Detecting edge effects of geese grazing at the boundary of woodland and grassland

The presence of geese on different areas of lawn was estimated by the length of droppings on the lawn. Geese defecate frequently and seemingly indiscriminately. Counting dropping is a well-known method for estimating their density on areas of land (Owen, 1971). However, we found it difficult to distinguish individual defecation events as the dropping tend to break apart as they are released. Therefore, we measured the total length of dropping in an area. Geese dropping are more or less cylindrical and we consider a measure related to the volume of droppings is more reliable than a count of their number.

Observations were conducted in July 2014 and March and April 2015 at Meise Botanic Garden, Meise, Belgium. Rectangular plots were laid out perpendicular to a woodland-lawn boundary on sections of a Botanic Garden frequently used by geese. These plots are detailed in file DroppingsPlots.csv. The sites for these plots were chosen because they were well separated from each other; were away from other trees and faced different directions. The plots were marked out using bamboo canes and a tape measure. Then either 20 or 30 randomly chosen 1 m² square quadrats were surveyed within the rectangular plot. The cumulative length of dropping in a quadrat was measured to the nearest centimeter with a ruler.

The results are found in file DroppingsMeasurements.csv.

The columns of this file are as follows

Plot - The identifying number given to the plot

X - The distance parallel to the woodland-lawn boundary

Y - The distance from the woodland-lawn boundary

Length - The total length in centimeters of the dropping found in a 1m² quadrat

Prunella - coverage of Prunella vulgaris L. in the 1m² quadrat on the DAFOR Scale (dominant 5, abundant 4, frequent 3, occasional 2, rare 1, absent 0)

Renoncule - coverage of Ranunculus sp. in the 1m² quadrat on the DAFOR Scale (dominant 5, abundant 4, frequent 3, occasional 2, rare 1, absent 0)

Bellis - coverage of Bellis perennis L. in the 1m² quadrat on the DAFOR Scale (dominant 5, abundant 4, frequent 3, occasional 2, rare 1, absent 0)

Lotus - coverage of Lotus sp. in the 1m² quadrat on the DAFOR Scale (dominant 5, abundant 4, frequent 3, occasional 2, rare 1, absent 0)

Glechoma - coverage of Glechoma hederacea L. in the 1m² quadrat on the DAFOR Scale (dominant 5, abundant 4, frequent 3, occasional 2, rare 1, absent 0)

Four species of geese are present in the Botanic Garden and may have contributed droppings to the observations. These species are Alopochen aegyptiaca (L. 1766) (Egyptian geese), Branta canadensis (L. 1758) (Canada geese), Anser anser (L. 1758) (greylag geese) and Branta leucopsis (Bechstein, 1803) (barnacle geese).