Biological research
Biological research
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A major strength of Biotrack is its direct involvement in research, constantly meeting new technological challenges. Right from the start, Biotrack employees were making tags for their own research into goshawks and squirrels. We believe this strong interest in biological research allows us to understand your needs and meet them more effectively.

[Dragonflies]  [Buzzards]  [Nightjars]  [Thrushes & Blackbirds]  [Bearded Tits]  [Barn Owls]  [Sika Deer]  [Vocal Individuality]  [Other Projects] 

Radio-tracking male Emperor Dragonflies


Over the summer of 2010 Sarah Levett and Dr. Sean Walls completed a pilot study on radio-tracking male Emperor Dragonflies (Anax imperator) on Dorset Heathland. This is believed to be the first Dragonfly radio-tracking project in Europe and the first radio-tracking study to examine Dragonfly behaviour on a home range scale. Radio tracking gives unique insights by allowing you to locate the dragonflies when they would otherwise be difficult to sight.

Anax imperator is the largest British Dragonfly species in the UK and is known for its territorial behaviour over water. This study showed that the dragonflies were able to fly, patrol and maintain territories whilst tagged, with one dispersing over 1.5km from the catch site.

Our tracking results hinted at two behavioural patterns; one of dispersal away from the catch pond, and one of timetabling behaviour between a territory and roost sites. We also collected measurements of light and temperature data, hinting at a correlation between weather variables and activity levels (figure right - light level in red, temperature in purple and signal strength in blue).

This was a successful pilot study that we hope to expand next year by tagging more Emperors to gain more quantiative data. For more information, please see the Dragonfly Radio-tracking pdf.

Nightjar project


Brian Cresswell’s nightjar project has got much more exciting recently, with the return of birds with geolocators. These LightBugs have shown that the birds wintered in the Democratic Republic of Congo, outside their known wintering range. For more information see Nightjar Geolocation.

This latest investigation builds on previous work started in the 1980s with the Stour Ringing Group, that found nightjars foraging in meadows far from the heathland on which they nested, thus establishing the need to look after areas surrounding the nesting areas. With geolocation it seems that conservation in wintering areas can also be targeted.

Radio-tracking buzzards


When Sean Walls started working on buzzards with Robert Kenward (Centre for Ecology and Hydrology) in the 1990s, they were still rare over much of the UK. 20 years later they are the most commonly seen raptor. Working during that time, when buzzards were still spreading back into their previous distribution, enabled them to consider how birds colonise new areas.

Radio-tracking revealed some surprising findings:

  • Buzzards were philopatric; preferring to stay where there were lots of competing buzzards rather than use the emptier areas
  • Survival was better than expected, leading to the understanding that only a quarter of the birds in the study area were breeding, thus the population was much bigger than assessed from a survey of breeding pairs.

Both of these findings are crucial to conservation of large raptors and probably to many other species too.

Thrushes and Blackbirds

Thrushes and Blackbirds

We were closely involved with Ian Hill's doctoral project at the University of Oxford. Ian's study was conducted in the gardens and farmland around Biotrack. His main aim was to establish why the British song thrush (Turdus philomelos) population is in steep decline.

To do this he has compared the survival and behaviour of radio-tagged fledgling song thrushes to fledglings of the more common blackbird (Turdus merula). Though a similar species to song thrush, blackbirds have had a stable national population during the period of the song thrush decline. Ian completed his doctorate in 1998.

Song thrushes were significantly more mobile than blackbirds when leaving the nest. They continued to drift away from the nest over an extended period and were associated with habitats found in the periphery of the garden. In contrast, blackbirds stayed closer to the nest and then had a few days dispersal before settling into a new range. They associated with the more managed garden centre. Being in more open habitat to begin with, blackbirds suffered higher mortality initially. However, after the blackbirds had dispersed survival improved, whilst song thrush numbers continued to decline markedly.

The cooperation between us encouraged new developments including the evolution of a backpack with an elasticated wing loop harness that accommodates growth. The design was presented at the Proceedings of the Fifth European Conference on Wildlife Telemetry (held in Strasbourg in 1996). The project also gave us the opportunity to test our smallest "Pip" transmitters before supplying them to other projects.

Radio-tracking study of Bearded Tits

Bearded Tits

In 2002, working with The Wetland Trust and an MSc student from Reading University, Brian Cresswell initiated a radio-tracking study of Bearded Tits. The research was conducted at a private nature reserve in East Sussex (UK), and compared the foraging behaviour of adults and independent young.

Using 'RANGES 6' range analysis software, we analysed range overlap within and between age classes, looked at habitat preferences and used dynamic interaction analysis to investigate the formation of juvenile pairs (an interesting behaviour in bearded tits).

Juvenile females ranged further overall than adult and juvenile males, but their core ranges were the same, suggesting that juvenile females were more excursive. Range overlap within age classes was greater than between age classes at most levels of range core area (as estimated by location data utilisation in cluster analysis). Areas with the densest locations appeared to be exclusive. Adult ranges excluded juveniles, and vice versa, at 65% location data utilisation (65% cores). Adult ranges were exclusive of other adults at 35% cores and juveniles of other juveniles at 20% cores.

Dynamic interaction analysis indicated that at least two of the juveniles had formed pairs, but there was little evidence of flocking, and static range overlap was a poor predictor of dynamic associations. The most used habitat in proportion to availability for both age classes was Phragmites. The second most used habitat for adults was Typha, whereas for juveniles it was small pools of open water (probably the water's edge was used).

Study of barn owl dispersal

Barn Owls

Brian Cresswell is leading a study of barn owl dispersal; to investigate movements, habitat use and causes of mortality during their first year of life. This is a joint venture with The Wetland Trust and 'Chalk & Hawks', a European-funded project combining conservation with wildlife tourism.

The project started in Sussex in 2003 where we monitored the behaviour of a brood of barn owls before and after tagging (using CCTV). The owls habituated almost immediately to their backpack and harness.

In 2004 the study was extended to three more broods (nine birds), this time in Dorset, and three birds which survived now have young of their own.

Sika Deer, Cervus nipon

Sika deer

Sean Walls is currently advising a local study on Sika Deer, Cervus nipon started by Bournemouth University and the Royal Society for the Protection of Birds to look at the management of the fast increasing population. It is early days, so there are no publications yet.

Vocal Individuality in reed buntings and Cetti's warblers

Vocal Individuality

The ability to distinguish one individual bird from another by its song can add valuable detail to a breeding bird census. It can be used to monitor local movements within and between years, and provide long-term data on survival. It can enable census methods to be calibrated (e.g. how many birds are missed and how many are counted more than once?), such that a more accurate estimate of population size is obtained from basic census methodology.

Brian Cresswell initiated a study of Vocal Individuality in reed buntings and Cetti's warblers at a private nature reserve owned by The Wetland Trust in Sussex. Three MSc students from Reading University and University College London have worked on the project since 2002. Sonograms and spectrograms of song recordings from reed bunting and Cetti's warblers have been analysed using discriminant function and cluster analyses.

Male Cetti's warblers appear to be highly vocally distinct. Reed buntings also appear to be separable by their song, but may be more variable depending on which neighbouring birds are singing at the same time. The student in 2005 set up an experiment to compare the response of Cetti's warblers to different playback songs (self, known neighbours and strangers), which has yielded some interesting results.

The techniques developed in these projects are being used to monitor the number of male Cetti's warblers on the Sussex reserve where the research is taking place.

Other Projects

Oxford University expeditionThe members of the Biotrack team have also been involved more briefly with other projects such as an Oxford University expedition to study Giant Jumping Rats in Madagascar, Squirrels in Dorset (UK), Purple Sandpipers in Norway and snipe in Cambridgeshire (UK).

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