Rank grass and sugarcane provide succour to north's endangered finches

A TS–CRC project on why the tiny crimson and star finches of northern Australia might be declining has unearthed enough information on the birds’ biology, feeding habits and breeding patterns, to develop some initial conservation plans for the species.

Finches in decline | Study shifts to WA | Rank grass | Agriculture provides shelter | Feeding strategy | More information |

The best habitat for the endangered white-bellied crimson finches (inset) is provided by rank grasses (shown above). The long grass is Chionachne cyathopoda, cane grass, and is a perennial that provides year-round shelter. Photos: Mick Todd

Finches in decline

Crimson and star finches are among a number of granivorous birds—which that feed on the seeds of grasses, both perennial and annual—across northern Australia. Overall, the researchers obtained information on food, breeding, moult and habitat, all of which help explain why these bird populations have declined, as well as providing a basis for the development of management plans.

Study shifts to WA

Through 1998-99 studies concentrated on Cape York Peninsula where the species have contracted in range. However, during the wet season of 1999-2000 the project shifted its emphasis to Kununurra where both species of finch are thriving. At Kununurra the birds were studied in both pastoral and agricultural landscapes throughout the wet season. Comparisons between these two areas suggest that the structure of the vegetation—such as rank grass—is more important than grass type.

While the star finch requires rank grass only during its breeding season the crimson finch—which nests in pandanus or palm fronds—relies on rank grasses all year round. The short, broad wings and long tails of the crimson finch means it has only a limited flying ability and the bird relies on long undergrowth to hide it while it feeds, and to shelter from predators.

Unfortunately these grasses are both grazed and trampled by cattle as well as being vulnerable to late dry-season fires. Two of the most northerly populations of the white-bellied subspecies, at Aurukun and Lockhart River in Cape York Peninsula, are now extinct probably because of ill-timed fire. In this area, patches of good habitat are often further apart than they are in the Northern Territory and these isolated populations of finches are therefore more vulnerable to local extinctions.

Rank grass

In northern Australia rank grass is produced annually on floodplains that are usually too wet at the time star finches breed to be affected by grazing cattle. However, this would not be true of the rank grass that would have grown around waterholes in the southern part of the species range from which the star finch is now likely to be extinct. These areas tend to undergo heavy grazing and trampling by stock, and become devoid of lush, rank grasses that would have once marked their perimeters.

Agriculture provides shelter

While pastoralism threatens the rank grasses both finches need, some forms of agriculture, in particular sugarcane, are replicating the environment these native grasses provide. Kununurra’s sugarcane and other crops are one of the reasons finches are abundant in this area. For the star finch sugarcane provides excellent sites for nesting while food is available in surrounding shorter grass and from weeds growing beside irrigation channels. The black-bellied crimson finch prefers pandanus when nesting, but will resort to buildings or any sort of introduced palm.

With the help of traditional owners, Queensland Parks & Wildlife Service and Birds Australia volunteers, a large area of finch habitat was surveyed on the southern shores of Princess Charlotte Bay, revealing a feeding strategy of the star finch.

Feeding strategy

It survives the annual seed shortage at the beginning of each wet by feeding on seeds of grasses growing along saltpan fringes. Though these grasses require extensive rain to germinate, they still have some seeds early in the wet. Similar habitats occur in many areas across northern Australia where star finches are still found.

The study is proving valuable for managing conservation areas on Cape York with the results already incorporated into fire planning.