Geology topics

Jeb A. Barzen

Publications and source records attributed to Jeb A. Barzen.

4 recordsLinked to original sources

USGS2019

The dilemma of pest suppression in the conservation of endangered species

In the conservation of endangered species, active suppression of a population of one native species to benefit another native species poses particular challenges. Obvious examples include predator control and nest parasite reduction. Less obvious is the control of blood-feeding arthropods. We present a case study on the effect of blood-feeding black flies (Simulium spp.) on reintroduced Whooping Cranes (Grus americana). Our intent is to provide a transferrable, science-driven approach for determining the effects of blood-feeding arthropods on endangered vertebrates, and demonstrate an approach for guiding selection of management actions for managers faced with competing objectives. A multi-year experiment demonstrated that black flies reduce nest success in reintroduced cranes by driving the birds off their nests during incubation. Deciding how to respond, however, is complicated because the target black flies are native species that serve important ecological functions. We suggest that a decision-analytic approach can inspire the development of creative management alternatives and facilitate a transparent process that evaluates trade-offs among competing objectives. Recognizing that these decisions involve trade-offs, which must be weighed in the context of each case, is crucial to identifying alternatives that best balance multiple management objectives. Given the uncertainty about the population dynamics of blood-feeding arthropods, an adaptive management approach will offer substantial benefits.

Wisconsin↗

USGS2019

Revisiting the historic distribution and habitats of the Whooping Crane

The endangered Whooping Crane ( Grus americana ) historically had a wide distribution that covered diverse ecoregions across North America while retaining consistent habitat preferences within each ecoregion. We reevaluate the historic information compiled by Robert Porter Allen in 1952 and added 74 other records. Based on the ecological features of historic locations relative to crane life history, we revisit Allen’s description of the whooping crane’s niche and identify four features common to breeding and wintering areas: (1) gentle to rolling topography with an interspersion of wetland and prairie habitats, and relatively sparse cover of trees and shrubs; (2) high densities of shallow, open wetlands or wetland complexes; (3) hydrological regimes that provide reliable conditions for nesting, brood rearing, and flightless adults; and (4) high plant and animal productivity due to fertile soils, hydrological pulsing, periodic inflow of nutrients, or other periodic perturbations. Accurate determination of the ecological features that compose Whooping Crane habitats should stimulate renewed discussions about habitat requirements and can support development of improved reintroduction strategies for the long-term success of recovery efforts.

Book chapter↗

USGS2019

Reproductive failure in the Eastern Migratory Population: The interaction of research and management

The reintroduction of the Eastern Migratory Population of Whooping Cranes ( Grus americana ) has shown the most promise of any effort to date toward the establishment of a self-sustaining population. However, reproduction – including both nest success and chick survival – has been a major challenge. Here, we review the research and management efforts deployed to identify and address this challenge. While there is evidence that a proximal cause of nest failure is harassment by blood-feeding black flies ( Simulium spp. ), this is not likely to be the only contributing factor, and we present alternative hypotheses. There is less understanding of the causes of poor chick survival, and we present hypotheses for factors that may be contributing to chick mortality, including environmental, genetic, and behavioral factors. For both nest success and chick survival, we carried out a value of information analysis, using expert judgment, which allowed us to prioritize the alternative hypotheses for evaluation based on the expected management benefit of addressing each hypothesis. On the horizon are multiple opportunities to explore hypotheses about environmental factors as well as genetic and behavioral characteristics of the birds themselves that may contribute to poor reproduction. If bird-specific characteristics, such as genetics or rearing methods, are hindering reproduction, this has important implications for all efforts to restore Whooping Crane populations.

Book chapter↗

USGS2018

Examination of multiple working hypotheses to address reproductive failure in reintroduced Whooping Cranes

Understanding multiple challenges that restrict conservation success is a central task of applied ecology, especially when resources are limited and actions are expensive, such as with reintroduction programs. Simultaneous consideration of multiple hypotheses can expedite identification of factors that most limit conservation success. Since 2001, reintroduction of a migratory population of Whooping Cranes ( Grus americana ) has been under way in eastern North America. Hatching success, however, has been extremely low. In our study area, in and near Necedah National Wildlife Refuge in central Wisconsin, USA, we simultaneously tested 3 hypotheses explaining poor hatching success: harassment of incubating birds by black flies (Simuliidae), effects of captivity, and inexperience of breeders. When black flies were experimentally suppressed, hatching probability doubled. Daily nest survival for Whooping Cranes was strongly and negatively related to an index of black fly abundance, particularly of Simulium annulus . Daily nest survival was negatively but only weakly related to the number of generations that ancestors of breeding Whooping Cranes had been in captivity and was not related to nesting experience. We also examined whether Whooping Cranes were nesting later to avoid stress from black flies. Phenology shifted earlier with more growing degree days and greater nesting experience and was only weakly related to year. Overall, improved hatching success did not lead to better reproductive success. Although effects of black flies on hatching success can be mitigated through management, such actions would not be adequate to generate satisfactory population growth. Recognition of this limitation was hastened through experimentation.

Wisconsin↗