An experimental investigation into the effects of traffic noise on distributions of birds: avoiding the phantom road

Many authors have suggested that the negative effects of roads on animals are largely owing to traffic noise. Although suggestive, most past studies of the effects of road noise on wildlife were conducted in the presence of the other confounding effects of roads, such as visual disturbance, collisions and chemical pollution among others. We present, to our knowledge, the first study to experimentally apply traffic noise to a roadless area at a landscape scale—thus avoiding the other confounding aspects of roads present in past studies. We replicated the sound of a roadway at intervals—alternating 4 days of noise on with 4 days off—during the autumn migratory period using a 0.5 km array of speakers within an established stopover site in southern Idaho. We conducted daily bird surveys along our ‘Phantom Road’ and in a nearby control site. We document over a one-quarter decline in bird abundance and almost complete avoidance by some species between noise-on and noise-off periods along the phantom road and no such effects at control sites—suggesting that traffic noise is a major driver of effects of roads on populations of animals.     

Do changes in climate patterns in wintering areas affect the timing of the spring arrival of trans‐Saharan migrant birds?

The life cycles of plants and animals are changing around the world in line with the predictions originated from hypotheses concerning the impact of global warming and climate change on biological systems. Commonly, the search for ecological mechanisms behind the observed changes in bird phenology has focused on the analysis of climatic patterns from the species breeding grounds. However, the ecology of bird migration suggests that the spring arrival of long‐distance migrants (such as trans‐Saharan birds) is more likely to be influenced by climate conditions in wintering areas given their direct impact on the onset of migration and its progression. We tested this hypothesis by analysing the first arrival dates (FADs) of six trans‐Saharan migrants (cuckoo Cuculus canorus, swift Apus apus, hoopoe Upupa epops, swallow Hirundo rustica, house martin Delichon urbica and nightingale Luscinia megarhynchos), in a western Mediterranean area since from 1952 to 2003. By means of multiple regression analyses, FADs were analysed in relation to the monthly temperature and precipitation patterns of five African climatic regions south of the Sahara where species are thought to overwinter and from the European site from where FADs were collected. We obtained significant models for five species explaining 9–41% of the variation in FADs. The interpretation of the models suggests that: (1) The climate in wintering quarters, especially the precipitation, has a stronger influence on FADs than that in the species' potential European breeding grounds. (2) The accumulative effects of climate patterns prior to migration onset may be of considerable importance since those climate variables that served to summarize climate patterns 12 months prior to the onset of migration were selected by final models. (3) Temperature and precipitation in African regions are likely to affect departure decision in the species studied through their indirect effects on food availability and the build‐up of reserves for migration. Our results concerning the factors that affect the arrival times of trans‐Saharan migrants indicate that the effects of climate change are more complex than previously suggested, and that these effects might have an interacting impact on species ecology, for example by reversing ecological pressures during species' life cycles.     

Influence of habitat modification by livestock on páramo bird abundance in southern Andes of Ecuador

Livestock grazing on natural grasslands is widespread with negative consequences to biodiversity. In the High Andes, páramo grassland is a distinctive ecosystem where the influence of livestock grazing on páramo birds is poorly documented. We assessed the influence of habitat modification of páramo grassland related to livestock grazing on bird habitat guilds in the southern Andes of Ecuador. We recorded birds occurring along transects located in areas which showed a gradient (low to high) of grazing pressure. We found a decrease in abundance of páramo specialists in transects with more grazing pressure. We interpret this habitat modification as loss of key habitat necessary for habitat-specialized birds.     

A review of survival estimates for raptors and owls

This paper reviews the literature on survival estimates for different species of raptors and owls, examines the methods used to obtain the estimates, and draws out some general patterns arising. Estimating survival usually involves the marking of birds so that they can be recognized as individuals on subsequent encounters. Annual survival can then be estimated from: (1) birds ringed at known age (usually as nestlings) and subsequently reported by members of the public (usually as found dead), the ratio of recoveries at different ages being used to calculate annual survival; (2) marked breeding adults, trapped or re‐sighted in subsequent years in particular study areas, with the proportion re‐trapped (or re‐sighted) in each year being taken as the minimum annual survival; (3) live encounter (trapped or re‐sighted) of birds marked either as nestlings or breeding adults analysed using the capture–mark–recapture (or re‐sighting) methods to estimate annual survival; (4) a combination of reports of known‐age dead birds and re‐trapping/re‐sighting of live birds; (5) use of radio‐ or satellite‐tracking to follow the fates of individuals; and (6) the integration of these methods with other information, such as change in numbers between years, to derive estimates of survival and other demographic parameters. Studies confined to particular areas usually give estimates of ‘apparent annual survival’, because they take no account of birds that leave the area. However, radio‐ or satellite‐tracking makes it possible to estimate true survival, including survival of prebreeders that have low natal‐site fidelity (this usually requires satellite telemetry). As in other birds, the preferred method for estimating survival has changed over time, as new and more robust methods of estimation have been developed. Methods 1 and 2 were the first to be developed, but without statistical underpinning, while methods 3–6 were developed later on the basis of formal statistical models. This difference has to be borne in mind in comparing older with newer estimates for particular species. Published survival estimates were found for three species of Cathartidae, one of Pandionidae, 29 of Accipitridae, 12 of Falconidae, one of Tytonidae and nine of Strigidae, almost all from temperate Northern Hemisphere species. In most of these species more than one estimate was available, and in some separate estimates for different age or sex groups. The main patterns to emerge included: (1) a significant tendency for annual adult survival to increase with body weight, smaller species having annual survival rates mainly of 60–70%, medium‐sized species having rates mainly in the range 70–90% and the largest having rates of > 90%, in the absence of obvious human‐caused losses; (2) a lower survival in the first or prebreeding years of life than in subsequent years; (3) a lack of obvious or consistent differences in survival between the sexes, where these could be distinguished; and (4) in the few species for which enough data were available, a decline in annual survival rates in the later years of life.     

The role of farm structure on bird assemblages around a Kenyan tropical rainforest

Although it is clear that the farmlands neighbouring fragmented forests are utilized by some forest birds, it is not clear how birds in general respond to farmland habitat mosaic. An effort was made to determine how bird density and foraging assemblages were influenced by farm structural characteristics and distance from forest edge. Thirty farms up to a distance of 12 km around Kakamega forest in western Kenya were studied. Farm structure entailed size, hedge volume, habitat heterogeneity, woody plant density, plant diversity and crop cover. Birds were surveyed using line transects and DISTANCE analyses and classified into six feeding guilds and three habitat associations. Size of farms increased away from the forest, as woody plant density, plant diversity, indigenous trees and subsistence crop cover declined. The most important farm structure variable was hedge volume, which enhanced bird species richness, richness of shrub‐land bird species and insectivorous bird density (R = 0.58, P < 0.01). Bird density increased with tree density while indigenous trees were suitable for insectivores and nectarivores. There were very few forest bird encounters. Agricultural practices incorporating maintenance of hedges and sound selection of agroforestry trees can enhance conservation of birds on farmland, though, not significantly for forest species.     

利用红外相机技术对安徽省鹞落坪国家级自然保护区大中型兽类及林下鸟类的调查

鹞落坪国家级自然保护区位于大别山脉南麓的核心地带。2014-2017年, 作者采用红外相机技术对鹞落坪国家级自然保护区的大中型兽类及林下鸟类进行调查。研究共布设了72个相机位点, 累计完成16,658个相机工作日, 获得独立有效照片2,142张, 共记录野生兽类9种、鸟类15种, 隶属8目15科。包括国家一级重点保护野生动物1种, 即安徽麝(Moschus anhuiensis), 国家二级重点保护野生动物2种, 分别是勺鸡(Pucrasia macrolopha)和白冠长尾雉(Syrmaticus reevesii)。相对多度排名前五的兽类分别为小麂(Muntiacus reevesi)、野猪(Sus scrofa)、赤腹松鼠(Callosciurus erythraeus)、猪獾(Arctonyx collaris)和岩松鼠(Sciurotamias davidianus)。相对多度排名前五的鸟类为白冠长尾雉、勺鸡、松鸦(Garrulus glandarius)、灰背鸫(Turdus hortulorum)、红嘴蓝鹊(Urocissa erythroryncha)。此外红外相机还拍摄到大量人类活动照片, 表明当地人类活动较为严重, 应加强管理。本研究初步了解了保护区内大中型兽类和林下鸟类群落信息及人类活动的干扰情况, 为保护区未来的保护和管理工作提供了数据基础。     

Sperm head abnormalities are more frequent in songbirds with more helical sperm: A possible trade‐off in sperm evolution

Sperm morphology varies enormously across the animal kingdom. Whilst knowledge of the factors that drive the evolution of interspecific variation in sperm morphology is accumulating, we currently have little understanding of factors that may constrain evolutionary change in sperm traits. We investigated whether susceptibility to sperm abnormalities could represent such a constraint in songbirds, a group characterized by a distinctive helical sperm head shape. Specifically, using 36 songbird species and data from light and scanning electron microscopy, we examined among‐species correlations between the occurrence of sperm head abnormalities and sperm morphology, as well as the correlation between sperm head abnormalities and two indicators of sperm competition. We found that species with more helically shaped sperm heads (i.e., a wider helical membrane and more pronounced cell waveform) had a higher percentage of abnormal sperm heads than species with less helical sperm (i.e., relatively straight sperm) and that sperm head traits were better predictors of head abnormalities than total sperm length. In contrast, there was no correlation between sperm abnormalities and the level of sperm competition. Given that songbird species with more pronounced helical sperm have higher average sperm swimming speed, our results suggest an evolutionary trade‐off between sperm performance and the structural integrity of the sperm head. As such, susceptibility to morphological abnormalities may constrain the evolution of helical sperm morphology in songbirds.     

Connectivity with primary forest determines the value of secondary tropical forests for bird conservation

Species extinctions caused by the destruction and degradation of tropical primary forest may be at least partially mitigated by the expansion of regenerating secondary forest. However, the conservation value of secondary forest remains controversial, and potentially underestimated, since most previous studies have focused on young, single‐aged, or isolated stands. Here, we use point‐count surveys to compare tropical forest bird communities in 20–120‐year‐old secondary forest with primary forest stands in central Panama, with varying connectivity between secondary forest sites and extensive primary forest. We found that species richness and other metrics of ecological diversity, as well as the combined population density of all birds, reached a peak in younger (20‐year‐old) secondary forests and appeared to decline in older secondary forest stands. This counter‐intuitive result can be explained by the greater connectivity between younger secondary forests and extensive primary forests at our study site, compared with older secondary forests that are either (a) more isolated or (b) connected to primary forests that are themselves small and isolated. Our results suggest that connectivity with extensive primary forest is a more important determinant of avian species richness and community structure than forest age, and highlight the vital contribution secondary forests can make in conserving tropical bird diversity, so long as extensive primary habitats are adjacent and spatially connected.Abstract in Spanish is available with online material.     

Field of Dreams: Restitution of Pollinator Services in Restored Bird‐Pollinated Plant Populations

Ecosystem functionality is an increasingly important objective of ecological restoration. Despite this, a few studies have rigorously assessed reproductive functionality within restored plant populations, and it is largely assumed that pollinators follow restoration of plant communities—“build it and they will come.” Here, we applied an ecological genetic approach to determine the impact of spatial separation on mating in Banksia menziesii (Proteaceae), a dominant bird‐pollinated species of Banksia woodlands of Western Australia. All plants at three post‐mining restored sites (n = 72 [13 years old], n = 21 [8 years old], and n = 20 [9 years old]), as well as a sample from an adjacent natural reference site (n = 42), were genotyped at nine microsatellite loci. Seed set, mating system parameters, realized pollen dispersal through the assignment of paternity to seed, and avian pollinator species composition, abundance and behavior, were assessed. All patches displayed equivalent heterozygosity (H_e = 0.53–0.59) and very weak genetic divergence (F_ST ≤ 0.01). Seed of plants within restored sites showed complete outcrossing and relatively high seed set, 26% of which were sired by pollen donors located beyond the local patch. Similar abundance and movement of nectar‐feeding birds was observed in restored and natural sites, despite lower bird species diversity in the restored site, where a smaller, less aggressive species was dominant. Our results demonstrate the restitution of wide outcrossing in these restored Banksia patches within an active mine‐site, and suggest that restored bird‐pollinated Banksia populations are resilient to human impacts, due largely to their generalist pollinator requirements and highly‐mobile avian pollinators.