Effect of Landscape Elements on the Symmetry and Variance of the Spatial Distribution of Individual Birds within Foraging Flocks of Geese

Behavioural instability is a newly coined term used for measuring asymmetry of bilateral behavioural traits as indicators of genetic or environmental stress. However, this concept might also be useful for other types of data than bilateral traits. In this study, behavioural instability indices of expected behaviour were evaluated as an indicator for environmental stress through the application of aerial photos of foraging flocks of geese. It was presumed that geese would increase anti-predator behaviour through the dilution effect when foraging near the following landscape elements: wind turbines, hedgerows, and roads. On this presumption, it was hypothesized that behavioural instability of spatial distribution in flocks of geese could be used as indicators of environmental stress. Asymmetry in spatial distribution was measured for difference in flock density across various distances to disturbing landscape elements through the following indices; behavioural instability of symmetry and behavioural instability of variance. The behavioural instability indices showed clear tendencies for changes in flock density and variance of flock density for geese foraging near wind turbines, hedgerows, and roads indicating increasing environmental stress levels. Thus, behavioural instability has proven to be a useful tool for monitoring environmental stress that does not need bilateral traits to estimate instability but can be applied for indices of expected behaviour.

[1]  Anne L. Harrison,et al.  Scale-dependent habitat selection by wintering geese: implications for landscape management , 2017, Biodiversity and Conservation.

[2]  J. M. Rowcliffe,et al.  Competition, predation risk and patterns of flock expansion in barnacle geese ( Branta leucopsis ) , 2003 .

[3]  J. Madsen Impact of disturbance on field utilization of pink-footed geese in West Jutland, Denmark , 1985 .

[4]  E. Rees,et al.  Impacts of wind farms on swans and geese: a review , 2012 .

[5]  C. Strobeck,et al.  Fluctuating Asymmetry: Measurement, Analysis, Patterns , 1986 .

[6]  Jesper Madsen,et al.  Effects of wind turbines and other physical elements on field utilization by pink-footed geese (Anser brachyrhynchus): A landscape perspective , 2000, Landscape Ecology.

[7]  V. Loeschcke,et al.  Developmental instability as an estimator of genetic stress , 2006, Heredity.

[8]  Cino Pertoldi,et al.  The Novel Concept of "Behavioural Instability" and Its Potential Applications , 2016, Symmetry.

[9]  Jennifer A. Gill,et al.  Habitat Choice in Pink-Footed Geese: Quantifying the Constraints Determining Winter Site Use , 1996 .

[10]  Magda E. Chudzińska,et al.  Using habitat selection theories to predict the spatiotemporal distribution of migratory birds during stopover – a case study of pink-footed geese Anser brachyrhynchus , 2015 .

[11]  J. M. Black,et al.  Foraging dynamics in goose flocks: the cost of living on the edge , 1992, Animal Behaviour.

[12]  G. Roberts Why individual vigilance declines as group size increases , 1996, Animal Behaviour.