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Critically endangered lark rebounds after successful reintroduction

Until recently, the entire world population of Raso Lark Alauda razae was confined to Raso Island, a small volcanic island in the Barlavento Archipelago of Cabo Verde. On the island, this small passerine bird only had 4 km2 of suitable breeding area. Rain is very important to this bird: it depends on the rain to get enough food for the brood. During periods of drought that lasted for several years, the Raso Lark population declined dramatically and touched the limits of extinction. In contrast, when the population was at its ceiling, the island appeared to be almost flooded.

For the past 17 years, the Raso lark population has fluctuated between 1550 and only 60 birds. Urgent action was needed on this critically endangered species, and in 2018 a team consisted of Biosfera (NGO Cabo Verdean), SPEA (Portuguese Society for Bird Research, BirdLife partners) and DNA (Cabo Verde Environment Agency) with the support of The Raso Lark- Expert Dr. Mike Brooke decided to relocate (in other words “move”) some birds to the neighboring larger island of Santa Luzia in order to restore a new population of the species there.

Santa Luzia, an uninhabited island in Cabo Verde, was chosen as the site because of its proximity to Raso Island, the presence of similar habitats, and the subfossil evidence that confirmed the species’ presence in the past.

After colonization attempts were stopped centuries ago, threats to the Raso Lark, such as human activity and the trampling of cattle, disappeared. However, the presence of invasive alien species – feral cats and mice – still posed a major threat that prevented a successful translocation (or, in this case, late reintroduction). As a ground nest, the raso lark is at high risk from invasive predators.

The groundbreaking reintroduction took place in April 2018 and a total of 37 birds, 25 males and 12 females were moved to two different locations previously identified in Santa Luzia. All translocated birds were colored rings and monitored monthly to determine variations in fluctuations and to review how they have adapted to their new environment. At the end of August 2018 it was discovered that a recently grown bird was being fed, which confirms the very first Raso Lark breed on Santa Luzia!

Later that year, the team recorded independent movements of other larks crossing from Raso to Santa Luzia, as well as others returning to the Raso population source. Confirmation for the first time that the species was traveling between islands. Several other unmarked birds have been spotted in Santa Luzia that may either be from Raso or other locally born juveniles.

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By March 2019, the number of Raso larks on Santa Luzia was around 20: five after the original relocation, two more women with colored rings who had flown from Raso to Santa Luzia, and twelve unmarked birds. This last group included birds raised on Santa Luzia and possibly other birds without a ring that had flown from Raso to Santa Luzia. Although the population of Santa Luzia seemed well-established, the team decided to move 33 more birds (19 men and 14 women) from Raso to Santa Luzia in order to strengthen the population and increase the chances of success.

After a very dry rainy season in 2019, we only found a single nest with a chick in Santa Luzia. This confirmed reproduction on the island, but at a very slow pace. By the end of the year, the Raso Lark population in Santa Luzia was estimated at around 40 birds. At that time there were still some wild cats on the island, albeit in much fewer numbers than in the previous year.

Check in at the Raso Larks in 2020

The first preliminary population assessment in February 2020 was worrying: Signs of wild cats were numerous in the main area where the larks were raised and fed, and not many birds were seen. Because of the travel restrictions associated with the COVID-19 pandemic, monitoring was then suspended for more than six months.

However, it turns out that 2020 has some advantages too. In October 2020 the team received amazing news: seven breeding pairs with 17 young animals were discovered on Santa Luzia! Cabo Verde finally had a good rainy season which resulted in an increase in the food resources of the Raso Lark. And at the beginning of November they found a second location: In the northern area, four nests with seven chicks were found, all near their old nest. These results confirm the success of the translocation and give hope for a bright future for the Raso Lark, which is now officially an island species again.

Dealing with Invasive Species

The project’s invasive species management efforts appear to be producing results. The team has not registered any signs of wild cats since August. The population density of the mice is also very low, which contributes to a successful breeding season for several native species:

  • The bar-tailed Lark Ammomanes camera has now spread across the island, unlike the few pairs that were appreciated at the start of the project.

  • Species like the cream colored Courser Cursorius cursor or the Common Quail Coturnix coturnix are more frequently sighted;

  • Terrestrial reptile populations (geckos and skinks) are increasing and many juveniles are regularly observed across the island.

  • For the first time, not a single newly hatched turtle was attacked by cats.

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Support that saves the Raso Lark

Thanks to the MAVA Foundation, the Critical Ecosystem Partnership Fund (CEPF), the RSPB (BirdLife in the UK) and Sea Shepherd. Find out more here.

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