ORNIS SVECICA 21: 109–118, 2011 Field notes on the breeding biology of the Dotterel Charadrius morinellus in arctic Norway Fältnoteringar om häckningsbiologin hos fjällpipare Charadrius morinellus i arktiska Norge LUTZ LÜCKER, SIEGFRIED KRAATZ †, BÄRBEL KRAATZ Abstract From 2002 to 2010 twenty-four Dotterel nests were ob- Several nests were found less than 100 m apart. One bird served on Varangerfjell plateaus near Batsfjord. Females laid eggs in the same nest in 2 consecutive years. These definitely took part in incubation in 18 cases. However, findings complement previously published observations shared incubation could not be ruled out for the remain- and hypotheses. ing 6 nests. One female defended the chicks against her own partner before they left the nest. Another lone fe- male was seen leading 3 chicks for 5 days in a very small Lutz Lücker, CH-1213 Petit-Lancy/Geneva, 5, section of the study area, to our knowledge the only case Fort-Ecluse, email: [email protected] of a female with chicks outside the nest ever recorded. Bärbel Kraatz, D-17489 Greifswald, Hoher Weg 9a Received 15 May 2011, Accepted 1 August 2011, Editor: S. Svensson in order to see how faithful Dotterel are to former Introduction nesting territories. Dotterel females have been known to be polyan- Population density does not exceed 17 nests/100 drous for a long time (Berg 1917, Géroudet 1982, hectares (6 nests and 4 broods on 58 ha) on moun- Cramp & Simmons 1983, Owens et al. 1995), de- tain tops with restricted suitable habitat surface serting their males after egg-laying in order to lay (Pulliainen, Saari & Tunkkari 1992, Nethersole- more clutches (normally three eggs) with other Thompson 1973, Piersma & Wiersma 1996, Cramp males. Females may maintain a loose relationship & Simmons 1983). Dispersal of chicks after hatch- with the incubating male, especially to warn the ing is believed to be fast and over large distances male of potential dangers. Otherwise, very little is (Géroudet 1982). Generally, Dotterel are thought known about the role of females; only a few au- to be extremely confiding. Some authors (Cramp thors (Géroudet 1982, Cramp & Simmons 1983, & Simmons 1983, Géroudet 1982, Hable 1975) Nethersole-Thompson 1973) mention that some give the impression that sexing of adult birds is ex- females may occasionally take part in incubation, tremely difficult, even from a short distance. the only precise proportions recorded so far being The Dotterel seems to be common all over the 9 out of 27 nests on Hardangervidda in southern Varanger peninsula on uninhabited plateaus and Norway (Kalas & Byrkjedal 1984) and 4 out of slopes which are not too steep, between 320 and 32 nests on Värriötunturi in Finland (Pulliainen 420 m. above sea level. More than 1800 km2 of the & Saari 1997). However, there are no records of area is now a national park with strict protection of females attending chicks after leaving the nest, or this species. It is one of the largest virtually treeless double-clutching (male and female incubating two areas in Fennoscandia, home to endangered species clutches, which occurs with Mountain Plover Cha- like Gyrfalcon Falco rusticolus and Arctic Fox radrius montanus (Cramp & Simmons 1983) and Alopex lagopus, as well as an important moulting certain Calidris species (Maynard Smith 1978). site for Bean Geese Anser fabalis (Aarvak & Øien Site fidelity is believed to be weak (Cramp & 2009). Here the Dotterel reaches the northernmost Simmons 1983, Hable 1975), but each year we fringe of its distribution. Unfortunately, even these systematically tried to findthe location of old nests seemingly virgin habitats might be threatened by 109 indirect effects of climate change. Lemming peaks Our observations led us to four more issues: have become scarce and irregular (Kausrud et al. – Are females also able to take care of chicks dur- 2008), and some of their traditional predators like ing and after hatching? skuas have to forage on wader or grouse chicks and – Could double-clutching be proved? eggs. Red foxes Vulpes vulpes hunt at higher alti- – Do all Dotterel have the same confidingattitude tudes, endangering both arctic foxes and breeding near their nests? birds in these fell habitats. – Was there any evidence of site fidelity between One of our research motivations was the fact that years? the number of Dotterel have decreased dramatical- ly since the 1950–1970s (Saari 1995) and figure as Material and methods “near threatened” on the Finnish Red List (Rassi et al. 2010). In spite of its decline the Dotterel is still Study areas a species of least concern for IUCN (Birdlife In- Our study areas were less than 1800 m from road ternational 2009) since the world-wide population 891 which leads from Gednje T-junction to Bats- is estimated to be somewhere between 49,000 and fjord at 70°32’N / 29°22’E. Nests were found 210,000 birds (Wetlands International 2002). Nev- between 320 and 420 m. a.s.l. in only inch-high ertheless our firstpriority was conservation and we vegetation of Salix glandulosa, Salix herbacea, always tried to disturb the birds as little as possible. Loiseleuria procumbens, Silene acaulis, Arctostap- In the Varanger type of habitat Dotterel nests hylos uva-ursi, Cladonia rangiferina and Vacci- are to be found in the vicinity of nests or territo- nium myrtillus. Frequently eggs are laid next to a ries of Ptarmigan Lagopus mutus, Ringed Plover house brick-sized stone, covered with Rhizocarpon Charadrius hiaticula, Golden Plover Pluvialis geographicum and other lichens. The approximate apricaria, Purple Sandpiper Calidris maritima, size of the three areas where nests were found is 35 Temminck’s Stint Calidris temminckii, Turnstone + 75 + 25 (= 135) hectares, to which we may add Arenaria interpres, Shorelark Eremophila alpest- another 60 ha of identical habitat that was system- ris, Northern Wheatear Oenanthe oenanthe, La- atically searched but with no success. pland Bunting Calcarius lapponicus and Snow Bunting Plectrophenax nivalis. Potential predators of eggs and chicks, such as Arctic Skua Stercora- Data collecting rius parasiticus and Long-tailed Skua Stercorarius When we firstmet in early July 2002, Siegfried and longicaudus, may breed within 400 m of the near- Bärbel Kraatz had started observing their second est Dotterel nest. Dotterel clutch where male and female were shar- Other occasional or rare threats include Gyr- ing incubation. We found four more such pairs in falcon, very rare, Merlin Falco columbarius and 2004 and Siegfried, in spite of his declining health, Rough-legged Buzzard Buteo lagopus, both rare found two more in 2005. Shortly before his pre- above the tree-line, Golden Eagle Aquila chry- mature death he wrote his second article on incu- saëtos, rare, and Snowy Owl Nyctea scandiaca, bation-sharing female Dotterel (Kraatz & Kraatz only recorded in July 2003. Raven Corvus corax 2004, 2006). From 2007 to July 2010 Bärbel Kraatz and Herring Gull Larus argentatus are no threat to and I returned to our study areas each year to ex- adult Dotterel. We observed Red Fox three times tend our knowledge of this practice. The length of above 320 m. a.s.l., Arctic Fox was recorded only our 10 stays went from 6 to 43 days (mean: 26,5 once, and Stoat Mustela erminea were not seen an- days; see Table 1). nually; they are rare except during Lemming peaks Throughout the study period sampling was dif- (which we only noticed in 2008 before mid-June). ficult and irregular. In six years we only arrived Once we found fox sp. droppings in a nest that had after the 27 June when most clutches had been laid. been used a year earlier. On the other hand, Rein- In seven years we had to leave by 25 July, before deer Rangifer tarandus can be quite numerous in the last clutches had hatched. Thus, we could not July (a trampled Dotterel nest was found in 2008). check if females continued or resumed their par- ticipation until or after hatching. In 2004 and 2005 The main questions we wanted to answer in our Siegfried’s health problems did not allow him to study were: study the birds regularly. Weather conditions made – How common is female participation in incuba- field work often difficult, as snow storms or show- tion in this area? ers occurred even in June or July, as well as thick – How long do females participate in incubation? coastal fog and 25 m/sec gales, which made stand- 110 Table 1. Observation periods, and data on participation by the different sexes in chick attendance. Observationsperioder samt data om deltagande i omvårdnaden av ungarna för de olika könen. Year Observation period Nests with female Nests with no No. of cases No. of cases (no. of days) participation proved female with chicks with chicks (no. of days with participation attended by attended by female on nest) male from female from unknown nest unknown nest Observationsperiod Bon med hona Bon utan Antal fall med Antal fall med (antal dagar) deltagande (antal bevisat ungar vårdade ungar vårdade dagar med honan deltagande av av hane från av hona från på boet) honan okänt bo okänt bo 2001 13 Jun–8 Jul (26) 1 (10) 2002 6 Jun–9 Jul (34) 1 (13) 2003 7–11 and 29 Jul (6) 1 1 2004 27 May–8 Jul (43) 4 (1,6, 8, 8) 1 2005 28 Jun–8 Jul (11) 1 (8) 1 2006 5–13 Jul (9) 2007 28 Jun–22 Jul (25) 1 (1) 2 2008 18 Jun–22Jul (35) 3 (6, 9, 16) 1 2009 26 Jun–25 Jul (30) 3 (3, 3,11) 1 1 1 2010 28 Jun–31 Jul (34) 4 (1, 1, 3, 8) 3 Total 265 days 18 (116 days) 6 6 1 Mean 26.5 days 6.42 days Range 6–43 days 1–16 days 1–2 1–3 ardized sampling just impossible.