Behind the scenes

What happens once you've submitted your Big Garden Birdwatch or Big Schools Birdwatch results? We asked RSPB Conservation Scientist Daniel Hayhow to explain...

Making your results count

After the long build up to Big Garden Birdwatch, maybe it feels like everything's gone a bit quiet once you've submitted your results.

But at the RSPB UK Headquarters in Sandy, Bedfordshire, a frenzy of activity is just beginning. It's something I and lots of other people here have been looking forward to all year – the Big Garden Number Crunching Fortnight!

Processing all the data is a big job - luckily I don't work alone! The process involves dozens of people from multiple teams, all with different specialisms. 

Once you've completed your results online and hit the 'submit' button, or completed your paper form, licked a stamp and handed it to your local postie, here's what happens: 

Stage 1: Results collation

After the Birdwatch is over, we wait three weeks to make sure everyone who participated has had a chance to send in their results. This is where the fun begins. 

If you sent your results on a paper form, it goes to a data processing agency who manually enter all of the results into the online system.

These join all the other records from people who submitted their results online (which is much quicker and easier). 

Then, the RSPB's computer team – Information Technology – collate all those hundreds of thousands of records into one giant set of data.

Stage 2: Cleaning the data

The Information Technology team scan through everyone's results checking for any anomalies.

It's really important that the data is accurate, or the scientific value of the results would be weakened. So they check for any mistyped postcodes which might transport someone's results from one end of the country to the other.

They check for duplicate entries, because sometimes people are very enthusiastic and submit their results on paper and online.

Man at computer

Stage 3: Looking for oddities

This is where I come in.

When Information Technology send me the data, it is all divided up into the different regions of the UK. I scan through the data looking for birds that are easily misidentified and do not exist in a particular region.

For example, hooded crows and carrion crows are often mixed up. But hooded crows are only found in Northern Ireland and in West Scotland. So if someone has reported one in Cornwall, then it was almost certainly a carrion crow.

I also look through the number of each species counted, using my own common sense, wildlife knowledge, and also data from previous years about the number of species present in particular regions.

It's unlikely, for example, that someone saw 500 robins at one time in their garden. It's more likely that they saw five and in their excitement hit a few extra keys. But we can't be sure how many they really did see, so these records cannot be counted. Again, scientific accuracy is essential. 

This process takes a couple of weeks – remember, there are half a million people's results to sift through. 

Stage 4: Getting geographic

Once we're sure we've got a clean and accurate set of bird data, we sort it in various different ways. This gives counts for the whole of the UK, for each of the UK's constituent countries, for each of the counties, and for each of the 400 local authorities.

It's a lot of work, but it means we can do some really interesting and accurate comparisons. 

Big Garden Birdwatch map

Stage 5: Comparing the results

When I'm comparing the results for individual species, I look at the average number of each species seen in each garden, which gives me an indication of their abundance. I also look at the percentage of gardens that the birds were seen in, which gives me a picture of their distribution.

You can really understand how numbers of birds using our gardens are changing, and get a good idea of how different bird species are doing, when you compare their abundance and distribution over several years.

For example, in the winter, if you see starlings, you usually see them in flocks. So someone who recorded starlings in their garden will most likely have seen lots of them. So their abundance could seem high. But this doesn’t necessarily mean they're doing well this year.

If you look at the distribution and see that starlings were only seen in 39 per cent of gardens, whereas 10 years ago they were seen in 50 per cent of gardens, then you know there has been a decline in the population.

House sparrow in hedge

Stage 6: Publicising the results

After all the number crunching is over, and we've been able to take an accurate health check of the UK's birds, we announce the findings on our website, and we send out press releases to the media. We want everyone to know which birds are doing well and which aren’t doing so well.


Because when a species isn't doing so well, such as starlings, which have dropped by 81 per cent since the Big Garden Birdwatch began in 1979, we want people to know that they have the power to make a difference.

These are garden birds we're asking people to monitor. Gardens are an essential part of their habitat. You can help a struggling species by making simple changes in your garden which benefit them.

The RSPB's job is to give nature a home. The best way we do that for garden wildlife is to make people aware that by planting a particular shrub, or digging a small pond, they could make a real difference.


The power of Big Garden Birdwatch is that when thousands of people are inspired to make small changes in their gardens to benefit wildlife, then it can really change the fortunes of an entire species.

By being a citizen scientist and taking part in the Big Garden Birdwatch, you are playing a vital role in the health of the UK's wildlife. Thanks for your help!

Take a look at the results for 2021!

House sparrow male, perched on edge of garden shed roof

Find out who came top of the flocks in last year’s Big Garden Birdwatch.