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Use of West Coast Waikato estuaries by Canada geese and black swans

TR 2019/16

Author: Brian Taylor Smith (Tonkin & Taylor Ltd)

About this report

The exotic Canada goose and the native black swan are present in Waikato estuaries, and there are concerns that bird numbers are increasing. These waterfowl have various potential ecological effects, the most significant of which is damage to seagrass

This report reviews available information on the use of estuaries on the west coast of the Waikato region by Canada geese and black swans, including the potential effects of these species on estuarine ecosystems.

Read or download the report

Use of West Coast Waikato estuaries by Canada geese and black swans [PDF, 377 KB]

Contents
1 Introduction
1.1 Context
1.2 Overview of ecology
1.2.1 Canada geese
1.2.2 Black swans
1.3 Literature review objectives and outline
2 Literature review methodology
3 Findings
3.1 Population estimates
3.1.1 Geese
3.1.2 Swans
3.2 Habitat, diet and feeding
3.2.1 Geese
3.2.2 Swans
3.3 Ecological effects of swans and geese
3.3.1 Water quality
3.3.2 Changes to estuarine vegetation through feeding behaviour
3.3.3 Effects on indigenous birds
3.3.4 Dispersal of plants and invertebrates
3.4 Population management
3.4.1 Reducing reproductive success
3.4.2 Physical isolation of individuals from habitats/food sources
3.4.3 Lethal control of adults
3.4.4 Coordination
4 Conclusions and recommendations
5 References
Appendix A: Key search terms
Appendix B: Lakes and estuaries of the western Waikato surveyed annually for black swans and Canada geese by Fish & Game New Zealand