Winter is without doubt a spectacular time to visit a WWT centre if numbers are what you’re after. Tens of thousands of ducks, swans and geese have spent the last few months with us and many of those birds are now preparing for long journeys back to their breeding grounds of Iceland, northern Europe and Russia.

If you haven’t managed to visit us over the winter, now is your last chance to see our migrant visitors. With westerly winds forecast over the coming days, the conditions will be perfect for their return journeys and many will be leaving – get here quick!

The behaviour they’re currently exhibiting is typical of birds that are restless to leave and push on with the task of breeding – they’re spending a lot of time resting and conserving energy in preparation for flights that are often over 1,000 miles in distance in complete contrast to how they were when they arrived back in October.

But just because the swans and geese are ready to make their return journeys doesn’t mean there isn’t plenty to see at our centres over the coming months.

In fact this time of year, when the signs of spring are just beginning to show themselves, is a fascinating one for wildlife watching. Many of our centres will be seeing new birds arriving on a daily basis. As they head east or north across the country on their migrations, many will stop off in unexpected places.

And of course there’s the opportunity to see the first incoming songbirds, which will be arriving here from central Africa for the summer. The first spring birds will include sand martins, chiffchaffs and wheatears – one of the first wheatears was spotted in Cornwall last week. March will also bring with it the first swallows and willow warblers.

Other signs of spring are already apparent at some of our reserves – the first snowdrops for instance. As the first trees begin to flower we’ll start to see a number of insects and, in turn, they will provide food for our arriving passerines.

Of all the seasons, spring is arguably the most inspiring and dramatic to witness. Keep up to date with the natural highlights at your local centre by visiting their wildlife sightings pages.

Back in January an expert team that included WWT scientists headed out to Bulgaria to catch wild red-breasted geese in the wintering grounds for the first time.

The goal was to fit transmitters to a number of these endangered birds in order to track their movements. Until now these enigmatic geese have been a bit of a mystery and in order to understand why their numbers are plummeting (the population suffered a 50% decline at the start of the century) we need to know more about them – in particular, their feeding distribution, their roosting behaviour, and their migration routes.

Over the next few years, several different types of tag will be fitted to the birds. Some will last only a few months but record the birds positions many times each day – these will give lots of detailed information about how they use fields in Bulgaria.

Others will last several years but record locations just a few times per day – these will help clarify the birds’ migration routes and perhaps identify previously unknown wintering sites.

After we had caught birds in Bulgaria in January, the weather turned unseasonably mild and nearly all of the red-breasted geese headed north – just 200 remained in the country at the end of that month.

Colder weather in February saw 3,000 return, including one of the two tagged birds, enabling us to download the data using a radio aerial.

The tag records the bird’s position very accurately using GPS every four hours and has already revealed much useful information.

Although Durankulak and Shabla Lakes are the preferred roosts, geese will also roost on the sea – normally when there is intense hunting pressure around the lakes or when the lakes are completely frozen.

Our bird roosted on the sea on several nights, and on one occasion – seemingly drifted by the current overnight – was 7 km from shore by 4:00 am. It left Bulgaria on 15 January for an area of Romania 100 km to the north where it stayed for the next two weeks. (It returned to Durankulak on the same evening that we arrived there for our second catching trip!)

Unlike Bulgaria, where birds are restricted to a thin coastal strip, our bird used an area about 50 km inland in Romania, adjacent to the Danube River. It roosted on a very small lake, just 500 m long by 50 m wide, but on several nights it remained in the fields throughout darkness.

On 7 February, having fed in the fields by Durankulak in the afternoon, its next location was 130 km to the north, yet by 4:00 am the next morning it was again back on the sea off Durankulak. Perhaps an aborted attempt at migration as the weather warmed up?

The next day we could not find the bird and, like many of the red-breasts, it had presumably started its migration in earnest. The tag also contains an accelerometer, which records small movements in the bird (similar to the handset of video games).

This will enable us to determine how long it spent feeding, resting and flying each day and will provide yet more insights into the bird’s response to weather, hunting and other factors, and, for example, whether it continued feeding when it remained in the fields overnight.