Nocturnal singing by diurnal birds in a temperate region of central Europe

Michał Budka,Kinga Kułaga

doi:10.1007/s10336-020-01794-5

Abstract

Most bird species sing by day, with two distinct peaks of vocal activity—around sunrise and sunset. However, even typically diurnal birds also sing during at night what is for them an atypical part of the day. To date, the mechanism and function(s) of such behaviour remain unclear across bird taxa. In our study we focused on night singing by diurnal birds in two different types of environments—forests and open areas in eastern Poland. We examined: (1) which diurnal species sing at night (defined as the period between astronomical dusk and dawn); (2) how intensively different species vocalise at night; and (3) whether the occurrence of nocturnal singing by diurnal birds depends on the type of environment. To do this, we used autonomous sound recorders to record soundscapes in 27 points located in open habitats and 27 points located in forests. At each location the recorder continuously collected data for an entire day during the breeding season, from one hour before dawn to 10 AM the next day. All night songs were classified to their species of origin via manual spectrogram scanning. We recorded 88 bird species in total (12 orders, 32 families), of which 24 species (7 orders, 15 families) sang at night. Night singing was observed significantly more often in open areas than in forests. The frequency and intensity of night singing was species-specific and ranged from occasional singing to regular and intense singing. We hypothesise that elevated light levels have a crucial influence on night singing, but that the effect of light may also be modified by environmental factors (e.g., predator pressure).

Highlights

Animals communicate by transferring information from a sender to a receiver using various types of signals: visual, auditory, chemical, or tactile (Bradbury and Vehrencamp 1998)
In our study we focused on a few basic questions related to night singing by diurnal birds in central Europe: (1) Which diurnal species sing at night? (2) Of the species that sing at night, how intensive is night singing? (3) Is night singing by diurnal birds probable in two different habitat types—forest and open habitat? To answer these, we utilised autonomous sound recorders to collect soundscape recordings in 54 locations and manual spectrogram scanning to detect and identify each song produced at night to its species of origin
The results of this study revealed that nocturnal singing by diurnal birds in central Europe is quite common

Summary

Introduction

Animals communicate by transferring information from a sender to a receiver using various types of signals: visual, auditory, chemical, or tactile (Bradbury and Vehrencamp 1998). Two peaks of vocal activity can be distinguished per day: around the sunrise (dawn chorus) and around the sunset (dusk chorus). The same study reported that, of 126 bird species that sing by night, 52% do so regularly, 27% occasionally, and 21% rarely These results indicate that nocturnal singing by diurnal birds, at least in North America, is quite common. We do not understand even basic aspects of this phenomenon, such as its commonness across bird taxa and the intensity of night singing by diurnal birds. Without this knowledge, it is difficult to explain the mechanism and function of such behaviour. An understanding of why some bird species vocalise during atypical parts of the day may help explain the evolution of acoustic signals in birds, which are under both interspecific as well as intraspecific evolutionary pressure

Methods

Results

Conclusion