Chapter 17 of 23

The Nest Cam Decoder

What you are actually watching, and what it all means

About 10 minute read

Watch a Barn Owl nest camera for ten minutes and you will probably have questions. Why is she making that noise? Why did he land on her back? What was that thing she just coughed up? Is that egg supposed to be pushed over there? This chapter is a decoder for the live view. It explains the main behaviours you will see on camera, when they happen and what they mean, so you can enjoy the show and know what you are looking at.

Everything here is based on what Barn Owls do in the wild, and on hours of watching real nest boxes. Barn Owls are wild birds and every nest is different, so treat the timings as a guide, not a rulebook.

Start here: what am I seeing?

Chittering, snoring and screeching

Barn Owls make far more sounds than most people expect, and once you know which is which, the audio on a nest camera becomes a running commentary.

Chittering and twittering are soft, friendly, excited sounds. Between a pair, you will hear little squeaks, chirrups and twitters when they meet or when one preens the other. A male often twitters as he arrives with food. Newly hatched owlets have a thin, shivery twitter that can sound just like a tiny bird shivering, and it is heard most in the first month.

Snoring is a rough, wheezy hiss repeated over and over. It is mainly a female and owlet sound. It is not only a food call. It is a steady way of saying I am here, and it also helps the male find the nest and keeps the pair bond strong. It gets louder when the bird is hungry. Owlets start snoring within a day of hatching, and by eight weeks old a hungry one can be heard from a long way away.

Screeching is the famous call, a long, drawn out, shivery scream. It is usually given in flight, so you may only catch it on camera as a distant sound outside the box. Unpaired birds do it for minutes on end in spring.

Hissing and bill clicking are warnings. If you see an owl swaying, spreading its wings and hissing at the lens or at an intruder, it is a defensive display, and it is completely normal.

Mounting: why does he keep landing on her?

It can look abrupt, and it happens a lot, but mounting is simply mating. It begins during courtship, becomes frequent as the female nears laying, and carries on through egg laying and into incubation. It very often follows a prey delivery, when the male arrives with food and the female accepts it. You may hear the female make a frenzied, purring snore and the male a quick, staccato squeak.

Why so often? Partly it is because the eggs are laid over a week or more, and partly it is because the male wants to be the father. In my nest boxes, I have seen mounting continue through much of the breeding process, long after you would think it was needed. It is normal, and it does not mean anything is wrong.

Prey deliveries: the male's night shift

A prey delivery is the most important thing you will see on camera. The male arrives, usually with a vole or other small animal in one foot. He often pauses at the entrance and transfers the prey to his bill before he comes in. The female may call to him in a louder version of the begging call, and she will take the food and either eat it whole, head first, or tear it up.

How many deliveries should you expect? In the final ten days before laying, a male may bring ten to seventeen animals in a day. That falls to about eight to ten a day while the female is sitting. Once the owlets are growing it climbs to around fourteen a day, and it drops to about seven as they get ready to fly. Some males are far better providers than others, and a good hunting night after a poor one can leave a small heap of uneaten prey by the nest. That heap is a larder, and it is a very good sign.

Not everything that comes in is a vole. Voles are grey brown with a blunt nose, small ears and a short tail. Shrews are tiny, with a long pointed snout. Wood mice have a long tail and big ears. A young brown rat is much bigger, and now and then a small bird or a frog turns up.

Egg turning and sitting

A sitting Barn Owl looks still, but she is busy. Like most birds, she moves her eggs during incubation, using her bill and feet and shuffling her body to roll them gently and rearrange them, so that they warm evenly and do not stick to the lining of the nest. You will often see her rock slightly, settle and shift, especially after she has had a break.

She rarely leaves for long. The male brings her food, and she gradually loses weight over the month. The eggs are laid two to three days apart, and she starts sitting as soon as the first is down, so the first egg is well on its way by the time the last is laid. Incubation lasts about 30 to 32 days.

You might notice that an egg is pushed towards the edge of the nest and left there. It is quite normal for one or two eggs to fail, because of infertility or chilling, and unhatched eggs often stay on the edge until they are buried in the pellet debris. When a hatching is near, you may see a tiny crack, and later a chick with a small bump on its bill, called the egg tooth. The female often helps by moving pieces of shell out of the way.

Pellets: what did she just cough up?

Sooner or later you will see an owl look thoroughly miserable. She lowers her head, shakes it from side to side, opens her mouth several times and, with a bit of effort, a dark, tidy lump drops out. That is a pellet, and it is made of the fur and bones she could not digest. Barn Owls produce about one a day.

Fresh pellets are black, smooth and glossy. Over time they pile up on the nest floor and turn grey. Before she lays, the female often breaks them up and scatters the pieces with her feet, which makes a warm, soft, absorbent bed. So a nest full of pellets is not a mess. It is the whole point.

Other things you will see

• Preening. A pair often preen each other, and in the pairs I have watched, the female usually does more of it, and the male ends up rather henpecked. It is also a helpful clue to which bird is which.
• Owlets lying flat. Perfectly healthy owlets often lie down to rest until they are almost full grown. A chick lying flat is not necessarily a dead one.
• Owlets of different sizes. The eggs hatch one at a time, so the chicks are different sizes. The oldest is largest and gets first pick of the food.
• Wing flapping. From about five or six weeks, the owlets flap a lot, which helps clear the down, practises flying and gets attention when food arrives.
• Jumping on imaginary prey. Owlets pounce on pretend mice, and it is a sign they are getting ready to hunt.
• The male roosting nearby. During the day he often roosts close to the nest, and in a box with an upper ledge, you may find him sitting up there.

What to expect, week by week

Normal, or a worry?

Most things that look worrying on camera are perfectly normal. A tiny owlet getting less food than its brothers is a natural part of how Barn Owls cope with lean years. So is the occasional egg that never hatches. What would be a concern is a young owl outside the nest that seems injured or in danger. Barn Owls are protected by law, so please never approach a nest yourself, even if you think you can see a problem on camera. If you are worried about a wild owl, contact a wildlife rescue.