|Scientific Name:||Alauda razae|
|Species Authority:||(Alexander, 1898)|
|Red List Category & Criteria:||Critically Endangered B1ac(iv)+2ac(iv) ver 3.1|
|Reviewer/s:||Butchart, S. & Taylor, J.|
|Contributor/s:||Brooke, M., Donald, P. & Hazevoet, C.|
This species is confined to one very small island, where its population fluctuates in response to rainfall and appears to reach extremely small numbers. Climate change may increase drought in Cape Verde, adding to the likelihood of extinction. As a ground-nester, the species is highly at risk from the accidental introduction of predators. For all of these reasons, it is classified as Critically Endangered.
|Range Description:||Alauda razae is restricted to the very small (7 km2), arid, uninhabited island of Raso in the Cape Verde Islands, although evidence from sub-fossil bone deposits suggests that the species also occurred on Santa Luzia, São Vicente and Santo Antão prior to human colonisation in the 15th Century, after which extinction on these islands appears to have been rapid (Mateo et al. 2009). It is likely that the species also occurred on Branco, which formed a single island with São Vicente, Santa Luzia and Raso during the last glacial low 18,000 years BP. Suitable breeding habitat covers less than half the area of Raso. The lark's population is believed to fluctuate in response to climate and continues to do so. From the mid 1960s to the early 1980s, the population was estimated at only 20-50 pairs (Ratcliffe et al. 1999). In early 1985, however, a survey showed at least 150 birds to be present. Subsequent day visits resulted in the following estimates: 75-100 pairs in early 1986 and early 1988, c.250 birds in late 1988, c.200 birds in early 1989, c.250 birds in early 1990 and 1992. Complete censuses of the island in 1998 and 2003 found 92 and 98 birds respectively, restricted to the south and west of the islet (Ratcliffe et al. 1999, P. Donald in litt. 2003), but following rain in 2004 the population rapidly increased to 130 individuals in 2005 (Donald and Brooke 2006), 190 in November 2009 (M. Brooke in litt. 2008, 2010), and 1,490 in November 2011 (Brooke et al. 2012). When the population is low only a third of birds are female (P. Donald in litt. 2003, Donald and Brooke 2006).|
|Range Map:||Click here to open the map viewer and explore range.|
|Population:||The population was estimated at 1,490 individuals in November 2011 (Brooke et al. 2012), which equates roughly to 990 mature individuals. However, when the population is lower it can be strongly male-biased, meaning the effective population size is smaller than it first appears (M. Brooke in litt. 2008, 2010, Brooke et al. 2010), and the population is therefore placed in the band 250-999 mature individuals.|
|Habitat and Ecology:||It is found on level plains with volcanic soil and is associated with small vegetated patches along dry stream beds in which it feeds and breeds (Ratcliffe et al. 1999). There is significant difference in bill size between males and females, enabling the species to exploit limited food resources, with both sexes having relatively larger bills than congeners (Donald et al. 2003, Donald and Brooke 2006). A number of desert-dwelling larks have evolved long bills, apparently to aid digging for food in a sandy environment (Donald and Brooke 2006). Flocks have also been observed feeding among rocks close to the sea, and the birds (particularly males) excavate holes in sandy soil to extract the small bulbs of nutsedges Cyperus bulbosus or C. cadamosti (Donald and Brooke 2006). Breeding is erratic and governed by the slight and irregular rains (Hazevoet 1995, Donald et al. 2003). The population changes rapidly in response to rain; a prerequisite for breeding, (Ratcliffe et al. 1999, Donald et al. 2003, Donald and Brooke 2006) and has fallen to extremely low levels during droughts (Ratcliffe et al. 1999, Donald et al. 2003, Donald and Brooke 2006). At times the population has been strongly male-biased (P. Donald in litt. 2003, M. Brooke in litt. 2008, 2010, 2012). During the non-breeding season birds aggregate into flocks (Donald and Brooke 2006) and can be found in other parts of the island. Adult survival appears to be high and the species is thought to be relatively long-lived (Brooke et al. 2012). Breeding success is sometimes very low, due to high predation by the near-endemic gecko Tarentola gigas.|
|Major Threat(s):||Drought over successive breeding seasons reduces the population. Given the species's sensitivity to drought, long-term desertification in the Cape Verdes is clearly a major threat (Ratcliffe et al. 1999). In addition, nest predation (probably by a near-endemic gecko) is high in some years (Donald et al. 2003). Ground-nesting makes it extremely vulnerable to the potential accidental introduction of rats, cats and dogs brought to the island by fishers (C. J. Hazevoet in litt. 1995). The danger of such introductions (and the potential impact of non-native plant introductions) is now exacerbated by increased tourist activity in the Cape Verde Islands. Evidence of cats (Ratcliffe et al. 1999, Donald et al. 2003) and dogs (Donald et al. 2003) on the island was found during surveys in 1998 and 2001 but these populations did not appear to establish themselves and the island is currently mammal-free. Global climate change is likely to threaten this highly-restricted and precipitation-dependent species.|
Conservation Actions Underway
Raso Lark has been officially protected under Cape Verde law since 1955 (Donald et al. 2003), and in 1990 Raso was declared a national park (Hazevoet 1995). To date there has been limited enforcement of these laws on the ground (Hazevoet 1999a). Surveys have revealed the absence of cats on the island. Collecting of young and eggs has now been halted by the activity of a local NGO, Biosfera (M. Brooke in litt. 2008, 2010). Annual population monitoring has been carried out since 2001, and future research is planned to understand the conditions needed to enable successful breeding (M. Brooke in litt. 2008, 2010). The practicalities and desirability of a possible translocation project are being investigated (M. Brooke in litt. 2008, 2010). Conservation Actions Proposed
Conduct research into other potential nest predators. Investigate the suitability of Santa Luzia as a potential location for the establishment of a second population by conducting appropriate ecological research (Donald et al. 2003). Raise awareness amongst tourists and tour operators visiting Raso to ensure precautions are taken to avoid the accidental introduction of alien species and safeguard the fragile island ecology. Maintain good relations with fishers using the island and engage them in conservation activities. Continue regular monitoring of the population and the status of introduced predators. Prevent the establishment of non-native mammalian predators and plants on Raso.
|Citation:||BirdLife International 2012. Alauda razae. In: IUCN 2012. IUCN Red List of Threatened Species. Version 2012.2. <www.iucnredlist.org>. Downloaded on 19 May 2013.|
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