Despatches from across the ditch 4: A New Zealand Dotterel

Gary & Robyn Wilson | Guest Contributors

I have been working on an article on the recent survey in New Zealand of the Australasian Bittern. However, the final data from the survey has not been forthcoming and in the interim I am presenting a review of an interesting endemic New Zealand species.

Red-breasted (New Zealand) Dotterel, Maori name: Tūturiwhatu, Anarhynchus obscurus, Charadriidae

Protonym: Charadrius obscurus Gmelin, 1789. Systema Naturae. Editio decima tertia, aucta, reformata. Cura Jo. Frid. Gmelin (etc.). Tomus I. Pars II 1 pt2, p.686.

Type locality: New Zealand, i.e. Dusky Sound, South Island, ex Latham.

I have included the description details as it highlights the early involvement by European biologists in what was to become New Zealand (NZ). The author, Johann Friedrich Gmelin (1748–1804) significantly expanded and revised Carl Linnaeus's Systema Naturae in its 13th edition (1788–1793), with Volume 1 published in 1789.

The species includes two taxa: the nominate A. obscurus obscurus as described from Dusky Sound in the South Island; and the northern subspecies, A. o. aquilonius from the North Island. There is currently a 1,100 km gap between the ranges of the two (Figure 1).

Figure 1. Red-breasted Dotterel distribution: the northern subspecies, A. o. aquilonius of North Island; and nominate subspecies A. obscurus obscurus of South Island. Source: Gary W Wilson.

The subspecies differ in morphology and breeding ecology, sufficient that one recent global checklist (del Hoyo & Collar, 2014) treated them as separate species. However, these authors considered their treatment to be “tentative and provisional“, acknowledging the possibility that differences were formerly clinal, but this has now been lost with the extinction of South Island populations.

More recent treatments, e.g. Kirwan, et al. (2024) in Birds of the World recognise the two subspecies. The Southern birds are larger and generally darker in colour (an example of Bergman’s Rule in action?). Both are reliant on human management, particularly nest protection and non-native predator control.

The northern subspecies is impacted by coastal developments, high tides and storm-water incursions, rising sea levels, and recreation activities, but the population appears to be stable at approximately 1,500 individuals, and is classified Least Concern.

The southern subspecies has a conservation status of Critically Endangered. Since 2012, its population has declined, catastrophically, to 120 individuals and no more than 30–40 pairs, but recently there has been a slight recovery to an estimated 173 individuals in 2020. The subspecies suffers from exceptionally high rates of annual adult mortality (Dowding, 1999), particularly as the birds incubate at night and are more vulnerable to predation at that time.

Red-breasted Dotterel: nominate subspecies, A. obscurus obscurus, New Zealand. Photo by Gary W Wilson.

A pair of Red-breasted Dotterel, A. obscurus obscurus, New Zealand. Photo by Gary W Wilson.

Northern birds breed on beaches and sand spits around most of the North Island, but sparsely on the west and south-east coasts. Many move to estuaries after breeding. Southern birds breed only on subalpine habitat of Stewart Island, with some individuals traveling to estuaries and mudflats to feed. They winter along estuaries and rivers of Stewart Island and Southland; but some birds wander farther during winter (Dowding, 2020).

The Latin name for the Red-breasted Dotterel has recently been changed, from Charadrius obscurus to Anarhynchus obscurus. There was no change to the species name obscurus, which is derived from the darker colour dotterels develop on their breast during mating season. Their closest relative, the Banded Dotterel (another NZ endemic) also received a name change, to Anarhynchus bicinctus.

The new genus name is taken from that of their other close relative, the New Zealand Wrybill (also endemic to NZ), which has been known as Anarhynchus frontalis since 1830. A. frontalis was found to be deep in the clade and thus the name Anarhynchus was given to it. The name, Anarhynchus, is derived from the Greek rhynchos (having a beak or snout), with the prefix “Ana” having multiple meanings, but presumably here referring to the Wrybill’s tweaked beak.

The genus Anarhynchus now contains 24 or 25 species worldwide: a recent expansion from the traditional single species (the Wrybill, A. frontalis) (Figure 2). This expansion included many birds previously in Charadrius (some of which are recorded in Australia): Caspian Plover; Chestnut-banded Plover; Collared Plover; Double-banded Plover; Greater Sand Plover; Javan Plover; Kentish Plover; Kittlitz's Plover; Mountain Plover; New Zealand Plover; Oriental Plover; Puna Plover; Madagascar Plover; Saint Helena Plover; Red-capped Plover; Snowy Plover; Malaysian Plover; Siberian Sand Plover; Tibetan Sand Plover; Two-banded Plover; White-faced Plover; White-fronted Plover; and Wilson's Plover.

Figure 2. The Charadiidae Plover and Lapwing branches. Source: Birds of the World Phylogeny Explorer.

We really enjoy seeing this species when we are doing beach surveys. We regularly see nesting attempts but are concerned for the long-term survival of both subspecies for the reasons given above.

References

Dowding, JE (1999). Past distribution and decline of the New Zealand Dotterel (Charadrius obscurus) in the South Island of New Zealand. Notornis 46(4):167–180.

Dowding, JE (2020). Record of a southern New Zealand dotterel (Charadrius o. obscurus) in the northern North Island. Notornis 67(4):729–731.

del Hoyo, J & Collar, NJ (2014). HBW and BirdLife International Illustrated Checklist of the Birds of the World. Vol. 1: Non-passerines. Lynx Edicions, Barcelona, Spain.

Kirwan, GM, del Hoyo, J, Wiersma, P, Collar, N, Boesman PFD, & Sharpe, CJ (2024). Red-breasted Dotterel (Anarhynchus obscurus), Version 2.2. In Birds of the World (BK Keeney, Editor). Cornell Lab of Ornithology, Ithaca, NY, USA. https://doi.org/10.2173/bow.rebdot1.02.2

I hope to return to considering species shared with both countries in future posts.

Gary W Wilson