1 Fencing Issues and Risks for Cranes

Across the seasons, cranes use wetlands ranging from small farm dams to vast floodplains. Fencing is being promoted to fix wetland damage (or perceived damage) from grazing or feral animals. But fencing can create problems for cranes and other large waterbirds. Based on crane ecology and behaviour (see Brolga and Sarus Crane) there are three concerns: entrapment on fences, barriers to movement and rank dense growth in and around roost and breeding sites.

1 Entrapment

Brolga killed by fence collision, S of Normanton and N of Bourke & Wills, far NW Qld. Photographer Peter Merritt reports that 3 or 4 barb fences are normal for the area, 4 barb closer to yards as cattle tend to lean on them during yarding. Taken on 26 December 2009, at the height of the northern crane breeding season. (P. Merritt) ↓

Brolga fencekill

Crane wingspan is 2 metres or more, and their long legs hang down for landing and take-off. Fences in flight paths can entangle cranes and other large waterbirds such as endangered Black-necked Storks, especially on barbed wire. Young, less experienced birds are most vulnerable. Expected risk is low in areas with less fencing infrastructure. Both Brolgas and Sarus Cranes have been reported killed by barb wire fence entanglement in the significant winter flocking area of the Atherton Tablelands.

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2 Barriers to Movement

To cut costs, fences will likely be close to water: this will inhibit crane movement. To gain take-off momentum cranes need clear space to walk up a slope or to do a ‘run-up’ on flat ground. At Dry season roosts, flocks tend to land some distance away then walk slowly towards water to drink, bathe, ‘dance’ (display) and finally roost, often in shallow water. Fencing close to water will inhibit this natural behaviour and may totally block some roosts.

Fencing close round the wetland is a barrier to movement for young cranes, and may trap adults on barbed wire. Wet Season breeding territories are large (70ha to 300+ha) and may include several wetlands. Young cranes can't fly until up to 14 weeks old, and once beyond the chick stage cannot walk under fences either. So fences will likely increase predator and flood risk, as well as feeding effort for parents and young, and can lead to chick starvation. The most extreme case is pig mesh – a cage no young could enter or leave from hatching to fledging (first flight).

3 Overgrown habitat

Cranes do not breed, feed or roost in sites overgrown by rank grasses or shrubby vegetation. These plants may be native, like woody plants invading grasslands or introduced, eg para, buffel, guinea, gamba or brachiaria grasses, and the fodder shrub leucaena. Where the rise and fall of water across the seasons does not keep habitat open enough, moderate grazing and/or fire will. Fencing to exclude cattle permanently will likely exclude cranes permanently from many sites – owners cannot be expected to micro-manage growth around every dam or swamp, for cranes. An extreme case is revegetation with original plant species on sites that were densely wooded before clearing for agriculture transformed them into crane habitat.

Next: Fences 2 | Decision Guide»

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