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Breeding biology and behaviour of the forest raven Corvus tasmanicus in southern Tasmania

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Lawrence, Clare (2009) Breeding biology and behaviour of the forest raven Corvus tasmanicus in southern Tasmania. Research Master thesis, University of Tasmania.

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Abstract

The Forest Raven, Corvus tasmanicus tasmanicus, is the only crow or raven
species found on mainland Tasmania. Although members of the genus Corvus
have been comprehensively studied, relatively little is known about the Forest
Raven. While recently studies have been made of the closely related Northern
Forest Raven (C. t. boreus) in New South Wales, this is the first study to be
undertaken on the biology of the Forest Raven in Tasmania. Overall, the results of
this study suggest that Forest Ravens are similar in their breeding biology and
behaviour to other corvid species with similar life-histories, both in Australia and
overseas.
Adult breeding Forest Ravens maintain large self-sufficient territories year-round.
Juvenile ravens remain in these territories with their parents for some months after
fledging, before leaving to join nomadic flocks comprising immature birds and
non-breeding adults. This study focused on the breeding biology and the
behaviour of territory-holding adult Forest Ravens in six territories in light
bushland around Hobart, southern Tasmania. Ravens built nests in trees
characteristic of the tallest vegetation of the area, nests being situated on average
24m above the ground. The Forest Raven nesting season began in August.
Incubation and nestling periods lasted around 22 days and 37-49 days
respectively, with second clutches being laid in the event of the failure of the first.
Forest Ravens produced on average 1.9 fledglings per pair per nesting season,
with most pairs producing two fledglings. The survival rate of fledglings to one
month was very high.
Away from the nest, and outside the breeding season, Forest Ravens are consistent
with other bird species in spending most of their time in perching behaviour and
foraging.
The Forest Raven is a common and distinctive member of Tasmania's avifauna,
and is of commercial importance due to the damage it causes in orchards. Due to the perception of the Forest Raven as an agricultural pest the species is one of
only three native bird species not protected by Tasmanian law. In a number of
countries corvids are becoming increasingly urban, causing problems through
aggressive behaviour, noise and unsanitary mess. Although this has not yet been
reported in the Forest Raven, a potential increase in food sources as a result of
suburban spread in Tasmania may in the future lead to greater numbers of ravens
in such areas. By providing information on the breeding and behaviour of the
Forest Raven, the results of this study may be of use in the development of plans
or devices to manage the species in a controlled, effective and non-lethal way.

Item Type: Thesis (Research Master)
Copyright Holders: The Author
Copyright Information:

Copyright 2009 the Author

Additional Information:

Available for library use only and copying in accordance with the Copyright Act 1968, as amended. Thesis (MSc)--University of Tasmania, 2009. Includes bibliographical references

Date Deposited: 19 Dec 2014 02:57
Last Modified: 11 Mar 2016 05:53
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