Vocal performance varies with habitat quality in black-capped chickadees (Poecile atricapillus)

Abstract

In vocal learners, such as songbirds, the ability to maintain an internal acoustic structure between songs during a chorus seems to be positively correlated with the singer’s condition and may, therefore, represent a reliable measure of the singer’s condition. For instance, some internal ratios in the black-capped chickadee ( Poecile atricapillus) fee-beesong are more stable in the song of dominant males than in the song of subordinate males, suggesting that dominant birds are better at maintaining the internal song structure than subordinate males. Habitat quality is also known to affect the behaviour of this species. Birds settling in young forest have a lower song output and lower reproductive success than birds occupying mature forests, and it is suggested that those differences arise from differential food availability across habitats. As recent studies suggest that song performance can be altered by food limitation at the time of song learning, we explore whether habitat quality has a similar effect on the ability to maintain internal song structure as does social rank. We paired males by similar social rank, but who occupied different habitat types, and compared the consistency of male song within his dawn chorus. The ability to maintain an internal song structure of birds occupying young forests was consistently lower than birds occupying mature forests. Our results demonstrate that the same difference that exist in song structure between male differing in social rank also exist between males differing in the habitat in which they sing.

Black-capped chickadees categorize songs based on features that vary geographically

“…50-2000 km; Brewer et al, 2006), so birds may encounter individuals originating from different geographical regions. Chickadees from different habitat types (high-and low-quality habitat; Grava et al, 2012) or habitats with different levels of anthropogenic noise (Proppe et al, 2012) produce songs with acoustic differences. In addition, the habitat of origin of both the singer and the song receiver influence how the singer is perceived (Grava et al, 2013).…”

Effect of habitat quality on communication and signalling in the black-capped chickadee.

“…The posterior pathway or song motor pathway (SMP) controls the production of song and includes HVC (higher vocal center) and RA (robust nucleus of the archistriatum), which innervate nXIIts (tracheosyringeal portion of the hypoglossal nucleus) that control the syrinx ((for review see Mooney 2009; Fig 1.1). Normal development of the song system is crucial during the sensitive period for normal development of song (Nowicki et al 2002;Christie et al 2004;Grava et al 2012). Two different signals within the fee-bee song in the black-capped chickadee give reliable information about the signaller's condition.…”

“…The posterior pathway or song motor pathway (SMP) controls the production of song and includes HVC and RA, which innervate nXIIts (tracheosyringeal portion of the hypoglossal nucleus) that control the syrinx (Mooney, 2009). Normal development of the song system is crucial during the sensitive period for normal development of song (Nowicki et al 2002;Christie et al 2004;Grava et al 2012; Chapter 3).…”

“…Because these calling rates were correlated with immediate hunger levels (Otter et al 2007a Although song output is increased with supplementation of resources, other condition-dependent signals in the chorus are not affected by supplemental feeding in the early spring, even though this likely increases the immediate condition of the birds. This is the case with the fidelity with which birds render their songs: subordinate birds are less able than dominant birds to maintain internal frequency parameters between successive renditions of their songs (Christie et al 2004), and birds in high-quality habitat also show a higher ability to maintain consistent note structure between songs than do birds in poor-quality habitat (Grava et al 2012;Chapter 2). I have also shown that males assess rivals on this ability to accurately maintain internal note structure; males show lower response to perceived intruders with low consistency in song structure than they do to playbacks that maintain higher consistency in song structure (Grava et al in prep;Chapter 3).…”

“…These combined results suggest that the ability to maintain consistent song structure throughout the chorus is a condition-dependent signal in the black-capped chickadee. However, food supplementation at the time of singing has no effect on this ability, suggesting that it does not reflect the shortterm condition of the birds at the time of singing (Grava et al 2012; chapter 2). Rather, internal song structure consistency may reflect the condition of the birds at the time of song learning, but no study has tried to estimate the early condition of the birds and its implication on song structure in the black-capped chickadee.…”