Social experience modifies behavioural responsiveness to a preferred vocal signal in red crossbills, Loxia curvirostra

Early learning of discrete call variants in red crossbills: implications for reliable signaling

“…Early call learning from family members may facilitate family cohesion and concurrently ensure that discrete contact call variants reliably reflect ecomorph, permitting calls to mediate assortment based on ecological specializations and genetic background. The present work, in conjunction with previous studies showing that crossbills maintain and assort by discrete contact call variants in adulthood (Smith and Benkman 2007; Summers et al 2007; Keenan and Benkman 2008; Sewall 2009; Sewall and Hahn 2009), supports the role of contact call variants as cultural isolating mechanisms in red crossbills.…”

“…I played each nestling a unique exemplar of its biological parents’ call variant (variant 3 or 4), two familiar crossbill call variants it had been exposed to during early development (variant 2 and variant 3 or 4), a novel crossbill call variant it had not been exposed to (variant 5) and a heterospecific call (evening grosbeak, Coccothraustes vespertinus , another Cardueline finch that co-occurs with crossbills in the wild) in randomized order with 2 min of silence between stimuli. I generated playback files using a protocol described in detail elsewhere (Sewall and Hahn 2009). I video- and audio-recorded all trials and scored the response of each nestling on a scale of 1 to 3 based on whether the subject engaged in begging (score of 3), neck extensions (score of 2) or repositioning in the nest (score of 1; Nethersole-Thompson 1975).…”

“…For instance, in red crossbills ( Loxia curvirostra ), discrete contact call variants are associated with morphological variation (Groth 1988, 1993), suggesting that call variants do reflect genetic background and may play a role in limiting the intermixing of different lineages (Snowberg and Benkman 2007; Sewall and Hahn 2009). Crossbills in North America are composed of several sympatric ecomorphs (see “Methods” for terminology) that exhibit variation in body size and beak morphology, thought to facilitate specialization on different conifer resources (Benkman 1993; Benkman 2003; Groth 1988; Groth 1993).…”

“…Discrete contact call variants are well positioned to serve as cultural isolating mechanisms in crossbills because they are the most conspicuous difference among ecomorphs (Fig. 1), they mediate the assortment of foraging flocks and breeding pairs (Adkisson 1996; Smith et al 1999; Smith and Benkman 2007; Summers et al 2007; Sewall and Hahn 2009), and adult birds rarely change the call variant that they produce (one of 79 wild adult crossbills changed call variant over more than one year (Keenan and Benkman 2008); none of 42 captive adult crossbills changed call variant over 2 years (Sewall 2009)). However, for discrete contact call variants to serve as cultural isolating mechanisms, young birds would have to initially learn the call variant appropriate for their lineage from members of their family or natal group.…”

Sex-Dependent Species Discrimination in Auditory Forebrain of Naturally Hybridizing Birds

“…Recent experience with song also appears to modulate forebrain sensitivity to familiar traits as measured by Zenk expression [Sockman et al, 2002;Maney et al, 2003]. Further, this neural response possibly modulates the behavioral response to song and has led to the proposition that experience and modulation by the auditory forebrain enable a greater flexibility in mate choice decisions through the lowering or raising of thresholds of mate acceptability [Sockman, 2007;Sewall, 2009;Sewall and Hahn, 2009]. This model might also explain heterospecific mate choice in songbirds, which could be similarly contingent upon mate availability and the cost of interbreeding [Pierotti and Annett, 1993;Good et al, 2000].…”