The daylight activity of Barn Owls

Published on 08 July 2013 in Letters

Barn Owl, pic by Richard Chandler

Barn Owl, pic by Richard Chandler

The occurrence of daylight hunting by Barn Owls Tyto alba (BB 106: 416) goes back to the beginning of the last century and is an important subject that has an interesting history in the UK which I have discussed elsewhere in more detail (Martin, 2008).  The question that we should be asking is why is it that a bird, which has evolved over millions of years to be a supreme nocturnal hunter, be out at all during the day.

The subject was first raised by Eric Dunlop (1911), a naturalist of the Lake District, who noted Barn Owls out hunting ‘whilst the sun is yet high in the heavens’, especially when there were young in the nest. This was followed by a note from Smalley (1911) who, like Dunlop, noted Barn Owls flying in winter time, and he also noted them flying ‘all day’ in north Lancashire, where he lived. He attributed this behaviour to a shortage of food. The noted Cheshire naturalist T.A.Coward (1930) also noted occasional daylight hunting.

The subject of Barn Owls hunting by daylight faded away after the early decades of the 20th century but it was briefly raised again in 1946, through some correspondence in The Field magazine. This culminated in a note on August 31st 1946, from Leslie Turner who was also from Lancashire. He wrote that earlier in the year it had been quite common to see up to a dozen Barn Owls hunting for food at any time of the day ‘whether the light be dull or brilliantly sunny’. A staggering number of Barn Owls compared to the present day.

It was Derek Bunn (1972) who grasped the reality of this behaviour during the course of his study in north Lancashire. He was not expecting to find Barn Owls out hunting during the day when he started his study, yet he found that some of the birds he was studying were nocturnal, while others were diurnal. He also noticed that some would change from being active nocturnally to being active diurnally and vice versa and he wondered whether the aggressiveness of corvids and gulls was responsible for this change in hunting activities, with the owls moving from diurnal to nocturnal activity to avoid the attentions of these birds. In my Suffolk survey I found that Barn Owls were often out during the day, despite being mobbed by Rooks Corvus frugilegus, Magpies Pica pica and Black-headed Gulls Larus ribundus. Iain Taylor points out that the owls in his study area were very rarely mobbed, but he states that in the tropics those Barn Owls which hunt diurnally are violently mobbed by a wide variety of birds, ranging from starlings to crows.

In the face of the information that was available to him at that time, Derek Bunn came to the conclusion that it might be relatively poor eyesight which was responsible for daylight hunting because in daylight, their vision was improved. Dunlop (1911) observed that with the Barn Owl ‘its vision must be very acute’ due to its ability to be able to easily locate prey amongst the herbage. At this stage the acute hearing of Barn Owls had yet to be recognised.

The publication of Bunn’s report was followed by a number of letters from birdwatchers and ornithologists around the UK, some of whom thought that this behaviour was quite normal, while others were surprised. The conclusion he reached was that around Britain there were Barn Owls which were hunting by night, and there were others that were habitually hunting by day, the proportions of which he did not know.

Derek Bunn found that some of the owls he was studying were active during the day either in the middle or late afternoon, with some of his birds’ out hunting in October (103 minutes before sunset), and others active in February and March (169 and 268 minutes respectively), before sunset.

Nothing further on this subject was reported until Iain Taylor (1994) completed his study in south-west Scotland, in which he reported that Barn Owls would often hunt by day. He found that Barn Owls in south-west Scotland and northern England hunted during the day as a matter of course, even delivering prey in the middle of the day, often but not totally, when there had been prolonged heavy rainfall the night before, and he further considered that those of northern Europe are the most diurnally active of all the world’s Barn Owls, with those of southern Europe and the tropics being strictly nocturnal. It is important to note that his study concurred with the earlier study of Bunn et al., (1982) which was the first study that linked diurnally hunting Barn Owls to the activity patterns of the main prey which was the Field Vole Microtus agrestis followed by Common Shrew Sorex araneus.

However, conclusions should not be drawn from this because the reason for the behaviour is likely to be more complicated than might be presently thought. Hunger and vole activity may be contributory reasons why Barn Owls are diurnally active, but together they are unlikely to be all of the reasons (Martin and Mikkola, in prep.). Some Barn Owls spend a great deal of time during the day just sitting around on fence posts. Often these birds are to be seen around mid-day, but sometimes in the mornings and afternoons and clearly some of the owls I see are apparently not interested in hunting.

It is clear, however, from my own and other observations, that Barn Owls are active throughout the day, and not just in the middle or late afternoons and not just in the winter months or in times of bad weather. The large numbers of Barn Owl photographs that are now posted on various web-sites support this. I even had one apparently experienced observer say to me, upon seeing a Barn Owl out during the middle of a bright sunny day, ‘Oh yes, a typical daylight sighting’.

In addressing the concerns of predation on Barn Owls, it seems likely that the owls would not receive the attentions of Common Buzzards Buteo buteo or Northern Goshawks Accipiter gentilis so much if they behaved in their familiar nocturnal manner but clearly they do not.

Predation by Goshawks is certainly on the increase in the UK and Mikkola listed this as the top diurnal predator of the Barn Owl in Europe (n13) but that will have now changed as this species is increasing in numbers and range. It is a species that Bunn et al. (1982) thought might impact upon Barn Owl numbers, in the face of a rising population, while predation by Buzzards is also on the increase. While the rise in numbers of diurnal predators and their impacts upon diurnal hunting Barn Owls may be due to less persecution of the predators, it is important to remember that the persecution of raptors has not been confined to the British Isles. It has also been prevalent across the wider Europe, during which time there appears to be no history of diurnal hunting by Barns Owls as there has been in the UK.

Heimo Mikkola (1983) has listed the Eagle Owl as the top predator of the Barn Owl in Europe (n46), but the number killed by this species has undoubtedly increased in recent years (see Penteriani et al., 2012 for example) due to the greater protection that Eagle Owls are now afforded.

It is of considerable interest to note that all the historical records relating to daylight activity of Barn Owls in the UK (Dunlop, 1911 through to Taylor, 1994) occurred in the same region, ie Lancashire, the Lake District and south-west Scotland. These are areas that have held populations of Buzzards, Goshawks and other raptors at times when large areas of the UK were without them (Holloway, 1996; Sharrock, 1976; Lack, 1986 & Gibbons, et al., 1993). Now, though, daylight hunting by Barn Owls is a widespread habit across much of the UK.

While we have seen a steady rise in the daylight activity of Barn Owls, we have also seen a corresponding rise in the daylight activity of Tawny Owls over a similar period of time. By this I mean mid-day activity, whether it is summer or winter, and not just at the ‘tail ends’ of the day (Martin and Mikkola, in prep.).

Phil Palmer points out that Tom Noah, of the German rarities committee, has never seen Barn Owls hunting in daylight in his life. In our search for records of daylight activity by Tawny Owls, we have now received a number of interesting records from various parts of the EU, as well as from the Ukraine and Russia. It is therefore interesting to note that to date we have not received one record at all of Tawny Owls calling in daylight from Germany or indeed France. Clearly there is something going on in the British countryside which needs some explanation but for which, at present, we do not yet have the complete answer.

Acknowledgments Derek Bunn is an astute and reliable recorder, and so I am most grateful to him for correcting, adding and suggesting additional points to improve this article.

References

Bunn, D. S. 1972. Regular daylight hunting by Barn Owls. Brit. Birds 65: 26–30.

––, Warburton, A. B., & Wilson, R.D.S. 1982. The Barn Owl. Poyser, Calton.

Coward, T. A. 1930. The Birds of the British Isles and their Eggs. Warne, London.

Dunlop, E. 1911. The Diurnal Flight of the Barn Owl. Brit. Birds 4: 314-315.

Gibbons, D. W., Reid, J. B., & Chapman, R. A. (eds.) 1993. The New Atlas of Breeding Birds in Britain and Ireland: 1988-1991. Poyser, London.

Holloway, S. 1996. The Historical Atlas of Breeding Birds in Britain and Ireland: 1875–1900. Poyser, London.

Lack, P. (ed.) 1986. The Atlas of Wintering Birds in Britain and Ireland. Poyser, Calton.

Martin, J. R. 2008. Barn Owls in Britain. Whittet, Yatesbury

Mikkola, H. 1983. Owls of Europe. Poyser, Calton.

Sharrock, J. T. R. (ed.) 1976. The Atlas of Breeding Birds in Britain and Ireland. Poyser, Calton.

Smalley, F.W. E. 1911. The Diurnal Flight of the Barn Owl. Brit. Birds 4: 339.

Taylor, I. 1994. Barn Owls: predator prey relationships. Cambridge University Press, Cambridge.

Jeff Martin, 17 Moss Way, West Bergholt, Colchester, Essex CO6 3LJ; e-mail jeff.r.martin@btinternet.com

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