Colour-marked Waterbirds in the Severn Estuary

Birdwatchers are being asked to look out for colour-ringed and dye-marked waders and ducks on and around the Severn Estuary.

BTO alongside WWT are working on a project to understand more about the home ranges of three species of waders (Curlew, Redshank and Dunlin) and a range of duck species on the Severn Estuary between Newport and Cardiff. As part of this work the Redshank and Curlew have been colour-ringed and Dunlin and some ducks marked with yellow dye. In addition, state-of-the-art tracking devices have been placed on some of the Curlew, Redshank and Shelduck, which is providing information about how birds use the estuary through the winter during both the day and the night.

Dunlin, by shell game on flickr

The work is funded by Tidal Lagoon Power, to provide high quality scientific information for the environmental impact assessment for a proposed tidal power lagoon (Tidal Lagoon Cardiff), and to inform their conservation and biodiversity programme – the Ecosystem Enhancement Programme (EEP).

If you see any colour ringed or dyed birds when you are birdwatching either on the Severn or elsewhere, we would be very grateful for any sightings of these birds. Of particular interest is any records of birds with yellow dye. Birds of different age have been marked on different parts of the body so please record the location of the dye and, if possible, the total number of birds in the flock, the date, time and location (ideally including a six-figure grid reference) alongside sightings of colour-marked birds.

Birds have been marked as follows

  • Redshank have yellow over white colour-rings on the left tarsus (below the ‘knee’), and a colour over a metal-ring on the left tibia (above the ‘knee’), plus two colour rings on the right tibia.
  • Curlew have orange over white colour-rings on the left tarsus, a single colour-ring on the left tibia, the metal ring on the right tarsus and two colour-rings on the right tibia.
  • Dunlin adults have yellow dye on the breast, while first-winter Dunlin have yellow dye on the undertail/flanks/rump
  • Shelduck have yellow dye on the normally white plumage on the neck/upper breast.

Any records of colour-ringed birds on the Severn would also be extremely valuable and all observers are given information on the history of any colour-ringed birds.

BTO are very keen to follow up any records quickly and would be grateful if you could phone 01842 750050, or email Emily Scragg ( with any records of colour-marked waders as soon as possible. Please email duck records to Ed Burrell (


Potential Impact of Severn Tidal Power Development

In October 2010, the Government announced:

that it does not see a strategic case to bring forward a tidal energy scheme in the Severn estuary at this time (Severn Tidal Power, Feasibility Conclusions).

In this month’s British Birds, a short article reports BTOs findings on the potential impact that each of the proposed five alternative developments would have on the estuary’s avifauna.

All five schemes would reduce the available inter-tidal habitat available to waders and Shelduck.  The remaining habitat would be underwater for a greater length of time, resulting in less time available for birds to feed.  The largest barrage scheme would result in the loss of up to three quarters of inter-tidal sandflats and a quarter of saltmarsh being lost.  All five schemes would result in significant declines in waterbird populations.

Water flow would be reduced as a result of each scheme, resulting in a less murky estuary, enabling plankton to flourish along with other species up the food chain, including the invertebrate prey of birds.  This positive effect however, would be small in comparison with the predicted large-scale loss of habitat.  Furthermore, increased long-term erosion of habitat is also predicted, again resulting in waterbird decline.

Wright, L.; Burton, N. & Clark, N. (2011) The potential impacts of tidal-power development on the Severn Estuary, British Birds 104, pp. 161.

Severn by saras2uk, on Flickr
Severn by saras2uk, on Flickr