Chesil Beach and Fleet Lagoon are exciting areas for birdwatching all year round, but as we head into autumn, it's my favourite time of year for birding, when we start to see numbers of birds build on this internationally important nature reserve.

One of my personal highlights of autumn is the return of the dark-bellied brent goose, with up to 4,000 individuals expected to overwinter, spending their time feeding on the eelgrass found within the lagoon. These small geese start to arrive from the end of September, having travelled an incredible 3,000 miles (4,800 km) from their breeding grounds along the coasts of Arctic Russia or Siberia.

Some of the other birds are small and well camouflaged against the mudflats. Initially, you may not be able to spot them, but if you grab a pair of binoculars, the mudflats of the lagoon begin to resemble a moving carpet, with hundreds of small waders – like dunlin and ringed plover – searching for food in the mud. One of the more seasonal waders we see during autumn and winter is the bar-tailed godwit, characterised by its slightly upturned bill. Like many waders, bar-tailed godwits breed in Arctic Scandinavia and migrate to the UK for the winter months.

The final two highlights are the Mediterranean gull and red-breasted merganser. Although the Mediterranean gull can be seen all year round, numbers start to build in autumn, with upwards of 1,000 individuals counted around the Wild Chesil Centre during peak counts. The Mediterranean gull originates from the Black Sea and is a recent natural coloniser of the UK, with the first pair breeding in 1969. It is distinguished from black-headed gulls in winter by the lack of black wing tips and its brighter red legs and bill.

The red-breasted merganser is one of only two members of the sawbill family and starts to arrive in October. These are diving ducks, similar to the goosander, but lack the hooked end to the bill. The bill has serrated edges, making them perfectly adapted to catch fish, their main food source. You can often spot over 20 individuals between the Fleet and Portland Harbour during the winter months.

There are so many other birds we look forward to spotting throughout the autumn and winter months along Chesil Beach and the Fleet Lagoon, including some rarities. So, if you are visiting the Wild Chesil Centre, let us know what you have seen and if you are unsure of anything we would be happy to help you identify it!