Mainland studies of the masked owl

Studies of the masked owl T.n.novaehollandiae in south-east mainland Australia on territory size and habitat use (Kavanagh and Murray 1996; McNabb et al. 2003) and breeding behaviour and diet (Debus 1993, Kavanagh 2002, Todd 2006) may provide relevant information for management of the Tasmanian masked owl. However, few mainland masked owls have been radio-tracked illustrating the paucity of knowledge on the species despite its threatened conservation status across Australia.

Attempts have been made to relate forest management with masked owl distribution and abundance, however, all studies suffered from small sample sizes. Modelling of the distribution of large forest owls in Victoria was unable to come to conclusions on the masked owl due to the low number of records (Loyn et al. 2001). In New South Wales, some work has suggested that masked owls may be negatively associated with some forms of logging (Kavanagh & Bamkin 1995, Kavanagh et al. 1995). While Cann et al. (2002) found that Masked owls were more often located at sites post-logging than pre-logging, though they were still found more frequently at sites within 1.5 km of areas with a high proportion of senescent trees.

This illustrates the difficulties of assessing the habitat use of the masked owl, a nocturnal, mobile and difficult to detect species. The direct relevance of the results of mainland studies  to the Tasmanian masked owl ,should be treated with some caution because the Tasmanian masked owl differs in being significantly larger (Higgins 1999), taking larger prey (Mooney 1997) and having a wider variety of colour morphs. It has been released from competition with other larger forest owls in Tasmania for at least 10,000 years and so may be responding to its environment differently to the masked owl on the mainland.

What will this study attempt?

Bell and Mooney (2002) identified the need for research into territory size and habitat use of the Tasmanian masked owl to better plan for its conservation management, particularly in relation to habitat fragmentation and production forestry. The current study proposes to investigate the breeding requirements, territory size, habitat use and their relationship to each other of the Tasmanian masked owl. Forest stand variables that define suitable nesting habitat and the value of habitat retained after logging will be investigated.

Some of the important questions that will be asked include:

Do more masked owls occur in dry forest than in wet forest?

Do more masked owls occur in low altitude forests than in high altitude forests?

Depending on the results above, what is the reason for this? Possible causes could be tree hollow abundance and/ or prey abundance.

Is the masked owl occurring in areas with an above-average density of large owl-suitable tree hollows? If so is a specific density of tree hollows required for their survival?

Is there a relationship between masked owl abundance and prey abundance?

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