Importance of Algarrobo Trees Prosopis flexuosa for Territory Establishment of Three Seed-Eating Passerine Species in the Central Monte Desert

Abstract

In the central Monte desert in Argentina, feeding site selection by seed-eating birds and their high abundance associated with the presence of trees (particularly Algarrobos Prosopis flexuosa) are well known patterns during the breeding season, but these associations disappear during autumn and winter. In order to understand habitat selection by these bird species, we assessed the importance of Algarrobos during the defence and establishment of breeding territories in the open Algarrobo woodland of the central Monte desert for the three most common resident seed-eating birds: Ringed Warbling-finch Microspingus torquatus, Many-coloured Chaco Finch Saltatricula multicolor and Rufous-collared Sparrow Zonotrichia capensis. Despite some ecological differences between the species (e.g. nest site selection, feeding behaviour) all of them selected Algarrobos as song posts. Height, density and spatial configuration of these trees were features associated with the selection of territories. The patterns of selection we found at previously unexplored spatial scales (territory and within-territory) and associated with territorial defence, provided plausible explanations to seasonal shifts in the space use reported for central Monte desert seed-eating birds and highlight the close link between central Monte desert avifauna and Algarrobos. As in many arid regions, tall scattered trees are keystone features of the central Monte desert and management plans should be implemented in order to stop the current degradation and loss of these arid woodlands.