That was in Opawa, near Taupo in 1881. No possums then, less habitat destruction and probably fewer mammalian predators. Comparisons are useful to make if not totally reliable. These figures would suggest more than one kereru per acre, without counting those that survived the snaring. Translated to Tuateawa, with all things being equal, this would suggest a population into triple figures. Of course, it is very far from this level.
Kereru populations are in general decline in the N.I.. The major factors identified being, loss of habitat, competition for food with possums and mammalian predation. Within that last category hunting must be included. Kereru were given total protection in 1921. Some still continue to exercise customary rights, and for them, these remain an issue under The Treaty of Waitangi. In the absence of any solid data the exact population in Tuateawa is unclear. Anecdotally there is a suggestion of an increase from the lower levels of the past.
We are fortunate that in depth studies have been carried out in a number of other locations. Census information is also being collected in a coordinated and standardized way to provide baseline and continuing data. This will permit evaluation of the effectiveness of conservation tactics. There are some years when an entire kereru population will not attempt to breed. In areas where miro berries are a major food source a poor fruiting will have this effect. Kereru are totally vegan, no grubs for them. They are fruit eaters first, followed by flowers like kowhai and also new leaves. In years that they do breed there may be a total lack of success. Their reproductive potential is not great. Only one egg is produced per nest and nest predation of both egg and nestling is very significant. In a really good year though, they may nest three times. In circumstances of really good predator control 90% of fledglings will leave the nest. A Whirinaki study is of interest. The possible lifespan of Kereru is thought to be around 20 years. Published estimates of actual lifespan are around the five year mark. In Whirinaki they used radio monitoring of a number of birds. Lack of movement would suggest death and they would usually be able to find the body and determine the cause of death. Predation was a major factor, falcons, which we lack, were a minor factor in this predation and some were lost from hunting. The average life span however was less than two years. Not very long to produce the offspring to replace you.
Our pigeon is rather special when compared to those in Europe. It has an amazing display flight and the sound of it passing overhead is quite magical. What's more it doesn't cover buildings with excrement. It does it in much more ecologically significant places! Excepting a few iconic species like kowhai and pohutakawa, most of our trees produce seeds covered in succulent fresh. Many of our native birds are involved in transporting these to new locations. Foremost of these is the keruru. It consumes 70 different fruits, digests the flesh and deposits the seeds. The digestive process removes any inhibitory chemicals in the flesh and abrasions to the seed speeds up water intake. The seeds germinate more quickly and in greater quantity. There are five species that only the keruru is capable of eating. They are the very large seeds of miro, puriri, tawa, taraire and karaka. Most of these are major components of Tuateawa bush. Without these species regenerating bush will be very different in composition to our established bush. More bush means more birds, in fact more of just about everything. The kereru is a very pivotal species in this whole process.
The situation in Tuateawa looks very promising. From a very small population base there is an effective team of volunteers. Predator control is happening, as is monitoring of effectiveness. New initiatives are being used and Habitat Tuateawa has also been effective in securing significant funding for their continuing work. CONGRATULATIONS!!! How wonderful it would be to see kereru numbers approaching historical levels.
No comments:
Post a Comment