Ecology of the birds of Kaingaroa Forest
- Animal Ecology Division, Department of Scientific and Industrial Research, Lower Hutt
In common with other pine forests consisting of large blocks of even-aged trees usually of a single species (Voute 1946). Kaingaroa Forest is vulnerable to outbreaks of insect pests. With their low reproductive potential, birds cannot cope with plagues of insects once they have broken out; but at the more prevalent endemic levels of their prey they can eat a significant fraction of their food stocks (Gibb 1958, 1960; Tinbergen 1960), and under certain circumstances their predation can dampen down oscillations in insect numbers which might otherwise develop into serious outbreaks (Tinbergen & Klomp 1960).
It is therefore prudent to know what insectivorous birds live in such forests as Kaingaroa, and to know something of their feeding habits and population ecology. In the natural ranges of the exotic conifers planted in Kaingaroa there are species of birds that have evolved in such forests. As this is not so in New Zealand where the trees lack their natural fauna, it is also intriguing to see which native and introduced birds have managed to colonise them.
The present paper describes the birds' density more precisely than has been done hitherto, and includes a quantitative description of the feeding habits of the four commonest insectivores—pied tit, whitehead, grey warbler and white-eye. It also reports the use of nest-boxes by pied tits. I am indebted to Dr. K. Wodzicki, Director, and Mr. P. C. Bull, Animal Ecology Division, D.S.I.R., for constructive criticism of this paper.