Communication breakdown? Habitat influences on black-capped chickadee dawn choruses

Abstract

The dawn chorus of the black-capped chickadee (Poecile atricapillus) is a communication network that functions in the dissemination of essential information for both males and females. Habitat type may influence the performance of this network, and if recognized, chickadees may attempt to behaviorally compensate for detrimental changes in the form of increased movement. We studied the dawn chorus of 66 black-capped chickadees in two adjacent, yet structurally different, habitats (disturbed and undisturbed) during the summers of 2000-2003 and recorded via point counts the number of neighboring males heard singing simultaneously while following a focal chorusing male and observing his movement. A transmission study to detect differential degradation due to habitat type was also conducted within the same research site. Observers in the disturbed sites heard significantly fewer neighboring males in the focal male's territory than in the undisturbed site, yet individual movement did not differ between habitat types. Propagation of song of varying frequencies, as measured by entropy, suffered less degradation in the disturbed site for high-frequency songs, but there was no effect of habitat on low-or mid-frequency songs. Greater interneighbor distance in the disturbed site likely explains some of the reduction in audibility of neighboring males during the dawn chorus, but the reduced condition of birds in the disturbed site (implicated from other studies) may also be a factor in explaining the difference in networks. The findings of this study suggest that chickadees in the disturbed habitat are experiencing a compromised communication network, which could impact breeding and other social behaviors.

Sounds of the city: The effects of urbanization and noise on mountain and black-capped chickadee communication.

“…Within the range of habitats tested, this study suggests that the effects of ambient noise outweigh habitat-dependent effects on signal transfer and detection, despite the fact that open habitats generally result in better signal transmission than closed habitats (Fotheringham & Ratcliffe, 1995;Hansen et al, 2005;Proppe et al, 2010;Mockford et al, 2011; but see Slabbekoom et al, 2007). These experimental results match theoretical findings that communication distances in urban areas are much smaller compared to forested rural sites when both habitat structure and ambient noise are considered (Nemeth & Brumm, 2010).…”

“…I obtained song stimuli of black-capped chickadees from a previous study (Hansen et al, 2005), and song stimuli of mountain chickadees from the Stokes field guide (Colver et a l, 1999). Calls and songs were broadcast at 63 ± 2 dB(Z) and 74 ± 2 dB(Z), respectively (mean ± standard deviation, measured at 5m).…”

Dominance and geographic information contained within black-capped chickadee (Poecile atricapillus) song

“…Grava et al (2012) found that when comparing the songs produced by black-capped chickadee males of similar dominance rank, but from varying habitat quality, males in young forests (lower-quality habitat) produced songs with less consistent interval ratios compared to birds from mature forests (higher-quality habitat). Previous studies have found no difference in song transmission through these adjacent habitat patches (Hansen et al, 2005), suggesting that condition-related features of songs influence song structure within and between regions.…”

Relative effects of ambient noise and habitat openness on signal transfer for chickadee vocalizations in rural and urban green-spaces

“…Our findings suggest that the effects of ambient noise outweigh habitat-dependent effects on signal transfer and detection of chickadee vocalizations, despite the fact that open habitats generally result in better signal transmission than closed habitats (Fotheringham and Ratcliffe 1995;Hansen et al 2005;Proppe et al 2010;Mockford et al 2011; but see Slabbekoorn et al 2007). Therefore, we address here some methodological aspects that may have resulted in underestimating the effects of habitat structure on signal transmission.…”

“…We obtained black-capped chick-a-dee calls from recordings made during previous studies on dawn vocalizations (van Oort et al 2006), and obtained mountain chick-a-dee calls from field recordings in a previous study (Grava et al 2013). We obtained blackcapped song stimuli from a previous study (Hansen et al 2005), and mountain songs from the Stokes field guide (Colver, Stokes, and Stokes 1999). Amplitude of the transmission broadcast was set by the volume on the MP3 player and was consistent throughout the study.…”