Despite growing interest in using phylogenetic and functional methods to understand community assembly, few studies have examined how these methods can be used to assess seasonal variation in assembly mechanisms among migrant species.Migration can rapidly alter the relative influence of stochastic processes, species interactions, or environmental factors in shaping communities across seasons. Here, we describe seasonal dynamics in the phylogenetic and functional diversity of waterbirds in Mai Po Wetland, a subtropical region with significant and predictable temporal variation in climate and migratory bird density. Phylogenetic α diversity varied seasonally, exhibiting a clustered structure (indicative of environmental filtering) in summer, and over-dispersed structure (indicative of biotic filtering) in winter.Phylogenetic diversity in spring and autumn exhibited a more intermediate, random structure, consistent with stochastic arrivals and departures of migrants. Functional diversity was clustered in spring but showed over-dispersion in the other three seasons. Phylogenetic β diversity in summer and winter assemblages was characterized by two distinct groups, while spring and autumn assemblages were mixed. Our results suggest that waterbird assemblages were primarily shaped by interspecific competition in winter, while random processes tended to shape assemblages in spring and fall. Environmental factors played a more important role in summer, during periods of high heat stress. In addition, species co-occurrence patterns were significantly more strongly related to phylogenetic similarity in winter than in summer. Our results suggest that the relative importance of assemblage mechanisms can vary seasonally in response to changing environmental conditions, suggesting that studies attempting to infer a single dominant assembly mechanism may ignore important assembly processes. Temporal shifts in assembly mechanisms may play an important role in maintaining diversity in subtropical and temperate wetlands and perhaps also in other dynamic systems.

Light pollution is increasing and artificial light sources have great impacts on animals. For migrating birds, collisions caused by artificial light pollution are a significant source of mortality. Laboratory studies have demonstrated that birds have different visual sensitivities to different colors of light, but few field experiments have compared birds’ responses to light of different wavelengths. We used 3 monochromatic lights (red, green, and blue) and polychromatic yellow light to study the impact of wavelength on phototaxis at 2 gathering sites of nocturnally migrating birds in Southwest China. For both sites, short-wavelength blue light caused the strongest phototactic response. In contrast, birds were rarely attracted to long-wavelength red light. The attractive effect of blue light was greatest during nights with fog and headwinds. As rapid urbanization and industrialization cause an increase in artificial light, we suggest that switching to longer wavelength lights is a convenient and economically effective way to reduce bird collisions.

Context Nearly 20% of black-faced spoonbills (Platalea minor), a globally endangered species, winter along the coasts of the Pearl River Estuary, China. However, these wintering habitats are threatened by urban development. Especially in Macao, road construction for the tourism industry has resulted in habitat deterioration. Aims Our study aimed to assess the effects of traffic noise on the distribution and behaviour of black-faced spoonbills in the Taipa–Coloane Wetland Reserve, Macao SAR. Methods We built a traffic-noise prediction model for habitat-suitability division. Then we investigated the relationship between traffic noise and diurnal of spoonbill behaviours by collecting traffic-noise data on surrounding roads and observing the activity of black-faced spoonbills in the area over two winters, from 2007 to 2009. Key results The maximum number of individuals present in a single month was 50 in the winter of 2007–08 (in February) and 52 in the winter of 2008–09 (in January). Continuous traffic noise was 46.5 and 45.4 dB(A), respectively, at roosting sites in two ecological zones. On the basis of the prediction model, only 10.8 of 30.3 ha were suitable for spoonbills, with noise levels lower than 47 dB(A). Most of the time, the spoonbills were acclimated to the traffic and were not alarmed. However, heavy trucks with a high noise level of 81.8 ± 2.3 dB(A) sometimes disrupted spoonbill behaviour. Conclusions The traffic noise around the Taipa–Coloane Wetland Reserve did exist but did not substantially affect black-faced spoonbills. For the birds mainly roosting in a quieter area, the small area of suitable habitat may indirectly limit population growth. Implications The fences around Ecological Zone I were successful in minimising visual stimuli from human activities and passing cars. To maintain the suitability of the winter habitat in Macao, restrictions on traffic flow, especially on heavy truck volume, are necessary for spoonbill conservation.