The Dotterel certainly lives up to its reputation as being a ‘quirky’ bird when it comes to breeding and rearing its chicks, writes Dominic Couzens
It’s high summer on the mountaintops of Britain, and you might think that, for a short time, at least, life is settled. Birds are incubating eggs or tending chicks; the frantic schedule of the montane migrants – arrival, setting up territory, pairing up – ought to be on pause. The highland days are long, and perhaps they should be lazy, too.
It seems, though, that at least in the case of that colourful wader, the Dotterel, nothing is ever peaceful. There is plentiful evidence that these birds are not content to rest on their laurels in summer, even if their breeding season is conspicuously successful, with fluffy chicks the proof. Dotterels do something very odd, of which more in a moment.
Let’s face it, though, ‘odd’ is the Dotterel default setting. This member of the plover family doesn’t follow a conventional breeding pattern. Nesting on high altitude plateaux, it is most famous for role-reversal, in which the ‘standard’ male and female identities and to-do-lists are swapped.
Thus, the females, rather than the males, have the more colourful plumage, and the males are the chick-rearing gender. Both sexes sport subtle and pleasing colours, with grey-brown upperparts, intense chestnut-cinnamon, black and white on the belly and with a bold white stripe over the eye and bordering the throat and breast.
This combination of features is more striking and well-marked in the female, and it is this gender that, bearing the smarter attire, takes the initiative in courtship.
Courtship is a little like an awkward human dancefloor, with males and females eyeing each other across the scree, with the females doing the asking, so to speak. The lead birds tend to try to isolate a chosen male from the rest of its flock, or ‘trip’, a bit like a sheepdog expertly corralling an individual ram.
Once this is done, the birds pair up. It is interesting to note here that females don’t hold any territories as such, and that much pairing takes place in a communal setting.
The term pair is a little loose when it comes to Dotterels, because not only do they practise role reversal, they also take a flexible attitude towards pair-bonds. This is necessary because the sex ratio might not be equal up on the hills, and time is limited at extreme latitudes or altitudes, so the birds need to be practical.
In many cases, though, it is simply a question of monogamy, with the female taking a single partner and laying four eggs. In these arrangements, the female might take part in incubation, usually at the beginning or end of the 24-28 day period.
However, the female is virtually never around when the chicks actually hatch; males almost invariably are the sole carers. Another common pairing arrangement is for a female to be involved with more than one mate. And why not, since she doesn’t have to bother about the patter of tiny feet? Emancipation from chick-rearing gives her options.
Once she has completed a clutch for one male, she can simply move on and get involved with another male, and even another after that. It’s
a system called sequential polyandry, and the second clutch may be completed only five days after the first.
In these circumstances females take no part in any incubation, which is also the usual state in monogamy. Very occasionally, there are only a few males around, and then a male may mate with several females. Usually, however, the males have only one mate and sire all the eggs in their clutch. They are diligent about their paternal duties.
They sometimes adopt chicks from another brood, and sometimes two males will attend to the same offspring.
Dotterel's quirky behaviour
So, what do the females do when the males are working? Well, one thing is to feed up and fatten up. The long days on the high tops are a time of plenty, and one of the Dotterels’ favourite foods is an insect known as the Mountain Cranefly, which abounds in the summer on the short turf.
The birds eat a variety of insects and spiders, particularly flies, and in the late summer they take a few nutritious berries, too. Feeding is easy for females, and probably does not constrain them in any way. However, the summer doesn’t pass in a picnic-like feast for all individuals.
As I mentioned at the beginning, the Dotterel has a very strange behavioural quirk that is only found in a small number of species worldwide
(as far as is known). Dotterels, it seems, routinely move around in the breeding season, almost in a migratory sense.
They will leave the scene of their nest and eggs and fly away to another place. This might well be elsewhere in the Highlands, but there is increasing evidence that some birds leave the country altogether and end up on the continent, in Norway or Sweden. The truly unusual aspect of this is that, once they have arrived in a new place, many of these birds set out to breed again.
In other words, they attempt to pair up as if nothing had happened earlier several hundred kilometres to the south.
If successful, they could be laying new eggs in their new location before their previous brood has fledged. Hardly any other bird species do this.
Of course, a second breeding attempt is much easier for a female. Having laid its clutch, a female is essentially free to fly away and do whatever it wishes, leaving the parental male in charge of the clutch, which is standard Dotterel behaviour.
You might view such an arrangement as highly advantageous to a female to increase her seasonal productivity, and expedient for the species as
a whole. There might, for example, be a good number of ready and willing high quality individual males available in Norway that happened not to be present in Scotland.
Furthermore, Dotterels have a long breeding season; arriving initially in mid-May, sometimes already paired, they have been recorded still displaying in the second week of July. They have plenty of time to relocate and start all over again.
Interestingly, though, this intra-seasonal movement is not confined to females; males have been recorded doing the same. The sex ratio is probably the trigger. If a male finds itself unpaired through a lack of available females in one location, then it would also make sense for it
to make a journey somewhere else.
Dotterels are powerful and swift flyers, easily able to average 70km/h over many hours in the air, so a transfer to another part of the Highlands, or over the North Sea, is very easy for them – they are also thought to fly to the wintering sites in North Africa in a single hop.
Nonetheless, a transfer also holds risks, particularly for an unpaired male. It might not be able to find a suitable population with plenty of grateful females, and it might miss out on females making the same later-season movements mentioned above. So, most males, if they are going to move at all, do it very early on.
More precise details about the within-breeding-season movements of Dotterels are still being worked out. But they do beg a question. Although complete role reversal is quite rare, with phalaropes and Dotterels being the best known British examples, it is very common, among waders in particular, for chick-rearing to be left almost entirely to males.
In such circumstances, why shouldn’t females of many species simply leave the area and try to start another family in another place?
Perhaps they do. As many of us are aware, waders, and many Arctic-alpine breeding species, are nothing if not practical.
Where to see Dotterel
In summer months, Dotterel is found only on Scotland’s high tops. You can look for them on spring and autumn migration. Passage birds can be seen at traditional stopping points in eastern England, such as the Chosely Drying Barns in Norfolk, not far from RSPB Titchwell Marsh. Another good spring site is Pendle Hill, Lancashire. They arrive from mid-April to mid-May and leave breeding areas in July and August. Autumn passage birds can be seen in August and September.
Scientific name: Charadrius morinellus
UK numbers: 510-750 breeding males
Habitat: Mountain areas
Diet: Insects and worms