..why would they leave..?
2,155 Sarus Cranes flew into Dry season roosts on the night of the 2004 annual Atherton Tablelands Crane Count. Some roosts continue from year to year, cranes desert other roosts temporarily or permanently and (so far) find new ones. Can we be complacent about this important wintering population? Could more and more roosts be hit by factors that force cranes to move?
These factors can be as diverse as tree-planting, concern for water quality if cattle can access dams, suburban development within local planning schemes, or farmers varying dam water levels or switching crops to meet market demand. Ozcranes takes a hypothetical look at how Sarus Cranes might be persuaded to leave – by people and organisations doing their best for the local economy and environment.
Here's where the 2,155 Sarus Cranes roosted. Two sites, Bromfield Swamp and Mareeba Wetlands, also had about 200 Brolgas each.
|Roost||No. of Sarus Cranes|
|Tinaroo Dam roosts||933|
|Quincan Swamp & other farm dams||262|
|Hasties Swamp National Park||124|
1 | To remove 933 Sarus from Tinaroo Dam
- In the interests of water quality ban grazing on the Lake margin
- Extend suburban subdivision of farmlands on the Lake margin
- Sell so much water, dam levels are always <50%
- Raise the level of the dam wall
← Pelican Point, where Sarus Cranes were first seen on Tinaroo Dam in 1967. Grazing ceased in 1990. Tall, dense pasture grasses and 8ha of planted trees now cover the site. Cranes only roost on the exposed margins for a short time after water levels drop. No cranes landed on 2 October, 2004 (TREAT and Eagle Eye). More images here and here.
Explanation This 3,500 ha irrigation storage and a margin of surrounding land are owned by a government corporation, Sunwater. Grazing leases on this margin have been cancelled or not renewed but adjacent properties are still permitted to graze cattle down to the water. This is where most Tinaroo cranes roost, in at least eight (8) locations. Occasionally, when people are absent, cranes use grassed areas slashed for public camping adjoining State forest. Otherwise, due to dense tropical grasses and other regrowth, there are no roosts on ungrazed land except when water levels drop: but unless there is little rain, weeds quickly grow and invade this exposed shoreline. Some sites are subject to disturbance from waterskiers, more so since suburban subdivision of one former farmland roost. One significant site has no water (so no roost) at low dam levels. Some roosts are not used at high water level, raising the height of the dam wall would drown more roosts in wet years.
2 | To remove 778 Sarus from Bromfield Swamp
- Fence cattle out permanently from the swamp and perimeter
- Replant rainforest in the surrounding crater
Explanation This renowned crane roost was created by clearing rainforest from a swampy volcanic crater on a headwater of the Johnstone River. Cranes feed, bathe, drink and roost in the swamp and climb the surrounding grazed slopes to get liftoff for morning flight.
← Bromfield Swamp, Atherton Tableland far N Queensland, early morning. 778 Sarus landed at Bromfield on 2 October, 2004 (cranesnorth)
The site is a nationally significant wetland, listed as an endangered ecosystem, and an historic site for Wet Tropics rainforest history with pollen cores dating back 10,000 years. The swamp is in good and stable condition (FNQ planning documents, no on-line link). The current owners are committed to good grazing management and their cranes. Birdwatchers and local ecotourist operators, too, would resist change disadvantaging cranes. But calls (some apparently uninformed about the significance of the site for Sarus Cranes) regularly surface for conservation instruments, compulsory purchase as a National Park, grazing bans, or restoration of the original rainforest habitat. Rainforest restoration is a regional funding priority.
3 | To remove 262 Sarus from local farm dams
- Deepen water levels, excavate shallow edges
← Google Earth view of Quincan Swamp, three adjacent farm dams. Crane numbers vary from 1,000 to 2, depending on depth. Depth is adjusted for grazing and fish farming
Explanation Cranes need shallow edges to access water and roost. Farmers adjust dam water levels to suit current cropping or grazing and at times, aesthetic requirements. Over several years one farm dam roost has varied from over 1,000 Sarus to only 2.
4 | To remove 124 Sarus from Hasties Swamp National Park
- Do nothing
← Hasties Swamp, Atherton Tablelands. 124 Sarus landed on 2 October, 2004 (cranesnorth)
Explanation Many criticise this small wetland National Park surrounded by farming and urban pressures, but few offer solutions and funds are limited. It is a tiny remnant of more extensive swampy woodlands now largely cleared and drained for building or agriculture. Apart from the general health of the swamp, more direct threats to cranes include weeds, feral pigs, and dogs.
5 | To remove 58 Sarus Cranes from Mareeba Wetlands
- Delay effects of weed management program
Pandanus Lagoon at Mareeba Wetlands, Dry season. 58 Sarus landed on 2 October, 2004 (cranesnorth) →
Explanation This created wetland complex is managed for non-profit education, environment and tourism. Water levels can be raised and lowered to simulate natural wetland conditions, or to provide a refuge for selected species in very wet (or very dry) years. If cattle grazing is removed, weed and pasture species invade lagoon shores. Control plans are underway, but assuming these take a few years to succeed..
So... Goodbye Sarus?
Burning for Brolgas» and grazing too, in experiments to remove choking weeds from a once significant natural Brolga wetland.