A five-day bird-counting contest has thrown South Africa’s Cape gannet monitoring programme into sudden dispute, after the winning team recorded 52,180 breeding pairs at the Bird Island colony — 24,220 fewer than the 76,400 pairs in the latest official estimate. The Meridian Biodiversity Ratings Council, which assesses species at risk, has asked South African researchers to explain the gap before it decides whether to begin an accelerated status review.
The figures were announced on Sunday in Gqeberha, the Eastern Cape port city nearest the island, at the finish of the annual Count the Coast challenge. The panel’s Monday request turns a friendly competition between 11 research teams into a high-stakes test of how the country counts one of its most recognisable seabirds.
A contest becomes a warning
Teams counted visible breeding pairs from fixed observation points, using synchronised photographs and binocular surveys rather than disturbing the nesting birds. Judges compared the entries for consistency across the five-day window. The winning team, led by field ecologist Elčins Lībietis, submitted its tally after reconciling counts from three sections of the colony.
“We expected differences between teams, not a gap this large against the number used in the national trend,” Lībietis said. He called the contest result a “signal to check the counting rules before anyone treats it as a final population estimate”. The older figure was assembled from separate survey periods, a possible source of some of the discrepancy, he said.
A count is not a verdict, but this one is too large to file away as noise.
Gudrun Thiel, marine ecologist
Thiel, who advised the contest’s judging team, said Cape gannets have faced sustained pressure from changes in the supply and location of small fish. The latest contest does not establish how many birds have died or vanished: it measures occupied breeding sites during a limited period. But if the lower total holds up, it would mean the long-running population decline has been underestimated.
Status review on the table
The Meridian council said it had requested the survey protocols, the dates behind the official estimate and a comparison of how both teams defined an active breeding pair. Its scientific chair, Philipp Hildebrandt, said the panel could open a review within two weeks. A move to a more severe risk category would require evidence that the lower count reflects a lasting change, not a short-term shift in nesting.
South African monitoring officials have until 2 November to send their explanation. They say the contest’s result cannot be compared directly with the official figure until researchers account for survey timing and colony coverage. The council’s request echoes a familiar dispute in financial markets, where index providers ask for clarification before deciding whether a country or company deserves a lower rating.
The contest organisers said they would publish the teams’ methods and anonymised count sheets next week. Lībietis’s team has been invited to join a verification survey planned for November, when researchers will repeat the count using the same boundaries and timing. The panel says it will publish its decision by 15 December.
