Abstract
This paper discusses the interaction between birds, mistletoes and host plants, focusing on 2 desert mistletoes, i.e. Tristerix aphyllus and Phoradendron californicum. The seeds of the species are primarily dispersed by the Chilean mockingbird (Mimus thenca) and Phoradendron californicum, respectively. In the first section, patterns of variation in mistletoe infection are outlined. This section identifies the contrasting scales at which these patterns are found and the mechanisms that shape them. In the second section, a unified framework is proposed for the study of mistletoe populations. This framework emphasizes the role of mistletoes as plant parasites, recognizes that they have a patchy metapopulation-like structure and accentuates the fact that their seeds are dispersed by mutualistic birds.