|Avian Demography Unit
Department of Statistical Sciences
University of Cape Town
Terminology and concepts in the oiling of seabirds
We make the following distinctions.
Cleaning. This is what SANCCOB does. When a bird satisfies all the criteria for release from the rescue station, we say that it has been cleaned.
Rehabilitated. A cleaned bird is said to be rehabilitated if it makes the transition back to living in the wild, after the period in captivity during cleaning.
Restoration. A rehabilitated bird is restored to the population once it commences breeding.
The following six stages are critical to an understanding of the process that a seabird undergoes from oiling to restoration. At each stage death can occur. These stages form a chain, and the success of the rescue process depends very much on the link in the chain where performance is poorest.
(1) Oiled seabirds do not come ashore, but die at sea. For the African Penguin, this seems to be a rare event. All evidence points to most penguins coming to shore alive. It appears that they usually head for the nearest breeding colony, but many oiled birds also come ashore on the mainland. They usually do not return to sea, but remain on the shore, surviving on their fat and other reserves, until they eventually die. This behavioural trait of staying put works in the African Penguin's favour – essentially, they await rescue.
(2) Oiled seabirds die before being captured. Most of the penguin breeding islands are staffed, and there are few sections of shoreline in the Western Cape which are so isolated that no one visits them regularly. We believe that few oiled African Penguins die during this period.
(3) Oiled seabirds die during transport to the rescue centre or during the initial period of stabilization at the rescue centre. This was the weakest link in the chain during the Apollo Sea oil spill in 1994; 60% of all deaths of penguins during this incident took place during this short period. Significant advances in the design and management of the boxes used for transporting penguins have been implemented. Stabilization procedures have also been transformed beyond recognition. During the Cape Town Harbour spill of 1998 less than 2% of penguins died during this period; admittedly this was a "manageably-sized" event, involving less than 600 penguins.
(4) Penguins die during treatment at the rescue station. There are enormous risks in housing birds in captivity, especially in relation to the outbreak of disease epidemics. Oil spills involving large numbers of birds stretch capacity to the limits, and lead to overcrowded facilities.
(5) Penguins due shortly after release, and thus fail to be "rehabilitated". Experience in Europe and North America demonstrates this to one of the weak links of the chain there; some studies have shown that about half of the cleaned birds are dead within 10 days, and thus fail to be rehabilitated. With African Penguins, follow up of penguins flipper-banded after many spills indicates that failure to be rehabilitated is the exception to the rule. Preliminary studies indicate no significant difference between the survival rates of cleaned and "control" birds which have never been oiled.
(6) Rehabilitated penguins do not breed or have impaired breeding productivity, and thus fail to be "restored". For the African Penguin, extensive studies in which at least one of a pair was cleaned at SANCCOB after the Apollo Sea incident show, that if a bird breeds, productivity is either similar to that of "control" pairs breeding at the same time, or is slightly depressed. However, substantial numbers of Apollo Sea survivors are known to be alive, and have not been observed to breed, or were observed breeding for the first time several years after the incident. It is thus likely that failure to breed for several years after being oiled is one of the impacts of oiling. If a bird fails ever to be restored to the breeding population, it is competing for food with birds that do breed, and thus is conservation liability.
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Document posted on 27-June-2000