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A key factor analysis of a sparrowhawk population.
1Monks Wood Experimental Station, Institute of Terrestrial Ecology, Abbots Ripton, PE17 2LS, Huntingdon, UK.
Oecologia
|March 18, 2017
Summary
Overwinter loss is the primary driver of Sparrowhawk population stability. This key factor, occurring after fledging, regulates breeding numbers and explains most annual population fluctuations.
Area of Science:
- Ornithology
- Ecology
- Population Dynamics
Background:
- Sparrowhawk breeding populations exhibit annual fluctuations.
- Understanding factors influencing population stability is crucial for conservation.
Purpose of the Study:
- To identify key factors affecting Sparrowhawk population dynamics in Eskdale, Scotland.
- To analyze the causes of population change and stability in a Sparrowhawk population.
Main Methods:
- Key factor analysis was used to identify critical periods of loss.
- A simulation model was employed to test the impact of overwinter loss.
- Data collected from 1972-1986 on nest numbers and annual production of young.
Main Results:
- Overwinter loss, between fledging and recruitment, explained 77% of the variance in total annual loss.
- Overwinter loss was the only density-dependent factor identified and could stabilize the population.
- Breeding season losses were inversely correlated with subsequent overwinter losses.
Conclusions:
- Overwinter loss is the critical factor regulating Sparrowhawk breeding population size.
- Density dependence in overwinter loss ensures population stability.
- The dynamics of breeding success and winter mortality are inversely related.
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