Breeding season is the most important time of the year for owls. All animals are biologically predisposed to want to reproduce and therefore they are eager to find a mate and pass on their genes. The question I will be answering in this post is ‘How do owls mate?’ and this will in return answer when the breeding season begins and how exactly does this breeding take place.
So to summarise, How do owls mate?
Owls courtship routine varies between the different species of owls but the most important aspects of meeting a mate and preparing to breed will include calling, food offerings, mutual preening and preparing a suitable nest site.
When do owls mate?
Most owls will mate in the spring, although this may vary to coincide with the best possible weather, food availability, smaller numbers of prey and availability of the perfect mate so it can be any time from March-August. Owls will breed when everything is effectively lined up, they have their nesting site secured and prepared, they have found the perfect mate and the current environmental situations surrounding the owlet’s upbringing will be manageable e.g. warmer temperatures, and plenty of food source.
In the below blog post I will be considering the breeding rituals of different species of owl and explaining how and when this breeding will usually take place. I will focus on the most popular and therefore the most understood owls on this subject and this will include Barn owls, Great-Horned owls, Snowy owls, Tawny owls and Barred owls.
The general order of an owl courtship looks a bit like this:
- First the male will choose a nest site. They will have to defend this nest site from being stolen by other owls.
- Once his site is secured, the male will prepare the nest (roost) by digging out a shallow hole for the female to sit and lay the eggs.
- The male will search for his perfect mate and the courtship ritual will begin.
- The female will inspect the nest thoroughly to ensure it is up to her standards as a safe place to bring up her young.
- Once the perfect mate has been found, they will secure their bond by mating.
- The female will lay her eggs over a 10 day period.
- A month of incubation will occur where the female sits on the nest. The eggs will then hatch.
So let’s look into each of these 7 stages in more details focusing on specific owl species.
Barn Owls:
First of all, let’s start with the well-loved Barn owl – many owl lovers favourite owl. These owls are known for their romantic breeding rituals (Read my post here on mating for life where I explain more about Barn owls romantic displays). The Barn owl is not afraid to show affection to its mate and will do so even when breeding is not directly occurring.
Choosing the nesting site
Barn owls will often nest in holes found in tree stumps, or outbuildings on farms or derelict land. The correct term may be roost as owls do not create stereotypical nests but they will tend to create a small hole or concave. The main aim is to find adequate shelter from different weather conditions, high enough to keep away from most predators. Basically, any site will do if it is isolated and feels safe to the owl. According to Barn Owl Trust, In the west of Britain most nest sites are in buildings, whereas about 70% of nests in the east are in the hollow of trees. This tends to relate to what is most available in each area, rather than a predisposition to certain sites.
Isolation is important for Barn owls but being out of site is deemed enough isolation. They can still nest in building near busy farms or close to humans. Farms were known to have Barn owls nesting in their barns for hundreds of years, the Barn owls became part of farming life. These nest sites will tend to be the owls nest for the rest of its life, and it is common that owls will always use the same sites over and over. If the current owl dies and leaves the nest unattended for a long period of time, another owl will eventually move in. This shows that whatever draws the Barn owl to the nest site, tends to appeal to all Barn owls universally and not individually.
Preparing the Nest:
Barn owls do not make what you would consider a conventional ‘nest’, instead they roost which means they might not collect things together to make a nest but they will still set up an area to sleep safely and comfortably. The most a Barn owl will do is burrow into soft ground to create a small hole to keep the eggs together. They will usually not bring anything to the nest to create a bed, although females may use nearby objects to secure the eggs such as old owl pellets.
Searching for a Mate:
The search for a mate often begins in late winter so that by early spring the Barn owls are prepared to breed. The barn owl will begin to display its nest site which it may have been protecting and roosting in for a while before finding a mate to share it with. The male displays the nest to the potential mate so the female barn owl knows the male is prepared for breeding. The male will do this by calling from the nest site to advertise it and to let other males know that this is their territory, they may also put on a flight display. Most pairs will preen one another and rub their cheeks together to show courtship and bonding. Barn owls are specifically known for doing this. The female will begin to hunt less and less once she falls into the courtship routine and the male will bring food to her. The female will enter ‘breeding condition’ which means she will gain around 100g. Copulation between the pair will then occur when food is presented to the female. The female will inspect the nest before she begins copulation to ensure that the nest is appropriate for breeding. She will thoroughly check the nest for potential danger spots and further prepare the nest to perfection.
Copulation:
So, copulation doesn’t vary between owl species so this section will cover all the species. Unlike us mammals, owls don’t copulate in quite the same way because both the male and the female bird have something called a Cloaca. This is an internal chamber with an opening, when this is opened it contains the testes or the ovaries containing sperm or eggs. This is the same opening used for owls to go to the bathroom (lovely, I know!). When an owl pair want to mate, the cloacal will begin to protrude slightly so that the birds are able to rub them together – this is what is considered owl sex…. weird right? The male sperm will be deposited into the females cloaca, where it can fertilise the egg. Owls will have sex in just one position, so no Kama Sutra for these couples! The male will tend to get on the females back for ease of access as she can move her tail feathers to expose her cloaca easily. This might be the best method that owls have found for breeding, since it is used universally, but even so this isn’t as easy as they would hope. It can take many attempts to be successful.
Egg laying:
The eggs laid are referred to as a ‘clutch’ and a clutch can vary from between 3-11 eggs but the usual amount will be around 4-7 rather small, white eggs. The clutch size will vary due to food availability and how easy the breeding season was to survive. The female will lay her first egg a few days before her next two. She will continue to lay eggs with intervals of two to three days, the time between the first and last egg laid can be 10 days. Incubation will last for around a month, and then the eggs will hatch every 2-3 days, often in the order they were laid so they are at different stages of development. The youngest can often die if food is short as they will not be as strong as the others in the fight for food. Sadly, sometimes they may also lose an egg, sometimes they just never hatch. 75% of young Barn owls die in their first year, some surviving for only 1-3 years. The oldest known Barn owl in Europe is over 21, but the lucky ones are considered to survive usually around 12-17 years.
Great horned Owl:
Due to being largely nocturnal you might not realise this but the Great Horned owl comes alive during their breeding season, and this is why it is known as ‘hooting season’ because these owls become more vocal than ever and can be seen and heard more that any other time in the year.
Choosing the nesting site
Great Horned owls are some of the earliest breeders, in North America the courtship is from October to December with a mate being secured by December/January. Around October time the male Great Horned will begin to choose a nesting site and prepare their territory for breeding season. If possible, they may try and scout out an old abandoned nest to use since they do not build their own. Great Horned’s like a high nesting site, so they can have a good look out over their territory for potential predators and prey. Any tree that overlooks an open area would be a perfect roosting spot. They are pretty large owls so nests with an easy access point are preferred such as tress with fewer branches, hollows of dead trees or on cliff edges. Those living in very desolate areas may use the ground to nest if there is tall grasslands such as in Florida. It seems the most important factor for the Great Horned is being close to prey and they will favour this over a warmer nest protected from seasonal conditions.
Preparing the Nest:
Since the Great Horned aims to take over an old abandoned nest from a past large bird they will usually not need to do too much preparing of the nest, and like all owls, they don’t do much anyway. Occasionally the male may add some feathers to the nest but they will not actively seek anything out to add to the nest. They are more likely to focus on the structure of the nest and maybe reinforce an organised shape to the nest.
Searching for a Mate:
To find the perfect mate, the male Great Horned will hoot excessively, they are known for this loud display which can last from a month to 6 weeks of loud hoots. This hoot is unmistakable as it is a long hoot, followed by two or three shorter hoots. They also have a range of vocalisations that can mirror dog barks and cat noises. The female will tend to only hoot in response to a mate and this will be for around a week to 10 days. This hooting will continue until a female is spotted and a kind of mating ritual will ensue where the males lean over, cock their tail, and puff up their throat. They will eventually approach the female of interest and try to rub bills with her while bowing to her, if she agrees to rub bills and hoots in return this will mean that she has accepted his advances. Males have also been known to bring freshly caught prey to the female to impress her with a meal to share. Since they often mate for life, this courtship may happen each winter to strengthen the bond ready for another breeding season. The male will show the nest that he has prepared to the female by flying to the nest and stomping on it to show this is its territory. By January, the pair will begin setting in the nest, far earlier than most birds.
Egg Laying and Incubation:
Egg laying varies from late November to late January/early February. This variation can occur due to weather conditions and egg laying can occur a month earlier than usual if food is available and weather is good. The clutch sizes vary from 1-6 dull whiteish eggs but it tends to be around 2 eggs. One egg is usually laid every two days, sometimes with a week between laying. The female will incubate the eggs for a period of 28-37 days rarely leaving the nest while the male brings the food back but sometimes it has been known for the male to share the incubating even though they do not have the same effect. Females have a ‘brood patch’ which is a patch on her abdomen which is featherless with lots of blood vessels beneath the skin which transfers heat well to eggs. Great horned’s tend to only have one brood per season but may have a replacement one if their eggs are taken or not incubated properly.
Snowy Owls
Male Snowy owls begin to attract a mate in late winter and will breed between May and September. Sometimes Snowy’s will gather in groups of around 20 perching together or close by around February and March time but once they pair up they move to breeding spots.
Choosing the nesting site
Snowy owl pairs will often choose a nest site together, arriving at the site around April time. The male will establish the territory which they will dominate but the female will choose the nest site and build the nest. The nest site chosen will be somewhere high to keep it as safe as possible. Snowy owls will nest right on the tundra so will want a nesting site with plenty of wind so they can have the snow blown away from them, keeping them as dry as possible.
Preparing the Nest:
The female Snowy will spend a few days preparing the nest by scraping out a shallow hole in the nesting site. The most this nest will contain will be a few of the females feathers. She will press her body into this hole to ensure the nest fits her body perfectly as this may be the same nest she uses for all future breeding seasons.
Searching for a Mate:
The male Snowy will seek out the female Snowy by performing a courtship display. This display shows a male Snowy carrying a lemming and swooping in front of the chosen female. The male will then land facing away from the female and lean forward with his head lowered to the ground known as the ground display. Sometimes the male and female will pass the lemming between one another while putting on a combined display.
Egg Laying and Incubation:
The female will lay a clutch of around 11-12 white eggs if the lemming population is booming but if not, the clutch may only be around 4-7 white eggs, so food supply has a big impact on clutch size because when lemming population is extremely short, Snowy owls may not breed at all. Every 2 days an egg will be laid, and incubation will begin from the first egg laid. The female will then incubate the eggs for around 32-34 days. Hatchings will take place around every 48 hours so each owlet will be at a slightly different stage of development so the younger ones can end up dying if food is short so the smaller clutches in these situations make sense. Snowy owls tend to stay very independent until breeding season where they trade their solitary existence to life with a mate. The male can help to rear the owlets and keep them and the mother safe. Only the female will incubate the eggs, therefore the male will feed his mate and his owlets by capturing lemmings and bringing them back to the nest.
Tawny Owls
Choosing the nesting site:
Unlike other owls that like a spacious entry to the nest, Tawny owls prefer a shallow entrance so that their young are not at risk of falling from the nest since they are often very active owlets. For this reason, Tawny’s like to nest in nest boxes if they can find one available, otherwise they will find a tree cavity with a hole or a ledge to perch, an old nest built by another bird that is now abandoned is also an option to Tawny’s. They will focus on wooded areas where they can hide from people, wind, heavy rain and direct sun, it is quite rare for a Tawny to choose a nest site in an out building like Barn owls sometimes do.
Searching for a Mate:
When winter comes, mating for Tawny’s begins and can go all the way through to February, early spring time. Like most owls, male Tawny’s will bring food to the female to try and woo her. The males will start calling for a female regularly and by doing so they are advertising their nest site to them.
Egg Laying and Incubation:
Egg laying usually begins around late winter / early spring, eggs will be laid at the most favourable time for chick rearing. Therefore they can be born several weeks earlier than usual or a couple weeks later if the conditions are better. Around 2-3 eggs are usually laid, with one coming every 2 days. The female will incubate the eggs for around a month. The eggs are pure white, smooth and glossy and are almost identical in size.
Barred Owl
Female Barred owls have a year off every third year from breeding to have a rest.
Choosing the nesting site
Barred owls like to nest up high in trees in natural holes and cavities. Often this may mean that the Barred owl takes over an old animal nest such as. hawk, crow or squirrel nests that have been abandoned. A Barred owl will also stay in human made nest boxes if they can find one, it isn’t clear which partner chooses the nest site, it seems it could be the male or the female.
Preparing the Nest:
Barred owls don’t do much preparing of the nest, they may if it is easy to access extra additions like some lichen, or feathers to the nest but mostly the owl will just reposition nests so that they fit their body more effectively by flattening already existing nests and rearranging what was already there. Owls are known to not add to their nests, unlike other birds they do not have the drive to create a nest, instead they like to inhabit another birds that has been abandoned – talk about lazy!
Searching for a Mate:
In February, the Barred owl courtship rituals begin so that they can hopefully breed between March and August. To catch a females attention, the male will send out a contact call to let the females know where they are and that they are looking for a mate. Once a female is spotted, the male will chase her while hooting and they will then put on a courtship display from a nearby branch where they raise their wings and sidle along the branch while swaying. Once the pair establish that they will become mates, they will pass food between each other and preen one another to strengthen the bond.
Egg Laying and Incubation:
A typical Barred owl clutch is made up of 2-4 eggs which are laid every 2 days with the incubation beginning from the first egg being laid. Incubation lasts for about 28-33 days, but if this clutch is lost or taken by other birds, they will lay a replacement clutch and therefore breeding season can be long for Barred owls. The eggs are white, perfectly round and slightly rough. The male will provide food to the nest and will not do any of the incubating, this is left solely to the female but she can leave the nest for around 20 minutes before the nest would begin to be at risk of dying from cold. The females are covered in thick feathers even on their feet which keep the nest extremely warm.
Conclusion
In conclusion, breeding for owls follows a general pattern that is very similar but each owl species will practise this pattern in their own ways so this leads to small differences between the species. In general we can see that the male will pursue the female and secure the nest site, whereas the female will perfect the nest before laying and incubating the young for around a month. This breeding can occur at slightly varied times but spring time is favoured.