How to Survey Breeding Birds (UK)

As well as being an absorbing hobby, birdwatching is also a source of important data about the environment.

In the UK, it is very easy to get involved with surveying birds through the British Trust for Ornithology.

They run a number of different kinds of survey throughout the year, each with a different methodology.

This is a run-through of the Breeding Bird Survey process, and a fairly blatant request for other readers to get involved.  A lot of the information and methodology comes from the BTO/BBS website, but modified from my own experiences.

(I will be assuming that you are already a birder of some level)

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Firstly, just what is the BBS?

It is a nation-wide survey, designed to be simple to take part in, aimed at keeping track of the wild bird population of the United Kingdom.

The data is used to provide both national and regional trends for bird populations.

The status of wild bird populations is an important indicator of the health of the countryside, and has received much greater interest from the Government and wider public in recent years. ...  BBS results are being increasingly used to set conservation priorities by Governments and non-Governmental organisations.

To perform the survey, you need your own square.

Firstly, register online.  It is possible to take part in the BBS without working online, but it is a darn site easier online.

Registering online automatically gets you in touch with your local Regional Organiser.  If you live near a county border, you may find yourself being assigned to the next county, as the regions are arranged according to the Ordnance Survey grid system.

Once you get in touch with your local RO, they will negotiate a semi-random location in your area.  The location will be a 1km square ("your" square).  The RO has to try and assign squares as randomly as possible to prevent people only surveying "juicy" (bird-rich) sites - knowing that a location is poor in birds is almost more important than knowing where there are plenty of birds.

You will get a grid reference for your square, and your RO will surface-mail all the maps and forms you need.

So far, all you have done is click a few buttons online, but you will eventually be taking part in an official, national survey.

You will need to do it properly.

Naturally, you will have a decent pair of binoculars (if you don't, the Viking 8x30 Standards are good value at around £30 ($45).  Otherwise, go with a brand you know, and spend as much as you can afford.  If possible, visit a specialist local dealer to try them for feel and ease of use.)

Where BBS differs from "normal" birding is the likelihood of going "off piste" - most of the time you will be on private land, away from public access and footpaths.  Prepare for the worst - in my square, I spend part of the survey pushing through chest-high grass and following deer-tracks to get over waterways with no bridges.  I went poorly-prepared the first time, and came back soaked to the skin, even though it wasn't raining.

• Tough footwear.  Weatherproof clothing.  A hat.  If you can, avoid the garish hiking gear  - you don't need to go full camouflage, but wearing fluorescent yellow Gortex will keep you dry but bird-free.
• Clipboard.  You will be making a written record of your observations in the field.  Literally.
• Pencil.  Better than a pen, because it won't run if it gets rained on.
• Maps.  You will get a map of your square, but not of where it is - especially the first time you visit your square, you will need to orient yourself with the landscape.  The Ordnance Survey site can help you select the map you need, as well get a digital image of your square.
• Compass.  Not essential, but useful if your square is fairly uniform, or your map-reading skills are rusty.
• ID.  Tramping around on private land, you may run into people who don't know you are allowed to be there, so take your ID, and make sure you carry the (supplied) letter from BTO that acknowledges you are doing an official survey.
• Bird book.  Just in case.

You do not need to be an expert birder, but you do need to have a reasonable awareness of the species you are likely to encounter.  You can do training courses on survey techniques, but the best thing is to practice birding at every opportunity.

You will need to know birdsong.  If you already do, then kudos to you.  If not, your RO will be able to send you a CD or cassette of British birdsong, or you can browse it on the net (for instance, the RSPB website has audio recordings of most of the birds you are likely to see, as well as video clips of many).  You can buy CDs, DVS and software for learning birdsong, even an iPhone app.

Once you are registered and equipped, you will probably need to obtain permission to actually visit your square.  This being the UK, so most squares will be near roads, but, this being the UK, most squares will be on private land.

Your RO will give you the land-owner's details, but it is up to you to give them a ring to ask permission to cross their land.  Very few landowners will deny access (in which case you contact your RO and arrange a different square), but you must always obtain at least verbal permission to enter, otherwise you are liable under trespass laws.

When you call, be polite.  Identify yourself as doing a survey for the British Trust for Ornithology (most people are unaware of what "BTO" means), and be prepared with a brief run-down of the purpose of the visit.

You should also be prepared with a diary, just in case you can only access the square on certain dates - farmland is working land, after all.  I have to contact the owner of "my" square because he breeds pheasant and suffers from poaching - if he doesn't know I'm coming, I might get shot.

Before you survey the birds, you need to survey the land.  This should be done in March or early April.

Firstly, you will need to select your route.   A survey route is called a "transect", and you will need two.  If your square has been surveyed before, your transect routes will be marked on your paperwork - check you can still follow them, and alter your maps if required (you will need to submit new routes to your RO).

If you are the first person to survey your square, you have the privilege of setting the routes for all future surveys 9even if your square is taken over by another birder in the future).  "Perfect" transects cross your square in either a North-South direction or an East-West direction, 500m apart, and 250m from the edge of your square (see the first image).  each transect is divided into five, 200m sections for recording purposes.

The world is rarely perfect, though, and your routes may need to divert from perfect, even stop part-way across your square (see the 2nd and 3rd images). 

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The habitat of your square will affect the birds that choose to breed there.  Changes to the habitat will change the bird population.

At the same time as checking your route, you need to record the habitat adjacent to your route.  This is simply a matter of noting codes on a form you are sent by your RO.

As you walk each transect, keep an eye on landmarks every 200m along the route, to keep you on track in the survey visits.

The actual bird survey takes two visits, but they both follow exactly the same procedure.

The "Early" visit should happen from Early April to Mid May, and the "Late" visit should happen some time from Mid May to Late June.  There must, however, be at least four weeks between them.

The "Early" visit covers resident birds, the "Late" visit covers migrants.

Do not visit on days of extreme weather (heavy rain, strong winds) as birds will not be active at those times, and avoid days of poor visibility (fog, heavy drizzle), as you will miss the birds that are about.

You should start no later than 09:00, preferably between 06:00 and 07:00, but try to avoid the peak period just after dawn, as this will give artificially-high bird numbers.

The forms you take with you have spaces to record basic details of the weather (see the first image), as well as the times you start and finish each transect.

Each 1km transect should take about 45 minutes to walk.  You can pause occasionally to scan for birds, but you should not pause for long periods.  The BTO say you should walk at "a slow, methodical pace", but I think of it as plodding along.

You do not record birds that are behind you, or birds that are beyond your transect (no matter how interesting).

Instead, you note the number of each species at the appropriate distance from your route.  Try and use the BTO species codes, as it saves time in the long run.  You should also note if they are flying past (see the second form-section below).

The form is split into ten sections.

Each section stands for 200m of a transect -you switch sections on the form as you walk the transect.

You fill in birds you see and birds you only hear (which is why you need to practice your bird calls).

You will also need to not any changes in the habitats between visits, such as crops growing higher or bushes being removed.

After you have done the survey (between each visit, if you want), you log on to the BBS site and enter your bird sightings.  The website uses the BTO species codes, which is part of the reason for using them to fill in the original form.

Once you have filled in your data, you can sit back and relax - the BTO do the rest of the work on the BBS, keeping track of the coverage, and trends in the data.

The map below shows how much more help is needed for better coverage.

You can also track the spread or decline of individual species on a series of animated maps.  Some of the animations are quite horrifying, showing huge declines in once-common species.  Others are curious, such as the raven, which showed a large growth and spread in the earlier years of the survey, followed by a decline.  "Why?" is one of the questions the survey tries to answer.

• March – April

Reconnaissance visit to set up or check transect route and access, and complete habitat recording form.

• Early April – mid May

Early BBS visit, during the period of main breeding activity of resident birds in your area, which will vary depending on where you are in the UK.

• Mid May – late June

Late BBS visit, during the period of main breeding activity of migrant birds in your area, which will vary depending on where you are in the UK.

• July – August

Enter data on BBS-Online or return completed forms to your RO.

Once you are into surveying, you may find that your once-a-year contribution is not enough to keep boredom at bay, or you want excuses to roam more widely across private land to find your birding targets.

In that case, you may want to take part in other surveys.

The most important projects are the core surveys, which require varying skill-levels and varying levels of commitment.

Later in the year, you could change focus and re-survey your BBS square, this time looking for butterflies, moths and dragonflies.

Whichever route you take, your birdwatching hobby can be an important contribution to UK conservation science.

Maybe you don't want to do an official survey, but you want to take your casual birding a step further?  Then why not try seawatching?

Enjoy.