Surveillance Vol.15 No.2 1988

in 1980 to 35 in 1985. No major may have occurred, making even losses were recorded during this time, histological interpretations difficult. and although in 1982 avian pox virus There are no freezer facilities on infections appeared to be prevalent the island which can be used to pre- among and prions on South serve fresh samples for microbio- black East Island, only one robin nestling logical examination. 0 The conservation officers on the robin-disease island were issued with instructions for taking samples, detailed speci- su rveiI la nce men submission forms, and a sam- pling kit but, having had no formal training in pathology, they could Over the past 18 months the Central miss some significant gross patho- Health Laboratory (CAHL), logical lesions. Wallaceville. has been assisting Don Under these conditions any diagno- Merton of the Department of Conser- sis is based heavily on the history and vation to identify the causes of death in to a lesser extent on histopathology. black robins on South East Island. This programme has highlighted the di’- culties in obtaining diagnostic samples ,from remote and isolated geographical ureas. Summary of results The successful management pro- To date we have recieved samples gramme that brought the black robin Fig. I: Chatham Islands black robin. from 15 dead black robins (two adults, population back from the edge of two fledglings, and 11 chicks), three extinction is well known and exten- Chatham Islands , three dun- sively re~orded,’.~.~,~but it is far from with diseased tit foster parents died nocks, one Chatham Island warbler. complete. For although the black rob- with pox lesions. During the 1985/86 and one starling. The pathology in the ins on South East Island and Mangere breeding season a high mortality rate tissues of black robins submitted at Island now number 58 birds (eight occurred in nestlings, fledglings, and the beginning of the programme was breeding pairs) and 12 birds (five adults, effecting a decline to 25 birds difficult to interpret because of inade- breeding pairs) respectively, the popu- by February. These losses were attrib- quate preservation. Likewise, in a lation is still small, and vulnerable to uted to disruption in food supplies, number of birds the tissues had under- many adverse enviromental influ- caused by severe winter storms, and gone extensive autolysis before being ences, such as food shortages, habitat also to avian pox virus infections. formalised. The results could be classi- destruction, and disease. This situa- During February 1986 pox lesions fied into four groups: tion will persist until self-maintaining were seen on two robin fledglings and populations of the robin are located at three adults. The two young birds died Traumatic injury with no histologi- several different sites. within 2 weeks of the appearance of cal evidence of disease: This was a A management programme that has the lesions. Samples from the superfi- common finding, and in some cases the objective of increasing num- cial leg lesions of one of the fledglings the injuries appeared to be a result bers must take into account mortality were sent to CAHL and pox virus sub- of either attack from or collision rate and aim at keeping this to a mini- sequently isolated and identified, sug- with other birds (e.g. petrels at mum. To do this, the various causes of gesting that the pox virus infection night). A number of black robin death have to be identified. While may have contributed to the fledg- nestlings had broken legs which many causes of mortality are unavoid- lings’ death. were thought to have resulted from able, for example aging and accidents. In 1986 it was decided to set up a excessive handling. These chicks others, such as faulty management or sampling programme that would allow were also heavily infested with some diseases are controllable. us to monitor more effectively the mites and had been treated with cause of disease and death in the black “Dri-die” powder. Background robin population, and also in species KO signfieant gross or microscopic of birds closely associated with them. lesions: The death of these birds During the breeding programme the had to be assessed from the histov, robin population grew from five birds Disease surveillance programme and as only black robin nestlings and problems were involved in this category a likely cause was starvation/expo- The black robin conservation pro- sure or smothering. gramme usually involves only a small party in the field for 4 months of the Gross and histological evidence yf year during spring and summer, so disease: Four black robin chicks that disease and mortality occurring that were suspected of dying of outside this period cannot be exposure were found to have exten- appraised. In addition, it was appar- sive inflammatory lesions associ- ent that there were to be many ated with fungal hyphae in a problems associated with obtaining number of organs. Because no fresh adequate sanples for disease samples could be taken, identifica- diagnosis: tion of the agent was not possible. Avian pox virus lesions were found 0 South East Island is a remote place, externally on three dunnocks and a located 44”sin the path of the roar- Chatham Islands warbler-there ing forties. The only form of trans- were no internal lesions. port to and from the island is by fishing boat, which is infrequent Advanced autolysis, inadequate pre- and dependent on favourable servation: The death of the bird was weather conditions. assessed on the history, and fortu- 0 Very few birds that die are ever nately in most cases this appeared found. When they are, there is often to be the result of traumatic injurq. a long delay between the death of Inadequate preservation or exten- the bird and its discovery. In that sive autolysis made histopathologi- time a certain amount of autolysis cal interpretation difficult.

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Conclusions One of the main purposes of this disease surveillance programme was to identify causes of mortality that could be eliminated by minor changes in management or use of treatment or control methods. It was soon apparent that achieving this aim was going to be difficult in a situation where there were serious problems with sample collection, preservation, and transportation. Initially the only effective way of obtaining specimens was fixing them in formalin, and obviously a precise determination of the cause of death of individuals, on the basis of history and pathology, would in many cases be impossible. As was expected a number of deaths were due to old age, accident, and other uncontrollable factors. The fact that this population is already subject to a high degree of human interference makes it likely that some management procedures may at times cause mortal- ity. It is, for instance, possible that the fungal infection that killed four chicks may have originated from an imported artificial diet, or perhaps from a contaminated nest box enviroment. In future breeding seasons we hope to increase our diagnostic capability by employing liquid nitrogen as a transport medium. With modern con- tainers, liquid nitrogen can be kept for many weeks without replenishment. This will allow fresh specimens to be frozen and transported fresh to the laboratory for microbiological examination.

References 1 Flack, D J A, 1975: The Chatham Islands ' black robin, extinction or survival? XII Bulk- tin International Council of Bird Preservation. 2 Merton, D, 198 1: Black robin capable of full recovery. Forest and Bird, 9: 6-7. 3 Merton, D, 1984: Chatham Islands black robin. yildlife-a review, No. 12: 42-46. 4 Munn, A, 1984: The black robin-back from the brink of extinction. ICBP Newsletter, 6(3): 1-2.

D J Tisdaii, MAFQual Central Animal Health Laboratory Upper Hurt

D Merton Conservation Officer () Department of Conservation Wellington

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