Bird use of almond plantations: implications for conservation and production

Abstract

Context Farmland crops may suffer damage from native animals, but also provide a critical resource during times of food scarcity. We know little about bird use of almond crops. Aims To examine factors influencing temporal and spatial variation in the use of almond crops in north-western Victoria by bird species, including the threatened regent parrot (Polytelis anthopeplus), and to record levels of crop damage. Methods We measured bird occurrence in 15 transects during the almond-growing season of 2009/10, and 32 transects during 2010/11. Crop-damage assessments were conducted in 2010/11. Spatio-temporal variation in bird occurrence was related to seasonal factors, landscape variables and bird-control activities. Key results Significantly more regent parrots and small parrots (e.g. Platycercus elegans and Psephotus haematonotus) were recorded in almond plantations in 2009/10 than in 2010/11. Rainfall and wheat production was much higher in 2010/11, and we hypothesise that the availability of alternative foods reduced parrot dependence on almonds. Regent parrot occurrence did not differ across months within a season, but more small parrots were recorded during almond nut maturity. Regent parrots appeared to prefer locations where almond crops abutted native vegetation, but only during 2009/10, a dry year with likely limited food availability. Small parrots occurred more often in crops close to riverine vegetation and distant from farm offices. Nut damage was generally low, with only 7 of 32 transects sustaining >4% total damage, but damage assessments were conducted during a season of high rainfall, with likely greater availability of alternative food. Percentage damage was significantly correlated with the number of regent and small parrots. Shooting activity did not deter birds from using almond crops. Conclusions Parrots appear to rely more on almond crops for food when environmental conditions limit other food resources. A key strategy for managing bird impacts on almonds while supporting species conservation is to provide decoy crops of preferred native plants. Implications Rapid loss of almond plantations may lead to population declines in the threatened regent parrot if the availability of alternative food is not simultaneously increased. The role of production land uses in supporting native birds needs to be recognised by conservation management agencies.