 80 (3), 1992 was revealed from sightings ofthem. Out of48 dif­ they flew a few laps over the beach, before resum­ ferent individuals sighted in Sandgerdi during the ing their feeding activities. On five occasions, all spring seasons 1985-91 eight birds are known to resembling each other, a smaller group parted from have been present for at least 10-12 days in one the main flock, and landed further out on a part of season, and one bird was recorded present for 15 the beach that was free from seaweeds. These birds days (11-25 May 1990). Of 28 different colour­ did not feed but were mostly standing still, others marked individuals identified at Sandgerdi until were preening or bathing. This was accompanied 1989, 15 (54%) were seen at the same site in more by excited twittering, never heard from feeding than one year. Seven birds were sighted in three or flocks. After several minutes on the outer beach the four different years, and two were seen in five dif­ small flock took offand disappeared on a northerly ferent years. Thus, many Sanderlings showed a course out over the open sea. Soon after, the next high stopover site fidelity between years. Itshould flock landed at the same spot on the outer beach be noted that territory defence by Sanderlings was and began the same preparations for departure. rarely observed. Highly aggressive behaviour was In 1989 and 1990, 42 h and 50 h respectively, only seen in small Sanderling flocks foraging in were spent looking for departing flocks at Sand­ banks ofrotting seaweeds along the high tide levels gerdi and Gardskagi. In addition, some observa­ of the shores. The majority of Sanderlings fed in tions were made 4 June 1988 (2 h). Further 60 h flocks on the open sandy beaches, where intraspe­ were spent in the area in other field activities in cific aggressions were only rarely encountered. 1989-90. Observation hours were unevenly distri­ buted over the day, from 10.00 - 24.00 h, mainly Departure behaviour, timing and orientation between 14.00 hand 21.00 h. However, the There were never any difficulties deciding observation time was evenly spread in relation to whether a flock was about to initiate a migratory the tidal stage, with onaverage460 min (range 360­ flight or not. The departure of Sanderlings was al­ 500) of observations devoted to each hour of the ways connected with intensive calling from the ofthe tidal cycle (1-6 h before and 1-6 h after LW). birds (cf. Alerstam et al. 1990, Piersma etai. 1990), Departures of Sanderlings were recorded be­ rarely heard from feeding orroosting flocks. Some tween 24 May and 4 June 1988-90 (Fig. 2). Alto­ flocks initiated migration after being scared offthe gether 35 Sanderling flocks comprising 1045 indi­ beach by humans (cf. Piersma et ai. 1990). Many viduals were seen departing from SWIceland. The flocks circled over land when gaining height and meanflock size was 29.9± 3.9 (=SE; range: 2-90). later spread out on a horizontal formation line, In addition 2 flocks with a mixture of Sanderlings when a firm direction had been established. Other and Tumstones were seen (5S+7T and lOS+14T, flocks kept a constant direction from the time they respectively). left the ground, steadily gaining altitude until they The Sanderlings left mainly during late after­ were out of sight. On several occasions we saw noon and in the evening. Only 15 h ofobservations flocks make sudden dives once or twice during the (16% of the total) were carried out between 20.00 ascent, but immediately afterwards they regained - 24.00 h, but still 17 flocks (49%) comprising 683 height and direction. Most flocks were followed individuals (65%) were seen departing in these late for 3-7 min (average 230 s, range 87-594 s). hours. Most Sanderlings (770 individuals in 27 A fascinating eventwas the departure of5 Sand­ flocks) left at low tide (± 3 h). This timing may be erling flocks (containing 73, 90, 39, 73, and 10 linkedto aratherunusualtime utilizationinrelation individuals) from the shores of Sandgerdi in the to the tidal cycle observed amongst Sanderlings in evening (21.30 - 23.50 h; sunset at 23.10 h) of 25 SW Iceland as compared to other shorebirds. Dur­ May 1990. About 500 Sanderlings were foraging ing the first hours offlooding tide the Sanderlings high up on a beach sparsely covered with rotting were less active foraging on the shores than during seaweed. The birds were quiet, but now and then the ebb and often roosted (own obs.). Gudmundsson & Lindstrom: SANDERLING MIGRATION 319

• :• neither winds nor the topography were the cause . ,, I of the northerly orientation of the Sanderlings. .,. Ringing recoveries and sightings of colour­ .\.. marked birds • Until 1992 about 640 Sanderlings had been • ringed in Iceland (A. Petersen, pers. comm.). Of these 11 have been recovered or controlled abroad during the non-breeding season (Appendix 1). Furthermore, 196 ofthe ringed birds were provided with colour-rings indicating the ringing site, but not allowing identification on individual level. At least 24 different sightings of these have been re­ ported. Ten foreign ringed Sanderlings (all from the British Isles) have been recovered orcontrolled in Iceland (Appendix 2). Furthermore, 55 different individually colour-marked Sanderlings, again all Fig. 3. Flight directions of flocks of Sanderlings de­ ringed on the British Isles, have been identified. parting from SW Iceland in May-June 1988-90 as mea­ sured by visual observationin field. Thedirection ofeach These birds have so detailed history ofpresence at flock is indicated by a dot, to the nearest 10 degrees. The the ringing sites that they can with reasonable cer­ mean vector and the angular deviation (shaded sector) tainty be classified as wintering or passage birds. were calculated to the nearest degree. In addition at least 18 individuals have been ob­ served with permanent or temporary colour-mar­ All waders seen departing from Sandgerdi and kings indicating different foreign ringing sites and Gardskagi flew out over the open sea. The average catches. direction of the Sanderling flocks was nearly due The Sanderling recoveries linked to Iceland are north, with little scatter (355° ± 15° angular devia­ widely distributed along the coasts of the East tion, r =0.96, n =30; Fig. 3). As Gardskagi is the Atlantic, with a heavy concentration to the British northern tip ofa peninsula pointing towards north, Isles (111 of 117 records; Fig. 4). Altogether 66 of there may be a bias towards observing more flocks the records (56%) are from winter (1 November ­ migrating in a northerly direction, as flocks leaving 28 February). These winter records ofthe Sander­ Sandgerdi inother directions might notpass within lings migrating through Iceland range from Ork­ the range of detection to such a high extent. We ney' Scotland in the north to Ghana in the south therefore comparedSanderling directions obtained (Fig. 4). There are so far no recoveries of Sander­ at Gardskagi to those from Sandgerdi (5 Ian to the lings between Iceland and potential breeding south - where from the birds initir.lly departed), and grounds. found no difference between the sites (356° ± 18°, Four of the Sanderlings recovered in Iceland r =0.95, n =20 and 355° ± 7°, r =0.99, n =10 re­ had been ringed in England after mid May in a dif­ spectively; F 1,28 = 0.04, N.S.). The average depar­ ferent year (Appendix 2). Many ofthe individually ture direction of the Sanderlings differed signifi­ colour-marked birds from Teesmouth, England cantly from the directions ofKnots (329° ± 47°, r have remained there well into May (one as late as =0.67, n = 12 flocks) and of Turnstones (332° ± 29 May, butin a different year thanrecorded in Ice­ 23°, r =0.92, n =26 flocks) observed departing in land). One Sanderling, ringed and temporarily the same period, and under the same conditions, colour-marked 19 May 1988 on the Outer Hebrides from the study area (F1,40 = 5.0, p < 0.05 and F 1.54 in Scotland, was sighted six days later in SW Ice­ = 14.6,p < 0.001, respectively). This suggests that land. 320 ARDEA 80 (3), 1992

3A

Fig. 4. All recoveries and sightings of marked Sanderlings which are linked with Iceland, until February 1992 (only records outside Iceland are shown). Sites ofrecoveries (solid symbols) and sightings ofcolour-marked birds (open symbols). Circles indicate the recovery site of Sanderlings ringed in Iceland, and squares show the ringing sites ofthose recovered or sighted in Iceland. The non-breeding season was divided into three periods indicated by different letters: S = spring (March-June), A = autumn (July-October), W = winter (November-February). Figures indicate the number ofrecords from each site.

DISCUSSION fidelity ofmigrating Sanderlings has beenreported from several other studies (e.g. Green & Green­ Occurrence in Iceland in spring wood 1978, Clark et al. 1982, Myers et al. 1990). Sanderlings are among the latest of the Arctic Sanderlings are also known to return to the same breeding waders to arrive inIceland in spring, with wintering grounds year after year (Evans et al. only small numbers arriving before 10 May (Wil­ 1980, Myers 1980, Myers et al. 1988, Summers et son 1981, Gudmundsson & Gardarsson 1993). The al. 1987). main departure from Iceland to High Arctic bree­ ding grounds starts around 25 ofMayandcontinues Where do they winter? a few days into June (Fig. 2). Thus, the last The breeding origins ofSanderlings migrating Sanderlings leave Icelandslightly laterthanthe last through Iceland will be discussed in the next sec­ Knots and Turnstones do (Alerstam et at. 1990). tion. Here it is justassumedthatSanderlings occur­ The median staging time ofSanderlings (14 days) ring in Iceland are bound for Nearctic breeding is shorter than the 21 days recorded for Knots dur­ grounds, i.e. in Greenland and/or Canada (Fig. 1). ing spring in W Iceland (Gudmundsson & Aler­ Ringing recoveries and sightings of colour­ stam 1992). marked birds connected to Iceland from the winter Many Sanderlings were found to return to the period, are mainly from the British Isles (63 out of same stopover site for several years. Stopover site 66 winter records; Fig. 4). Thus, Great Britain is Gudmundsson & Lindstrom: SANDERLING MIGRATION 321 apparently an important wintering area for Nearc­ with little geographical segregation in winter of tic Sanderlings. However, as ringing activities birds of different breeding origins. along the EastAtlantic flyway are unevenly distrib­ An interesting observation is a bird reported uted, the proportion ofbirds wintering in different from the Baltic Sea. One ofthe 75 Sanderlings col­ regions cannot be quantified. our-marked inMay 1989 in SWIceland was sighted Nearly 14000Sanderlings have beenestimated on the island Gotland, Sweden on 26 July the same to winter in Britain (Moser 1987) and an additional year; a site which normally is regarded to be within 2000 in Ireland (Smit & Piersma 1989). In May the migratory flyway between Siberia and western there is a marked influx ofSanderlings to the Brit­ Europe. It would involve an unnecessary detour ish Isles, mainly to NW England (estimated total and ocean crossings to migrate between W Europe inMay 30000; Prater 1981) andthey remain in high and Siberia via Iceland. Itseems therefore very un­ numbers until late May, some eveninto June (Ferns likely that this Sanderling went to Siberian breed­ 1980, Clark et aI. 1982). An unknown proportion of ing grounds from Iceland. We suggest that this bird these spring birds are bound for Iceland and the was migrating to E Greenland, or possibly Sval­ Nearctic, since some Sanderlings present on the bard, when caught in Iceland and drifted eastward British Isles as late as the end of May have been when returning from there in late summer. Many found in Iceland during spring in different years. recoveries of High Arctic waders during autumn Also, Sanderlings have been reported to depart in SW Norway (amongst these one ofours; Fig. 4) both from the Severn Estuary in England and from are from birds ringed in Iceland, Greenland and Firth of Forth in Scotland in northwesterly direc­ even Canada (cf. Wilson 1981), indicating that au­ tions in late May and early June (Ferns 1980), i.e. tumn migration from these areas occurs on a broad towards Iceland and/or E Greenland. Whether front. Sanderlings migrating through W Denmark these late departing Sanderlings occur in Iceland are believed to be of Nearctic origin (Ferdinand every year or only in some years cannot be deter­ 1953). Nehls (1987) suggested that Nearctic Knots mined from the data available at present time. occur as far east as on the coasts of southwestern Sightings on the British Isles in autumn and Baltic Sea in autumn. The sighting on Gotland of spring of Sanderlings colour-marked in E Green­ a Sanderlingringedin Iceland, indicates thatrecov­ land, suggestthatthe Greenlandic populationoccur eries connecting British wintering birds with the in Britain mainly on passage to and from more Baltic region (thereby assumed ofSiberian origin) southerly winter quarters (Green & Greenwood shouldbeinterpreted with care (cf. Prater& Davies 1978, Prater & Davies 1978). That at least a part of 1978, Prater 1981, Cramp & Simmons 1983). the Nearctic population winters south of Britain is Our measurements of wing- and bill lengths of further supported by recoveries of birds ringed in Sanderlings inIceland (Table 1) are similarto mea­ Iceland. There is one winter record from The surements available from Greenland in the north Netherlands, one spring record from western to southern Africa in the south. However, several France, and one autumn and two winter records significant differences were found by pairwise from Ghana. Since Sanderlings ringed in S Africa comparisons (t-test). The average bill length ofthe have been recovered in England in May (Summers S African birds is longer than averages both from et aI. 1987), and since Nearctic and Siberian birds Teesmouth and SW Iceland. The bill lengths mea­ seem to occur together along the coasts of Europe sured on the Uist, Scotland were on average longer and W Africa, itis temptingto speculatethatNearc­ than all the other samples, which may be explained tic Sanderlings may even winter as far south as in by an uneven sex ratio in favour offemales (Prys­ S Africa. The migration system of Sanderlings Jones 1988, cf. Wood 1987). Wing lengths ofS Af­ along the East Atlantic flyway seems therefore to rican Sanderlings were on average longer than av­ be very complex (cf. Prater & Davies 1978, Prater erages from both Mauritania and Greenland. These 1981, Smit & Piersma 1989, Wymenga et aI. 1990), differences reveal no consistent pattern except that 322 ARDEA 80 (3), 1992

Table 1. Wing and bill lengths of adult Sanderlings caught in Iceland in spring, compared to measurements from other regions (sexes combined).

Wing Bill length SD Range length SD Range N Source (mm) (mm)

126.9 3.7 121-137 24.8 1.5 20.6-27.0 38 E. Greenland1 127.8 3.3 117-135 24.6 1.6 20.1-29.9 224 SW Iceland (this study) 127.3 3.5 113-135 25.4 1.5 22-28 61 S. Vist, Scot1.2 127.5 4.7 117-134 24.4 1.7 21-28 42 Teesmouth, U.K.3 126.8 3.7 118-133 24.6 1.9 20.9-27.9 31 Mauritania4 128.0 3.1 117-136 25.0 1.3 22-29 342 Southern Africa5

Idata from Green & Greenwood 1978 and De Korte et al. 1981 combined (Scoresby Land and Jameson Land, breed­ ing); 2Prys-Jones et al. 1988; 3Wood 1987; 4Smit & Van Spanje 1989, Banc d'Arguin 1985-1986; 5Summers et al. 1987 (March).

Sanderlings from southern Africa are on average 1960, Salomonsen 1967, Nettleship & Mahler 1973, slightly larger than the birds from the other sites, Meltofte 1985). In E Greenland, Sanderlings breed which may be due to a pronounced dominance of mainly between Scoresby Sound in the south to Siberian birds in S Africa (Summers et ai. 1987). Peary Land in the north (Salomonsen 1950, 1967, Siberian Sanderlings have possibly on average Meltofte 1985). Furthermore, breeding of Sander­ 1 mm longer bill than Greenlandic ones (Prater et lings has been reported from northwestern Sval­ ai. 1977). Inview ofthe small absolute differences bard, although only small numbers are involved between averages, the almost complete overlap in (LlZlvenskiold 1964, Kalas & Byrkjedal1981). The ranges, and the potential errors in measuring tech­ Sanderlings departing from SWIceland are clearly niques, we think that the morphology of Sander­ oriented towards breeding areas in NE Greenland lings may be of little help to separate different (the E Greenland breeding area lies in compass breeding populations. bearings ranging between 345° and 9° from SW Iceland, and Svalbard in 35°). One observation of Where do they hreed? departing Sanderling flock from NE Iceland is also Thedeparturedirections ofSanderlingsleaving available (Whitfield & Magnusson 1987). A flock SW Iceland (Fig. 3) do not indicate that they are of20 Sanderlings was seen departing on 1 June on destined for breeding grounds in NW Greenland a direction that wouldtake them to Scoresby Sound or in Canada, as has previously been found for in E Greenland (330°). Knot, Turnstone and BrentGooseBranta bernicla Meltofte (1985) estimated the breeding popula­ departing from W Iceland (Alerstam et al. 1990). tion of Sanderlings in NE Greenland to 17 000 Even though the fat stores of Sanderlings staging pairs, i.e. 34000 adults. Gudmundsson & Gardars­ in SW Iceland seem to be sufficient for a direct son (1993) gives a minimum estimate of 8000 flight to NE Canada (Gudmundsson et ai. 1991), it Sanderlings staging in Iceland in spring. Most of remains to be shown to what extent Sanderlings these were seen in a single roost of7000 birds the use the migration route over the Greenland icecap 22 May 1990 at Akrar, Myrar, on the west coast. As (Alerstam et al. 1986). there was most certainly a high turnover rate at the Sanderlings are known to breed in NW Green­ beaches of Sandgerdi, many more than 8000 San­ land and on Ellesmere Island (Fig. 1), but the den­ derlings may actually make a stopover in Iceland sities are probably low (Parmelee & MacDonald in spring. Thus, it seems as if a considerable part Gudmundsson & Lindstrom: SANDERLING MIGRATION 323

of the NE Greenland population does stage in Ice­ REFERENCES land in spring (:2: 25%). It has long been suspected that most Sander­ Alerstam, T., G.A. Gudmundsson, P.E. Jonsson, J. Karlsson & A. Lindstrom 1990. Orientation, lings heading for NE Greenland overfly Iceland in migration routes and flight behaviour of Knots, spring (Wilson 1981). This still remains to be Turnstones and Brant Geese departing from Iceland shown, but there are several indications that this in spring. Arctic 43:201-214. may be the truth for an unknown part ofthe popula­ A1erstam, T., C. Hjort, G. Hogstedt, P.E. JOnsson, J. tion. Ifthe estimate of the NE Greenland breeding Karlsson & B. Larsson 1986. Spring migration of birds across the Greenland Inlandice. Meddr. GrjZjn­ population (Meltofte 1985) is correct, there is still land, Biosci. 21:38 pp. a large proportion (up to 75%) of the population Batschelet, E. 1981. Circular Statistics in Biology. Lon­ which has not been accounted for during spring in don: Academic Press. Iceland. Radar studies in Iceland in late May and Clark, N.A., B.S. Turner & J.E Young 1982. Spring early June have revealed that some flocks of mi­ passage ofSanderlings Calidris alba on the Solway Firth. Wader Study Group Bull. 36: 10-11. grating birds, which probably have departed from Cramp, S. & K.E.L. Simmons (eds) 1983. The Birds of staging sites south ofIceland, pass on northwester­ the Western Palearctic, Vol. III. Oxford University lytracks withoutmaking a landfallinIceland(Gud­ Press, Oxford. mundsson, 1993). Sanderlings may take part in this De Korte, J., c.A.W Bosman & H. Meltofte 1981. Ob­ migration. servations on waders (Charadriidae) at Scoresby Sund, East Greenland. Meddr. GrjZjn1and, Biosci. 7: 21 pp. Evans, P.R., D.M. Brearey & L.R. Goodyer 1980. Studies on Sanderling at Teesmouth, NE England. ACKNOWLEDGEMENTS Wader Study Group Bull. 30:18-20. Ferdinand, L. 1953. SandljZjberens (Crocethia alba (Pall.» trrekforho1d i Nordeuropa. Dansk Om. We thank Sigrid Kristinsson, Gudmundur Kr. Kristins­ Foren. Tidsskr. 47:69-95. son, Ho1mfridur Magnusdottir and Gretar Olafsson for Ferns, P.N. 1980. The spring migration of Sanderlings logistic support. We thank Kristjan Lilliendahl who Calidris alba through Britain in 1979. Wader Study participated extensively in the fieldwork and read this Group Bull. 30:22-25. paper in manuscript, Dr Thomas Alerstam for discus­ Gardarsson, A. 1975. Islenskir votlendisfuglar. Rit sions and for commenting upon an earlier draft of this Landverndar 4:100-134. paper, and Professor Arnthor Gardarsson at the Institute Godfrey, WE. 1986. The Birds of Canada. Revised edi­ of Biology, University of Iceland, for lending the can­ tion. National Museum ofNatural History (Canada). non-netting equipment. We also thank everyone who Green, G.H. & lJ.D. Greenwood (eds) 1978. Joint bio­ logical expedition to North East Greenland 1974. reported sightings of colour-marked birds and counted Dundee University North East Greenland Expedi­ Sanderlings in Sandgerdi, especially Kristjan Lillien­ tion, Dundee. dahl, Gunnlaugur Petursson, Gunnlaugur Thrainsson Gudmundsson, G.A. (1993). The spring migration pat­ and Gudmundur V. Helgason. tern of arctic birds in SW Iceland, as recorded by Ringing and recovery data were kindly provided by radar. Ibis 135: in press. Dr Aevar Petersen, Icelandic Museum of Natural His­ Gudmundsson, G.A. & T. Alerstam 1992. Spring staging tory. Sightings of colour-marked birds were processed of Knots in Iceland. Wader Study Group Bull. 64, by the Wader Study Group Colour-marking Register. Suppl.:ll0-113. Ringing details on colour-marked birds sighted in Ice­ Gudmundsson, G.A. & A. Gardarsson (1993). Numbers, land were obtained from Professor P.R. Evans and Dr geographic distribution and habitat utilization of waders (Charadrii) in spring on the shores of Ice­ D.B. Jackson at the University ofDurham, and from Mr. land. Ecography 16: in press. B.M. Lynch at Dundee University. Gudmundsson, G.A., A. Lindstrom & T. A1erstam 1991. Financial support was received from the Swedish Optimal fat loads and long-distance flights by mi­ Natural Science Research Council (to Thomas A1er­ grating Knots Calidris canutus, Sanderlings C. starn), Nordic Council for Ecology (to G.A.G.) and the alba and Turnstones Arenaria interpres. Ibis 133: Royal Swedish Academy of Sciences (to A.L.). 140-152. 324 ARDEA 80 (3), 1992

Kalas, J.A. & I. Byrkjedal 1981. Vadefuglenes hekke­ Salomonsen, F. 1967. Fuglene pa Gr~nland. Rhodos, status i Norge med Svalbard. Proc 2nd Nordic Copenhagen. Congr.Ornithol. 1979:57-74. Smit, C.J. & T. Piersma 1989. Numbers, midwinter dis­ W>lvenskiold, H.L. 1964. Avifauna Svalbardensis: with tribution and migration ofwader populations using a discussion on the geographical distribution ofthe the East Atlantic flyway. In: H. Boyd & J.-Y. Pirot birds inSpitsbergen and ajacent islands. Nor. Polar­ (eds) Flyways andreserve networks for water birds: inst. Skr. 129. 24-63. IWRB Spec. Publ. 9, Slimbridge. Meltofte, H. 1985. Populations and breeding schedules Smit, C.J. & T.M. Van Spanje 1989. SanderlingCalidris of waders, Charadrii, in high arctic Greenland. alba. In: RJ. Ens, T. Piersma, w.J. Wolff & L. Meddr. Gr~nland, Biosci. 16:43 pp. Zwarts (eds) Report ofthe Dutch-Mauritanian pro­ Morrison, R.I.G. 1984. Migration systems ofsome New ject Banc d'Arguin 1985-1986: 276-283. PNBA/ World shorebirds. In: J. Burger & B.L. Olla (eds) NIOZ/RIN/WIWO report. Behaviorofmarine Animals, Vol. 6. Plenum Press, Summers, R.W., L.G. Underhill, M. Waltner & D.A New York. Whitelaw 1987. Population, biometrics and move­ Moser, M.E. 1987. A revision of population estimates ments of the Sanderling Calidris alba in southern for waders (Charadrii) wintering on the coastline of Africa. Ostrich 58:24-39. Britain. BioI. Conserv. 39:153-164. Tinunermann, G. 1938-49. Die Vogel Islands. Visinda­ Myers, J.P. 1980. Sanderlings Calidris alba at Bodega felag Islendinga, Reykjavik. Bay: facts, inferences and shameless speculations. Whitfield, J.P. & 1. Magnusson 1987. The migration of Wader Study Group Bull. 30:26-32. waders through north-east Iceland. Wader Study Myers, J.P., M. Sallaberry, E. Ortiz, G. Castro, L.M. Group Bull. 49, Suppl.: 85-89. Gordon, J.L. Maron, C.T. Schick,E. Tabilo, P. Antas Wilson, J.R. 1981. The migration ofHigh Arctic shore­ & T. Below 1990. Migration routes of New World birds through Iceland. Bird Study 28:21-32. Sanderlings (Calidris alba). Auk 107:172-180. Wood, A.G. 1987. Discriminating the sex ofSanderling Myers, J.P., C.T. Schick & G. Castro 1988. Structure in Calidris alba: some results and their implications. Sanderling (Calidris alba) populations: the mag­ Bird Study 34:200-204. nitude of intra- and interyear dispersal during the Wymenga, E., M. Engelmoer, C.J. Smit & T.M. Van nonbreeding season. Proc. XIX Int. Ornithol. Spanje 1990. Geographical breeding origin and mi­ Congr. (Ottawa):604-615. gration of waders wintering in West Africa. Ardea Nehls, H.W. 1987. Does the Knot Calidris canutus 78:83-112. islandica migrate through the south-western Baltic. Wader Study Group Bull. 51:53-55. Nettleship, D.N. & Mahler, w.J. 1973. The avifauna of SAMENVATTING Hazen Camp, Ellesmere Island, N.W.T. Polar­ forschung 43:66-74. De voorjaarstrek van Drieteenstrandlopers door het Pannelee, D.F. & S.D. MacDonald 1960. The birds of zuidwesten van IJsland (Fig. 1) werd bestudeerd van West-central Ellesmere Island and ajecent areas. 1989 tot 1990. Aanvullende informatie is verzameldvan National MuseumofCanadaBulletin No. 169, Bio­ 1985 tot 1988 en in 1991. Op grond van terugmeldingen logical Series No. 63, Ottawa. Piersma, T., L. Zwarts & H. Bruggemann 1990. Behavi­ van geringde vogels en van waamemingen van vogels ouralaspectsofthedepartureofwaders beforelong­ metkleurringen konwordenvastgesteld datde Drieteen­ distance flights: flocking, vocalizations, flight strandlopers die op IJsland pleisteren, de winter door­ paths and diurnal timing. Ardea 78:157-184. brengen langs de kusten van de Britse eilanden. Sommi­ Prater, AJ. 1981. Estuary Birds of Britain and Ireland. geDrieteenstrandlopersverspreidenzichechterovereen T. & AD. Poyser, Calton. aanzienlijk groter gebied; dit wordt gei1lustreerd door Prater, AJ. & M. Davies 1978. Wintering Sanderlings drie waamemingen uit Ghana (Fig. 1, Appendices 1 en in Britain. Bird Study 25:33-38. 2). De gemiddelde vertrekrichting is 355 0 (Fig. 3). Dit Prater, AJ., J. Marchant & J. Vourinen 1977. Guide to wijsterop dat deze dieren in hetnoordoosten van Groen­ the identification and ageing of Holarctic waders. land broeden. De biometrische gegevens spreken deze BTOGuide 17, BritishTrustfor Ornithology, Tring. ideeen over verspreiding met tegen (Tabell). Prys-Jones, R.P., J.S. Kirby & A Evans 1988. The role of the Uists as a late spring staging post for some Er zijn geen aanwijzingen dat de in zuidwestelijk Nearctic-breeding waders. BTORes. Rep. 38,Tring. IJsland pleisterende Drieteenstrandlopers deelnemen Salomonsen, F. 1950. Gr~nlands Fugle. Munksgaard, aan de trek dwars over de ijskap naar de broedgebieden Copenhagen. inhetnoordwestenvanGroenlandofinhetuiterste noor- Gudmundsson & Lindstrom: SANDERLING MIGRATION 325 den van Canada. Dit is weI aangetoond voor Kanoet­ tonen een sterke plaatstrouw tussen jaren. De gegevens strandlopers en Steenlopers. wijzen verder op een sterke uitwisseling van individuen, De meeste Drieteenstrandlopers komen na 10 mei vooral in de laatste week van mei. Dat betekent wellicht aan op IIsland envertrekken weer tussen 25 mei en 4 juni dat minstens een kwart van de Drieteenstrandlopers die (Fig. 2). Waarnemingen van vogels met kleurringen in noordoostelijk Groenland broedt, in het voorjaar in wijzen op verblijfstijden tot 15 dagen. Veel dieren ver- IIsland pleistert. w Appendix 1. All ringing recoveries and controls ofSanderlings ringed in Iceland and recovered abroad. The status ofthe recovery is indicated as follows: ~ c = control, d = found dead, s = shot.

Ringing Recovery

Ring Site Coordinates Date Site Coordinates Date Status number dd/mm/yy dd/mm/yy

Reykjavik 92065 Hafurbjarnast., Midneshr., Gull., SW Iceland 64°04'N 22°43'W 22/05/53 Gweebarra Est., Donegal, Ireland 54°52'N 08°23'W 01/11/54 Reykjavik 92090 Hafurbjarnast., Midneshr., Gull., SW Iceland 64°04'N 22°43'W 04/06/53 Coney Island, Sligo Bay, Sligo, Ireland 54°18'N 08°36'W 28/11/54 Reykjavik 91521 Hafurbjarnast., Midneshr., Gul!., SW Iceland 64°04'N 22°43'W 30/05/55 St.Palais, Charente-Maritime, France 45°39'N 01 °OTW 09/05/57 Reykjavik 920146 S. Skogarnes, Miklaholtshr., Hnapp., W Iceland 64°4TN 22°36'W 14/05/72 Point of Air, Flintshire, Wales 53°21'N 03°19'W 11/05/75 c Reykjavik 920660 Akrar, Hraunhr., Myrasys1a, W Iceland 64°38'N 22°23'W 16/07/72 Snettisham, Norfolk, England 52°51'N 0002TE 29/07/73 c Reykjavik 924508 S. Skogarnes, Miklaholtshr., Hnapp., W Iceland 64°4TN 22°36'W 02/06/74 Holy Island, Northumberland, England 55°41'N 01 °48'W 20/03/75 d Reykjavik 924523 S. Skogarnes, Miklaholtshr., Hnapp., W Iceland 64°4TN 22°36'W 02/06/74 Seaforth, Liverpool, Lane., England 53°28'N 03°01'W 20/11/76 c Reykjavik 852649 Sandgerdi, Gullbringusysla, SW Iceland 64°03'N 22°42'W 24/05/89 Barnhill, Dundee, Tayside, Scotland 56°28'N 02°50'W 05/01/90 c Reykjavik 852676 Sandgerdi, Gullbringusys1a, SW Iceland 64°03'N 22°42'W 28/05/89 St.Mary's, Scilly Islands, England 49°55'N 06°18'W 12/10/90 c Reykjavik 852773 Sandgerdi, Gullbringusys1a, SW Iceland 64°03'N 22°42'W 27/05/90 Esiama, Ghana 04°56'N 02°21'W 13/10/91 c Reykjavik 856094 Hraunhafnartangi,Slettuhr., N.Thing., NE Iceland 66°32'N 16°02'W 22/05/90 Esiama, Ghana 04°21'N 02°21'W 08/02/92 ~ 00 o ~ ...... Appendix 2. All ringing recoveries and controls of Sanderlings ringed abroad and recovered in Iceland. The status of the recovery is indicated as in ~ Appendix 1.

Ringing Recovery

Ring Site Coordinates Date Site Coordinates Date Status number dd/mm/yy dd/mm/yy

Brit. Mus. NB29961 Coatham Sands, Tees, Cleve!., England 54°36'N 01 °04'W 01/09/77 Vogur, Myrar, Myrasys1a, W Iceland 64°36'N 22°21'W 21/05/89 Brit. Mus. NS19800 Saltburn, Cleveland, England 54°35'N 00059'W 02/12/81 Sandgerdi, Gullbringusysla, SW Iceland 64°03'N 22°42'W 28/05/89 c Brit. Mus. NS15238 Ducky, Redcar, Cleveland, England 54°38'N 01°0TW 19/08/86 Sandgerdi, Gullbringusysla, SW Iceland 64°03'N 22°42'W 24/05/90 c Brit. Mus. NS15247 Ducky, Redcar, Cleveland, England 54°38'N 01°0TW 19/08/86 Sandgerdi, Gullbringusys1a, SW Iceland 64°03'N 22°42'W 24/05/90 c Brit. Mus. NR04400 Rhubda Ardvule, S. Dist, W. Isles, Scot!. 57°14'N 07°26'W 18/10/87 Vogur, Myrar, Myrasys1a, W Iceland 64°36'N 22°21'W 21/05/89 Brit. Mus. NS85153 Dubmill Point, Allonby, Cumbria, England 54°48'N 03°2TW 15/05/88 Sandgerdi, Gullbringusysla, SW Iceland 64°03'N 22°42'W 23/05/89 Brit. Mus. NS85678 Dubmill Point, Allonby, Cumbria, England 54°48'N 03°2TW 15/05/88 Sandgerdi, Gullbringusysla, SW Iceland 64°03'N 22°42'W 27/05/90 c Brit. Mus. NR34712 Ardivachar, S. Vist, W. Isles, Scotland 57°22'N 07°2TW 19/05/88 Sandgerdi, Gullbringusys1a, SW Iceland 64°03'N 22°42'W 24/05/89 c Brit. Mus. NR08808 Barnhill, Dundee, Tayside, Scotland 56°28'N 02°50'W 24/09/88 Sandgerdi, Gullbringusys1a, SW Iceland 64°03'N 22°42'W 24/05/90 c Brit. Mus. NR21275 Dubmill Point, Allonby, Cumbria, England 54°48'N 03°2TW 20/05/89 Sandgerdi, Gullbringusysla, SW Iceland 64°03 'N 22°42'W 29/05/90 c