Reducing bird damage—what are the options?

Birds have been frustrating New Zealand grain and seed growers for well over 150 years. In the early days, management was down to scarecrows, poison, shooting and egg destruction, while today’s growers are more likely to use to gas guns, netting or lasers.

WORDS & IMAGES SUPPLIED BY OWEN GIBSON & PHIL ROLSTON, FAR losses to cereal growers annually, and the potential for similar losses to the vegetable seed industry without good management. Because birds are also an issue for horticulture and viticulture, FAR has recently started working with a pan-sector group of growers and other industry reps to investigate the best management options across the board. The group met in May to discuss each sector’s particular problems, with arable growers providing input into what technologies do and don’t work on farm. Owen Gibson, from FAR, who is coordinating the group says that while a number of different techniques and tools are used across the agri-food sector, there is no single solution. “Successful bird management relies on choosing a range of approaches that are appropriate for the crop and bird species concerned and also for the size of the paddock and its location.” Current solutions

Netting offers the greatest protection from bird damage, but is also expensive (typically $1,200 to 1500 ha per season) and seldom provides complete crop protection. Losses through nets can be as high as 5%, as birds learn to feed through the nets. This, along

with netting has seen a reduction in the use of nets, with a number of seed firms opting to use field lasers as the preferred option in larger areas. Field lasers work by scanning a green laser over the paddock, either in a predetermined pattern or randomly. To get the best control when using lasers, it is important to include not only the paddock, but also the birds’ resting areas (e.g. hedges). Owen says if the laser beam cannot be set to random, change the pattern(waypoints) every 7–14 days to maintain the best control. “Birds are smart, and no matter what kind of deterrent system is employed, if you don’t tweak it regularly they’ll either learn to ignore it, or figure out a way around it. Using a mix of scaring devices and moving them, or altering their sound/light pattern, will help to avoid this ‘habituation’ and provide more effective control.” Netting and lasers aside, there are numerous other options for deterring birds. Gas guns have long been used in arable cropping situations, but they are not suitable for farms bordering onto urban areas, especially as the most vigorous feeding occurs around dawn and dusk—not good times to be annoying your neighbours. Other sonic systems, such as bird distress or predator calls, can offer similar results to gas guns, although unless high quality sound formats are used and libraries are rotated regularly. birds will quickly habituate to these units. Kites, balloons and janglers are also tools for bird management. Attracting predator birds, especially swamp harrier (kāhu) with dead carcasses of rabbits, possums and ducks is also practiced as a biological means of protection. Good seed hygiene around the farm is extremely important to limit easily available food sources, especially during the winter months to reduce the localised bird population. When to start

Controlling birds early, before the crop has started to set seed is essential for adequate control. Once birds know there is a food source available it is hard to dissuade them from predating the seed, especially highly palatable seeds such as sunflower, radish and hemp. The future?

Drones, especially larger units (700 to 1000 mm) coupled with sound devices are reported to be very effective, but current regulations constrain their use. Unmanned ground vehicles (UGV) are likely the future of selfpropelled bird scaring devices. Regulation still restrict the use of UGVs, however this is likely to be relaxed before drone regulation. Landscape management, hedge and shelter species and the interactions between improving biodiversity of birds, pollinators and predator insects are not yet well understood. FAR continues to explore how all these options can be integrated to avoid habituation to any one of the options available to growers. The culprits

House sparrows (Passer domesticus) and greenfinches (Carduelis chloris) are the most damaging of the introduced bird species, with the greatest economic losses occurring as a result of feeding at grain fill. However, depending on the variety and species of birds present, damage can occur at any time. For example, pigeons, pukeko, ducks, shelducks (paradise ducks) and geese can be very damaging at establishment. Radish, brassicas, sunflowers and hemp are particularly attractive food sources for birds, while early maturing cereals are also vulnerable. Non-field related bird damage includes nesting in farm machinery and faecal contamination in sheds and around grain drying/stores.