Study Group

 
  

 
 
 

 
 

Glen Clunie

Glen Clunie Ring Ouzel Breeding Ecology Project

Summary of Results 1998-2004

Part 6

What is driving the population trend?

Ultimately, we want to know which factor(s) are driving the population trend in Glen Clunie. This may then provide a clue as to which factors are driving the national population decline. We looked at correlations between the population trend and (a) productivity (b) chick return rates and (c) adult return rates. There were no apparent relationships for (a) or (b), but there is an indication that the population was higher in years where adult return rates were high (Fig.10). This suggests that it may be survival, and not productivity, that is driving the population trend in Glen Clunie. However, we will need comparable data for several more years to determine if this apparent relationship is statistically robust.
adult_return_rates2_graph

Future work

We plan to continue the study until at least 2005, and hopefully beyond. Our priorities are to monitor future population trends and breeding success, to continue with the colour-ringing programme, to measure chick and adult return rates, and to quantify chick dispersal. The seven years of data we have collected is currently being used to model territory occupancy and breeding success in relation to habitat and topography, in collaboration with the RSPB Conservation Science Department. These results could potentially be used to recommend appropriate habitat management in the many areas where Ring Ouzels are declining or have disappeared.
In 2005-06 we plan to organise a sabbatical project, in which several glens within 30km of Glen Clunie and Glen Esk are searched for dispersing colour-ringed birds. SOC members will be invited to participate in this part of the project. We may be then able to estimate the number of birds dispersing from both glens, and thus measure more accurately survival rates. If this is possible, we will then be able to produce a full population model to examine which factors (e.g. productivity, first-year survival, adult survival) have the greatest effect on population dynamics.

Products

Two papers, one on status and another on catching methods and biometrics, have been published in ornithological journals (Rebecca 2001, Sim & Rebecca 2003). A summary of results for 1998-2002 was recently published in Scottish Bird News (September 2003). IS has given talks on the project at the 2002 Scottish Ringers Conference, three SOC and two RSPB local members groups, and at all seven of the annual Ring Ouzel Study Group meetings. We envisage producing at least another four ornithological papers on (1) nest site selection and breeding success (2) territory occupancy in relation to habitat/topography (3) survival/return rates and nest site fidelity in adults and (4) dispersal/survival of chicks. No data on topics (2) - (4) have been published for the species.

Acknowledgements

We thank Invercauld Estate for co-operation with the study. Raymond Duncan, Judy Duncan, Rik Smith, Justin Prigmore, Alan Leitch, Ian Rendall, James Pearce-Higgins and Graeme Buchanan helped with the fieldwork. The RSPB provided fieldwork time for Graham Rebecca in 1998-2004, and for Innes Sim in 1999, and provided grants in 2000-2004. We thank the SOC for providing grants in 2000-2004.

 

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