Oiseaux et Mammifères - du Maroc au Cap Nord

Male (left) and female fighting about their chicks. Unprecedented document.

 
Lutz Lücker, Siegfried Kraatz †, Bärbel Kraatz
  

 
 
From 2002 to 2010 twenty-four Dotterel nests were observed on Varangerfjell plateaus near Batsfjord. Females definitely took part in incubation in 18 cases. However, shared incubation could not be ruled out for the remaining 7 nests. One female defended her chicks against her own partner during and after hatching. Another lone female was seen leading 3 chicks for 5 days in a very small section of the study area. Several nests were found that were less than 100 m apart. One bird laid eggs in the same nest in 2 consecutive years. Some of these findings complement previously published observations and hypotheses.
 
Female evacuating an eggshell & letting us alone with its chicks



 
When we first met in early July 2002 on a high plateau of the Varanger peninsula, Siegfried and Bärbel Kraatz had started observing their second Dotterel clutch where male and female were sharing incubation. We found another four similar pairs in 2004 and Siegfried, in spite of his declining health, found two more in 2005. Shortly before his premature death in December 2005 he wrote his second article on the role of female Dotterel, which was published posthumously in 2006 (Kraatz & Kraatz 2004 and 2006). From 2007 to July 2010 Bärbel Kraatz and I returned to our study areas each year to extend our knowledge of this practice which had previously been believed to be infrequent.
 
Dotterel females have been known to be polyandrous for a long time (Cramp & Simmons 1982, Owens et al.1995, Géroudet 1982), mostly deserting their males after egg-laying in order to lay more clutches with other males. Only a few authors mention that some females may occasionally take part in incubation, the only precise proportions recorded so far being 9 out of 27 nests on Hardangervidda in southern Norway (Kalas & Byrkjedal 1984) and 4 out of 32 nests on Värriötunturi in Finland (Pulliainen & Saari 1997). However, there are no records of females attending chicks after leaving the nest or double-clutching (male and female incubating two clutches, which occurs with Mountain Plover Charadrius montanus (Cramp & Simmons 1982,) and certain Calidris species). Site fidelity is believed to be weak (Cramp & Simmons 1982, Hable 1975), population density does not exceed 17 nests/100 hectares on mountain tops with small suitable habitat surface (Nethersole-Thompson 1973, Piersma & Wiersma 1996, Cramp & Simmons). Dispersal of chicks after hatching is believed to be fast and over large distances (Géroudet 1982). Generally Dotterel are thought to be extremely confiding. Nevertheless, most authors claim that sexing of adult birds is extremely difficult, even from a short distance.

Incubating female, male coming to take over. Very rare document.
 
 
  
Both our study areas were not far from road 891 which leads from Gednje T-junction to Batsfjord at 70.54674 degrees north/29.44370 east on the vast shrub- and treeless plateaus of the Varanger peninsula. Nests were found between 320 and 420 m asl in only inch-high vegetation of Salix glandulosa, Salix herbacea, Loiseleuria procumbens, Silene acaulis, Arctostaphylos uva-ursi, Cladonia rangiferina and Vaccinium myrtillus. Mostly eggs are laid next to a house brick-sized stone which is often covered with Rhizocarpon geographicum and other lichens. In this habitat the Dotterel's immediate feathered neighbours are Ptarmigan (Lagopus mutus), Ringed Plover (Charadrius hiaticula), Golden Plover (Pluvialis apricaria), Purple Sandpiper (Calidris maritima), Temminck's Stint (Calidris temminckii), Turnstone (Arenaria interpres), Shorelark (Eremophila alpestris), Northern Wheatear (Oenanthe oenanthe), Lapland Bunting (Calcarius lapponicus) and Snow Bunting (Plectrophenax nivalis). Potential predators such as Arctic Skua (Stercorarius parasiticus), and Long-tailed Skua (Stercorarius longicaudus) may breed within 400 m of the nearest Dotterel nest..

Other occasional or rare threats include Merlin (Falco columbarius), Gyrfalcon (Falco rusticolus), Rough-legged Buzzard (Buteo lagopus), Golden Eagle (Aquila chrysaëtos) Snowy Owl (Nyctea scandiaca, only recorded in July 2003), Raven (Corvus corax), Herring Gull (Larus argentatus), Red Fox (Vulpes vulpes), Arctic Fox (Alopex lagopus, recorded only once), and Ermine/Stoat (Mustela erminea). Once I found fox droppings in a nest that had been used a year earlier. On the other hand, Reindeer (Rangifer tarandus) can be quite numerous in July; a trampled nest was found in 2008 but after we had cleaned up the mess the bird continued incubating the only intact egg for several days.

All nests were found either on dry, flat terraces and plateaus or on slightly inclined slopes, never on a hilltop or a summit ridge. Only one nest was virtually surrounded by small rivulets coming from a huge melting snowdrift. Hatching dates went from 4th to 27th July; replacement clutches may have been laid as late as 9th July so that some chicks may have hatched in early August.
 
Typical, drab male, "flagging", i.e. showing the chicks where he is.

 

 
It would be presumptuous to call this article “research” or “study”; sampling was indeed difficult and irregular. For work-related reasons I often arrived after egg-laying. We occasionally had to leave the Arctic before the last clutches had hatched, and Siegfried's health problems did not always allow him to study his birds as often or as long as he wanted. The weather on those windswept high plateaus was the main problem. There may be snow showers even in July, hazardous coastal fog and 25m/sec gales. When the weather was suitable, we tried to identify the sex of the birds on each nest twice a day, which sometimes involved a lot of walking and driving.
 
Our first priority was conservation, not research, so, to avoid disturbance, we sometimes did not check nests for several consecutive days during periods of poor weather. Except for hatching periods I rarely observed the same nest for more than 60 minutes whereas Siegfried sometimes stayed near a clutch for up to 14 consecutive hours, and often checked on the birds at night. We never used hides but stayed at some distance so that the incubating birds were not stressed. Before leaving at the end of our observation period we left a few mealworms. The birds then associated our visits with food and of no threat.
 
We never attempted to find more than 4 nests each year but since Dotterel are certainly commoner in this habitat than most other breeding species (except for Ringed Plovers Charadrius hiaticula), we also came across up to 3 families per year from other, unknown nests. We repeatedly observed feeding males in July for more than 3 hours before we lost them because they finally flew away, disappearing behind a low hump and never allowing us to find their clutch. Indeed, incubation-sharing means that the relieved bird can go and feed far away from its nest for long periods. This may be an advantage for breeding birds in arctic weather conditions but it makes nest-searching more difficult.
 
Sexing of incubating birds surprisingly turned out to be less difficult than we had expected. In all cases we found that breeding females in this area have a set of distinctive diagnostic features in late June and July. Their extremely white cheeks have very few or no dark streaks, the rear part of the crown is blackish with very few or no light brown streaks (see Appendix 5), the dark belly patch is much larger than that of a male where most have a number of light feathers showing well in this dark patch, probably a sign of early contour feather moult. In August however, those differences tend to disappear rapidly which makes it impossible to sex migrating adults. But in July it never took us long to tell which of the two birds was incubating provided that we could approach closely enough in good light.

     Pictures from 3 nests: males left, females right.
 
 
    
 
From June 2002 to July 2010 we found 24 nests, 18 (= 75%) of which were definitely incubated by two different birds, sometimes for up to 12 consecutive days (Fig.6).- However, the remaining 6 nests (with males only) could never be observed long enough to completely rule out any female participation. Either the nests were found too late, robbed or destroyed, or we had to leave the area before hatching. As for the 18 females, some only stayed with their mates during the early stages of incubation, or until hatching; but there was no consistency. In two cases the female was only seen once on the nest, on one or two days before hatching.

 
In July 2002, Siegfried was probably the first person to publish a photograph of a female Dotterel incubating a nest containing chicks. When the second chick had hatched, the female disappeared and the male took over. On 16th July 2008 we discovered another female incubating two chicks. When the third had hatched, a male bird arrived and tried to take over, trying to brood the firstborn chick which was looking for food about 4 m from the nest but he was violently driven away by the female (see Appendix 1). These skirmishes with leap-frogging and shrill calls were repeated 6 times over 3 ½ hours; the female won each time. We stopped observing in late afternoon because of cooler weather coming in. On the next morning we found the male, still brooding the chicks in the nest, nearly 24 hours after the last chick had hatched; the female had vanished. As far as we know this behaviour has not been previously reported.

http://www.vimeo.com/7435068
 

Female on nest with hatched chick.- Phot.: S.Kraatz
 
 
On 18th July 2008 we found two adult birds leading 3 chicks each, about 400 m from each other. One male, not far from a nest that had hatched a few days earlier, and a female (see Appendix 4)! The birds were in a small area, situated between the new Batsfjord road, the parallel old road, a creek and an impenetrable area with boulders that were too big for small chicks. The female stayed there for 5 days, the male for a week. They never came close to each other. The chicks were about the same size so a case of double-clutching between these two birds seemed to be unlikely. But there may have been a second male with whom the female might have paired up. To our knowledge, there have been no other records of females escorting three chicks without a partner.
 
Lone female with several day-old chicks. Unprecedented document. 
 
 
Each year, we systematically tried to find the location of old nests in order to see how faithful Dotterel are to former nesting territories. Since these birds often pair up in their winter quarters and sometimes breed thousands of miles from last years' site (Géroudet 1982), we were not surprised to find little evidence of site fidelity. However, in 2009, a nest was found only about 20 yards from one used in 2008. This might have been a coincidence but in 2004 I spotted a clutch in the very same depression where I had found one the previous year, a phenomenon that must be quite rare in any Charadriiform species!
 
Varanger's true Dotterel population density has always remained a mystery to us. Over the years we found 3 loose “neighbourhoods”, that is pairs of nests which were less than 100 m apart. In 2008 both nests were incubated by different females and males, which means that close vicinity is not necessarily a consequence of serial polyandry; we were able to prove that there were four different birds, not three. In 2009 we found a cluster of three nests in an area of less than 20 hectares. But we were unable to explain why in spite of great efforts we did not find any other nests for miles around in optimum habitat. The only area with a greater chance to find nests than elsewhere was along the reindeer fences that run along road 891, as well as along two dirt roads. We actually found at least 10 nests that were less than 50 metres from one of these conspicuous lines in the monotonous countryside, among which there were at least 6 nests that were no more than 20 metres away. It seems that Dotterel are sometimes attracted by man-made structures.
 
 
Although our sample (n= 24) is statistically not very significant, a percentage of min. 75% of shared incubation seems to show that this practice can be more frequent at the northern fringe of this species' breeding range than in subarctic and southern Fennoscandia. L. Saari (1996 and written comm.) suggests that most females on Värriötunturi (N 67° 41' 0'') in Finland leave the area in mid-June after egg-laying, perhaps in order to look for more males further up north. It is a fact that they can lay up to 5 clutches (Holt et al. 2002), so if the sex ratio in one area is sufficient to allow all males to have a clutch, why not go elsewhere to maximize reproductive success? Such a female's last male partner may have better survival chances in the harsh climate of the high arctic if shared incubation allows him to feed more often and for much longer periods. The hypothesis of females covering large distances between two clutches might one day be studied using telemetry and colour-banding. But catching an egg-laying female is not easy. Moreover, this may jeopardize the success of the clutch. And the probability of a satellite-tagged bird flying to an accessible part of the Arctic where its behaviour can be studied further is very low.
 
Contrary to common belief some incubating birds were so shy that they left the nest when we were between 80 and 300 m away, rarely allowing us to identify their sex. The question is: are these individuals exceptions or more frequent than we think? Why do some pairs breed in close vicinity when no other nests can be found for miles around in the same habitat? Perhaps researchers mostly find the nests of confiding birds which might not be the majority, and the real number of breeding birds is much higher than the few nests we managed to find. We think that Dotterel densities may be highly underestimated in vast areas like the Varanger plateaus. They may be even more numerous than Ringed Plovers (Charadrius hiaticula) and are definitely more common than Golden Plovers (Pluvialis apricaria). Dotterel are altogether far less visible than all other fell breeding wader species. To assess the true density of this species in this area , large teams of searchers would be needed.
 
As for the unlikely but not impossible occurrence of double-clutching, our observation of a lone female with several day old chicks remains at least very suspicious. It is true that Kalas (1986) had once removed a breeding male from a nest and showed that the female managed to take care of eggs and chicks. Predation of “our” female's partner is not impossible although the number of potential predators is extremely low in this area. But we think that this risk is unlikely. We have indeed never witnessed an attack on adult Dotterel in 10 years and I was once surprised at how relaxed a brooding bird remained in spite of a Gyrfalcon and a Skua that sped by very close to its nest. Since Dotterel on Varangerfjell breed during the midsummer night sun period on flat, open terrain, no predator can approach their nests unseen.- Among the hundreds of Dotterel pairs that have been watched by scientists so far, no other chick-leading females have been recorded. But does this mean that a case of double-clutching in Dotterel can be totally ruled out? It is certainly a rare phenomenon, probably limited to the birds' northernmost frontier in the high arctic but we do not think it is impossible.
 
 
On these immense plateaus where Dotterel habitat is not limited by higher vegetation such as on smaller Tunturi hilltops, it is extremely difficult for two or three people to collect enough data during a four or five week holiday. However, the possibilities for further professional scientific research are reasonably good on Batsfjordfjellet. There is a small town with all the necessary facilities and infrastructures a quarter of an hour's drive from the study area, a good number of birds within less than 20 minutes' walk from drivable roads and even a restored public mountain cabin on the edge of the study area. However, further research on this enigmatic species would certainly involve considerable amounts of time, money and staff.

 Postscript 2011
 
L.L. and B.K. studied the birds in the two main areas from 22nd June to 31st July, aided by J.M. Lustrat. All our findings confirm our hypotheses made since 2002.
 
We found 9 nests, two of which might have belonged to the same pair. One very late clutch (completed on 9th July) was abandoned, most of the other nests must have been robbed by Arctic Skuas relying on wader nests after a Lemming peak crash. Only two clutches, perhaps three, hatched for sure.
 
Five clutches were checked for at least five days. Four of those (80%) were found with females that incubated at least once, well after egg-laying. One female incubated at least from 5th to 27th July, before the second chick hatched. This is the 4th time we found a female Dotterel with at least one chick. (Video on http://www.youtube.com/watch?v=ePfnurgoWII  )
 
We found at least 11 other families, only 2 or 3 of which might have been counted twice or belonged to a known nest. On 31st July we found 5 different families in an area of less than 50 hectares within 1 hour and 40 minutes, which seems to prove that Dotterel on Varangerhalvöya are actually rather abundant. They are just extremely difficult to detect when incubating (which corresponds to the period when most birdwatchers try to find them, thus believing that they are much less common than other plovers).
 
Again, four of the 9 nests were less than 20 metres away from man-made structures (fence, road, track or ditch).
 
The most surprising occurrence this year: the very same nest scrape that had been used in 2003 (male) and 2004 (male and female) was used again this year (by male and female). To our knowledge such a phenomenon has never been found in any Charadriiformes species. (Photo proof on https://picasaweb.google.com/117170977024927019906/Lapland2011#5628159771688284242
and
https://picasaweb.google.com/lutz6lucker/LAPLAND2003#5120944232100499938

This sheds new light on the supposedly “weak” site fidelity of this species. One may speculate that some males tend to be extremely faithful to their once chosen breeding place, whereas certain females may pair up in their winter quarters, and then, after laying a first clutch, wander across large parts of Fennoscandia and Russia. This would explain the birds (of unknown sex) that were ringed in Europe and found later in central or eastern Siberia (Hable, 1975, Géroudet 1982).
 
About 80 m from this nest scoop, there was another clutch, only a few metres away from nests discovered in 2004 and 2006. 
 
   
..............................................................................................................................................
 
 
 
 
I am very grateful to the Norwegian Red Cross, Ms Inger Klausen and the Bremnes family from Batsfjord for helping me with accommodation. I am particularly grateful to Ted Green, Alex Parker and Mike Bowman for valuable comments on an earlier draft of the manuscript and proofreading. I also thank Lennart Saari and for his insightful suggestions on this article as well as Bo Fagerström for the Swedish version of the abstract..
 
 
     Appendix
 
Rare or unique photo and video documents
 
Fig. 1. Male and female bitterly fighting for parental care of the chicks. Female wins.
http://www.vimeo.com/7435068

and

http://picasaweb.google.com/lutzluecker/Laponie2009#5367870744640804418
 
2. Female incubating, male coming to take over.
http://picasaweb.google.com/lutzluecker/Laponie2009#5367873405947429394
 
3. Female on nest with 2 newly hatched chicks
http://picasaweb.google.com/lutzluecker/Laponie2009#5367248718737463362
 
4. Female with several day old chicks
http://picasaweb.google.com/lutzluecker/Laponie2009#5367249378545583266
 
5. Males and females of 3 different pairs
http://picasaweb.google.com/lutzluecker/Laponie2009#5372898321555852114
 
 
Fältnoteringar om häckningsbiologin hos Fjällpipare (Eudromias/Charadrius morinellus) i arktiska Norge
 
Från och med 2002, till och med 2010, observerades 25 fjällpiparbon på Varangerfjell-platån nära Båtsfjord. Honor tog med säkerhet del i ruvningen i 18 fall, men delad ruvning kunde inte uteslutas i de övriga 7 bona. En hona försvarade sina ungar mot sin egen partner under och efter kläckningen. En annan ensam hona sågs leda 3 ungar i 5 dagar inom en mycket liten del av det studerade området. Flera bon befanns vara mindre än 100 m ifrån varandra. En fågel lade ägg i samma bo 2 år i rad. Några av dessa fynd kompletterar tidigare publicerade observationer och hypoteser.
 
 
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