> It is interesting to consider what this says about the relationship
> these species. We were surprised to see two large Tyto owls so close to
> each other. I imagine that they compete for the same prey. Does the fact
> that the Sooties called suggest they are normally the more aggressive
> species, and would seek to excluse Masked Owls from their territory?
Masked Owls, Sooty Owls and Powerful Owls can have very substantially or
completely overlapping territories - but in my experience they utilise these
territories in subtly different ways. Territories can be HUGE - one pair of
Masked Owls I know of in the Otways in SW Victoria probably range over a
territory of between 1,000-2,000 hectares. There are probably two Powerful
Owl territories conained completely within it. These particular Masked Owls
don't seem to be overtly territorial for much if any of the year. There
aren't any Sooties in the Otways, but those I've encountered elsewhere are
territorial at most times of year. I don't know what kind of territorial
conflicts might occur between the species, but given the fact that
territories often overlap, it seems that they co-tenant their sites.
I think I'm also correct in saying that recent radio-tracking work in NSW
has indicated more overlap in foraging than was previously thought to be the
case between the big three, but very generally speaking, Masked Owls favour
edges and ecotones for mostly terrestrial/scansorial mammals, Sooties forage
more under cover for terrestrial mammals, and Powerful Owls prowl the ridges
and slopes for more arboreal mammals and birds as prey.
If Paul Peake is still online, he'll no doubt be able to fill you in with
more detail or correct any of my wilder generalisations!
Fitzroy North, Victoria, Australia
Tel AH +61 3 9486 4575