Evidence:
For Colonial nesting waterbirds to breed successfully, they need a flood of sufficient duration to allow the following:

a) build up their fat reserves (lag time);
b) build their nests;
c) lay and incubate eggs; and
d) feed and fledge their young.

For spring and early summer floods, a lag time of up to two months before breeding is required (and longer for other seasons). Herons, egrets, ibis and spoonbills then take about three and a half months to build their nests, lay and incubate eggs, and fledge their young (Marchant and Higgins, 1990). So, successful breeding requires a minimum of 4 months (where birds might start building up their fat reserves at another site) and ideally requires 6 months or more. (For further information refer to Scott 1997, 2001).

Note: This curve has been set up as a generic default, and might need to be adjusted if it is being used to model a particular species.

Confidence level: A

Sources:
Maher, M. T. (1991). Back o'Bourke: an inland perspective on the conservation of Australian waterbirds. PhD thesis, University of New England, NSW.

Maher, M. T. and Braithwaite, L. W. (1992). Patterns of waterbird use in wetlands of the Paroo: a river system of inland Australia. Rangelands Journal. 14: 128-142.

Marchant, S. and Higgins, P. (1990). Handbook of Australian, New Zealand and Antarctic birds. Volume 1. Oxford University Press.

Scott, A. (1997). Relationships between waterbird ecology and river flows in the Murray-Darling Basin. CSIRO Land & Water Technical Report 5/97.

Scott, A. (2001). Waterbirds. Rivers as Ecological Systems: the Murray-Darling Basin. Young, W. J. (ed.). pp.259-286. Murray-Darling Basin Commission.

Evidence:
The Colonial nesting waterbirds, such as egrets and particularly ibis, only breed successfully when their nest sites are surrounded by water. If the level of water surrounding the nests drops before the young birds fledge, the adult birds often abandon the nests, probably because falling water levels indicate to the birds that food resources will decline and be insufficient to complete the breeding event. Waterbirds are more sensitive to water levels drops during the early stages of breeding. In 1996 an entire colony of ibis abandoned their nests in the Macquarie Marshes when water levels dropped following a reduction in river flow (DLWC, 1997). (For further information refer to Scott 1997, 2001).

The default curve for colonial nesters has been set by the SRP as a linear drop in index value, reaching zero at 5cm/day.

Confidence level: A

Sources:
DLWC. (1997). Macquarie Marshes 1996 Water Management Plan: 1996-97 operational and performance report (draft). Department of Land and Water Conservation.

Scott, A. (1997). Relationships between waterbird ecology and river flows in the Murray-Darling Basin. CSIRO Land & Water Technical Report 5/97.

Scott, A. (2001). Waterbirds. Rivers as Ecological Systems: the Murray-Darling Basin. Young, W. J. (ed.). pp.259-286. Murray-Darling Basin Commission.

Evidence:
This curve indicates the relationship between the dry period before flooding and the food resources available for young chicks/ducklings. Productivity of wetlands that periodically flood and then dry tends to be higher than wetlands that are permanently inundated.

This curve has been set with a peak index for drying periods between 6 and 12 months. Dry periods of longer duration do not improve productivity (and in fact might start to impact on the survival of some aquatic species).

Confidence level: B

Sources:
Brinson, M. M., Lugo, A. E., and Brown, S. (1981). Primary productivity, decomposition and consumer activity in freshwater wetlands. Annual Review of Ecology and Systematics. 12: 123-161.

Dannell, K., and Sjoberg, K. (1982). Successional patterns of plants, invertebrates and ducks in a man-made lake. Journal of Applied Ecology. 28: 129-135.

Swanson, G. A., and Meyer, M. L. (1977). Impact of fluctuating water levels on the feeding ecology of breeding blue winged teal. Journal of Wildlife Management. 41: 426-433.

Evidence:
Flood magnitude is an important determinant of the size of a waterbird breeding event. Observations at the Macquarie Marshes indicate that the number of waterbirds breeding rapidly increases as the flood size increases (NPWS/DLWC, 1996; Scott, 1997, 2001). The very large infrequent floods are vital for the very large waterbird breeding events that have been reported both in the Murray-Darling Basin and the Eyre Basin (Richard Kingsford pers. comm.)

Confidence level: A

Sources:
NPWS/DLWC. (1996). Macquarie Marshes Water Management Plan 1996.

Scott, A. (1997). Relationships between waterbird ecology and river flows in the Murray-Darling Basin. CSIRO Land & Water Technical Report 5/97.

Scott, A. (2001). Waterbirds. Rivers as Ecological Systems: the Murray-Darling Basin. Young, W. J. (ed.). pp.259-286. Murray-Darling Basin Commission.

Evidence:
Although the lakes support large numbers of Colonial nesting waterbirds, there are larger breeding colonies elsewhere in the Murray-Darling Basin. There is not a significant amount of preferred vegetation for nesting as the lakes are dominated by low growing herbfields and grasslands rather than major stands of emergent rushes and reeds.

Confidence level: C

Sources:
REG D Members observations during site inspection.

Evidence:
The generic default indicates that a water body covering 60-80% of its maximum area will provide foraging habitat for most waterbirds, including those which prefer deep water (diving ducks and grebes) and those which prefer exposed mudflats or shallow water around the edges (e.g. waders, ibis, egrets). If the water body is completely full, the mudflats around the edge are lost, reducing the habitat for some species.

This curve might vary between water bodies depending on the depth profile, and might also vary depending on which species or group of birds are being assessed. For instance, waders might prefer water bodies that are only half full and contain large areas of mudflats and shallow water around the edges.

Confidence level: C

Sources:
SRP expert knowledge and judgment.

Evidence:
This curve describes the benefits of water depth variability for foraging. Increased variability provides better foraging conditions. However, even under a constant depth, there is still some foraging value, and the curve has been set to reflect this.

This default curve is a generic option. It can be customise for a specific wetland (or a group of wetlands) by adjusting the ideal depth variability (index = 1) to that which was experienced under natural flow conditions.

Confidence level: C

Sources:
SRP and REG waterbird discussion group expert knowledge and judgment.