Natural History, Distribution, and Conservation of Two NomadicSporophilaSeedeaters Specializing on Bamboo in the Atlantic Forest

Abstract

Abstract. Semelparous woody bamboos flower fairly synchronously and in clocklike fashion after many years, providing abundant and nutritious seeds. However, this resource is ephemeral, localized, and unpredictable from the perspective of birds that feed on those seeds. Birds specializing on bamboo seeds track this food source and are nomadic. We recorded Temminck's Seedeater (Sporophila falcirostris) at 29 localities and the Buffy-fronted Seedeater (S. frontalis) at 23 localities in Argentina, Paraguay, and southeastern Brazil. In these species, nomadism is unassociated with any seasonal factor: birds may persist year round over several consecutive years if the seed supply is constant enough. Most occurrences and all breeding records were related to masting of bamboo; records of isolated birds away from seeding bamboo must represent individuals searching for bamboo patches. We report winter breeding of these species for the first time and demonstrate that the supply of bamboo seeds is the main limitation ...