In the peak of their breeding season, hundreds of Robben Island’s Cape Cormorants abandoned their chicks, leading to a high mortality incident impacting breeding outcomes and recruitment.
On 28th November 2025, during a routine patrol, SANCCOB’s Seabird Ranger discovered a heart-wrenching scene; hundreds of Cape Cormorant chicks abandoned, left vulnerable to predators, dehydration and starvation.
This was a stark reminder of a similar incident that occurred in 2021 when over 2,000 Cape Cormorant chicks were abandoned on Robben and Dassen Islands, believed to be caused by a combination of food shortages and extreme heat.
SANCCOB and Robben Island Museum’s Environmental Unit assessed the situation and, with the help of the Two Oceans Aquarium’s vessel, rescued 49 of the biggest and healthiest chicks, using a triage approach which was developed after the 2021 response.
Despite intensive care, 18 chicks in care have died. Post-mortem examinations of the deceased chicks revealed lesions and physiological changes consistent with advanced starvation. These findings closely resemble those recorded during the Cape Cormorant abandonment event in 2021. The carcasses exhibited extreme emaciation, with virtually no detectable fat reserves and markedly reduced muscle mass around the keel. The gastrointestinal tract was largely empty, with stomachs containing only small stones, pebbles, nematodes, or bile residues, all characteristic signs of prolonged food deprivation. Furthermore, the birds showed signs of anaemia, which may have been aggravated by malnutrition, parasitism, or a combination of both.
Overall, the available evidence indicates that all the chicks were in a critically poor nutritional state upon rescue. The combination of prolonged starvation, dehydration, systemic weakness and concurrent parasitic infections offers a comprehensive explanation for the mortality observed to date. It remains difficult to quantify the exact rate of weight loss or the timeframe leading to this condition in Cape Cormorant chicks; however, the chicks had been without adequate parental care for an extended period before rescue.
This mass abandonment event is the second to affect Endangered Cape Cormorants on Robben Island in the past five years. Combined with the post-mortem findings, the evidence points to inadequate food availability as the most likely cause. Like African Penguins, Cape Cormorants depend on healthy fish stocks, particularly sardine and anchovy but during the breeding season in this region, they rely heavily on anchovy. It is especially concerning that sardine abundance has remained well below the long-term average for the past five years and this year’s anchovy biomass is the second lowest on record since annual biomass surveys began in1984; leading to the lowest combined anchovy/sardine recruit biomass on record.
