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This article was written by Chris Sperring MBE for the Spring/Summer edition of Peregrine Magazine 2020. Although two Tawny breeding seasons have successfully passed since then, the article is still highly relevant and applicable to the current courtship period that we are witnessing with our Tawny Owls at Sculthorpe Moor Nature Reserve.

Keeping Track of Tawnies


One of the Sculthorpe Moor Tawny Owls, taken by Sue Wood, in January 2022

The Tawny Owl is a relatively easy bird to keep track of in terms of gathering information about their population density and breeding success.  It is a very vocal owl, and one that will call throughout the year, even so serious surveying requires careful planning.  The most vocal time is the Autumn when young birds are on dispersal away from parental territories.  Counting birds at this time, however, may give a false number because you could easily be recording youngsters which are still looking for a home range of their own and just passing through the area.  By the end of winter most yearlings will have either found a territory, and hopefully a mate, of their own or will have perished in the pursuit of it.  It is now that the serious business of preparing for the nesting season begins. Surveying at this time gives a more accurate account of the number of potential breeding pairs, and where they are holding territory.

With time and patience it is possible to build a picture of how many owls are likely to produce young each year.  Not all pairs will breed, and sometimes none will.  This is dependent on various factors; prey availability and weather being the most important.  But, as a relatively long-lived owl they can always make up for any failures in subsequent years. 

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One of the Sculthorpe Moor Tawny Owls in March 2021

It is possible to encourage Tawny Owls to use nesting boxes, which not only provides the owls with a secure nesting site, but also helps us with monitoring, as accessing carefully positioned nest boxes is usually easier than reaching a natural tree cavity. 

I always try to avoid inspecting nests during the incubation stage as some birds can be susceptible to disturbance at this time and may abandon their eggs.  Instead, I monitor boxes when the young are old enough not to need much brooding, as I feel this causes the least distress to the birds. 

Two is the normal clutch size for Tawny Owls in the UK, although three or four is possible.  Hatching is staggered, so in years of food shortage the youngest will not survive.  This means that even by recording owlets in the nest we cannot take this as a final result.  A spell of prolonged wet or cold and snowy weather at the wrong time can reduce survival rates dramatically.  For this reason, I try to follow-up my nest visits with owlet counts over subsequent weeks.  When Tawny Owlets fledge they can still be 4 weeks away from proper flying, so this is a good window in which to keep track of how they’re doing.  They do not return to the nest, but climb and jump around in the tree canopy, calling to be fed.  Their calls are loud and continuous, which makes finding and counting them pretty easy, especially at dusk when they are at their hungriest, having not eaten all day.  They will be fed by their parents for a couple of months, so it is possible to record owlet survival rates with some accuracy. 


Once their voices break they will be moved on and that is where we lose them…until their BTO rings are recovered after their death and we learn how long they lived and how far they travelled.  The oldest wild Tawny Owl recorded through BTO ringing was 23 ½ years old, although the typical lifespan of ringed birds is just 4 years.

With numbers seemingly on a steady decline in the UK it will become more important than ever to keep track of our Tawnies in the years to come...

Chris Sperring MBE – Conservation Officer, March 2020

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