Hi Hedgehoggy,
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It was two Tawny owls, presumably fighting over territory.
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Awesome, I've never heard a fight between these critters before, although I know that they are tough cookies. They are monogamous and nocturnal all year and have been documented to drive larger owls (even long-eared owls), cats, foxes etc. from their territories. Indeed, you probably saw the footage on SpringWatch a year-or-so ago, where a Tawny swooped to attack a fox feeding in someone's back garden. There was a fascinating account in a 1964 issue of
British Birds describing an apparently unprovoked attack on a Red fox drinking from a pond in the owl's territory during January (even though this is too early to be protecting a nest!). There are also reports of Tawny owls eating other owl and raptor species, including Barn owls, Little owls and sparrowhawks.
Given that the males start singing in defence of their territory during late winter, and that females typically lay eggs during March, it may be that there was a nest nearby.
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Does anybody know how large the Tawnys' territory ranges are approximately?
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In his fascinating
Owls of Europe, Heimo Mikkola writes:
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At Wytham Wood, Oxford, the average territory was 12 ha in a closed woodland and 20 ha in mixed woodland and open land (Southern 1970). Territories were sometimes much smaller, but according to Southern and Lowe (1968), territories of less than about 8 ha were too small to be viable for breeding. Tawny Owls studied in Belgium had territories of about 65-75 ha when living in beechwood with little lesser vegetation (Delmee et al
1978). And in Norway, where the prey density is far less than in England or Belgium, the mean territory size was about 102 ha per pair (Hagen, 1948)."
Dr Mikkola goes on to mention that Tawny owl territories studied in Britain have almost always been in woodland, although subsequent authors have pointed out that they also inhabit parks, large gardens and occasionally conifer plantations. Additionally, in their 1997 paper to
Ibis Bridget Appleby and Stephen Redpath note that the average territory size of Tawny owls in Wytham Woods during their study was 22 ha, while in their second study population in Monks Wood (Cambridge), it was 15 ha and in nearby Fens it was 126 ha. Unsurprisingly, food availability does seem to play an important role in territory size and movement dynamics. A study of juvenile Tawny owls in Northumberland’s Kielder Forest during the mid-1990s found that some 25% of variation in time spent in different locations around the territory could be explained by variations in Field vole abundance.
I hear Tawny owls in our (communal) garden in the autumn; even though the garden is fairly small, it does have a line of trees running along the railway embankment at the back of the building. I get the impression that the owl(s?) hunts along the railway line, but I doubt that they roost/nest in the associated treeline. Each time I have seen them, they're flying off in the direction of the Common (a large expanse of mixed grass and woodland in the city centre).
I hope this is of some help.
Cheers,
Marc.