Southern Red-breasted Plover (or Southern New Zealand Dotterel) (Charadrius obscurus) is endemic to New Zealand. Once widespread in the South Island of New Zealand, it now breeds only on inland Stewart Island/Rakiura, mainly on subalpine herb-fields or rocky areas above the tree-line. During the non-breeding season all birds move to the coast where they feed on intertidal mudflats and beaches (Heather and Robertson 2015).
The species may be particularly vulnerable to invasive predators, which were thought to have contributed to historical declines. Males in particular were badly affected as they incubate at night and are more vulnerable to nocturnal predators, and this led to a severe gender bias in the early 1990s, with female-female pairs forming (Dowding 2013).
The population recovered from a low of 62 birds in the early 1990s following intensive cat and rat control around breeding sites, and by the late 2000s, numbers had stabilised (with some annual fluctuations) at 240-290 individuals. Although the cat and rat control has continued since then, the population has declined catastrophically since 2012 for reasons that are not clear. The recent decline has been 54% in the 4 years 2012-2016 (J. Dowding in litt. 2016), equating to an approximate 95% decline over three generations (15 years), though the reason for the sudden decline since 2012 is not known. The very high rate of the decline suggests that it is probably due to a loss of adult birds, rather than to breeding failure (J. Dowding in litt. 2016).
The population now stands at 120 individuals, which probably includes no more than 30-40 male-female pairs, and the gender bias appears to have re-established. Predator control is being intensified in part of the breeding range, but if the decline is not halted the species could become functionally extinct within 3-4 years.
C. obscurus is currently listed as Endangered under criterion D because of its low population. However, due to the ongoing levels of decline in this species and the lack of understanding of the cause of this decline, it is now recommended that this species is uplisted to Critically Endangered under criteria A4a; C1+C2a(ii).
Additional information and comments on this proposal are welcomed.
Dowding, J.E. 2013 [updated 2015]. New Zealand dotterel. In Miskelly, C.M. (ed.) New Zealand Birds Online. www.nzbirdsonline.org.nz
Heather, B. D.; Robertson, H. A. 2015. The field guide to the birds of New Zealand. Penguin Random House NZ, Auckland, N.Z.