This page gives you guidance on monitoring your nest box by visiting it or watching it from a distance. For instructions on entering your observations online, please click here.
When to start monitoring your nest box/nest
Birds can begin nesting in a box any time from February onwards, so it is important to start your monitoring as early as possible in the year. Birds may go in and out of the boxes very quickly, so even if you haven't seen any activity, it's always worth taking a careful look. Most Blue Tits and Great Tits will begin nesting in late March or April, but different species will start nesting at different times - visit the NNBW species ID pages for more information. If you see birds flying in and out of the box, it's definitely worth having a look inside, particularly if they are carrying nesting material.
Looking inside a nest box
Where possible, we ask NBC participants to look inside their nestboxes to note the stage of the nest, but minimising disturbance to the breeding birds is obviously of utmost importance. Looking inside a box will not automatically cause the parents to desert the nest, but it is important that you take great care when doing so.
If you have been watching your box from a distance and know that both the parents are away finding food or nesting material, you have an ideal opportunity to visit the nest. This may not always be possible or practical, however. If you don't know whether a bird is in the nest, then it is important to follow the guidelines below:
- Before looking in the box, give the side a light tap so that any adult birds can become aware of your presence and have the opportunity to fly away before you open the lid.
- To look inside, lift the lid very slowly. If there is an adult bird still sitting tight on the nest, quickly look to see if there are any eggs or young in view, before gently lowering the lid and leaving as quietly as possible.
- If there is no adult present in the box, you are free to make your observations, doing so thoroughly but quickly to avoid staying at the nest for longer than is necessary and leaving as quietly as possible.
Unlike mammals, the majority of birds have a relatively poor sense of smell, so there is no need to worry about leaving your scent around the nest box. However, handling of eggs and chicks is illegal without the required authorisation.
How often to look in a nest box
To get as much information as possible about each breeding attempt it is best to look in the nest box/nest on several occasions, however it is important to disturb the birds as little as possible. A few well-planned visits to the nest box can provide all the information we need. There is never any need to record the number of eggs or chicks in the box/nest more than once per day.
Even if birds are not using your box at the start of the season, it's still worth checking once a week to make sure that it is not being used for a repeat nesting attempt. If birds are nesting in your box or you have an open nest in your garden shrub, looking inside it once every 4-5 days should allow you to find out how many eggs have been laid and how many chicks have been produced without causing too much disturbance. Don't give up monitoring the box when the birds have successfully left, or the nest has failed, because either the same pair or another pair of birds may try to nest again.
What if I can't or don't want to look in the nest box?
If you are unable to look inside the box/nest, or do not wish to do so, you can still tell a lot about what is going on in the box/nest just by watching it from a distance. You will need to be close enough to see what's going on at the nest, but not too close as this may prevent the birds from visiting their nest. You may even be able to watch from the comfort of your own home with the aid of a pair of binoculars. There are several signs of breeding to look out for:
- Birds flying repeatedly to and from the nest.
- Birds carrying nesting material to the nest.
- Birds carrying food to the nest.
- Chicks calling from the nest.
- Young poking their heads out of the box/nest.
- Young leaving the box/nest when they are ready to fledge.
If you have found an 'open' nest in your garden, such as a Robin nest in a plant pot or a Collared Dove nest on a security light, you can register it, monitor it, and submit the details online for NBC just as if it was one of your nest boxes.
As with boxes, it is perfectly safe to monitor open nests, provided you strictly follow the guidelines below. Scientific studies have shown that, as long as observers are careful and follow the BTO's guidance, making several visits to a nest to record the contents does not increase the probability of it failing.
The rules for how often to visit an open nest are the same as for a nest box, so please see the section above—How often to look in a box—for guidance. Unlike a nest box, an open nest may not have been built in a place you can easily get to. For this reason, please be especially cautious of the following:
- Accidental damage – Be very careful when moving any vegetation around the nest, so as not to dislodge the nest or cause it to tilt and spill its contents. Be aware also of any other nests near the one you are trying to reach.
- Desertion – It is important not to startle a sitting bird, so if a female is sat tight when you try to visit a nest, just go away and check again later. If a bird does happen to leave the nest on your approach, make a note of the nest contents and leave the area straight away; she will quickly return. Chicks and eggs are exposed while a parent is off the nest, so do not visit in inclement weather.
- Revealing a nest to predators – Predators can be assisted by tracks and signs left by people and animals. Avoid leaving a trail to the nest by trying not to displace or trample any surrounding vegetation. Never inspect a nest if you think a predator may be watching you.
The above guidance is taken from the Code of Conduct that applies to the BTO's other survey of nesting birds, the Nest Record Scheme. To see the full Code of Conduct, please click here.
What to do if the nest has been abandoned
Unfortunately, not all nests are successful. Some may be abandoned by the parents or attacked by predators. If you do find what looks like an abandoned nest, you may be tempted to remove the contents in an attempt to clean the box out for other birds. However, under bird protection law, it is actually illegal to clean out nest boxes during the breeding season, from 1st February to 31st July, in case active nests are inadvertently disturbed. If you do want to clean out the box at the end of the season, wait until the autumn when you can be sure that it is no longer being used and follow the guidelines on the NNBW web pages. Remember to record the details in the Nest Box Challenge form.