Hello Judy, Brian and others,
Topknot pigeons, along with the fruit-doves (genus: Ptilinopus) and
imperial pigeons (genus: Ducula), do not have a muscular gizzard and act as
seed dispersers. All other Australian pigeons have muscular gizzards and
usually act as seed predators. I say usually because exceptionally hard or
small seeds are occasionally defecated intact by some of these 'seed
predators'.
In response to Brian's observations:
White-headed and topknot pigeon populations are likely to have directly
benefited from the spread of camphor laurel. Unlike many of the native
laurels which these birds feed on, camphor laurel produces large crops of
fruit annually. Thus camphor laurel constitutes a reliable and
superabundant food supply for fruit-eating birds.
The Richmond River district, where camphor laurel now occupies thousands of
hectares of abandoned pasture, originally supported the largest continuous
tract of lowland subtropical rainforest in Australia known as the Big
Scrub. By the turn of the century, most of the Big Scrub, an important
habitat for fruit pigeons, was cleared. Of the original 75 000 ha of
rainforest, less than 1% remains. It has been suggested that the spread of
camphor laurel in this region has helped fruit pigeon populations recover
from declines caused by the loss of their original habitat.
Damian
At 08:11 AM 7/20/99 +1000, you wrote:
>Hi Damien and others
>If white-headed pigeons do not spread camphor laurels because they are seed
>eaters and grind the seeds in their gizzard, but topknots are implicated in
>the spread, does that mean that topknots do not grind the seeds in their
>gizzard?
>Judy
>
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