Haematopus moquini has gone from “Near Threatened” to “Least Concern” on the Red Data List
South Africa (16 April 2024) — Conservation success tales are sometimes eclipsed by harrowing accounts of organic catastrophe and environmental tragedy – however one southern African hen species is offering a contented exception, to the delight of organic scientists and the conservation neighborhood.
This is the hanging African Oystercatcher, an iconic coastal hen whose shiny black plumage, shiny orange-red eye-ring and dagger-like invoice make it immediately recognisable within the slender inter-tidal zones of South Africa and Namibia the place it lives.
Bucking a staggering downward pattern in hen numbers globally, the good-looking oystercatcher has recorded a considerable inhabitants progress over the previous many years – a lot in order that its IUCN (World Conservation Union) Red Data List standing has been downgraded from Near Threatened to Least Concern.
This improve is confirmed at a key breeding web site on Robben Island, the place the outstanding success story of Haematopus moquini (named by Napoleon Bonaparte’s nephew Charles in 1856) is being intently documented by researchers, assisted by passionate volunteer citizen scientists in a research operating since 2001.
The mission – began as a joint initiative of UCT and the Robben Island Museum heritage unit – now falls underneath the Rondebosch-based Biodiversity and Development Institute (BDI). The BDI is an unbiased, non-profit firm staffed by lecturers and designed to foster analysis and neighborhood motion within the fields of biodiversity conservation and social improvement.
BDI founder and director Professor Les Underhill, a retired professor of statistics at UCT, is a life-long, extremely adorned birder with a specific curiosity in coastal and wading birds, hen ringing, and selling citizen science in biology whereas fixing environmental issues.
In the early Nineteen Eighties, the general African Oystercatcher inhabitants had plummeted to solely about 4,800 grownup birds, largely due to human interference in its very slender coastal breeding habitat. The scenario remained dire into the Nineteen Nineties.
Researchers discovered that within the 1996/7 season, for instance, breeding success on this species’ key West Coast vary was solely about 15% of what was wanted to keep up a steady inhabitants. On 60km of its Eastern Cape coastal habitat – an roughly 40-metre large strip across the high-water mark – they discovered no proof of profitable breeding in any respect.
But a multi-disciplinary, nationwide oystercatcher conservation programme was initiated in 1998, and it quickly achieved success.
One of the principle causes for the species’ sharp inhabitants restoration was the 1979 native look after which speedy unfold of the alien Mediterranean black mussel. Since the invasion, these mussels represent greater than 90% of the oystercatchers’ weight-reduction plan.
A second key issue was the nationwide ban on seashore driving, launched in December 2001.
A 3rd issue was simpler conservation administration on the breeding islands.
Underhill was in a position to report that the oystercatcher inhabitants was estimated at 6,670 birds within the early 2000s – a rise of 46% for the reason that early Nineteen Eighties – and was persevering with to rise. Also, its breeding vary had prolonged northwards alongside the KZN shoreline.
On predator-free islands, oystercatcher pairs now efficiently elevate on common one chick each two to a few years – nowhere close to as fecund as many different hen species, however however ample to keep up these island populations and to supply some “surplus” birds.
African Oystercatchers mate for all times and don’t migrate, being strongly territorial and counting on native shellfish provides year-round. Some surplus birds not in a position to obtain a territory of their very own depart the island and head for the mainland, however breeding success right here is restricted.
Robben Island, simply lower than 10km in circumference, holds some 8% of the worldwide African Oystercatcher inhabitants, making it a vital breeding web site.
In 2001, Underhill and his BDI colleagues initiated a long-term research of the species right here, assisted by volunteers. Since then, the island’s oystercatcher inhabitants has elevated four-fold and the variety of nests has almost doubled.
The major causes for this big improve was the elimination of feral cats, which have been predating greater than 80% of oystercatcher nests, in addition to the elimination of European rabbits and the sharply elevated provide of alien black mussels.
The researchers’ report depend got here within the 2019/20 breeding season (November to March). During monitoring of oystercatcher breeding efforts each six days, they counted 550 birds and recorded 158 nesting makes an attempt, thought to have been made by 133 nesting pairs. (Oystercatchers can lay a second time in a season if the primary clutch is misplaced.) An additional 300 or so non-breeding oystercatchers have been additionally current.
Of the 158 clutches, 47% produced a number of hatchlings, and of a complete of 288 eggs laid, 38% hatched.
In 2021/22, whole of 176 nests have been discovered on the island – an extra 11% improve.
Although full statistics are nonetheless being gathered for this present 2023/24 breeding season that’s now drawing to an in depth, some 450 grownup birds and between 15 and 20 juveniles have been recorded through the two most recent weekly counts, in addition to 130 to 140 nests.
“But a lot of those nests are actually re-nesting attempts after the eggs were washed away or predated, and then the adults tried again in the same spot,” explains present mission co-ordinator postgraduate scholar Karis Daniel.
While oystercatcher chicks depart the nest inside about 24 hours after hatching (they begin to fly at about 40 days), they’re nonetheless fed by their dad and mom for about 100 days whereas their payments develop robust sufficient to prize shellfish off the rocks for themselves.
“So it’s quite good to have this many juveniles this early in the breeding season,” says Daniel.
Although this season’s numbers seem like barely down from the pre-Covid peak, this isn’t essentially trigger for concern, she provides.
“It could just be natural fluctuation as part of a long-term pattern. We have to look at it in the context of all the other years, and the population on Robben Island does seem to be doing well.”
Underhill confirms that African Oystercatchers have carried out properly in recent many years, however he’s involved about what he phrases “their crazy vulnerability”.
“They breed about a metre from the spring high tide level, and nests have to survive two spring tides before they hatch. So a single storm surge event in the breeding season can wipe out all nests with eggs from Saldanha Bay all the way to Cape Agulhas,” he explains.
And if these occasions improve in frequency because of local weather change, as is predicted, the oystercatchers “may once again be in trouble”, he warns.
Sources: Groundup
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