Wood Warblers do not seem to attract as much attention as other declining species but the speed of their disappearance is only exceeded by Turtle Dove, Willow Tit and Pied Flycatcher. As Hampshire is now on the south-eastern edge of their range, the decline here has been particularly rapid in recent years. A small number of individuals and groups around the country are trying to understand the reasons for this.
As part of the ongoing research, the BTO applied to HOS to fund the cost of 15 geolocators. These are small tags which record the time of day and light levels and enable us to determine the location of the bird to within an accuracy of about 100km. This may not sound very good but for a migratory species it provides vital information about the timing of migration and the location of staging areas and their winter quarters. There have been no ringing recoveries of Wood Warblers from sub-Saharan Africa. HOS kindly agreed to fund the tags and these were deployed at various sites in the New Forest during 2018.
As the tags are so small, they are unable to transmit information and have to be retrieved in order for the data to be downloaded. So when the birds start to return in late April we will be scouring the New Forest to try to find the tagged birds so that they can be recaptured and the tags removed. Wood Warblers are not site faithful so the tagged birds could turn up anywhere. The birds will have moulted during the winter and it is likely that the tags will be hidden beneath the new feathers. However all tagged birds, and a number of others, are colour ringed.
Any birdwatcher who visits the New Forest to see Wood Warblers this spring can help by reporting the birds that they see or hear. If you don’t manage to see whether the bird is colour ringed, or cannot read the colours, don’t worry as we will follow up all sightings of birds that we don’t already know about. If you can read the colours, or better still obtain a photograph, that is especially useful. Photos do not need to be of high quality but please do not crop them before sending as we are likely to need to zoom in considerably in order to accurately read the colours. The most important thing is to be as precise as possible about the location. A report of a bird in a particular wood or inclosure requires are great deal of effort to refind. If you have access to GPS, that is ideal and we would appreciate the full grid reference. If not then a grid reference can be obtained from one of the on-line sites such as https://gridreferencefinder.com/ . Please do not think that someone else will have reported the bird that you see, we have received very few reports of birds in previous years (even when they have been seen by dozens of people). We would rather get a hundred reports of the same bird than no reports of it! Please send reports to email@example.com . Reports of unringed birds are also useful for other aspects of our study.
If anyone would like to get more involved in our studies of the breeding biology of Wood Warblers, we would welcome observers who can search for and monitor individual birds on a regular basis. Please get in touch via the email address above and we can discuss what contribution would be most suitable for you.