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The population of Red Lark Calendulauda burra satisfies the threshold for Vulnerable under the reduction in population size criterion (an estimated, inferred or suspected population size reduction of 30% over the past three generations, where the reduction or its causes may not have ceased). In addition, the population size is estimated to number less than10 000 mature individuals, all of which occur within a single population.
The Red Lark is endemic to South Africa's Northern Cape Province. Its restricted and fragmented distribution mostly follows red sand dunes south of the Orange River, and in particular the active and palaeo-dunes of coarse-grained, hematite-stained, deep red sands overlying a Precambrian basement in the Koa River Valley, and the stable dunes of finer-grained red and yellow sands overlying Karoo sediments to the south-west; it also occurs on shales and alluvial plains in parts of its range (Dean 1997). It occurs in areas with an annual rainfall of less than 100-200 mm, but mostly within the 100 mm isohyet, in a mainly spring and autumn rainfall region (Dean et al. 1991).
The distribution encapsulates the band from east of Steinkopf, eastwards to Aggenys and south to the Kliprand area, in the Pofadder, Kenhardt and Vanwyksvlei districts, and south to Klein Soutpan and east to Brandvlei and isolated dunes in the Brospan area (Dean et al. 1991, Barnes 2000). Sight records from near Kenhardt in the early 1960s and 1985 suggest that it occasionally occurs further to the north-east. There are also two putative specimen records from southern Namibia: one from dunes north of Oranjemund and one from Kleinkaras, but these are considered doubtful (Ryan and Bloomer 1997) or may reflect occasional vagrancy (Dean and Ryan 2005).
The Red Lark has lost c. 75% of its habitat in the last century to overgrazing and degradation. An apparently dramatic decrease in EoO and AoO is suggested when comparing SABAP1 data (on which the Vulnerable assessment of Barnes (2000) was based), and SABAP2 data. The c. 52% decrease in EoO of this species is partly an effect of limited field surveys within its restricted, barren and sparsely populated range. Dedicated atlasing efforts in areas where it was previously recorded are likely to reveal that it persists in at least some other localities, particularly in the east of its distribution range.
Dean et al. (1991) estimated its total global EoO to be 112 500 km2; however, at least 86% of this area represents unsuitable habitat for the Red Lark and a global EoO of 15 850 km2 is thus more likely (Dean et al. 1991). The 80% decrease in AoO is again partly an effect of incomplete sampling. This species was recorded in 45 quarter-degree grid cells during SABAP1, and in only 18 grid cells (representing 30 pentads) during SABAP2; only 9 grid cells overlap between the two atlas periods. However, excluding ad-hoc atlas cards and incidental observations, 21 of the grid cells in which the Red Lark was recorded in SABAP1 had not been surveyed in SABAP2 at the time of writing, and a further 12 only superficially explored. Of the 15 850 km2 estimated to represent the global EoO of this species by Dean et al. (1991), about one third (5 625 km2) constitutes suitable habitat for this species, but only a quarter of this (1 400 km2) is occupied. It is unknown to what extent the AoO of this species has changed since the estimation of Dean et al. (1991).
The Red Lark is locally common, but highly localised and fragmented in its distribution (Dean and Ryan 2005). Brooke (1984), considered it Indeterminate but probably Rare, i.e. a species which is not at present threatened, but is at risk. It was classified as Near Threatened by Collar and Stuart (1985). It is probably most continuously distributed and numerous in the Koa River Valley in Bushmanland, where densities of up to 1 bird/5.7 ha occur. Some 75% of a total of 5 625 km2 of historically suitable habitat has been overgrazed and degraded. The current AoO of 1 400 km2 is estimated to support c. 9 400 birds, calculated at 1 pair/30 ha (Dean et al. 1991). The morphologically distinct eastern population, occurring around Vanwyksvlei, has experienced the most severe decreases (Ryan and Bloomer 1997). The current regional population is certainly greater than 10 000 mature individuals, but an accurate estimate is not currently possible.
There is no evidence of a historic range contraction, but local population decreases and disappearances from some sites are documented (Barnes 2000). However, decreases in EoO and AoO may be due to incomplete sampling as opposed to real declines. The current population trend is unknown.
The biggest threat to the Red Lark is the poor representation of the species in formally protected areas, with less than 100 birds (c. 2% of the estimated global population) occurring in state-owned nature reserves (Siegfried 1992). As a naturally range-restricted species and habitat specialist, the Red Lark is influenced by changes in the structure of the sensitive dune vegetation it inhabits (Barnes 2000). It is threatened mainly by habitat loss and fragmentation through the impacts of intensive grazing and trampling by domestic livestock, which may cause changes in vegetation structure. Overgrazing reduces vegetation cover and available food, especially if coupled with droughts. A decrease in perennial grass and shrub cover may lead to eroding and shifting of dunes (Dean et al. 1991). Cattle uproot forbs and graze down grasses such as the important Stipagrostis ciliata, while sheep selectively remove forbs and annual grasses. Goats are thought to have the least impact on Red Lark habitat by browsing shrubs and some grasses, but leaving Stipagrostris untouched. Climate change may have a detrimental effect on range-restricted species linked to specific soil types, such as the Red Lark (Simmons et al. 2004). At a small number of publicly accessible and well-known sites, disturbance by birdwatchers may have a limited negative effect on the species.
No species-specific research or conservation actions are currently underway.
This species is poorly represented in state-owned reserves (Siegfried 1992). However, important populations occur in three IBAs: Mattheus-Gat Conservation area (SA034; 400-700 birds), Haramoep and Black Mountain Mine Nature Reserve (SA035; 1 500-2 000 birds) and Bitterputs Conservation Area (SA036; 300-600 birds). With the exception of Black Mountain Mine Nature Reserve, these IBAs consist of privately owned farms, typically extensively grazed by livestock. Proactive conservation measures are essential in these high priority areas, which support a significant proportion of the global population of the Red Lark; Black Mountain Mine Nature Reserve alone supports c. 7.5% of the global population, and together with the surrounding properties constituting the IBA, may hold 15-20% of the world's Red Larks. This presents companies and private land-owners with the opportunity to make an important contribution to biodiversity conservation (Barnes and Anderson 1998).
Cattle stocking should be reduced or eliminated on parts of the properties, particularly in the remaining sensitive red-dune vegetation that the Red Lark is reliant on. In many locations such exclusion zones need only to encompass a small area, given the habitat specificity of the Red Lark. In degraded habitats, re-establishment of appropriate grass and forb communities, and management of grazing levels could lead to population increases or local re-colonisation by Red Larks (Barnes 2000). Identification of other priority conservation areas, and establishment of reserves or conservancies focused specifically on the Red Lark, should also be undertaken.
Taxonomic studies have shown that birds from the three main habitat zones (north-western dunes, south-central alluvial plains and eastern dunes) do not represent different subspecies. Nevertheless, this variation in habitats and phenotypes should be conserved (Ryan and Bloomer 1997). Populations restricted to localised red dunes, particularly in the east of the range, are under greater threat from grazing than birds living on alluvial plains (Barnes 2000). An awareness campaign, targeting land-owners whose properties hold Red Larks, will be beneficial in the long-term. As this species and other arid-zone South African endemics are highly sought-after by local and international birdwatchers, controlled avitourism also presents a sustainable and economically valuable indirect conservation strategy and an impetus for local land-owners to conserve the species.
An accurate, updated population assessment should be regarded as a priority. In particular, potential habitat within the previously documented range needs to be revisited to determine whether Red Larks still occur there.