![]() ![]() 2013) and breeding status (Hanski and Laurila 1993 Foote and Barber 2009 Bruni and Foote 2014 Zhang et al. Many studies have revealed the strong influence of social forces such as pairing status (Catchpole 1973 Cuthill and Hindmarsh 1985 Demko et al. Several hypotheses have been proposed to explain why animal signaling behaviour varies seasonally, and these hypotheses fall into three main categories: (1) social processes, such as changes in social context, influence seasonal changes in vocal output (2) mechanistic processes, such as the hormones that influence vocal output, influence seasonal changes in vocal output and (3) environmental features, which place constraints on acoustic communication (for example, through changes in vegetation), influence seasonal changes in vocal output (Kacelnik and Krebs 1983 Mace 1987 Cuthill and Macdonald 1990 Staicer et al. 2004), or in relation to the rhythms of social activities such as changes in reproductive status (Slagsvold 1977 Amrhein et al. Many animals vary their vocal output seasonally, often in relation to changes in abiotic factors such as light and temperature (Runkle et al. Later-season dusk choruses, in contrast, appear to play a role in attracting mates and possibly acoustic mate guarding. These patterns suggest that Savannah Sparrows’ early-season dawn choruses are directed at males and serve a territorial defense function. Across the breeding season, the highest levels of song output occurred in late April and early May, soon after males arrived on the breeding grounds, and the lowest levels occurred in August, prior to the departure of birds for the wintering grounds. During the breeding stage, in contrast, the dawn chorus was diminished and males instead exhibited a pronounced dusk chorus with a peak in song output during the evening. ResultsÄuring the pre-breeding stage, prior to female arrival, males sang a pronounced dawn chorus with a peak in song output during the early morning. We described diel and seasonal variation across five different breeding stages based on recordings of more than 50,000 songs from 34 males. We used autonomous recorders to collect extensive recordings across the breeding season in a long-term, colour-marked study population of Savannah Sparrows in eastern Canada. In this investigation, we quantified diel and seasonal variation in song output by studying a breeding population of Savannah Sparrows ( Passerculus sandwichensis). By quantifying patterns of diel and seasonal variation in vocal output, we can gain insight into the ecology and evolution of birds and the function of their vocalizations. ![]() The vocalizations of birds are dynamic traits that often vary in output with time of day and time of year. ![]()
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