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Introduction.
The Little Owl, Athene noctua, or, as it is often called in this country, the German Owl, was introduced by the Otago Acclimatisation Society some 36 years ago, in an endeavour to control the numbers of the small introduced birds. According to Thompson, 28 owls were imported from Germany in 1906. Further liberations followed—39 in 1907, 80 in 1908 and 72 in 1910. Owls are also reported to have been liberated in North Canterbury, and in 1911, 66 were obtained by the Waimate County Council, at a cost of £50. A pair was also liberated in the North Island at Rotorua, about the same time, but does not appear to have become established. The bird soon began to increase and spread in the South Island, and before long was accused of being a serious menace to the native birds. At the present time, these accusations are widespread, and rewards are offered for the destruction of the owls.
This history is closely parallel to that in England. The owl, though widespread in the Palearctic region, had only been recorded as a rare straggler in the British Isles. It was introduced into England towards the end of last century, and is at present widespread in England and Wales, except in the north. It is now, if not actually decreasing, probably increasing much less rapidly than formerly. Soon after its introduction, it was accused of killing song-birds and the chicks of game and poultry. It was consequently selected by the British Trust for Ornithology for special study, and a long and detailed report on the investigation by Miss Hibbert Ware appeared in 1938. The result of this investigation was to show that only negligible destruction of game, poultry and wild birds took place, and that the owl fed almost wholly on such insects, other invertebrates and small mammals as can readily be picked up on the ground. The sweeping accusations were shown to be without foundation, though it is pointed out that the feeding habits may have been somewhat different when the numbers were increasing rapidly than at the time of the investigation, when the rate of increase was less. However, a previous investigation of the food, carried out by Collinge in 1918, gave the same results. The bird is regarded as beneficial on the continent of Europe, and is protected in some countries.
When the owl was brought to New Zealand, it was placed in a different environment, and changes, especially in its feeding habits,
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might be expected to have taken place. It was therefore decided to study the bird and its feeding habits, taking advantage of the fact that as it was being killed a large number might be obtained, and also that the report of the English investigation was available for comparison. It is not intended to enter into the controversy as to the habits and value of the owl in this country, which has been carried on without any adequate basis of fact. It has been suggested that the present investigation is an attempt to prove that the owl does not eat native birds. No such object is intended, the whole investigation is concerned solely with the accumulation of as many facts as possible concerning the owl and its food, from an examination of the actual birds and of their nesting places and castings. These facts may prove the basis for future discussion. On the other hand, many of the statements which are frequently made about the degree to which the owl destroys other birds, show a remarkable lack of reasoning power or appreciation of the value of evidence. For instance, when it is stated that, as the owl increased, the native birds decreased, it is apparently not realised that these changes, which would need actual numerical data to substantiate them, may be wholly unrelated. Similarly, when it is stated that the screams of birds being murdered by the owls are frequently heard, there is no evidence that the birds really are being murdered, and if so, by whom. A great deal of the so-called “evidence” is of this type. Statements of this kind have been excluded from the present paper, only those giving definite statements of fact being included.
Many of the statements bear so close a relation to ones which remain wholly unsubstantiated in England, that they appear to originate in the English press. It is perhaps worth mentioning some points which were studied in England. The owl is chiefly a twilight and night feeder, and does not habitually feed by day as is often supposed, though it does so occasionally. It is a ground feeder, as is shown by its food. The so-called “larders” are not used for storing excess food, but are more in the nature of “carving holes.” Very little evidence of nest raiding has been recorded, and no eggs of other birds have been found in the owl's nests or food. There is no evidence that the owl kills prey and leaves the body to attract beetles which the owl will return and eat later on. These conclusions were reached in England and, though it is of course possible that the owl changed its habits as it became adapted to life in New Zealand, this has not yet been demonstrated. Any reliable information about its habits here would be valuable and should be collected.
Finally, it should be pointed out that arguments as to the economic value or otherwise of the owl are worthless, as none of the requisite data is available. To determine whether the owl is beneficial or not, it would be necessary to know, not only the number of owls present and their food, but also the numbers, food and interrelations of almost all the other animals in the district, as well as the effect of fluctuating conditions of season, climate, etc.
I wish to record my indebtedness to the Royal Society of New Zealand for a grant from the Hutton Fund to defray the cost of
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the investigation; to Dr Miller, of the Cawthron Institute, for identifying insects; to Mr Ferguson, of the University of Otago, for assistance with statistical matters, and to all those who assisted by sending in material or information during the course of the investigation.