The role os stubble type and spilled seed biomass on the abundance of seed-eating birds in agroecosystems
Published: Volume 64.1, January 2017. Pages 31-48.
Croplands are habitats with high availability of food resources for seed-eating birds. The use of particular fields by birds may vary considerably depending on crop type. Some crop stubbles hold high amounts of spilled grain after harvest, which may support seed-eating bird populations throughout the year. We examined the role of crop stubble type and biomass of spilled grain on species richness and abundance of seed-eating birds in the Pampas of central Argentina. During 2011-13 we sampled 166 stubble fields: 77 fields during the austral spring-summer of 2011-12 and 2012-13 (44 wheat and 33 barley stubbles); and 89 fields during the austral autumn of 2012 and 2013 (49 soybean, 27 corn and 13 sunflower stubbles fields). We recorded birds on a 700×100 m transect and estimated spilled grain on 1 m2 of stubble cover in each field. Comparisons among species accumulation curves showed that wheat and barley stubbles had similar bird species richness in spring-summer, whereas in autumn, sunflower stubbles supported higher bird richness than soybean stubbles. Generalized linear mixed models revealed that the abundance of some seed-eating birds had significant associations with crop stubble types. Some species were positively associated with spilled grain biomass on particular stubble types. In general, these associations varied seasonally, being more evident in autumn than in spring-summer. Knowledge of bird species populations and their specific association with given food resources during periods when crops remain only as stubble could be a key tool to help plan management strategies designed to reduce bird impacts on agricultural crops prior to harvest, when they are most susceptible to significant levels of damage.