Changes of a forest bird community in Hong Kong of China in 10 years

The changes in the bird community structure of the largest natural secondary forest of Hong Kong over 10 years were investigated. Densities of the 10 most abundant species in 1993–1995 and 2003–2005 were compared using t-test. All resident habitat generalists showed significant decline in densities. Two forest specialists showed significant increase in densities: one is native and the other is exotic species. The trend of changes in the forest bird community of Hong Kong is mainly related to the absence of nearby forests that could act as “source” of forest dependent species to colonize the local secondary forests, and the invasion of exotic species.     

Changes of a forest bird community in Hong Kong of China in 10 years

The changes in the bird community structure of the largest natural secondary forest of Hong Kong over 10 years were investigated. Densities of the 10 most abundant species in 1993–1995 and 2003–2005 were compared using t-test. All resident habitat generalists showed significant decline in densities. Two forest specialists showed significant increase in densities: one is native and the other is exotic species. The trend of changes in the forest bird community of Hong Kong is mainly related to the absence of nearby forests that could act as “source” of forest dependent species to colonize the local secondary forests, and the invasion of exotic species.     

香港大埔滘天然次生林鸟类群落结构变化

观察了香港最大的大埔滘天然次生林内鸟类群落结构在10a间的变化。用t檢验比较了1993~1995年和2003~2005年间的10种数量最高的鸟类的密度变化。所有的泛生境留鸟种类的密度均呈显著减少。两种树林种类的密度有显著増加,其中一种是本土种,另一种是外来种。香港树林鸟类群落的变化趋势主要受到两个因素的影响,包括缺少有树林种类鸟居住的树林,和外来种的入侵。     

Rodent Diversity in a Highly Degraded Tropical Landscape: Hong Kong, South China

The diverse ecological roles played by different rodent species mean that the loss of some species and superabundance of others could potentially influence a wide range of ecological processes. Hong Kong (22° N, 114° E), with seven million people in a land area of 1100 km², could be considered a `worst case scenario' for the survival of mammalian diversity. Existing information on rodents in Hong Kong was compiled from previous published and unpublished studies, and additional trapping was conducted at 17 non-urban sites. The rodent fauna of modern Hong Kong consists of eight species of rats and mice (Bandicota indica, Mus caroli, M. musculus, Niviventer fulvescens, Rattus norvegicus, R. rattus, R. tanezumi, R. sikkimensis: Muridae), one porcupine (Hystrix brachyura: Hystricidae), and one recently introduced tree squirrel (Callosciurus erythraeus: Sciuridae). Six of the murids are urban or agricultural commensals, so only the porcupine and two murids, N. fulvescens and R. sikkimensis, are likely survivors of Hong Kong's pre-deforestation native rodent fauna. The two murids co-dominate in forest and shrubland, but can also move through grassland, which has probably enabled their survival through repeated cycles of fragmentation and regrowth. Additional forest rodents that may have inhabited Hong Kong in the past are tentatively identified from information on their recent distributions in the region. One possible ecological consequence of Hong Kong's depleted rodent fauna is a shift in the balance between seed predation and seed dispersal, in favor of the former.     

Changes in a forest bird community during a period of fire and drought near Bega,New South Wales

The bird community of a forested 13 ha plot was studied for 3 years, during which the plot was burnt by wildfire and was severely drought-affected. The combined effects of fire and drought were surprisingly limited. Similar numbers of species were recorded in each year and differences in species composition involved only rare visitors to the plot. Colour-banding indicated population declines in at least six resident species. The greatest decline was that of the Brown Thornbill (Acanthiza pusilla), from 20 pairs to 10 pairs. In general, insectivorous birds were most abundant and widespread on the plot during the first year, before the fire. In contrast, nomadic birds feeding on flowers or fruits were most abundant in the second year, when there was a prolific flowering and fruiting of several important food plants. After the fire, at least ten bird species avoided the burnt ridges and became more concentrated in the unburnt gullies. Most were species associated with dense shrub thickets, the layer of vegetation most affected by the fire. It seems that gullies are major refuge areas in these forests and are the key to the resilience of the bird community to fire and drought.     

Comparative demographics of a Hawaiian forest bird community

Estimates of demographic parameters such as survival and reproductive success are critical for guiding management efforts focused on species of conservation concern. Unfortunately, reliable demographic parameters are difficult to obtain for any species, but especially for rare or endangered species. Here we derived estimates of adult survival and recruitment in a community of Hawaiian forest birds, including eight native species (of which three are endangered) and two introduced species at Hakalau Forest National Wildlife Refuge, Hawai?i. Integrated population models (IPM) were used to link mark–recapture data (1994–1999) with long‐term population surveys (1987–2008). To our knowledge, this is the first time that IPM have been used to characterize demographic parameters of a whole avian community, and provides important insights into the life history strategies of the community. The demographic data were used to test two hypotheses: 1) arthropod specialists, such as the ‘Akiapōlā‘au Hemignathus munroi, are ‘slower’ species characterized by a greater relative contribution of adult survival to population growth, i.e. lower fecundity and increased adult survival; and 2) a species’ susceptibility to environmental change, as reflected by its conservation status, can be predicted by its life history traits. We found that all species were characterized by a similar population growth rate around one, independently of conservation status, origin (native vs non‐native), feeding guild, or life history strategy (as measured by ‘slowness’), which suggested that the community had reached an equilibrium. However, such stable dynamics were achieved differently across feeding guilds, as demonstrated by a significant increase of adult survival and a significant decrease of recruitment along a gradient of increased insectivory, in support of hypothesis 1. Supporting our second hypothesis, we found that slower species were more vulnerable species at the global scale than faster ones. The possible causes and conservation implications of these patterns are discussed.     

Figs (Ficus,Moraceae) in Urban Hong Kong,South China1

Hong Kong (22°N) is on the northern margins of the Asian tropics and has a native fig flora of 24 species. A total of 3.4 km² of the urban area on Hong Kong Island was surveyed for spontaneous and planted fig plants of reproductive size. The 1124 individuals included 14 species in four subgenera: seven native species (F. fistulosa, F. hirta, F. hispida, F. microcarpa, F. pumila, F. subpisocarpa, and F. variegata), four of which were sometimes planted, one probably native (F. virens), one naturalizing species (F. religiosa), and five exotic species that occurred only in cultivation, two of which (F. altissima, F. rumphii) are pollinated and produce viable seeds. The native species in the two most common subgenera form distinct ecological guilds: those in subgenus Sycomorus bear large, many‐seeded, green or yellow figs and are bat‐dispersed pioneers on exposed soil; those in subgenus Urostigma bear small, few‐seeded, dark‐purple figs and are largely bird‐dispersed and epilithic. The density of potentially fruiting fig plants in the study area (2.3/ha) was within the range reported for tropical forests and between them they were visited by the entire urban frugivore fauna. This study shows the importance of the urban fig flora to urban wildlife and also highlights the risk of cultivated Ficus species becoming invasive, despite their obligate species‐specific pollinator mutualisms.     

Effects of forest modification on bird community composition and seed removal in a heterogeneous landscape in South Africa

Human disturbance threatens and modifies forest ecosystems worldwide. Previous studies have investigated the effects of human impact on local bird communities in disturbed forests, but we still lack information on how bird species richness and ecological processes respond to different forest modifications present at a landscape scale. In a heterogeneous South African landscape, we chose six types of indigenous scarp forest, differing in the intensity of human disturbance: continuous natural forests and natural forest fragments in nature reserves, forest fragments in eucalyptus plantations, fragments in the agricultural matrix, forest gardens and secondary forests in game reserves. In 36 study sites, we investigated the bird community using point counts and observed the seed removal of birds at the native tree species Celtis africana. Species richness did not differ among the forest types, but abundance varied significantly with most birds observed in fragments in the agricultural matrix, forest gardens, and secondary forests. The higher bird abundance in these forests was mainly due to forest generalists, shrubland and open country species whereas forest specialists were rarely present. Changes in species composition were also confirmed by multivariate analysis which clearly separated bird communities by forest type. Frugivore abundance in C. africana was highest in natural forest fragments, fragments in the agricultural matrix, forest gardens and secondary forests. The same trend was found for the estimated total number of fruits removed per C. africana tree, though the differences among forest types were not significant. Consequently, modified forests seem to maintain important ecological functions as they provide food sources for generalist species which may, due to their mobility, enhance natural plant regeneration. However, we could show that protected forest habitats are important refugees for specialist species sensitive to human disturbance.     

中国香港外来入侵植物

该文于2015—2016年通过野外实地调查并结合整理、查阅相关的文献资料,研究了中国香港特别行政区外来入侵植物的种类组成、原产地、生活型、入侵途径和危害状况等。结果表明:(1)中国香港有外来入侵植物共101种,隶属于36科77属,其中菊科(Asteraceae)植物的种类最多,有17种。(2)来源于美洲的外来入侵植物种类最多,占入侵植物总数的77.2%。(3)外来种类中草本植物占了绝大多数,占总种数的80.2%。(4)恶意入侵与严重入侵植物共42种,占总种数的41.6%。同时,通过与邻近的珠海、深圳、澳门、广州四个地区的外来入侵植物进行比较,提出了珠三角区域共防共治外来植物入侵、保障环境生态安全的建议。     

Foraging ecology of insectivorous birds in a mixed forest of Hong Kong

In a mixed forest in Hong Kong, the foraging ecology of nine species of insectivorous birds was studied. Leaves and branches of diameters smaller than 2 cm were the most frequently searched microhabitats. Gleaning was the most frequently used foraging method. Apart from Blue-winged Minla and Japanese White-eye, no two species used similar proportions of vertical strata and microhabitats at the same time. Bird species using similar proportion of microhabitats were foraging in different proportion of vertical strata. This niche segregation enabled the bird species to coexist in the same habitat. Velvet-fronted Nuthatch differed from other species by its more frequent use of branches of diameters larger than 2 cm and tree trunks. This might be one of the reasons why this exotic species successfully established a breeding population in the study area.     

Foraging ecology of insectivorous birds in a mixed forest of Hong Kong

In a mixed forest in Hong Kong, the foraging ecology of nine species of insectivorous birds was studied. Leaves and branches of diameters smaller than 2 cm were the most frequently searched microhabitats. Gleaning was the most frequently used foraging method. Apart from Blue-winged Minla and Japanese White-eye, no two species used similar proportions of vertical strata and microhabitats at the same time. Bird species using similar proportion of microhabitats were foraging in different proportion of vertical strata. This niche segregation enabled the bird species to coexist in the same habitat. Velvet-fronted Nuthatch differed from other species by its more frequent use of branches of diameters larger than 2 cm and tree trunks. This might be one of the reasons why this exotic species successfully established a breeding population in the study area.     

Changes in forest bird abundance,community structure and composition following a hurricane in Sweden

The effect that extreme natural events have on biological diversity is relatively poorly known. We used a before–after control‐impact (BACI) design to analyze changes in bird abundances and communities following Hurricane Gudrun, which struck southern Sweden in January 2005, felling 75 million m³ of forest and causing damage to 5% of forested areas (half a million hectares) in a few hours. We used recent measures of impact in combination with classical BACI contrasts to analyze bird count data from a monitoring program in Sweden. We investigated changes in the abundance of 17 species commonly found in forests, along with changes in species composition and functional structure of the bird community. In total, we considered 34 response variables and examined whether responses were immediate or long‐term. There was no evidence of a strong effect of the hurricane on the abundances of six species. Estimates of the effects on five species were too uncertain to draw inferences. We detected positive and negative effects of the hurricane on the abundances of the remaining six species, but the magnitude of effects often was small. Generally, the effects were in the expected direction: negative on birds associated with mature forest and positive on birds associated with open land or young forest. We found evidence of an increase in the proportion of species that nest on the ground and a decrease in the proportion of species that nest in cavities and trees. In contrast, the hurricane had no discernible effect on functional measures of diversity (richness, evenness or divergence), or on communities’ reproductive or morphological characteristics. Our results suggest that the hurricane affected bird populations and communities, but the magnitude of effects was generally small.     

Seasonal changes in populations of three sympatric isopods in a Hong Kong forest

Data on the population dynamics of tropical isopods in general, and those inhabiting forests in particular, are scarce. Consequently, the population dynamics of three sympatric isopods, Burmoniscus ocellatus (Philosciidae), Formosillo raffaelei and Orodillo maculatus (Armadillidae), were studied at two neighbouring sites in a mixed forest in Hong Kong between March 1985 and December 1986. Isopod population densities varied with the species, site and season, with mean densities ranging from 100–150 m^-2. Burmoniscus ocellatus and F. raffaelei had a single recruitment peak per year, while O. maculatus had two. Results of the present study revealed that air temperature was the main factor explaining seasonal variations in population density, while rainfall exerted its effect with a two- to three-week time-lag, depending on the species studied. Approximately 20% of Formosillo raffaelei and O. maculatus sampled were found infected by Rickettsiella bacteria. The possible influence of pathogens, and other biotic factors, on the dynamics of the Hong Kong isopod populations was discussed     

Nodulation of native woody legumes in Hong Kong, China

Woody legumes can play an important role in forest restoration on degraded land but the knowledge of woody legumes has lagged behind their uses. This study is a pioneer investigation to explore the ability of native woody legumes to form root nodules and fix nitrogen in Hong Kong. Nine sites of different habitat types were surveyed during both wet and dry seasons for two years. Young plants of woody legumes along studied transects were excavated. The patterns of nodulation and nodule morphology were recorded and the nitrogen fixing ability was tested by acetylene-reduction-assay. Twenty-eight species in 16 genera were examined, of which 20 species were nodulating and eight non-nodulating, including all six species in the Caesalpinioideae. Five species were new records to the world’s nodulation inventory. Bowringia callicarpa was a new species and genus examined, which was non-nodulating. The overall nodulation pattern was consistent with previous studies. Nodulation was more profuse in some shrub species while inconsistent in most tree species. Species with higher proportion of nodulated individual plants also tended to have more nodules in each plant. Spherical nodules were common in shrub and woody climber species whilst tree species usually had woody indeterminate nodules. Seasonal difference in the amount of senescent nodules was noted in most species. All the nodules tested by acetylene-reduction-assay were effectively nitrogen-fixing, with nitrogenase activity ranging from 4 μmol C₂H₄ g^?1 h^?1 to 20 μmol C₂H₄ g^?1 h^?1, which was comparable to other tropical tree species. The findings in nodulation pattern and nitrogen fixing ability of these species are essential in their application in forest restoration on degraded lands.     

Role of magpie in bird community formation in secondary forest

We analyzed a bird community in a secondary forest and the results show that the magpie was one of the key groups in the secondary forest. The key group is identified based on the nests used by other birds at a rate of 25%–40.17%. The size of the community is different and the number of these key groups is not certain. __________ Translated from Journal of Northeast Normal University (Natural Science Edition), 2006, 38 (3): 644-651 [译自: 东北师大学报(自然科 学版)]     

Role of magpie in bird community formation in secondary forest

We analyzed a bird community in a secondary forest and the results show that the magpie was one of the key groups in the secondary forest. The key group is identified based on the nests used by other birds at a rate of 25%-40.17%. The size of the community is different and the number of these key groups is not certain.     

香港蕨类植物新记录

报道了香港蕨类植物新记录种5种,即台湾轴脉蕨(Ctenitopsis kusukuensis)、掌叶线蕨(Colysis digi-tata)、德化鳞毛蕨(Dryopteris dehuaensis)、海岛鳞始蕨(Lindsaeaorbiculatavar.commixta)和石松(Lycopo-diumclavatum),其中包括两个新记录属轴脉蕨属(Ctenitopsis)和石松属(Lycopodium)。另外,还列出了每个种的重要特征及其与相关种类的差异。     

Impacts of a volcanic eruption on the forest bird community of Montserrat, Lesser Antilles

Volcanic eruptions are an important and natural source of catastrophic disturbance to ecological communities. However, opportunities to study them are relatively rare. Here we report on the effects of the eruption of the Soufrière Hills volcano on the forest bird community of the Lesser Antillean island of Montserrat. The island's species-poor avifauna includes 11 restricted-range species, including the Critically Endangered endemic Montserrat Oriole Icterus oberi . Analysis of monitoring data from 1997 to 2005 indicates that counts of most species were substantially lower following major ashfalls. However, this effect was short-lived, with rapid population recovery in subsequent years. Furthermore, levels of seasonal rainfall appear to have been at least as important in determining population trends as ashfall. Overall, most species were at least as abundant at the end of the study as at the start, and no forest bird species have been extirpated from Montserrat. We discuss potential ecological drivers of ashfall impacts on populations: there is some evidence that terrestrial foragers were most severely affected.     

Assessing the potential for recovery of a Sargassum siliquastrum community in Hong Kong

Tung Ping Chau Marine Park in Hong Kong was designated in 2001 with aims to protect its highly-diverse marine habitats from destructive human activities. Sargassum spp. (mainly Sargassum siliquastrum) formed a dense canopy in Lung Lok Shiu (LLS) in southwestern side of the Marine Park. This Sargassum bed, however, disappeared and a barren ground developed 7 years after the marine park designation. The increase in density of the short-spined sea urchin Anthocidaris crassispina, and thus the grazing pressure, as a result of restriction on its commercial fishery within the Marine Park was hypothesized as the immediate cause of the barren ground formation. In this study, we tested this hypothesis and manipulated the density of A. crassispina in exclusion cages underwater in LLS, where S. siliquastrum canopy originally existed. Transplantation of S. siliquastrum thalli and ceramic tiles with their recruits was carried out in these cages in February–May 2012 and May 2013. The results showed that the transplanted Sargassum thalli could not survive outside exclusion cages, whereas the induced recruits were almost wiped out in all tiles even inside exclusion cages. This provides evidence that the sea urchin A. crassispina could have overgrazed S. siliquastrum thalli and decimated the Sargassum canopy in LLS. It also suggested that other than A. crassispina, other grazers also contributed to the removal of S. siliquastrum recruits. Therefore, natural recovery of Sargassum bed seems unlikely if the grazing pressure remains high in this site. Proactive management strategies may need to be adapted to restore this Sargassum bed.