The Tawny Owl Strix aluco is a widespread and common species throughout much of the Western Palearctic, where it is widely considered to be a predominantly nocturnal species. It has become increasingly clear, however, that at least in some parts of Britain, encountering birds calling during daylight hours is not uncommon. In 2013 we launched an enquiry into this phenomenon to find out more about this behaviour.
The survey, which we recognised from the outset could not be done systematically, was publicised in British Birds, Scottish Birds, BBC Wildlife magazine, other journals and periodicals, and bird club websites, while various individuals known to be particularly interested in the subject were contacted directly. We simply encouraged all observers to submit full details of any instances of Tawny Owls calling during daylight hours, both past and present. Because of the potential problems caused by mimicry by Eurasian Jays Garrulus glandarius, at least with the typical ‘kewick’ call of female Tawny Owls, we decided to accept only records of hooting birds.
We received nearly 500 records (past and present) of diurnal calling Tawny Owls, which demonstrates that this is not uncommon behaviour in some areas, notably southern and eastern England. While the records received are clearly dependent upon when observers were active, they suggest that peak activity was around midday (fig. 1). Not all records are included in fig. 1 because not all were timed.
Fig. 1. Records of Tawny Owls Strix aluco calling in daylight in relation to time of day (n=442); all observations are converted to GMT.
Several recorders suggested that proximity to a nest with newly fledged young stimulated adults to call during daylight hours in spring (April to June; see fig. 2). A number of records received from the European mainland were directly related to nest disturbance.
Fig. 2 shows the number of records by month, when dates were provided. The spring peak in daylight calling is seemingly clearly associated with the breeding season; interestingly, this contrasts with the well-established autumn peak in nocturnal calling by Tawny Owls, which is associated with the re-establishment of territories after the end of the breeding season.
Fig. 2. Records of Tawny Owls Strix aluco calling in daylight in relation to month (n=444).
In cases where weather conditions were reported, we received 131 (58%) records of birds calling in sunny, bright conditions, 58 (25%) when the weather was cloudy or dull and 38 (17%) where the conditions were mixed.
Few records were received in response to our survey appeal from the European mainland. One set of records was received from coastal areas of the Netherlands and another from Belgium, and these records matched the general pattern apparent in Britain. All other records away from Britain were received as a result of direct contact with nest workers. The brief staccato hooting sometimes uttered by Tawny Owls during the day was reported only from Britain.
We wish to thank everyone who responded to our survey request but in particular we should like to mention the following for supply of records and discussion of the phenomenon of daylight calling: Wouter Faveyts (Belgium); Peter Combridge, Stephen Edwards, Colin and Mike Everett, Robin Prytherch, Peter Rose and Doug Stapleton (Britain); Thomas Noah (Germany); András Schmidt (Hungary); Saulius Rambutis and Vladas NaruÅ¡eviÄius (Lithuania); H. Nuijen (the Netherlands); Jaroslaw WiaÃ§ek (Poland); Samuel Pacenovsky (Slovakia); IÃ±igo Zuberogoitia (Spain) and Yegor A. Yatsuk (Ukraine). Importantly, we are still keen to collect new data – please contact Jeff Martin (e-mail below) if you can help!
Jeff Martin, 17, Moss Way, West Bergholt, Colchester, Essex CO6 3LJ; e-mail email@example.com
Heimo Mikkola , University of Eastern Finland, Kuopio Campus, P.O. Box 1627, FIN-70211 Kuopio, Finland firstname.lastname@example.org