Waterbirds have been observed on constructed water storages of the irrigated cotton landscapes in northern NSW for decades and yet there have been few studies to quantify the importance of these structures. Additional research was needed to update and compare knowledge, to develop an on-going monitoring framework, and benchmark the current value of these storages to the conservation of waterbirds.

The study was conducted from September 2014 to June 2015 and involved a reconnaissance trip and six field surveys. Fifty water storages were surveyed, 30 in the Gwydir and 20 in the Namoi. The storages were mostly at low levels due to seasonal conditions.

A total of 31,006 waterbirds of 55 species were counted on the water storages. This is a higher number of species than recorded in previous studies, although additional species were represented by a low number of individuals. Ducks and coots were the most abundant waterbirds observed, as they were in previous studies. Threatened species observed included Brolga, Magpie Goose and Freckled Duck. Migratory species observed included Sharp-tailed Sandpiper, Black-tailed Godwit (which is also threatened), Latham's Snipe, Common Greenshank, Marsh Sandpiper and Red-necked Stint.

Counts of waterbirds per survey unit (no. storages x no. surveys) in the current study and previous studies were between 80 and 120 waterbirds, highest in the current study and lowest in Namoi 2008 study, a result attributable to a smaller sample size in the 2008 study. Counts were similar between the Gwydir studies, 93 waterbirds per survey unit in the current study compared to 97 in the 2001 study.

Observations of nesting were few in the current study, much fewer than in the 2001 study, attributable to low and inconsistent water levels during the current study. Clearing of dead trees from some storages has removed the nesting habitat of waterbird species that might otherwise breed in those storages, diminishing overall breeding opportunities.

In 2001 it was estimated that on-farm water storages represented 45% of the wetland area of the Lower Gwydir Valley but supported 1 to 5% of the Valley’s waterbirds. The results from the current study do not challenge that estimate.

The main value of the irrigation storages to the conservation of waterbirds appears to be as opportunistic foraging habitat. Irrigation farming has created an extension of this habitat in the landscape, although storages appear to support fewer species, individuals and breeding of waterbirds than do natural wetlands. Numbers of individuals and species of waterbirds are highest in storages that are shaped and managed such that a range of habitats (e.g. shallow/deep, vegetated/bare) are available simultaneously.

Future research should include: extending the scope of study into other cotton areas; integrating studies of natural and artificial wetlands; detailed studies of local waterbird ecology such as movement, habitat use and food webs, and; developing pro-active management strategies such as using environmental water in storages under stewardship arrangements and for environmental off-sets.