Understanding and mitigating the aggregative response to the magpie goose to mango orchards in the Northern Territory (MG15005)

What was it all about?

This project, which ran from 2016 to 2019 investigated the behaviour of magpie geese and ways to reduce the damage the birds cause to fruit, trees and irrigation equipment in mango orchards in the NT.

Field work for this project was undertaken during the 2016, 2017 and 2018 mango seasons in the Greater Darwin Region to find out why magpie geese move from their native wetlands into mango orchards. Individual geese were tracked by satellite and bird stomach contents were analysed, which together gave an understanding of how habitat resources influence magpie goose behaviour.

The researchers discovered that geese are returning not just to the same orchard, but to the same place on that orchard every year. They also found out the nesting areas the birds are coming from, and the resources they require on and off the orchard. 

In addition to the ecological work, studies were carried out to assess the effectiveness of acoustic, visual and chemical deterrents in reducing bird density and bird-crop interaction. Cameras set up in commercial orchards allowed the team to assess what proportion of mangoes the geese were taking from the trees, and what proportion were being found by the birds on the ground – and how this was being influenced by scaring techniques. 

The project team found that geese are migrating to the Darwin agricultural area from all over northern Australia. They are arriving from many different wetlands, suggesting that it is the draw of good habitat within the Darwin agricultural area that brings the birds together in late dry seasons. Culling of birds from a particular wetland would therefore not be effective at reducing damage.

Within any one mango season the geese are highly mobile, moving between orchards and other areas far outside the Darwin agricultural area. Geese that are in an orchard one week are unlikely to be the same birds in the orchard a few weeks later. This suggests that shooting birds would not be an effective long-term management strategy since new birds will arrive constantly throughout the season.

The researchers concluded that the way to deter the birds is to reduce the appeal of the environment, a measure that would require a coordinated effort between growers across the region. One example is disrupting one of the key resources that geese habitually visit each day.  Geese move between a mango orchard, a local roosting site (forested areas), and an open water source (for drinking and bathing) at least once each day. If one area is made less favourable, they suggest that the geese will move elsewhere.

Grower recommendations

• Estimate the amount of damage the birds do each season to see if action is warranted
• Remove fallen mangoes regularly
• Remove all mangoes from trees post-harvest
• Clear grass and weeds around trees
• Remove available water sources in the orchard
• Don’t dump waste mangoes where geese can access them
• Install a visual barrier fence, taller than a goose, under trees
• Develop trellised high-density crops that could be netted or poly tunnelled
• Increase the height of the lowest mango on trees to be higher than a goose.

ACT NOW

Read this summary of the project, Integrated pest management for reducing magpie goose damage to mango orchards, which includes practcial recommendations for growers.

You can read this profile with project PhD candidate Amélie Corriveau about the upcoming second season of the research.

You can also watch this video presentation relating to the project (17 minutes) from the Australian Mango Conference.