As daylight grows and temperatures start feeling a touch less nippy, the birds that have relied on the Solent through winter start preparing for the journeys that lie ahead.
For the birds that have spent the winter along the Solent, early spring marks the start of a remarkable transition. Longer days and rising temperatures signal that it’s nearly time to head north again. Species such as dark bellied brent geese, dunlins, grey plovers, black tailed godwits and sanderlings all begin the intense preparations needed for their journey to Arctic and sub Arctic breeding grounds, turning their attention from winter survival to the demands of migration.
What looks like enthusiastic feeding or gentle preening from a distance is, in reality, a finely tuned sequence of physical and behavioural changes. These birds are getting ready for one of the most demanding journeys in the natural world.
Feeding frenzy: building the fuel reserves they need
Before migration, coastal birds enter a phase known as ‘hyperphagia’, meaning they feed far more than usual. Fat is the vital fuel for long distance flight, and many species will almost double their body weight in the weeks before departure.
Along the Solent, this means:
- brent geese will be grazing intensively on eelgrass and coastal vegetation to build the fat they’ll need for their long journey to Arctic Siberia
- waders such as dunlins and grey plovers will be probing the mudflats for worms, molluscs and crustaceans, feeding almost continuously at low tide
- black tailed godwits will be building extraordinary fat stores that will sustain them through long migratory flights.
This makes it a crucial time to make sure birds can feed – and rest – without being disturbed, meaning it’s more important that ever that we give them plenty of space.
Hidden transformations: how their bodies change
While birds are busy feeding, their bodies are undergoing remarkable internal changes.
- digestive organs enlarge to process more food during the fat building phase
- as departure nears, these organs shrink, reducing weight and freeing up space for fat stores
- flight muscles strengthen in preparation for sustained flapping over thousands of miles
- hormonal changes triggered by increasing daylight stimulate both feeding and migratory restlessness
These shifts happen gradually, all driven by the need to optimise the body for long distance flight.
Black-tailed godwit fly to Iceland from the Solent
Restlessness on the shore: the onset of zugunruhe
As spring approaches, many migratory birds show a behaviour known as ‘zugunruhe’, or migratory restlessness. This can look like:
- increased preening and flapping
- more frequent short flights
- birds gathering in larger groups
- a noticeable alertness or agitation, especially at dusk
For Solent species, this restlessness is a sign that the internal clock is ticking. Brent geese, for example, begin to form tighter flocks and spend more time scanning the sky as their departure approaches.
Brent geese start preparing for their migration to Siberia in early spring
Feeding during migration: what happens once they leave the Solent
Once birds leave the Solent, their feeding patterns change dramatically.
Non stop flights
Some species undertake long, uninterrupted flights. During these journeys they do not feed at all, their digestive organs shrink further, and they rely entirely on the fat reserves built along our shores.
Stopover specialists
Other species, like our brent geese, migrate in stages, stopping at key wetlands across Europe. At each stopover they feed intensively to rebuild fat stores. These sites are as crucial as their wintering grounds, and without them birds cannot complete their journeys.
For many Solent birds, the next major stopovers include the Wadden Sea, the Dutch and German coasts, and estuaries along the North Sea.
The migration routes of dark-bellied brent geese take them along the Dutch and German coasts
Similarly, at this time of year many other migratory birds use the Solent coastline as a vital stop‑off on their journeys north, pausing here to rest and refuel after spending the winter further south. You can read more about these birds in our passage migrants blog.
Why March matters for the Solent
March is a critical month. Birds need space to feed undisturbed, safe roosting areas at high tide and minimal disturbance from dogs, people and water sports. Every extra calorie they gather now increases their chances of successfully reaching their breeding grounds and raising the next generation.
Thanks to everyone who gives birds space to feed and rest at this time of year: the final push before migration.
