A quarter of the world's population of brent geese winter in Essex and wildlife experts are now pioneering a way to track them from space.
Up to 1,500 to 2,000 brent geese come to the Essex Wildlife Trust Blue House Farm Nature Reserve on the River Crouch at Fambridge every year.
They fly in from Northern Siberia to feed on the grassland habitat.
- Click to watch a report by ITV News Anglia's Kate Prout
The Essex Wildlife Trust have captured five brent geese and attached GPS tags to their feet.
These tiny devices are solar powered and can upload the birds' location several times a day to satellites.
From the end of March thousands of Brent Geese migrate from our shores across to Holland up through the Baltic Sea to the Taymyr peninsula of Siberia.
It is a journey of around 2,500 miles that will take them around a fortnight to complete.
Brent geese are one of those rare British birds in that their numbers are actually really healthy.
That doesn't just depend on how much food they're getting when they're in the UK but it also depends on how many predators, like arctic fox, are around whilst they're breeding in Siberia.
Tracking the geese by satellite will reveal much more about their habits and their needs.