Wood Warblers and other Colour-ringed Birds

Posted April 4th, 2013 at 4:50 pm

As migrants start to arrive please look out for colour-ringed birds - there will be information on the Forum as well as here.

Ring Ouzels were "multi" colour-ringed last year, also Wood Warblers and some Pied Flycatchers had blue or red rings.  If you see any colour-ringed birds please let us know.

The Wood Warbler colour ringing project is to help:                                                          John WaltersWood Warbler sketch by John Walters

Investigate the decline of Wood Warblers in Devon

Since 2009, the RSPB has been carrying out research into the decline of Wood warbler populations in the UK. Initially working in one of the species main strongholds in mid-Wales, from 2012 we shifted emphasis to other regions -including Devon. The rationale behind this shift is that although the population in Wales has declined, by around 20% since the 1980s, the Wood warbler population in Devon has fared even worse, declining by almost 70% over the same period. If factors operating on the breeding grounds are driving these population declines, then we are more likely to identify this in an area  where birds have declined more severely.                     

In 2012 a total of 135 Wood warbler nests were monitored in woodlands across Dartmoor. Of these 38 were predated of which 19 could be attributed to actual predators through the use of nest cameras (6 Jay, 4 Buzzard, 4 Sparrowhawk, 2 Grey squirrel, 1 mouse, 1 rat and 1 Weasel). These predators are similar to what predated nests found in Wales, where jay was also the main predator. On Dartmoor in 2012 many nests were lost due to the terrible weather we all experienced which caused high rates of nest failure through starvation and desertion. Unfortunately comparisons of nest mortality, one of several possible drivers of the decline, between Devon and Wales were confounded by this. Work in Devon will be repeated in the same Dartmoor woodlands in 2013, and this work should enlighten us on whether poor nest survival is contributing to the species decline. We will also continue to collect data on invertebrate prey abundance, and predation, for comparison with equivalent data collected in Wales.

Now this is where you can help! As part of our work in 2012, 69 adult Wood Warblers (42 males and 27 females) and 191 nestlings that fledged were fitted with unique combinations of colour rings, and we hope to confirm that some of these return to Dartmoor woods in 2013. This will help us determine survival and recruitment rates, and the degree of site fidelity from one year to the next. Throughout their European breeding range Wood warblers typically show very low site fidelity, although return rates of birds are higher in the west of their range. As Wood warbler distribution in Devon has contracted to relatively small areas of Dartmoor and Exmoor we are hopeful that we can locate these returning birds – with your help. A small number of Wood warblers were colour ringed at East Dartmoor NNR in 2011 (19 adults and 37 young) and some of these did return to various Dartmoor woods to breed in 2012. So we do expect a significant number of returning Wood warblers this spring to be colour ringed. To help us we would be very grateful to learn of any sightings of colour ringed Wood warblers from birders out in the regions woodlands this spring and summer. The Wood warblers were ringed with a colour ring above a standard BTO numbered metal ring on the bird’s left leg, and two colour rings on the bird’s right leg. If you see one of these birds, please contact me with details of what you saw, when and where. In return we should hopefully be able to give you some history of the bird concerned.

I look forward to hearing from you, and let’s hope for a better summer!

Malcolm Burgess    Tel: 07816584083

Email:  Malcolm Burgess