The timing of arrival and departure of the Spotted Redshank erythropus in Finland

OLAVI HILDEN

HILDEN, O. 1979 : The timing of arrival and departure of the Spotted Redshank Tringa erythropus in Finland. - Ornis Fennica 56 :18-23. The Spotted Redshank is probably the best example of an "instinct migrant" among the breeding of Northern Europe, its time sche- dule apparently being controlled almost completely by an endogenous circannual rhythm. Its date of return is highly predictable (e.g. at Hel- sinki on 1-8 May, N=24) and within a few days it is present through- out the whole of Finland. Its southward departure starts on average on 10 June (N=24), more punctually than in any other Finnish . The first birds to depart are females that leave their mates about one week before the young hatch. Small annual differences in the date of departure are associated with differences in temperature on the breeding grounds in late May, which may speed up or retard the early phases of nesting. Olavi Hilden, Department of Zoology, University of Helsinki, P. Rauta- tiekatu 13, SF-00100 Helsinki, Finland

With respect to the factors controlling spending only a few weeks on the migration, it is customary to dis- breeding grounds . Weather factors af- tinguish two major groups, so-called fect this fixed time schedule very little. "weather migrants" and "instinct To illustrate this exceptional stability migrants" (e.g. Schuz 1971) . In the in the timing of migration in the Spot- former group, the movements are ted Redshank, I present in this paper largely dependent on prevailing wea- data on the arrival of the species in ther conditions, while in the latter different parts of Finland and on the group migration is determined mainly start of the post-breeding departure by endogenous, physiological factors. on the west coast. There is, however, no sharp distinction between these two categories, rather a Arrival continuous series from typical weather migrants to genuine instinct migrants. According to records of the arrivals of Perhaps the best example of the migratory birds in the Helsinki area, "instinct" type among the migratory covering 24 successive years (1947- birds of Northern Europe is the Spot- 70), based on the observations of ted Redshank : on almost the same dozens of ornithologists, the first Spot- date each year it arrives after a long ted Redshanks are seen on 1-8 May, migratory journey from Africa, and on average 4 May (SD±2.06) . No less with equal predictability it departs than 19 first sightings of the spring again in early June to the south, after fell within five days, 2 to 6 May. In O. Hilden: Timing of migration of the Spotted Redshank 19 its punctuality of arrival, the Spotted Redshank is unequalled by any other species . Similarly in the region of Vaasa, another area with reliable data covering a long succession of years, the dates of arrival of the Spotted Redshank during 17 springs are con- fined to the short period of 2-11 May, average 8 May (SD±2.44). The small annual variation in arrival dates is the more noteworthy when consider- ing the unpredictability of weather conditions in early May in Finland - in some years it is very cold, in others as warm as in full summer. Migration of the Spotted Redshank through Finland is very rapid : in a few days the species has reached the northern parts of the Gulf of Bothnia, and a little later even Lapland (Fig. 1) . In fact, the time difference be- tween the southern and northern loca- lities is probably even smaller than indicated in Fig. l, since the data from Rovaniemi are based on the observa- tions of only a few ornithologists and those from Muonio of one single per- son. In the speed of its migration FIG, 1 . Mean arrival dates (in May) of the through Finland, however, the Spotted Spotted Redshank in different parts of Finland. Redshank is not unusual, for some The localities, collectors of data and number of years of data (N) are as follows: Helsinki : other northern arriving late in O. Hilden, N=24; Lahti: E. Hietanen, N=18 ; the spring, e.g. Temminck's Stint Ca- Pori: A. Kaukola, N=13 ; Joensuu : M. Kapa- lidris temminckii, the Red-necked Pha- nen, N=8; Vaasa: O. Hilden & T. Hurme, larope Phalaropus lobatus and the N=17 ; Kokkola : R. Casen, N=13 ; Kajaani : P. Helo, N=14 ; Kemi : P. Rauhala, N=13; Broad-billed Limicola falci- Rovaniemi : Komonen (1962), N=15 ; Muonio: nellus, spread as fast or even faster Montell (1917), N=14. throughout the whole country (e.g. Hilden & Vuolanto 1972). The spring passage is of short dura- Departure tion, lasting about two weeks, and ter- minates quite suddenly, without the The Spotted Redshank starts its re- occurrence of late individuals so gular departure to the south in early typical of most migratory birds, in- .June, relatively earlier than any other cluding waders. On the islands of Va- wader in Finland. (The other two lassaaret, for example, the last obser- species that commence their south- vation of northbound migrants in each ward migration at about the same of 17 years has been on 18-30 May, time, the Green 'Sandpiper Tringa on average 23 May (SD±3.50). ochropus (Hilden 1961) and the Dun- 20 ORNIs FENNICA VOI. 56, 1979 lin alpina schinzii (Soikkeli in the time schedule of other waders 1967), breed considerably earlier.) The departing early (Table 1) . The obser- following tabulation summarizes the vations on the Ruff, however, are not first sightings of departing Spotted as reliable as those on the Spotted Redshanks during 24 summer of obser- Redshank, as in certain years the in- vation in the middle parts of the Fin- terval between the termination of nish west coast. Most of the data refer spring passage of birds moving to to observations made by me or my arctic areas and the start of departure assistants on the islands of Valassaa- of birds nesting in Finland was so ret, supplemented by five records from short that the very first southward Kokkola (1965, 1968, 1971, 1972 and migrating individuals might have been 1975, O. Hilden & H. Hongell) two misinterpreted as late spring migrants from Pori (1966 and 1967, M. Soik- and so excluded from the analysis. keli) and one from Norrskär (1970, The southward departure is as rapid O. Hilden) in years when no effective as the northward arrival. The first in- observation was carried out at Valas- dividuals already appear in southern saaret. Sweden in the first ten days of June (Edelstam 1972), and in Denmark, the 1949 : 11 June 1967 : 9 June Baltic coast of Poland and the north- 1951 : 13 June 1968 : 10 June ern parts of Germany in mid-June 1953 : 9 June 1969 : 15 June . at about the 1954 : 9 June 1970: 8 June (Glutz et al. 1977), i.e 1957 : 15 June 1971 : 9 June same time as on the west coast of Fin- 1958 : 13 June 1972 : 8 June land. 1960: 5 June 1973 : 12 June 1962 : 10 June 1974: 6 June 1963 : 3 June 1975 : 14 June 1964: 6 June 1976 : 5 June Breeding system 1965 : 14 June 1977 : 11 June 1966: 6 June 1978 : 9 June As Spotted Redshanks arrive in Lap- land in mid-May and are moving south The post-breeding departure of the again from about 10 June onwards, Spotted Redshank thus started on 10 their stay on the breeding grounds June (SD±3.37), on average, the ex- lasts no longer than three to four treme dates being 3 and 15 June. weeks . This time is shorter than in any Usually only lone individuals or 2-4 other Finnish breeding bird. The ex- birds together were seen in the early planation lies in certain special featur- phase of the southward migration, but es in the breeding system of the spe- a few larger flocks were also noted ; cies . e.g. 13 June 1964 8 (Valassaaret, O. According to the handbooks (e.g. v. Hilden), 9 June 1967 8 (Pori, M. Soik- Haartman et al. 1963-72, Haftorn keli) and 12 June 1979 27+21+8 1971, Glutz et al. 1977), the first birds (Norrskär, S. Vuolanto) . Considering to depart are females. After a short the scarcity of the species, which na- courtship period they lay eggs in late turally increases the chance of an atyp- May but, contrary to other species of ical date for the first sighting, the start the genus Tringa, leave at least most of the departure must be regarded as of the incubation to the males. The amazingly well synchronized . Except females still remain for some time on for the Ruff Philomachus pugnax, the breeding grounds and may pair there is much more annual variation with another male or, in case of nest O. Hilden: Timing of migration of the Spotted Redshank 2 1

TABLE 1 . Onset of the southward migration in some early departing waders at Valassaaret in 1949-78.

Earliest Mean ± SD Latest Years

Philomachus pugnax 11 June 16 June ± 3.40 23 June 14 Numenius phaeopus 13 June 20 June ± 4.70 28 June 15 Tringa glareola 13 June 23 June ± 6.20 2 July 15 T. nebularia 15 June 24 June ± 5.31 30 June 13 Calidris a. alpina 20 June 29 June ± 6.37 9 July 17 failure, lay a replacement clutch. breeding cycle then following each There are only two known cases of other on the hourglass principle, with- polyandry (Raner 1972, Danilow & out any further external stimuli. In Rjabizew in Flint 1973), but it may this case, the annual periodicity of the occur more commonly than is so far Spotted Redshank would be adjusted believed . About one week before once a year by photoperiod and sub- hatching of the young the females de- sequently follow an endogenous sert their mates, gather into flocks rhythm. Unfortunately, laboratory ex- and leave the breeding grounds (see periments conducted in constant con- the observations by P. Linkola from ditions to demonstrate the factors go- Enontekiö in 1965 : v. Haartman et al. verning the annual cycle of the Spot- 1963-72). More detailed studies of ted Redshank would be extremely dif- the breeding biology of the Spotted ficult to arrange. Redshank are urgently needed to con- However, not even the Spotted firm these suggestions. Redshank follows a completely fixed time schedule . There are small annual differences in the timing of south- Timing of the departure ward departure, which probably re- sult from corresponding differences in Evidently, the whole breeding cycle the time of breeding (cf. Hilden 1961) . of the Spotted Redshank - arrival, These, in turn, are likely to depend on courtship, breeding and departure - the temperatures in the latter half of is a sequence of events almost com- May and early June, and the conco- pletely controlled by an endogenous mitant melting of snow. In some years circannual rhythm. Each event fol- the conditions permit the birds to start lows the previous one, without any nesting straight after their arrival at external stimulus . The annual cycle the breeding grounds, while in other of photoperiod, for instance, can hard- years cold weather and thick snow ly act as the Zeitgeber, as in many cover delay the birds by some days . species, since breeding and departure To test this idea, I have compared take place in the continuous daylight the onset of departure on the west of Lapland. Other environmental fac- coast with the mean temperature in tors that might operate as a reliable Lapland during the early phase of Zeitgeber are equally difficult to breeding. Temperatures were measur- imagine at this time of the year. How- ed at Sodankylä (67°25'N, 26°30'E), ever, photoperiod could well initiate close to the centre of the species' the whole machinery during the spring breeding range in Finland, during the migration, the successive events of the 20-day period, 16 May to 4 June. Fig.

22 ORNIs FENNICA Vol. 56, 1979

FIG. 2. The relationship between the mean temperature on the breeding grounds (Sodankylii, 16 May to 4 June) and the onset of departure of the Spotted Redshank on the west coast of Finland during 24 summers from 1949 to 1978 .

2 depicts the result. The correlation Hence, we can conclude that al- between the temperature at the begin- though the timing of southward de- ning of the- breeding season and the parture in the Spotted Redshank is onset of departure is highly significant mainly the result of a circannual pro- (r = -0.693, P < 0.001) . Consider- gram determining the date of spring ing that the effect of mere chance on migration, the small year-to-year var- the date of the first sighting of a iation in departure date is caused by southbound migrant must be consider- temperatures in late May and early able, the relationship between tem- June, which either speed up or retard perature and timing of departure is the early phases of breeding. surprisingly clear. O. Hilden: Timing of migration of the Spotted Redshank 23

Acknowledgements. I wish to thank all those pakottavat odottamaan muutamia päiviä (ku- persons who have kindly placed data at my va 2) . disposal . I am also grateful to Dr. Peter Bert- hold for valuable comments on my manuscript and to Dr. Peter Evans for improving my References English . EDELSTAM, C . 1972 : The visible migration of birds at Ottenby, Sweden . - Vår Fågel- Selostus : Mustaviklon kevät- ja syys- värld, suppl. 7 :1-360 . FLINT, W. E. 1973 : Fauna i ekologija kulikow. muuton ajoituksesta - Moscow . GLUTZ v. BLOTZHEIM, U. N., K. M. BAUER & Mustaviklo on luultavasti kaikkein selväpiirtei- E. BEZZEL 1977 : Handbuch der Vögel sin "vaistomuuttajatyypin" edustaja Pohjois- Mitteleuropas. Band 7 . - Wiesbaden . maiden linnustossa . Keväällä se saapuu erit- V. HAARTMAN, L., O. HILDEN, P. LINKOLA, P. täin täsmällisesti toukokuun alussa, esim. Hel- SUOMALAINEN & R. TENOVUO 1963-72 : sinkiin 1-8.5. N=24) ja Vaasaan 2-11 .5. Pohjolan linnut värikuvin . - Helsinki . (N=17) . Muutto yli Suomen etenee hyvin no- HAFTORN, S. 1971 : Norges fugler . - Oslo- peasti (kuva 1) . Kevätmuutto kestää vain pari Bergen - Tromso . viikkoa eikä viivyttelijöitä juuri tavata. HILDEN, O. 1961 : Uber den Beginn des Weg- Syysmuutto etelään alkaa sekin hyvin täsmäl- zuges bei den Limikolen in Finnland. - lisesti kesäkuun alkupuolella, suhteellisesti ai- Ornis Fennica 38 :2-31 . kaisemmin kuin minkään muun kahlaajamme . HILDEN, O. & S. VUOLANTO 1972 : Breeding Länsirannikkomme keskiosista kootun 24 kesän biology of the Red-necked Pha- tilaston mukaan ensimmäiset syysmuuttajat laropus lobatus in Finland . - Ornis Fen- nähdään keskimäärin 10.6., ja äärihavainnot- nica 49 :57-85 . kin jäävät vajaan kahden viikon (3-15 .6.) KOMONEN, A. 1962 : Muuttolintujen saapumi- sisään . Muitten varhain pois muuttavien kah- nen Rovaniemelle vv . 1947-1961 (Refe- laajien aikataulu vaihtelee vuosittain huomat- rat : Ankunft der Zugvögel in Rovaniemi tavasti enemmän (taul. 1) . 1947-1961) . - Ornis Fennica 39 :102- Ensimmäisinä pois muuttavat mustaviklot 112. ovat naaraita, joiden vierailu pesimäpaikoilla MONTELL, J. 1917 : Fågelfaunan i Muonio kestää vain 3-4 viikkoa . Ne munivat pian socken och angriinsande delar af Enontekis saapumisensa jälkeen, mutta jättävät pääosan och Kittilä socknar. - Acta Soc. Fauna hautomisesta koiraille ja lähtevät syysmuutolle Flora Fennica 44, 7 :1-260 . noin viikkoa ennen poikasten kuoriutumista. RANER, L. 1972 : Förekommer polyandri hos Ilmeisesti mustaviklon koko pesimäkierto Poh- smalnäbbad simsndppa (Phalaropus loba- jolassa on miltei täysin sisäisen vuosirytmin tus) och svartsniippa (Tringa erythro säätelemä. Vaikka päivänpituus tuskin voi toi- pus)? (Summary : Polyandry in the Red- mia pesinnän ja poismuuton ajoittajana Lapin necked Phalarope, Phalaropus lobatus, and kesän jatkuvassa päivänvalossa, se silti saattaa the Spotted Redshank, Tringa erythro- käynnistää vuosikierron koneiston kevätmuuton pus.) - Fauna och Flora 67 :135-138 . aikana, minkä jälkeen jokainen vaihe seuraa ScHUz, E. 1971 : Grundriss der Vogelzugskun- toistaan ilman uutta ulkoista tahdistajaa . de. - Berlin and Hamburg. Täysin kiinteää aikataulua ei mustaviklokaån SOIKKELI, M. 1967 : Breeding cycle and popu- noudata . Pienet vuosittaiset erot poismuuton lation dynamics in the Dunlin (Calidris alkamisessa johtuvat pääasiassa toukokuun jäl- alpina) . - Ann. Zool. Fennici 4 :158- kipuoliskon lämpötiloista pesimäpaikoilla, jotka 198. eräinä vuosina sallivat pesimään ryhtymisen heti lintujen saavuttua, toisina vuosina taas Received January 1979