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The Barn Owl Trust

Conserving the Barn Owl and its Environment

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About the Barn Owl

American Barn Owl

 

About the American Barn Owl Tyto furcata

Some Barn Owl Trust information can be applied to Barn Owls in the Americas and some cannot. This is due to differences in things like diet, habitat requirements, and altitudinal distribution. Like many things in North America, Barn Owls are quite a lot bigger(!) so they need bigger nestboxes. This page provides a short introduction to the American Barn Owl and expands upon the differences.

Classification
With the exception of a few island species (or sub-species), there is only one species of Barn Owl in the Americas – the American Barn Owl Tyto furcata. However some authors still consider this to be the same species as the European, African and Asian Barn Owls, Tyto alba. Because of this, the North American species (or sub species – depending on your point of view) is sometimes referred to Tyto alba pratincola and sometimes as Tyto furcata pratincola. You shouldn’t worry too much about the name; it’s still the same bird!

 
American Barn Owl snow

photo Ed MacKerrow

Physical differences

Whatever you chose to call them, these birds are very different from their European cousins. Although their colouration and faces are similar, Barn Owls in North America are around 50% larger, with males averaging 474g, compared to just 312g in Europe. Body shape is also different, with proportionally shorter wings and longer legs. Despite their weight, wing length is only 12% more than for European birds, whereas leg length is 25% greater. However, in central and south America several different ‘races' of American Barn Owl occur, some of which are a good deal smaller.


Diet and foraging habitat

Due to its larger size, the North American Barn Owl is able to take larger prey. While various species of vole, such as the Meadow Vole (Microtus pennsylvanicus) are usually the favourite prey, an American Barn Owl's diet may also include Cotton Rats, Wood Rats, Ground Squirrels and Pocket Gophers. As in the UK, they will generally forage any open habitat (i.e. not inside dense forest) that supports small mammal populations, from Florida wetlands and southern deserts northwest to Vancouver International Airport and east to the small farmsteads of New York State.

 

Conservation issues

Road mortality
Barn Owls in the USA are often found dead on highways having been struck by vehicles. As in the UK, these deaths can occur more frequently at particular locations. Following BOT road mortality research in the UK, we were very pleased in 2010 to host a visit by Prof Jim Belthoff from Boise State University (Idaho) and exchange information and ideas. The numbers of American Barn Owls killed on Highway 84 in the Snake River Valley are quite shocking and if this is occurring across the continent, it must surely be affecting population levels.

Rodenticide
As in the UK & Europe, farming in North America is highly industrialised and there is widespread use of chemical rodenticides – poisons used to control rats, mice and other agricultural pests, such as gophers. The issues this raises for North American Barn Owls are largely the same as those discussed here. For example, a 2009 Environment Canada study of the livers of 164 Barn, Barred and Great Horned Owls from British Colombia and Yukon, found evidence of at least one anticoagulant rodenticide in 70 per cent of cases. Some differences exist, however, as there are substances used that are not licenced for use by the UK. These include:

Alpha-Naphthylthiourea “ANTU” The toxicity of this substance is relatively specific to rats so other species, including Barn Owls are at lesser risk. It is seldom used as first Warfarin and later other substances were developed that are far more effective rodenticides.

Bromethalin Another fast-acting toxin, bromethalin again carries a low risk of secondary poisoning. There is no antidote.

Cholecalciferol or Vitamin D3 It has been claimed that this substance is less toxic to non-target species, but in practice it has been found that use in rodenticides represents a significant hazard to other animals, such as dogs and cats. It is somewhat fast-acting, so again carries less risk of secondary poisoning compared to anti-coagulants. There is no antidote.

Sodium fluoroacetate “1080” Fast-acting and with sub-lethal doses typically excreted within a few days, this substance carries a low risk of secondary poisoning. Widely used as a rodenticide in the past, it is now only licenced in the US for the control of Coyotes. There is no antidote.

Strychnine Fast acting and quickly excreted, strychnine carries a low risk of secondary poisoning. However, poisoning can occur through inhalation, swallowing or absorption through the eyes or mouth. It produces some of the most dramatic and painful symptoms of any known toxic reaction. There is no antidote.

Further information on rodent control in North America is available from:
Canada: http://www.dfg.ca.gov/education/rodenticide/
United States: http://www.birc.org/
For information on campaigns to reduce the poisoning of owls and raptors by rodenticides see http://www.raptorsarethesolution.org/


Habitat loss
As in the UK, wildlife-rich land continues to be lost to urbanisation. Old buildings where the owls roosted and nested have been demolished or redeveloped with little consideration for the birds’ needs. Small mixed farms along with their old-style buildings tend to be replaced by vast single-enterprise farms with modern agricultural buildings and silos that are generally owl-proof. The steps to be taken (in terms of on-site protection, mitigation and enhancement) are basically the same as in the UK.

Climate Change: Around the world, extreme weather events are occurring more frequently, often with devastating consequences for wildlife as well as humans. Barn Owls are greatly affected by changes in prey availability. Whilst flooding can cause short term devastation, long-term severe drought such as the 2008-2011 California drought and those as experienced across much of southern and central USA in 2011-2013 are a far greater concern (http://droughtmonitor.unl.edu/). Similarly the big freeze that affected north-eastern states in 2010/11 no doubt resulted in widespread owl mortality. Northern Hemisphere weather extremes have been linked to the melting of Arctic sea ice, which alters atmospheric circulation in a way that leads to more snow and ice (National Geographic, March 2013). Tornados that can destroy nest sites are also becoming more frequent with the widest-ever recorded in Oklahoma in 2013.

 

Nestboxes
It stands to reason that larger birds will require more nesting space and it is worth bearing this in mind when looking at the information we provide. For North America, the recommended dimensions we give for UK Barn Owls should be increased by about 50%.

Thus, the dimensions of a box for erection in an outbuilding should be in inches:

Nestbox floor - 30 x 24”

Depth from floor to removable lid - 36”

Depth from floor to bottom of entrance hole – 27”

Entrance hole size – 7.5 x 7.5”

Exercise platform (immediately below the entrance hole) – 30 x 15”


Although the timber does not need to be thicker, your American Barn Owl Nestbox will be significantly heavier than those deployed in the UK, and therefore more difficult to erect. Where mechanical lifting equipment is not available, treat it as a (minimum) 2-person 2-ladder task, assessing risks as appropriate.

Migration
In their first autumn, most Barn Owls settle into a home range where they spend the rest of their life. The fantastically detailed local knowledge they gather helps them to avoid flying into obstacles in the dark, helps them hunt more efficiently, and thus helps their survival and nesting success. However, in the Canadian border area, some Barn Owls migrate south to escape cold winter weather. This may be of importance when considering things such as wind turbines. A migrating Barn Owl is likely to be flying much higher than a foraging Barn Owl, and is therefore at greater risk of collision.

 

Captive care
If you are considering keeping a captive bred North American Barn Owl, you should consider the size difference when thinking about aviary size and food requirements. Increasing the floor area of the aviary by about 50% and food intake by a similar amount (to three dead day-old chicks per day) should be about right.

Legal issues
All mention of Barn Owl related legislation on our website, whether it concerns wild birds, injured wild birds, or captive-bred specimens, refers to the UK only. In other countries, different national and/or state laws will apply. If a situation ever arises, whereby legal issues are a concern, please seek advice on the relevant legislation.

How you can help

  • Get involved with existing wild bird conservation projects in your area (such as nature reserve management tasks, bird surveying/counting/banding, or wildlife rehabilitation)

  • Start your own Barn Owl project by selecting an area of suitable landscape within driving distance and start your own Barn Owl survey (interviewing people and checking potential roost sites) to find out where the birds used to be, where they can still be found, and where landowners/farmers would like to have them around

  • Build nestboxes
  • Erect nestboxes in potential or occupied roost sites

  • Talk to land managers about creating additional foraging habitat to boost small mammal numbers

  • Talk to local people about the dangers of using rat bait and alternative methods of rodent control

  • Support the Barn Owl Trust with a donation or a leave a legacy to benefit this wonderful species - Barn Owl the bringer of dreams.

 

Captive care
If you are considering keeping a captive bred North American Barn Owl, you should consider the size difference when thinking about aviary size and food requirements. Increasing the floor area of the aviary by about 50% and food intake by a similar amount (to three dead day-old chicks per day) should be about right.

Legal issues
All mention of Barn Owl related legislation on our website, whether it concerns wild birds, injured wild birds, or captive-bred specimens, refers to the UK only. In other countries, different national and/or state laws will apply. If a situation ever arises, whereby legal issues are a concern, please seek advice on the relevant legislation.

How you can help

  • Get involved with existing wild bird conservation projects in your area (such as nature reserve management tasks, bird surveying/counting/banding, or wildlife rehabilitation)

  • Start your own Barn Owl project by selecting an area of suitable landscape within driving distance and start your own Barn Owl survey (interviewing people and checking potential roost sites) to find out where the birds used to be, where they can still be found, and where landowners/farmers would like to have them around

  • Build nestboxes

  • Erect nestboxes in potential or occupied roost sites

  • Talk to land managers about creating additional foraging habitat to boost small mammal numbers

  • Talk to local people about the dangers of using rat bait and alternative methods of rodent control

  • Support the Barn Owl Trust with a donation or a leave a legacy to benefit this wonderful species - Barn Owl the bringer of dreams.

 

 
 
 
The Barn Owl Trust is dedicated to conservation & education and does not operate a visitor centre.
Barn Owl Trust staff and volunteers
Waterleat, Ashburton, Devon TQ13 7HU
+44 (0) 1364 653026
info@barnowltrust.org.uk