About the Barn Owl
Population estimates and reasons for change
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Historical estimates The first reliable Barn Owl population estimate in the UK was not produced until 1999. Although the earlier surveys (Blaker 1932 and Shawyer 1987) were great achievements in their day, they do not stand up to scientific scrutiny. Therefore, the often-quoted figure of a 70% decline in England and Wales between the 1930s and 1980s cannot be relied upon. It is unfortunate that the evidence for the species' historical decline in Britain, although overwhelming, is largely anecdotal.
Reasons to think they were once common It's not so long ago that virtually every elderly farmer remembered seeing "fluffy white owls" up on the barn wall back in the 1930s and the impression given was that most farms had Barn Owls. Indeed, there is a strong consensus that Barn Owls must have been a lot more common before the mechanisation. When men and horses worked the land, farming was very much less intensive and (overall) wildlife was much more abundant. In particular, small mammals would have been much more common when there were more hedgerows, more marginal grazing land, and pasture was mainly permanent, "unimproved", and much less intensively grazed.
Stored cereal crops (in ricks or barns) became so infested with mice and rats that some enlightened farmers encouraged Barn Owls into their buildings via special access holes ("owl windows"). For a species that cannot hunt in rain and suffers high mortality in severe winters, imagine how indoor hunting might have helped survival. Also, there was no fast traffic or overhead wires for Barn Owls to fly into and no poisons in the food chain.
Reasons for the historical decline It's quite likely that Barn Owl decline started in the mid-1800s as a result of persecution by gamekeepers, egg collectors and the like. The fact is we shall never know to what extent these activities might have affected the Barn Owl population. Indeed they may have only caused the temporary suppression of local population levels.
In the late 1800s and early 1900s increasing human population levels and the proliferation of farm machines led to increases in the intensity of land management resulting in the loss of Barn Owl habitat. This accelerated during World War II with a drive for Britain to become more self-sufficient. The idea that British farmers had a duty to produce as much human food as possible (which became deeply ingrained during WWII) and a system of government grants that paid farmers to destroy wildlife-rich fields and hedges, continued right up to the 1980s. The changes in farming practices stimulated by the legacy of WWII, human population expansion, government policies, and consumer pressure for ever-cheaper food, are the main reason behind the Barn Owl's historical decline in Britain.
1995-97 Population estimate for the UK (produced by Project Barn Owl and published in 2000) was 4,000 pairs (plus or minus c.30%). Unfortunately no other reliable estimates have been made to date.
Population change between 1995-97 and 2009 The occupation of nestboxes indicated an overall increase in numbers between 95-97 and 2009 in parts of eastern England. However, no such increase was noted in central and western areas probably because Barn Owl numbers there were not generally limited by a lack of roost/nest sites. The 2007-2011 BTO Bird Atlas suggested that Barn Owl distribution in Scotland had increased possibly due to a run of relatively mild winters. Conversely, numbers in Ireland appear to have decreased.
Thus by 2009 it is possible that the UK Barn Owl population had reached significantly more than c. 4,000 pairs - no one will ever know for sure.
Reasons for low numbers in modern times Their is little doubt that the main factors are:
Population change 2009-2011 Winters 2009/10 and 2010/11 were unusually cold which no doubt resulted in increased mortality. The following springs were also very cold and unusually dry which suppressed small mammal activity (which in turn limits Barn Owl breeding success). By autumn 2011 Barn Owl numbers had probably been knocked back to around 4,000 pairs i.e. any increases in the period 2000-09 had probably been wiped out.
2012 and the disaster in June Generally speaking, winter 2011/12 was not too severe and March 2012 was unusually hot resulting in early egg-laying and above average clutch sizes. By the end of May many nests contained 4-6 young rather than the average of 2.9. In fact, 2012 was all set to be a bumper year for Barn Owls - then it all went horribly wrong. From 8th June onwards prolonged rain caused massive nestling mortality however some pairs did nest successfully later in the year. Overall 2012 was probably average year - not the bumper year that was so badly needed.
2013 and the disaster in March The late winter peak in mortality (which occurs every year) normally subsides as temperatures increase in March. But in 2013, extremely cold weather experienced through January and February continued throughout March and mortality kept increasing. By mid-April when temperatures finally increased, most Barn Owls were dead. The few that survived failed to breed or bred late. In most counties the number of nests at monitored sites dropped by 85-100%. However nesting numbers in Cumbria and SW Scotland were reported to be "low" rather than "disastrous". Numbers of non-breeding birds are always difficult to gauge. However, there can be little doubt that numbers dropped well below 4,000 pairs (the last reliable estimate), with possibly lower than 1,000 pairs nesting. In May 2013 there were probably less Barn Owls in Britain than at any time since farming became widespread (roughly 1,000 years ago).
Note: Although the weather in 1947 and 1963 was more extreme, it was affecting a much bigger BO population.
2014 - Nobody knows how many Barn Owl there are in the UK but there's almost certainly a lot less than 4,000 pairs.
Weather facts Dec '09 and Jan '10 - worst winter weather for 30 years; 2010 - coldest December for 100 years; first 2 weeks of Feb 2012 were the coldest since 1991; March 2012 was the hottest since 1997; June 2012 was the wettest in England and Wales since 1766; March 2013 was the coldest since 1962; hottest July for 7 years; December 2013 - worst floods since 1953.
You can help Barn Owls! All the information you need is in the Barn Owl Conservation Handbook.