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ABSTRACT. -
Inter- and intra-specific competition are known to influence feeding decisions, but relatively little research has investigated how inter- and intrasexual interactions can impact foraging. We studied foraging preferences of male and female Northern Cardinals (Cardinalis cardinalis) during winter and found they preferred sunflower seed to safflower seed when presented with paired feeders in the absence of conspecifics. Male cardinals avoided feeders occupied by other males and approached feeders occupied by females, regardless of feeder contents. Female cardinals avoided other females and especially males when choosing feeders. These changes in foraging behavior by male and female cardinals as a result of conspecific presence indicate inter- and intra-sexual interactions alter the attractiveness of a high or low energy food source.
Received 27 December 2011. Accepted 7 June 2012.
Organisms must be discerning when presented with conflicting options regarding foraging (Sih 1980, Lima and Dill 1990, Krebs and Kacelink 1991, Cuthill and Houston 1997). Individuals must optimize energy intake by trade-offs in both food quality and vulnerability to prédation (Stanback and Powell 2010). Competition (both inter- and intra-specific) can also have a substantial impact on the ability of individuals to access food sources (Nice 1927, Lima and Dill 1990, Shedd 1990, Belthoff and Gauthreaux 1991, Tarvin and Woolfenden 1997, Lima 1998, Rands et al. 2006). Finally, inter- and intra-sexual interactions, while often considered only in the context of breeding, can have dramatic effects on foraging in birds (Selander 1966, Schneider 1984). Inter-sexual niche separation, for species that lack substantial morphological differences in trophic structures, often results from social dominance of one sex over the other (Desrochers 1989, Hogstad 1991). It is unclear, however, whether males and females can cleanly separate their foraging and sexual interactions, even during winter. We investigated how the presence of conspecifics altered the foraging behavior of male and female Northern Cardinals (Cardinalis cardinalis) using feeders during winter. For example, males of this species are known to be dominant to females during winter (Nice 1927, Laskey 1944, Ritchison and Omer 1990); thus we might expect males to monopolize preferred foods - if nutrition was their only consideration. We provided Northern Cardinals with paired feeders containing different foods (sunflower vs. safflower seed) to test the extent to which their foraging decisions were influenced...