External threats and internal management: the hydrologic regulation of the Everglades,Florida, USA

The ecological character of seasonal marshes is determined in large part by the pattern of water level fluctuation. As a result, the ecological health of a wetland reserve can be controlled by hydrologic regulation external to its boundaries. As an example, the Everglades marsh of Everglades National Park in Florida, USA, has been severely effected by management of the inflow of surface water. The Everglades occupies most of the interior of southern Florida, but only the lower 6% of the original marsh is contained in Everglades National Park. Shallow surface water reservoirs north of the park enclose 3600 km² of Everglades. Their levee system confines surface water flow into the park to several structures. Historically this water flowed across the entire core of the natural drainage. Flows into the park have been on a congressionally mandated schedule of minimum deliveries that is supplemented by additional water released into the park in amounts determined solely by upstream water management needs. My research, aimed at evaluating the effects of water conditions, has shown that this regulatory system has adversely affected reproductive success, community structure, and population sizes of sensitive species whose population stability is tied to natural water level fluctuations. These adverse effects were caused by water levels that for over a decade have been maintained at unseasonably high levels. Mathematically deterministic models of water level effects can provide management options based on biologial criteria. Park managers must incorporate understanding gained from such models into internal management decisions. Modifications of water control structures and alternative policies for managing the distribution and amount of surface water flow into the park appear attainable, can improve biological conditions in the park, and need not be adverse to neighboring external interests. Thus far biological changes are severe, and to a large extent irreversible. Ecologically sensitive management of an external threat under constraints imposed by history and setting can better maintain some semblance of ecological processes in the Everglades. If management decisions do not reflect such understanding of ecological processes, further ecological deterioration will result.     

Examination of the effects of disturbance on birds with reference to its importance in ecological assessments

National, European and International legislation regarding the conservation of species and habitats requires professional statements to be made in respect of land use change, as, for example, illustrated by developments. Some developments may cause disturbance to wildlife. Knowledge of the way in which species respond to disturbance has been fragmented, yet is an important consideration in environmental impact assessments. This paper reviews what is known about disturbance factors on the best studied group, birds. A set of extensive appendices summarize the literature on disturbance effects on breeding, breeding success, nest-site choice, population density, community structure, distribution and habitat use. The paper considers human-induced disturbance, public access, water-based recreation, shooting and industrial developments. Mitigation measures are discussed.Human-induced disturbance can have a significant negative effect on breeding success by causing nest abandonment and increased predation. Outside the breeding season, recreation (particularly power boating, sailing and coarse fishing on wetlands) reduces the use of sites by birds. Compensatory feeding at night by some species can probably recoup some of the energy losses caused by disturbance. Public and vehicular access to open landscapes has been shown negatively to affect grazing geese in winter and lowland and upland waders during breeding. Shooting disturbance has been shown to be most important for herbivore feeders which need to spend long periods of the day feeding in order to maintain their energy balance, e.g. wigeon. The provision of refuges devoid of shooting has been fundamental in attracting wildfowl away from non-refuge sites. The response of birds to scaring devices and other control measures is discussed.Effects from industrial developments include direct loss of habitat, disturbance through the presence of humans during the construction process and the presence of artificial light used to illuminate construction sites. On estuaries, engineering operations should avoid the proximity to established roost sites of wading birds. A number of studies showed increased vigilance (and hence reduced feeding time) in flock members feeding near structures which impede their vision of the approach of potential predators.A number of principal management techniques used to reduce disturbance on a site, or to attempt to compensate for habitat loss, are given. For wetland sites, these include excavating new shallow lagoons and grading bank sides, flooding of low-lying pasture, reducing salinity levels in coastal lagoons thereby making them more attractive to the birds' food invertebrates, manipulating water levels to expose mud regularly and creating feeding areas for geese and wigeon, using manipulative livestock grazing. Also used are increasing nesting cover, planting macrophytes, providing islands, spits and promontories, purchasing more land to make a refuge bigger, concealing observers with banks and screens, zoning activities and prohibiting access and avoiding the obstruction of flyways between feeding and roosting areas.     

Long-Term Landscape Change and Bird Abundance in Amazonian Rainforest Fragments

Abstract:  The rainforests of the Amazon basin are being cut by humans at a rate >20,000 km²/year, leading to smaller and more isolated patches of forest, with remaining fragments often in the range of 1–100 ha. We analyzed samples of understory birds collected over 20 years from a standardized mist-netting program in 1– to 100-ha rainforest fragments in a dynamic Amazonian landscape near Manaus, Brazil. Across bird guilds, the condition of second growth immediately surrounding fragments was often as important as fragment size or local forest cover in explaining variation in abundance. Some fragments surrounded by 100 m of open pasture showed reductions in insectivorous bird abundance of over 95%, even in landscapes dominated by continuous forest and old second growth. These extreme reductions may be typical throughout Amazonia in small (≤10 ha), isolated fragments of rainforest. Abundance for some guilds returned to preisolation levels in 10- and 100-ha fragments connected to continuous forest by 20-year-old second growth. Our results show that the consequences of Amazonian forest loss cannot be accurately described without explicit consideration of vegetation dynamics in matrix habitat. Any dichotomous classification of the landscape into "forest" and "nonforest" misses essential information about the matrix.     

From Red Lists to Species of Conservation Concern

Abstract:  National red lists of threatened animal and plant species prepared according to the criteria of the World Conservation Union (IUCN) adequately reflect the extinction risk of species within a country but cannot be used directly to set conservation priorities. In particular, the significance of national populations for the conservation of the species as a whole is not taken into account. We present a procedure that can be used to assess national responsibility based on the national red-list status of a species, the international importance of the national population, and the species' "historical rarity" status. We distinguished five responsibility classes for breeding birds: B1, threatened species with internationally important populations in Switzerland; B2, threatened species with internationally less important populations; B3, nonthreatened species with internationally important populations; B4, nonthreatened species with internationally less important populations; and B5, species that have never been common in Switzerland. Two responsibility classes were distinguished for birds occurring in Switzerland as visitors: G1, species with large concentrations in Switzerland and an unfavorable conservation status in Europe, and G2, species with large concentrations in Switzerland and a favorable conservation status in Europe. Two additional classes (G3 and G4) for visiting species occurring in internationally less important numbers are possible but were not analyzed in detail. Responsibility classes B1, B2, B3, G1, and G2 were defined as species of national conservation concern. We developed the method for birds in Switzerland, but it can be used in other countries and for other taxonomic groups as well. It is particularly suitable where national red lists are established according to IUCN guidelines.     

Demographic Limitations of the Ability of Habitat Restoration to Rescue Declining Populations

Abstract:  Habitat restoration is often recommended in conservation without first evaluating whether populations are in fact habitat limited and thus whether declining populations can be stabilized or recovered through habitat restoration. We used a spatially structured demographic model coupled with a dynamic neutral landscape model to evaluate whether habitat restoration could rescue populations of several generic migratory songbirds that differed in their sensitivity to habitat fragmentation (i.e., severity of edge effects on nesting success). Simulating a best-case scenario, landscapes were instantly restored to 100% habitat before, at, or after habitat loss exceeded the species' vulnerability threshold. The vulnerability threshold is a measure of extinction risk, in which the change in population growth rate ( δλ ) scaled to the rate of habitat loss ( δh ) falls below −1% ( δλ/δh ≤ −0.01). Habitat restoration was most effective for species with low-to-moderate edge sensitivities and in landscapes that had not previously experienced extensive fragmentation. To stabilize populations of species that were highly edge sensitive or any species in heavily fragmented landscapes, restoration needed to be initiated long before the vulnerability threshold was reached. In practice, habitat restoration is generally not initiated until a population is at risk of extinction, but our model results demonstrate that some populations cannot be recovered at this point through habitat restoration alone. At this stage, habitat loss and fragmentation have seriously eroded the species' demographic potential such that halting population declines is limited more by demographic factors than the amount of available habitat. Evidence that populations decline in response to habitat loss is thus not sufficient to conclude that habitat restoration will be sufficient to rescue declining populations.     

Brood size manipulation affects frequency of second clutches in the blue tit

The reproductive trade-off hypothesis predicts that the investment made in current reproduction determines the breeders’ future fitness as a consequence of intra-or inter-generational reproductive costs. Long-lived species are expected to favour their own reproductive value at the expense of their offspring, hence incurring in inter-generational costs, whereas short-lived species are expected to invest in the current breeding attempt even at the expense of their own survival, thus incurring in intra-generational costs. We tested whether intensity of current reproductive effort has intra-or inter-generational costs in a short-lived bird, the blue tit Parus caeruleus, with a brood size manipulation experiment. We expected more intra-generational (parental reproduction and/or survival) than inter-generational (offspring quality and survival) reproductive costs. We found that parental effort, measured as the hourly rate of parental visits to nests, increased gradually with experimental manipulation. Brood size manipulation resulted in a gradual increase in the number of fledglings per nest from reduced to increased treatments. We found an effect of the manipulation on the probability of making a second clutch, with adults rearing enlarged broods being less likely to undertake such a second reproduction during the season compared to those rearing control or decreased broods. We found no evidence of other reproductive costs; neither as adult weight after manipulation, apparent parental local survival, apparent offspring local survival or local recruitment. Although the results seem to support the a priori expectations, alternative explanations are discussed.Communicated by M. Soler     

Selecting indicator species to monitor ecological integrity: a review

We review critical issues that must be considered when selectingindicator species for a monitoring program that aims to maintainor restore ecological integrity. First, we examine the pros andcons of different management approaches on which a conservationprogram can be based and conclude that ecosystem management ismost appropriate. We then identify potential indicators ofecological integrity at various levels of the ecosystem, with aparticular emphasis on the species level. We conclude that,although the use of indicator species remains contentious, it canbe useful if (1) many species representing various taxa and lifehistories are included in the monitoring program, (2) theirselection is primarily based on a sound quantitative databasefrom the focal region, and (3) caution is applied wheninterpreting their population trends to distinguish actualsignals from variations that may be unrelated to thedeterioration of ecological integrity. Finally, we present anddiscuss different methods that have been used to select indicatorspecies.     

滨海湿地退化区鸟类刨坑觅食行为促进植被的恢复

鸟类是滨海湿地生态系统中非常重要的组成部分,也是能够通过自身行为影响非生物环境以及生物过程的生态系统工程师。了解鸟类在滨海湿地生态系统中的生态系统工程效应,对于开展滨海湿地的生态修复具有重要作用。通过野外调查研究由灰鹤（Grus grus）和斑嘴鸭（Anas poecilorhyncha）主导的滨海鸟类的刨坑觅食行为对植被退化区的地形以及土壤环境理化指标的影响,进而促进盐地碱蓬（Suaeda salsa）植被的恢复。结果表明：鸟类在植被退化区的刨坑觅食行为改变了退化区的微地形及土壤环境,使得土壤硬度和土壤盐度显著降低,而土壤含水率和土壤碳氮营养指标则显著高于未经鸟类影响的退化平坦区域;另外,鸟类活动改善的凹坑微地形环境能够显著提高盐地碱蓬的种子保留量、幼苗定植量和成株存活量,有效促进盐地碱蓬在植被退化区域的恢复。通过鸟类改变微地形进而促进植被恢复的启发,提出可以尝试人为模拟改造退化区的微地形环境,以通过人为干预的方式促进滨海湿地退化区的植被恢复,对滨海湿地的生态修复具有重要指导意义。     

沙河航运工程对沙河国家湿地公园的环境影响分析研究

航运工程的开发与建设会对河道所处的生态环境产生一定的影响,特别是河道型湿地,因此在环评阶段如何分析航道建设对湿地的影响尤为重要.主要通过航运工程本身的特点和湿地公园的生态现状进行结合,通过使用GIS叠图法、生态机理分析方法分别从土地利用资源、湿地水资源、鸟类行为等方面进行影响分析,提出在航运工程施工过程中进行"湿地重建、支流保护"、鸟类监测等措施,以保护航运过程中的湿地生态环境,为航运工程生态影响分析提供一定的理论基础.     

Importance of set-aside for breeding birds of open farmland in Finland

The set-aside obligation under the Common Agricultural Policy (CAP) brought widespread benefits for wild farmland species. Shortly after it was abolished in 2008, the national political process in Finland replaced it with a targeted agri-environment scheme for environmental fallow. Though potentially highly valuable, the value of the current scheme for securing biodiversity is yet to be confirmed. This study evaluates the importance of set-asides established under CAP to all birds of open farmland based on national monitoring data from 2001 to 2006. The set-aside fields supported 25-40% more species and held 60-105% more pairs of birds typical of open farmland in comparison with cereal fields within a similar landscape setting. The estimated effect of set-aside presence in farmland on the studied bird species is large enough to trigger considerable changes in bird populations on the national scale. The relevance of the results to the novel agri-environment scheme is discussed.