BioOne Complete (complete.BioOne.org) is a full-text database of 200 subscribed and open-access titles in the biological, ecological, and environmental sciences published by nonprofit societies, associations, museums, institutions, and presses.

Background Birds have extremely well-developed acoustic communication and have become popular in bioacoustics research. The majority of studies on bird song have been conducted in the temperate zones where usually males of birds sing to attract females and defend territories. In over 360 bird species mostly inhabiting the tropics both males and females sing together in duets. Avian duets are usually formed when a male and female coordinate their songs. We focused on a species with relatively weakly coordinated duets, with male solo as the prevailing vocalisation type. Methods Instead of analysing a set of recordings spread over a long time, we analysed whole day microphone-array recordings of the Yellow-breasted Boubou (Laniarius atroflavus), a species endemic to West African montane rainforests. We described the structure of the solo and duet vocalisations and temporal characteristics of daily activity based on 5,934 vocal bouts of 18 focal pairs and their neighbours. Results Birds had small, sex specific repertoires. All males shared three types of loud whistles functioning as song type repertoires in both solos and duets. Females vocalised with five types of harsh, atonal notes with a more variable and usually lower amplitude. Three of them were produced both as solos and in duets, while two seem to function as alarm and excitement calls given almost exclusively as a solo. Solos were the most common vocalisation mode (75.4%), with males being more vocally active than females. Duets accounted for 24.6% of all vocalisations and in most cases were initiated by males (81%). The majority of duets were simple (85.1%) consisting of a single male and female song type, but altogether 38 unique duet combinations were described. Males usually initiated singing at dawn and for this used one particular song type more often than expected by chance. Male solo and duet activities peaked around dawn, while female solos were produced evenly throughout the day. Discussion Yellow-breasted Boubou is a duetting species in which males are much more vocal than females and duetting is not a dominating type of vocal activity. Duet structure, context and timing of daily production support the joint resource defence hypothesis and mate guarding/prevention hypotheses, however maintaining pair contact also seems to be important. This study provides for the first time the basic quantitative data describing calls, solos and duet songs in the Yellow-breasted Boubou.

Despite large conservation efforts to halt the loss of farmland biodiversity in Europe, negative population trends are still observed, especially for common species. Old villages and human settlements are biodiversity hotspots and important breeding habitats for farmland birds, but recent requirements for energy saving measures and improved living comfort have changed their architecture and habitats. Consequently, modernization of villages may negatively affect bird diversity due to the loss of nesting and foraging sites. We investigated how the abundance and diversity of birds breeding in 104 Polish villages varied in relation to the degree of modernization as estimated by the proportion of new and renovated homesteads. Abundance of building‐nesting species, but not tree‐nesting species, declined by 50% across a gradient of old to highly modernized villages. The contribution of new versus renovated houses to the observed decline was similar. Synthesis and applications. Rural modernization may have a dramatic effect on abundance of birds nesting on buildings, thus may be an important and overlooked contributor to farmland bird population declines in Europe. Villages and rural properties fall outside of current conservation policy as they are neither protected areas nor agricultural lands (where agri‐environmental schemes can be applied). The observed conflict between sustainability goals such as increased building energy efficiency and biodiversity conservation suggests that sustainable rural development should better link modernization with conservation measures, for example, by constructing nesting sites when renovating and building new houses. The challenge is to design modern buildings that are both energy‐efficient and biodiversity‐friendly to generally improve quality of life for rural communities and to halt or reduce farmland bird declines in rural landscapes. Designers and architects can find inspiration from traditional architecture and add a variety of nest‐box types.

Urban habitats differ from adjacent natural habitats in terms of disturbance regimes, light, temperature, rainfall, habitat distribution and resource abundance. Meteorological differences advance and prolong the growing season in urban habitats compared to nearby rural areas. In turn, urban bird populations may potentially start singing earlier, and reproduce earlier and more frequently than rural populations. However, this prediction has previously only been tested with data from single species using single spatial replicates from rural and urban sites. Here we provide the first general (paired urban and rural populations of 54 bird species) and large-scale (a 3800 km long latitudinal gradient across Europe) empirical evidence for longer and earlier singing periods in urban compared to rural habitats. Effects of urbanization on start and duration of the singing period (as a proxy for the breeding season) were positively related to size of cities and ecological characteristics of species. Bird species that have been urbanized for a long time started to sing earlier and had a more extended singing period in urban compared to rural habitats. We also found that the singing period started later and was shorter at higher latitudes. Geographical variation in phenology was related to temperature and rainfall, although differences between urban and rural habitats were not. Differences in duration of singing periods between paired urban and rural sites were as large as latitudinal differences between southern and northern Europe (5, 6 and 28 d for 3 common species, as compared to a mean latitudinal variation of 17.1 d). This suggests local adjustment to urban environments, either due to evolution or to plasticity of phenological behaviour.

No abstract

Duetting is a cooperative behaviour that can have multiple functions. All 22 species within the genus Laniarius (Malaconotidae family) produce duets and solos with varying levels of complexity. We experimentally investigated the Yellow-breasted Boubou (Laniarius atroflavus), an endemic species from W African montane forests, which uses sex-specific signals for both solos and duets. Using two different experiments, we tested the response of territorial pairs, during the breeding season, to the playback of male and female solos and duets in order to investigate their functions in context of territorial intrusion. For the experimental intrusions of duetting pairs, we simulated the male and female songs at a close distance to each other as well as at a larger distance. The first goal was to assess whether intruder type affects the responsiveness of territory owners. The second goal was to examine how spatial segregation of intruding pairs singing duets affects the response. The majority of tested pairs responded to playback by approaching speaker(s) and singing. We found the strongest approach response was to the playback of duets and male solos, with the response to female solo being weak or having no response. The male-initiated, and led, duet was the most frequent and intensive vocal response, while female-initiated duets and solos of both sexes were less often observed. Regardless of the treatment type, the joint response of a pair was stronger if females were involved in it. Results indicate that in Yellow-breasted Boubous, males have the leading role in responding to intruders regardless of the sex or if they intrude the territory as a solo or as a duetting pair. Males were observed increasing their response strength when motivated by their mates, suggesting that female vocalisations are addressed to their own partner. Our results suggest that the most probable function of duets in the studied species is joint resource defence; however, mate guarding and the guarding of paternity are still possible. Our results are consistent with earlier findings showing that structural differences in male and female song of several Laniarius species can be the result of evolution under similar pressure from the need to defend resources together and the potential betrayal of a partner.

No abstract

The central tenet of European farmland ecology is that agricultural intensification during the 20th century was largely responsible for dramatic declines in species abundances. However, during this time, human rural settlements were also undergoing radical changes through modernization, with undocumented biodiversity impacts in this important wildlife habitat. We performed the first ever large‐scale study to disentangle the impact of these simultaneous processes on farmland bird diversity in 104 Polish villages. We show that modernized villages and their surrounding agricultural fields had 50–60% fewer birds than those in and around comparable older villages. The relative contribution of modernization versus agricultural intensification to predicted bird declines was 88% versus 12% for bird communities in villages and 56% versus 44% in surrounding croplands, with considerable variation among ecological species subgroups. These results challenge our current understanding of agricultural ecosystem ecology and how best to implement conservation measures costing billions of euros annually.