Recent annual sand inundations at Goukamma and Gericke's Point on the Cape south coast have smothered mussel beds, which is what oystercatchers target as their primary food source.

Listen to this article 7 min Listen to this article 7 min While walking along the beach near his home, Mark Dixon, a passionate citizen scientist from Sedgefield on the Western Cape Garden Route, counted 84 African black oystercatchers along a 7.5km strip of coastline in the Goukamma Marine Protected Area.

This was a striking contrast to the 12 birds he observed in a similar stretch at Sandbaai, near Hermanus. What explained this dramatic difference?

Speaking at the Plett Marine Science Symposium last month, Dixon shared his observations and research as a citizen scientist into the African black oystercatchers.

Dixon founded a volunteer citizen science organisation, the Strandloper Project, in 2018 - originally wanting to look at the negative impact of fishing and plastic on birds. Over five years, Dixon and his team have hiked nearly 1,000km of the southern Cape coastline, documenting 1,801 bird species, and has been able to observe what factors have an impact on the population densities of this species in the region.

For oystercatchers, which are endemic to southern Africa (found along the coastlines of South Africa and Namibia) and can live for more than 29 years, the citizen scientists found that oystercatcher...