Singing behaviour of ruby-crowned kinglets Regulus calendula in relation to time-of-day, time-of-year, and social context

Observational field studies provide insight on the multifunctional nature of birdsong. For example, if song production were limited to pre-fertilization, then that would suggest a mate attraction function. If it were used throughout the breeding season and in response to intruding males, then that would suggest a territorial defence function. In the present study, we determined the daily and seasonal singing patterns of male rubycrowned kinglets Regulus calendula in Labrador, Canada, using microphone arrays in two breeding seasons. Using a playback experiment, we simulated a territorial intrusion to compare the structure of songs produced while defending a territory to the structure of songs produced during solo and contest singing. Singing peaked in the early part of the breeding season and then declined continuously for the remainder of the season, which suggests that the songs function in mate attraction. Singing peaked 2-3 h after dawn, and then declined steadily until it stopped at 10 pm. Some nocturnal singing was observed, but no dawn singing was observed. A high probability of signal overlap by heterospecific songs at dawn would hinder signal recognition and explain the observed delay in peak singing activity. Vocal responses to playback suggested a function in territory defence. However, there were no significant differences in the duty cycle, frequency modulation, and bandwidth of songs in relation to the context of song production, though songs were shorter in the intrusion context than during solo singing. Overall, the study provides the first quantitative description of the effects of time of day, time of year, and social context on singing behaviour in this understudied species

Song repertoires in a western European population of Yellohammers Emberiza citrinella

Geographic variation is one of the most intensively studied bird song topics. However, our knowledge of geographical song variations in most species studied so far is very sparse, with many areas of the species-typical geographic distributions still unexplored. One striking example is the Yellowhammer: for this species most song studies have been conducted along well defined dialect borders, but almost nothing is known about its song characteristics in other regions of its broad geographic distribution. In this study, we investigated the song structure variations and stereotypes in different areas of western Belgium and northern France. We described 66 different song types (a-elements) in 45 males recorded. Each male had a unique individual repertoire consisting of 1 to 4 of these song types. This high variability at the individual level contrasted with the high homogeneity of the specific repertoire over the whole geographic distribution of the species. The evolutionary implications of such specificity are discussed with regard to song learning and timing of singing activity. Finally, all males recorded belonged to the western regiolect, although some mixedsingers were also recorded. These results contrast with the very few studies previously conducted in western Europe which have suggested that eastern regiolect songs were common in this geographic area.