Status of Raso Lark Alauda razae in 2003, with further notes on sex ratio, behaviour and conservation

Abstract

The global population of the Critically Endangered Raso Lark Alauda razae was estimated in January 2003 at 93–103 birds and in November 2003 at 76–87 birds. Of these, only 25–35% were females. Counts were based on observations of individually colour-ringed and measured birds. Birds were not breeding during the January visit, and were concentrated in two small areas at opposite ends of the island of Raso. This distribution differed substantially from that recorded previously during the breeding season. Three different feeding strategies were apparent: flocking, aggregating around key resources and feeding singly or in pairs. Birds moving to new feeding areas immediately adopted the feeding strategy of other birds present. Birds were seen drinking seawater on several occasions. In November 2003, birds were breeding but nest survival was extremely low due to high rates of egg predation. No evidence was detected of introduced predators on Raso. However, a population of feral cats was found on nearby Santa Luzia, prohibiting natural colonization or deliberate introduction of Raso Lark to the island, despite much apparently suitable habitat there. Faecal analyses showed that these cats feed largely on skinks. Increased tourism development on neighbouring islands is identified as a potential threat to the species.