Nightjars in Britain have shown a 36% increase in breeding numbers between 1993 and 2004, following decades of decline. Although conservation measures within Britain have assisted the species’ recovery, we still know almost nothing about movements outside the breeding season. Ringing recoveries are few, with no records from the African wintering range.
To gain an insight into where British Nightjars overwinter and the migration routes taken, BTO staff, in collaboration with Biotrack, commenced a geolocator study in 2011. This work builds upon a pilot study started by Biotrack in 2008, which yielded data for three individuals.
During 2011, BTO staff attached 19 geolocators to Nightjars in Thetford Forest in East Anglia. The geolocators collected data during three periods corresponding to autumn, mid winter and spring.
These devices record light levels, allowing position to be calculated from daylength and the time of solar noon. Learn more about how geolocators work. Although the calculated locations may only be accurate to within 100km, this still provides detailed movement information at the Continental scale. However the birds need to be re-caught in order to retrieve the data.
The first of three birds tagged in Thetford Forest was recovered in May 2012; an adult male ringed in June 2011 (Fig 1). After leaving the UK, it appears that LB12420 moved fairly slowly through Europe, with the first locations logged in Libya in October. Thereafter he moved rapidly south east to Sudan and eventually wintered in the Democratic Republic of Congo.
During late February, LB12420 relocated to the northwest before migrating through West Africa (although the precise route is uncertain). This bird then moved steadily east through North Africa and across the central Mediterranean with a brief stop in northern France, before returning to Thetford Forest on the 10th May. Having completed his journey, LB12420 was found dead on 21st May 5km from where he had originally been ringed.
This geolocator study would not have been possible without the support provided by the Shoreham & District Ornithological Society and with money from a legacy from Clarice Dawson. We would very much like to acknowledge the support and assistance provided by the Forestry Commission, Biotrack and the Thetford Forest Ringing Group.
During summer 2014, BTO and Natural England staff embarked on a ground-breaking study using novel GPS tags (right), to examine the movements of breeding Nightjars in Thetford Forest and at Dersingham Bog NNR. The GPS tags, developed by Pathtrack, record hundreds of precise locations at five minute intervals over many nights, providing the most detailed information on foraging movements and habitat use ever obtained for the species. The results will greatly improve our understanding of species' habitat requirements and better inform management and conservation efforts.
Plans are in prepartion to use these GPS devices to reveal the actual migration routes and even to examine the habitats used in the African wintering grounds.
Find out more
- For further information please contact greg.conway [at] bto.org (Greg Conway) or ian.henderson [at] bto.org (Ian Henderson).