Populations of birds inhabiting wetlands and grasslands are decreasing globally due to farmland expansion and subsequent agricultural intensification. In addition to conserving natural habitats, managing cultivated farmland and abandoned farmland are likely to be important future conservation measures; however, their relative suitability as avian habitat remains understudied. In this study, we evaluated five habitat types (wetland, pasture, cropland, abandoned farmland, and solar power plant) for openland birds in an agricultural landscape in central Hokkaido, northern Japan. Abandoned farmlands had bird species richness and total bird abundance values similar to those of wetlands. These values were generally higher in abandoned farmlands and wetlands than in croplands, pastures, and solar power plants. The per pair reproductive success of Stejneger's Stonechat Saxicola stejnegeri and the amount of its prey (arthropods) did not differ among the five habitat types. Three species (Black-browed Reed Warbler Acrocephalus bistrigiceps, Common Reed Bunting Emberiza schoeniclus, and Japanese Bush Warbler Cettia diphone) arrived earlier in wetlands than in other habitat types. These results suggest that, although protecting the remaining wetlands is of prime importance for the conservation of openland birds in agricultural landscapes, valuing and managing abandoned farmlands would be a promising alternative.
In many songbirds, males vary aspects of their singing behaviour when engaged in territorial interactions. Song rate, song type switching rate, song matching, song overlapping, and the use of specific song or call types have all been proposed to be aggressive signals. It is not clear why such variability in aggressive signaling mechanisms exists among different species. We used a comparative approach to study how two Phylloscopus warbler species respond to playback-simulated territorial intrusion. We examined whether the spontaneous songs of Large-billed Phylloscopus magnirostris and Sulphur-breasted P. ricketii leaf-warblers differed from songs produced in response to playback. Song bouts were analysed by measuring 10–12 parameters, but we found no differences between spontaneous songs and playback responses in either species. All males clearly responded to playback by approaching the loudspeaker and flying around it. Large-billed Leaf-warblers produced ‘crackling' sounds in response to playback more frequently than during spontaneous singing, whereas the usually highly vocal Sulphur-breasted Leaf-warblers possibly (and surprisingly) did not use vocalizations (either songs or calls) to signal direct aggression. A comparison with other Phylloscopus species revealed that even closely related species (i.e. from a single genus) might use different strategies when responding to simulated territorial intrusion. The aggressive signalling strategy is therefore a labile trait that can potentially be exposed to fast evolutionary change.
Pelagic top predators that range widely over thousands of kilometres increase their turn rate and slow their movements within an area of mesoscale (<102 km). This behavior is known as "Area Restricted Search, or ARS" and is associated with aggregations of prey. Foraging range, diving behavior, and ARS were studied for nine Black-footed Albatrosses Phoebastria nigripes rearing chicks on Mukojima in the Ogasawara Islands, using GPS and time-depth data-loggers. Their prey composition was examined using regurgitations. They fed on fish, fish eggs and squid within a range of 96–427 km from the colony. They made shallow (0.6±0.2 m) dives in day-time (2.2 dives per hour of at sea time) but rarely did so at night (0.1 dives per hour of at sea time). ARS behavior was observed at the scale of 11–71 km during day- and night-time and tended to occur in locations with relatively high primary production.
Birds have long been considered indicator species of biodiversity and so ecologists use them as indices of abundance and diversity in order to assess environmental health. These indices are based on surveys which assess the number of species and number of individuals counted in an area over a set time. We can modify citizen science approaches as a way to increase the involvement of undergraduate students in research. However, undergraduate students may have little experience in ecological surveying. Therefore, we tested whether bird counts collected by inexperienced undergraduates were consistent and repeatable among observers. We also examined bird communities at three sites of different size in and around Kyoto University in Kyoto Prefecture. First, we found that there was a high level of consistency among inexperienced observers. We also found a positive relationship between urban park size and avian abundance and diversity. Finally, we found that the bird communities at the two larger sites were most similar to one another whilst the community at the smallest site was quite distinct from the two larger sites. Therefore, this study shows that using citizen science methods may be an effective tool for gathering meaningful scientific data with inexperienced undergraduate observers.
Migrating birds adjust their behaviour in order to reach their final destination safely and in a timely manner. In doing so, they fly at different altitudes, but unlike passerines, raptors do not explore all air levels searching for the best tailwind assistance. Soaring species migrate over the mainland using updrafts to optimize soaring-gliding flight and reaching higher altitudes during midday. However, there is little information on which variables affect their flight altitude when facing the open sea, where thermals are very weak and they are forced to use powered flapping flight for a long time. To fill this gap, we recorded the flight altitude of migrating European Honey Buzzards Pernis apivorus as they crossed the Tyrrhenian Sea (Central Mediterranean) and passed over a small island. During four migratory seasons, we recorded the altitudes of birds when they reached the NE coast of Ustica, a volcanic island between Sicily and central Italy, and analysed data in relation to several variables. The results showed that the tendency to continue migrating, flock size, and wind speed are the most important features in explaining height variation in migrating European Honey Buzzards facing the open sea.
Bowers are display structures built by male bowerbirds (Ptilonorhynchidae) to court females. Avenue bowers consist of two parallel walls of upright sticks. Visiting females enter the avenue between the walls to watch the male displaying on a platform at either end of the bower. According to the "Optimal Illumination" hypothesis, bowers are oriented to optimise the amount of sunlight falling on the displaying male and the decorations on the platform. We studied bower orientation and platform utilisation at bowers of the western race of the Great Bowerbird, Chlamydera nuchalis nuchalis, near Darwin, Northern Territory, Australia. Most bowers were oriented in a NNE-SSW direction, in contrast to the prevailing NNW-SSE pattern observed in the eastern race, C. n. orientalis, in north Queensland. The disparity between these study populations in bower orientation appears to be related to their geographic latitudes and, consequently, azimuth of the sun during the peak morning display period. Males displayed on the platform that received the most sunlight. Moreover, mating success at east-facing bowers was higher than at west-facing bowers. These findings support the "Optimal Illumination hypothesis". This is the first report demonstrating that bower orientation influences mating success based on quantitative data in avenue bower building species.
Agroecosystems consist of an agricultural matrix composed of plots under crop and livestock use, along with several elements that provide habitat diversity to the rural landscape. Avian species may respond to the presence of those characteristics at both landscape and local scales. We compared species richness between landbird assemblages from two previous studies carried out during the breeding season in temperate agroecosystems of Argentina at plot scale (local; n=23 sites) through samplings within plots, and at landscape scale (n=30 sites) through samplings along secondary roads, which can include plots, plot margins, roadsides, railways, woodlots and farmsteads. We standardized 100 min of observation for each sample in order to compare both studies. We recorded 60 species at plot scale and 72 species at landscape scale. Species accumulation curves indicated greater species richness at the landscape scale, which included some generalists that nest in exotic trees, shrubs and farmsteads. In addition, we found a higher relative abundance of species associated with open habitats at the plot scale, such as Correndera Pipit Anthus correndera and Short-billed Pipit Anthus furcatus which nest on the ground, whereas at the landscape scale we found a greater relative abundance of species nesting in shrubby and woody vegetation, such as Double-collared Seedeater Sporophila caerulescens and Rufous Hornero Furnarius rufus. Our results highlight the role of spatial scale in the analysis of landbird assemblages in agroecosystems, showing that species richness is higher at landscape than at plot scale.
Oil palm expansion has caused considerable biodiversity loss as rainforest has been converted to plantation. However, it is still possible to mitigate such biodiversity losses and increase agricultural sustainability by introducing sustainable oil palm farming practices. One such method is the use of biological control agents for understory weed management in place of herbicides. Integrating cattle into oil palm plantation management to control undergrowth is expected to improve biodiversity (including avian diversity) in oil palm plantations. This study investigated the association between cattle grazing and farmland bird species composition in oil palm plantations. We used point transect sampling to survey farmland birds in 45 oil palm plantations which were divided into systematically and non-systematically cattle grazed plantations and control plantations (without cattle grazing). We found that both oil palm plantations with systematic (P=0.001) and non-systematic (P=0.005) cattle grazing had greater avian diversity than plantations without cattle grazing. Based on feeding guild, avian insectivores made up the majority of farmland birds observed. Bird species composition was determined by four attributes in our model: number of cattle, selective weeding frequency, age of oil palm stand, and palm height. We conclude that systematic grazing can improve avian diversity in oil palm plantations. We stress, that cattle integration into oil palm agriculture can provide an excellent means of maximising agricultural land use efficiency as well as increasing biodiversity in agricultural landscapes by increasing habitat complexity.
The diet composition and dietary patterns of the Long-eared Owl Asio otus were studied in Mediterranean agrosystems in central Crete (Greece) over the winters of 2009–2015. Overall, 2,819 prey items were recovered from 1,207 pellets, belonging to six taxa of mammals, 22 taxa of birds and four taxa of insects. Small mammals were the most common prey species, accounting for 75.8% by frequency and 79.7% by biomass, followed by birds (23.2% and 20.1%); the latter being rather an island component compared to continental regions. The House Mouse Mus musculus was the most important prey species in the owl's diet (56.3%) ahead of the Wood Mouse apodemus sylvaticus (9.51%) and the Black Rat Rattus rattus (7.9%). The species proved to be a significant rodent predator in olive groves and vineyards during winter months, selecting Wood Mouse and young Black Rat more than expected. Long-eared Owl feeding ecology studies could lead to improved land management and agricultural practices in the rural landscapes of the Mediterranean.