Decline of tawny owl is a concern

Tawny Owl - Strix aluco. Photo: Moss Taylor
Tawny Owl - Strix aluco. Photo: Moss Taylor
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Back at the start of 2015 readers will have read of one of our earliest nesting species, the Tawny Owl.

he very early breeding of this species sees a peak in territorial activity through the first part of the winter, with owls claiming the ownership of breeding territories with their familiar ‘tuwit-tuwoo’ call. No doubt a few of you will have heard calling owls locally over recent weeks, the birds most commonly associated with woods, small woodlots and (just occasionally) larger gardens.

This year, however, it would seem that there are fewer calling owls about. Participants in the BTO’s weekly Garden BirdWatch survey record Tawny Owls heard from their gardens during early evening, the results of their observations generating a measure of Tawny Owl activity and population size (see www.bto.org/gbw). The figures for November and December 2015 are some of the lowest we have seen since the survey began back in 1995. The reason for this can be linked to the poor breeding season experienced by Tawny Owls during 2015, with the BTO’s Nest Record Scheme generating the information that shows this. A low in the small mammal population cycle almost certainly reduced the food available to breeding Tawny Owls (and other predators of mice and voles), leading to a reduction in the number of chicks fledged from the nest.

With fewer young birds around, there will have been less competition for breeding territories this winter and, consequently, a fall in the amount of territorial calling. Tawny Owls are rather sedentary in habits and an established pair is likely to remain together on the same territory over several seasons. The pair responds to the arrival of dispersing youngsters by hooting at or, in some cases, attacking the intruders. The owls can recognise the calls of their established neighbours and so respond less aggressively to these than they do to unfamiliar birds, the latter likely to be considered a greater threat to the pair.

Tawny Owl calling activity will continue through into the New Year, the birds more active on clear, moonlit nights than on cloudy, wet or windy ones – presumably because poor weather reduces the distance over which their calls may carry. While these year-to-year variations in the Tawny Owl population are to be expected, researchers at the BTO are concerned by the longer term pattern of population decline seen in this familiar species. The scale of that decline has prompted conservationists to place the Tawny Owl on the Amber list of Birds of Conservation Concern, where it joins species like Avocet, Bittern and Honey-buzzard. While Tawny Owl is certainly not as rare as these other species, the scale of its decline is a concern and we are likely to see more research directed towards this familiar species over the next few years.