Reduced Density and Nest Survival of Ground‐Nesting Songbirds Relative to Earthworm Invasions in Northern Hardwood Forests

Abstract: European earthworms (Lumbricus spp.) are spreading into previously earthworm‐free forests in the United States and Canada and causing substantial changes, including homogenization of soil structure, removal of the litter layer, and reduction in arthropod abundance and species richness of understory plants. Whether these changes affect songbirds that nest and forage on the forest floor is unknown. In stands with and without earthworms in the Chequamegon‐Nicolet National Forest, Wisconsin (U.S.A.), we surveyed for, monitored nests of, and measured attributes of habitat of Ovenbirds (Seiurus aurocapillus) and Hermit Thrushes (Catharus guttatus), both ground‐dwelling songbirds, and we sampled earthworms at survey points and nests. Bird surveys indicated significantly lower densities of Ovenbirds and Hermit Thrushes in relation to Lumbricus invasions at survey point and stand extents (3.1 and 15–20 ha, respectively). Modeling of Ovenbird nest survival (i.e., the probability that nestlings successfully fledge) indicated that lower survival probabilities were associated with increased sedge cover and decreased litter depth, factors that are related to Lumbricus invasions, possibly due to reduced nest concealment or arthropod abundance. Our findings provide compelling evidence that earthworm invasions may be associated with local declines of forest songbird populations.     

WATER RESOURCES MANAGEMENT AND THE CHOICE OF TECHNOLOGY

Asserting that the major problem in water resources management stems not so much from a lack of alternative technologies as from a failure to make a choice which is appropriate to the several factors involved, the author addresses himself to these factors and to the criteria which should be applied in the decision-making process. Particular attention is devoted to a consideration of the incentives, and of the institutional, infra-structural, analytical and policy measures required to facilitate the adoption of 'socially optimal' technology, including the relationship of these measures to the promotion of effective water resources management technology within the broader economic, social and cultural situations specific to each country.     

A Conceptual Framework for Analysis of Water Resources Management in Asia

Effective and efficient water resources management to meet the increasing demands for food, energy, and domestic and industrial water is an imperative for Asian countries. As a basis for analyzing Asian water resources management problems, a three-element conceptual framework is presented: (1) water resources management as a system, composed of a set of facilities, operating rules, and incentives applied to water resources through an institutional arrangement; (2) water resources management as a process involving several stages beginning with planning and continuing with design, construction, operation and maintenance; and (3) water resources management as a set of linked activities and tasks required to produce the desired outputs. Using this framework to assess performance it is possible to analyze the linkages among water resources problems, water resources management, and water resources organizations and administrative arrangements. Examples are presented of such linkages as applied to problems of erosion and sedimentation, flooding, salinity, water demand-supply imbalances, and water pollution. Brief analytical summaries of eight critical water resources management problems in Asia are presented, along with an illustration of the complexity of water resources organization and administration, using Thailand as the example.