Since 2004, there is an increasing number of reports on deaths 'in the wild' of Topknot Pigeon (Lopholaimus antarcticus) and other 'wild' Pigeon species, being received by the Camphor laurel Research Centre in Lismore, NSW. Also, from many districts, Torresian Crow (Corvus orru) is reported to have become both 'more aggressive', and bred-up into large populations since it was first observed commencing to consume Camphor laurel fruit in the mid-1990s. It is believed that the high population levels of Crow across the entire region has a bearing on the population levels of lesser-sized native bird species, especially the small/er native birds - most of which have been reported in the media as being almost non-existent in many districts.
Topknot Pigeons; instances involving multiple-death events have been repeatedly observed on and near roadsides, in both Lismore and Kyogle Shire, but always being found dead directly underneath the canopies of ripe-fruiting Camphor laurel trees; in one case, only Camphor laurel berries were found in the stomach and crop upon dissection. Some birds retained distinctly purple-stained beaks. These are the first records of this, the largest of all native rainforest pigeon species succumbing to the toxins contained in the berries and seeds of Camphor laurel. Other reports, by notable bush regenerators, and seed collectors (Phil Murray, Firewheel Nursery, Dorroughby and Lismore) centre on the occasional apparent 'drunkenness' caused to many species of native pigeons, after gorging themselves on (excess volumes) of ripe or over-ripe Camphor laurel berries.
Wonga Wonga Pigeons have been repeatedly observed paralysed, and totally unable to walk or to fly, panting heavily in the 'troppo' leadup to 'the wet', from mid-to-end of December 2005, in the Nobby's Creek area, near Murwillumbah; dissections revealed that the individuals died with green Camphor laurel berries in their crops; overhead, only Camphor laurel trees grew, forming a closed, interlocking canopy; the leaf litter the birds sat-in was principally of Camphor laurel leaves; it is postulated that in such hot and humid weather, even the 'fittest' Wonga Pigeon can become partly narcotised by volatile camphor,a nd related toxins emanating from the trees they 'camp in' at night, as well as on the litter floor; these observed Wonga Pigeons died within seconds of being delivered water, with paralysis of their left-sides proven (previously observed with King Parrot, at The Channon,2002).
Torresian Crow ; when in close proximity (20-50 ms) from abundant, ripe Camphor laurel trees, a multiple number of farmers, ex-Council staff, and other landholders from many districts within Lismore Shire have reported small (less than 12) flocks of Crow undertaking significant and considerable sustained damage to crops, property and, on occasion to other lesser bird species; at Lindendale on Marom Creek in Lismore Shire since 2004, one flock of Crows has caused almost $5 000 damage to all the door, and window screens of one house located close to Camphors; these birds are observed to most aggressive whenever the Camphor' fruit is ripe, and most abundant.
In other districts of Lismore Shire, many commercial farmers have repeatedly sustained gross-damage to crops, and the loss of significant amounts of income in recent years, especially on-farms in close proximity to certain types of Camphor laurel; whereas corn was the 'traditional crop' partially lost to Crows over past decades, even root-crops are now being attacked e.g. sweet potato near Eltham , with a clear and close correlation observed by farmers, seeing individual Crows fly-into and out-of nearby Camphor laurel trees when distrubed or left alone respectively.
Crows elsewhere, across a range of Shires are now known to have commenced searching-out the first, ripe Camphor laurel trees, and of having adapted to alighting into the top-third (tops) of the trees, to firstly consume the most moisture-rich green fruit of Camphor laurels!
Feral Bird Species ; one northern hemisphere species known to occasionally to build nests-in, and attempt to successully breed in Camphor laurel trees, is Noisy Miner ( ), on a multiple number of occasions since 2002 ( CRC Lismore, in Lismore); however, no pairs bred successfully in the Camphor trees closely observed, and many of the bird pairs attempted to move-nest with the onset of sustained periods of hot/ hottest spring weather. The birds temporarily resident within and near Camphor laurel trees were noted to be significantly more-aggressive than Miners in other nearby localities that were not nesting in Camphor laurels. Bird aggression was observed to 'disappear' or become non-significant once the breeding pairs moved away from teh Camphor trees.SUMMARY of FINDINGS To-Date
There is mounting evidence that even the larger native bird species are succumbing, albeit cumulatively and slowly to the various toxic chemical constituents contained in Camphor laurel tree berries, their fruit, and, where applicable seed.(e.g. frugivorous seed digestor species).
It is believed that individual bird aggression may very well be proved to be connected to, or a direct result of particular volatile chemicals contained within the ripe fruit of some Camphor laurel chemotypes ; this is especially probable, given the known wide range of Camphor laurel chemotypes/types, and the fact that the types appear to be most-diverse in Lismore Shire.
Just as the sterilisation effects of eating Camphor laurel fruit etc has been proved to be 'reversible sterility' in the case of geese and chooks (Hunter, 2002, Corndale), it also appears that native bird aggression - definitely in the case of Crows and Noisy Miners is both cumulative and reversible.
Populations of Native Pigeon species appear to be declining across many districts of northeastern Shires in northern New South Wales, with flock numbers, and the number of flocks having taken a serious downturn through the years of severe drought, since 1999-2000.