144 



BIRDS 



Philpott writes (1918): 



The song- thrush does not appear to penetrate far into the big forests, 

 nor to spread into unsettled areas. In the coastal forest of Fiord County 

 they are seldom to be heard, though plentiful enough about the settlements 

 of Tuatapere and Papatotara. Nor does the bird favour the mountains ; 

 I do not think I have ever heard one above the bush-line (about 3,000 feet). 

 They are certainly absent along the upper limit of the Titiroa Forest 

 (Hunter Mountains), and I have no record of meeting with them on the 

 Longwood tops or the Hump. 



The effects produced on the native and introduced vegetation of 

 New Zealand by the introduction of thrushes and blackbirds have 

 been very marked in at least one respect. The indigenous flora of 

 New Zealand contains an exceptionally high proportion of plants with 

 succulent fruit, amounting to approximately 16-55 P er cent. 



In Britain about 5 per cent., and in Australia 9 per cent, of 

 the whole flora have succulent fruits. The introduction of fruit- 

 eating birds such as thrushes and blackbirds, which in the case of 

 small fruits swallow them whole and so distribute the seeds, and in 

 the case of large ones like plums and apricots, carry them off to some 

 distance where they can pick off the flesh and leave the stone, has 

 led to a considerable increase in succulent-fruited plants. A con- 

 siderable proportion of the indigenous birds of New Zealand are 

 frugivorous, and it is their prevalence which, no doubt, accounts for 

 the abundance of indigenous succulent-fruited plants. But the advent 

 of the thrush and blackbird has increased this feature, though the 

 former does not penetrate far into undisturbed forest. For example, 

 in the Town Belt of Dunedin, a wooded area in which the vegetation 

 is protected from all grazing animals, there has been a marked increase 

 in the numbers of individual plants of Fuchsia, Coprosma, Melicytus, 

 Muhlenbeckia and other berry- and drupe-bearing genera. Along 

 with this, certain introduced plants, such as gooseberries, currants, 

 brambles, raspberries, cape fuchsia (Leycesterta), but above all the 

 elderberry (Sambucus) have spread through the native vegetation. The 

 last-named plant in particular threatens to crowd out everything else, 

 and a considerable sum of money is spent each year in eradicating it. 



In great parts of New Zealand, the Blackberry (Rubus fruticosus) 

 and the sweetbriar rose are most obnoxious pests, and thrushes and 

 blackbirds are to some extent responsible for their spread. This 

 question of the distribution of succulent-fruited plants by thrushes 

 and similar birds is of especial interest to naturalists in New Zealand, 

 and I have summarised a good deal of the evidence which Kerner 

 has given on the subject, especially that relating to plants which are 

 now found in these islands. Thus Kerner in Flowers and their Unbidden 



