Post-release monitoring of rehabilitated and released seabirds
SANCCOB admits over 2000 seabirds at its two seabird hospitals annually and is proud of its remarkable release rates of 75-85% of all African penguins released back into the wild. For most other seabird species, SANCCOB achieves a >50% release rate, which is because many flying seabirds can only be captured once they are severely injured or emaciated, or immobile and their rehabilitation is much more difficult compared to African penguins.
SANCCOB’s work is only successful in terms of conservation if rehabilitated and released birds join the wild population to breed in the wild. SANCCOB conducts several post-release monitoring programmes, jointly with our partners, the managing authorities and organisations such as SAFRING.
African penguins released from SANCCOB are inserted with subcutaneous Passive Integrated Transponders (PIT) and are monitored using remote ground readers and hand-held readers at all major seabird breeding colonies. Initial analyses have confirmed that SANCCOB’s released African penguins’ survival and breeding in the wild compare similarly as penguins in the wild that have not undergone rehabilitation. Thus, our efforts to support the conservation of the African penguins through hand-rearing of chicks and the rehabilitation of oiled, injured and emaciated adults is a worthwhile endeavour.
Post-release monitoring for other seabird species is more complicated as flying birds are not as easily detected when returning to colonies; they are often easily disturbed by human presence and often breed in large numbers, thus trying to find a marked seabird among hundreds of wild birds can be difficult. All flying seabirds released from SANCCOB are ringed with metal rings, issued by SAFRING, who also compile all resighting data. To facilitate easier resightings (as metal rings can often only be read when one has the bird in hand), in recent years, several species have been equipped with larger colour rings prior to being released from SANCCOB. Our current post-release monitoring focusses on gull and tern species including Kelp gulls, Hartlaub’s gulls and Swift terns; SANCCOB frequently admits these species from urban areas where seabirds breed on roof tops, causing human-wildlife conflict. It is therefore important to understand if the rescue of these birds, their rehabilitation and return into the wild is a successful conservation intervention or what preventative measures could be implemented to minimise the threats to these species when breeding in urban environments. Post-release monitoring has demonstrated that Swift tern chicks are not easily released back into the wild after rehabilitation as they rely on their parents to provide food for several months, even after the young has left the nests. Therefore, the removal of tern chicks is not a desired conservation intervention, due to the species’ extended post-fledgling care.
The mass abandonment of Cape cormorant chicks that occurred in January 2021 resulted in over 1,200 Cape cormorant fledglings released back into the wild after being hand-reared at SANCCOB. To assess the success of this intervention, all released birds were fitted with metal bands and over 700 cormorants were fitted with colour rings. Reported resightings of colour ringed Cape cormorants confirms that these birds integrated with the wild population however the analysis of how many birds successfully recruited into the wild breeding population will only become apparent in coming years when these individuals start to breed.
SANCCOB relies on the public to report any ringed seabirds to SAFRING. If you find a live seabird or a seabird carcass on the beach, please check for identification rings and report the full number (including letters) to SAFRING. If you spot a colour ringed bird in the wild, report the colour of the ring and the letter/number combination to SAFRING or SANCCOB.
African penguin Passive Integrated Transponder (PIT) Project
Marking of birds is performed to assess long-term survival and seabirds’ movements between different colonies. Marking enables identification of seabirds at the nest site, which assists with breeding success studies. African penguins were historically marked with metal flipper bands, after the Treasure oil spill in 2000, over 17,000 de-oiled African penguins were marked with flipper bands and much of what we know today about the species survival and movements is based on resighting data. For SANCCOB, it is very important to be able to “follow” seabirds that have undergone rehabilitation or hand reared as eggs/chicks to assess the effectiveness of the artificial hand rearing and rehabilitation processes.
Unfortunately, the use of metal flipper bands was shown to have negative effects in other penguin species and the use of these bands was discontinued in South Africa in the early 2000s. Several other methods were trialled, such as silicone flipper bands and individual’s spot pattern recognition. The use of Passive Integrated Transponders (PIT, also called RFID) was selected as the most effective method of marking African penguins. These subcutaneous transponders or microchips are the same as those used in domestic dogs and cats and are inserted under the penguin’s skin. These transponders carry a unique sequence of numbers which provide opportunities to re-encounter marked individuals when coming ashore at seabird colonies as the PIT can be read either using hand-held readers or ground readers which are installed at entry points to the colonies.
Since 2013, more than 10,000 African penguins have been marked with PIT, both in wild colonies and as released seabirds from rehabilitation centres in South Africa. All African penguins released from SANCCOB, including hand-reared chicks and other seabirds that were rehabilitated due to injuries, oiling or emaciation, are marked with transponders in addition to fledglings and breeding adults in the wild seabird colonies. SANCCOB Penguin & Seabird Rangers along with conservation authorities’ staff are equipped with hand-held readers and encounter marked birds on a weekly basis during their nest check monitoring, thus also obtaining valuable information on the breeding status of these individuals.
Due to the generous funding from the American Zoos & Aquariums (AZA) SAFE programme, 11 ground readers have been installed in 6 of the main seabird breeding colonies in South Africa. These remote readers are placed along main pathways into the colonies and marked penguins walk over a long cable antenna when leaving the colony to go to sea and when returning to attend to their eggs and chicks in the colony. The data from these readers is regularly downloaded and has provided an interesting insight into the penguins’ behaviour. The detection of marked birds allows us to assess their survival probability using mark-recapture models. It is possible to compare the survival probability of wild penguins, both chicks and adults, to those rehabilitated and hand reared at SANCCOB. Initial analyses have shown that the chicks hand reared at SANCCOB have the same chance of survival during their few first years at sea compared to chicks raised by their parents in the wild. This finding is crucial for SANCCOB as it shows that the Chick Bolstering Project contributes to the bolstering of the wild population and that this conservation intervention plays a significant role in conserving this endangered species. Despite a slightly reduced survival probability in rehabilitated adults compared to breeding adults in the wild, the calculated rates are still within the range of what is observed in wild colonies. Adult African penguins rehabilitated at SANCCOB have often endured severe injuries, pollution or malnutrition and undergone extensive rehabilitation. Therefore, a slightly lower survival rate is expected, however initial studies confirm that the release of these penguins back into the wild also plays an important role in saving this species from extinction.
Marked birds can tell us a lot more than just their survival rates. We are now discovering that they penguins visit several colonies before eventually deciding on where to breed. The transponder data has also revealed that many penguins chose a different colony to breed that was different to where they hatched and fledged. This is most likely linked to breeding sites with good food availability rather than returning to their natal colony.
To obtain further data on body condition, ground readers at Stony Point colony in Betty’s Bay and St Croix Island in Algoa Bay have been linked to a weighbridge in a joint project with BirdLife South Africa. Through this African Penguin Monitoring System (APMS), we can monitor how long penguins stay at sea foraging and how much food their bring back to their chicks as the penguins walk over the weighbridge as they exit the colony and, on their return, thus getting an idea of the food availability around the breeding colony. Data from GPS tracking studies have shown how far penguins travel in a certain amount of time when foraging, assessing important foraging areas. This information is used to inform government on an adaptive management framework, and in particular, an ecosystem approach to fisheries.
SANCCOB is actively involved in several tracking studies in collaboration with BirdLife South Africa and other partners, such as Nelson Mandela University, South Africa and University of Exeter, UK. By deploying seabirds with miniature GPS loggers during the breeding season, valuable information is obtained on the areas they use for foraging, especially when provisioning food to their chicks at the nest sites. Tracking studies led by SANCCOB’s Research Manager, Dr Katta Ludynia, during her PhD in Namibia have assisted in designing and implementing Namibia’s first Marine Protected Area around the main seabird breeding colonies.
In South Africa, tracking studies have been instrumental to demonstrate the overlap of seabird foraging areas with commercial fisheries for sardine and anchovy, the main prey of endangered African penguins, Cape gannets and Cape cormorants. BirdLife South Africa has mapped Marine Important Bird and Biodiversity Areas (marine IBA’s) using over 10 years of tracking data for the African penguin. SANCCOB, BirdLife South Africa and WWF South Africa is advocating for closing these areas to pelagic fishing.
SANCCOB has also been involved in tracking juvenile African penguins on their first trip at sea after fledging. This study, conducted by Dr Richard Sherley from University of Exeter, UK, showed that SANCCOB’s hand-reared chicks fared as well as their wild counterparts, travelling long distances once they have fledged or been released. Unfortunately, young African penguins travel into areas that historically had a high food availability but are now depleted, thus falling into an ecological trap. Many seabirds do not survive the first year at sea failing to eventually recruit into the breeding population. Further studies are currently looking at important areas for penguins during the non-breeding and pre-breeding periods as well as at other seabird species like Cape gannets and Cape cormorants. These studies are led by BirdLife South Africa and the University of Exeter; SANCCOB provides support and works closely with these organisations to improve our knowledge on important bird areas requiring better protection.