Because logging has replaced fire as the most extensive and frequent disturbance regime in northeastern Minnesota, monitoring bird populations and their habitats has become increasingly important. We surveyed early-successional forests created by fire or logging for birds and their habitat during the 1994 and 1995 breeding seasons. We found that overall bird species richness and number of individuals (territorial males/ ha) were higher (P < 0.05) in burned forests than in logged forests. The American crow (Corvus brachyrhynchos), house wren (Troglodytes aedon), common yellowthroat (Geothlypis trichas), clay-colored sparrov (Spizella pallida), song sparrow (Melospiza melodia), Lincoln's sparrow (M. lincolnii), and brown-headed cowbird (Molothrus ater) were more abundant in burned areas. The Nashville warbler (Vermivora ruficapilla), chestnut-sided warbler (Dendroica pensylvanica), black-throated green warbler (D virens), and mourning warbler (Oporornis agilis) were present in greater numbers in the logged areas. We related these differences in bird presence and abundance to vegetation differences in the burned and logged habitat types. Burned areas had higher densities of dead trees, wider size ranges of dead trees, and greater heterogeneity in the shrub layer. Logged areas had higher densities of live trees, more live tree species, and wider size ranges of live trees. Red maple (Acer rubrum) was the live tree species found in greatest abundance in logged areas. If management goals include simulating natural disturbances like fire and maintaining bird populations, more dead trees should be left within logged habitats and the variability among logged areas should be increased.
Abstract An in vivo fish model was adapted to monitor respiratory‐cardiovascular responses of spinally transected rainbow trout exposed to acutely toxic aqueous concentrations of two uncouplers of oxidative phosphorylation, pentachlorophenol (PCP) and 2,4‐dinitrophenol (DNP), and two narcotics, tricaine methanesulfonate (MS‐222) and 1‐octanol. The most evident toxic response to the uncouplers was a rapid 150 to 200% increase in ventilation volume (V G ) and oxygen consumption (VO 2 ) over the entire survival period. This caused an initial increase in total arterial oxygen (T a O 2 ) content of the blood, which then fell slowly as the tissues used more and more oxygen to generate ATP. Arterial blood pressure (BP a ) and other blood measurements did not change appreciably in response to PCP, yet DNP caused increases in hematocrit (Hct) and hemoglobin (Hb) and slight decreases in total arterial carbon dioxide (T a CO 2 ) and arterial pH (pH a ). In contrast to the uncouplers, the response of the respiratory‐cardiovascular system of trout to toxic levels of narcotics was a dramatic slowing of all respiratory‐cardiovascular functions. While V G and VO 2 decreased 40 to 50% from predose levels, oxygen utilization (U) increased 20 to 30%. Ventilation rate (VR) declined initially and then increased slowly until death occurred, but remained within the control range. As respiration declined T a CO 2 significantly decreased, as did pH a . In response to hypoxia, Hct increased substantially, and Hb increased slightly only in the 1‐octanol exposure. A rapid 40 to 50% drop in heart rate (reflex bradycardia) was also observed. The final phase of toxicity caused by both uncouplers and narcotics appeared to eventually produce acute tissue hypoxia, with a generalized loss of respiratory‐cardiovascular coordination, and finally respiratory paralysis. Individual principal component analyses of the cardiovascular‐respiratory responses of fish exposed to the first two principal components explained 68 to 76% of the variation in the 18 parameters analyzed. A two‐dimensional diagram of the first two principal components illustrated this multivariate response and the increased variability in the responses of exposed fish as compared with control fish. The general sets of responses described for these two fish acute toxicity syndromes have provided the initial information necessary to group similar responses caused by other chemicals into a fish uncoupler syndrome, a fish narcosis syndrome or some new syndrome.
Abstract : This study was designed to isolate effects of electromagnetic (EM) fields produced by extremely low frequency (ELF) antenna systems on bird species breeding in or migrating through Wisconsin. Specifically, the aim was to determine any differences in bird species richness and abundance between areas close to the antenna and those far enough away to be unaffected by the antenna. Characteristics examined included total species richness and abundance, abundance of common bird species, and abundance of birds within selected guilds. Measurements of vegetation identified differences and similarities between control and treatment areas. Habitat variables were used in analysis of covariance (ANCOVA) to compare numbers of abundant bird species in control versus treatment areas after adjustments for habitat differences. Extremely low frequency, Ecology, Electromagnetic fields, ELF Communications system, Environmental studies, ELF Ecological monitoring program
Avian mortality from collisions with windows and buildings is one of the top sources of anthropogenic mortality of birds. Each year in the United States, an estimated 100 million to one billion birds die from window collisions. Many studies of bird-window collision mortality have aimed to identify architectural, landscape, and species-specific factors that may influence collision rates, but little research has assessed the potential for spatiotemporal variation in collision mortality. We studied window collision mortality at 42 residential houses located within an urban landscape, along the shores of Lake Superior in Duluth MN, USA from 2006–2009 to quantify window-related fatalities during migration. The rate of window collision mortality was modeled as a function of house location and season using Poisson regression. We also conducted carcass distribution trials to estimate scavenging and detection rates, and analyzed the resulting data using a multistate Markov model. We used hierarchical models of scavenging probability to compare the relationship between scavenging rates and six measured covariates. Models for collision mortality and scavenging were evaluated using Akaike’s Information Criterion (AIC). The adjusted number of birds killed (Nk) over the full course of monitoring was estimated using the Horvitz-Thompson estimator. A total of 40 species and 108 individual birds were recorded as window kills. Fatalities increased with distance from the city center, were higher at houses on the lake side of the study site, and on windows facing Lake Superior. Scavenging rates also increased with distance from the city center, with small carcasses being removed more quickly than large carcasses, and removal rates decreasing over time for all carcass sizes. Because of the low detection probability of homeowners, combined detection by both homeowners and researchers was <20%. Although mortality and scavenging rates were not uniformly distributed, we estimated an adjusted mortality rate of ~11–16 birds per house during the study period. Mortality estimates for all residential houses on Minnesota Point (n = 520) during the study period (n = 211 days) was 5,819–8,382 birds, ~1,421 birds per season. Results suggest spatiotemporal variation in both mortality and scavenging rates within our study area, both of which increased with distance from the city center. Houses with highest collision mortality also had the highest scavenging rates. Our results are consistent with other studies that have observed heterogeneity in mortality and scavenging rates associated with local structural and landscape level variables. Documenting patterns associated with increased collision mortality will be important in identifying locations that may pose a greater risk to birds.
Abstract: We calibrated snowshoe hare ( Lepus americanus ) numbers with pellet counts in Minnesota, USA, to understand the relationship between hare numbers and pellets in the central portion of the hare range. We found a strong and significant correlation between hare numbers and pellet counts using either linear or functional regression with either annual or semiannual pellet counts. Equations we developed using linear or functional regression predicted >1 hare/ha at similar pellet‐density thresholds. These equations can be used to efficiently identify habitats that support hare numbers necessary for Canada lynx ( Lynx canadensis ) persistence in Minnesota.
Abstract Wetlands of the Laurentian Great Lakes of North America (i.e., lakes Superior, Michigan, Huron, Erie, and Ontario) provide critical habitat for marsh birds. We used 11 years (2011–2021) of data collected by the Great Lakes Coastal Wetland Monitoring Program at 1,962 point-count locations in 792 wetlands to quantify the first-ever annual abundance indices and trends of 18 marsh-breeding bird species in coastal wetlands throughout the entire Great Lakes. Nine species (50%) increased by 8–37% per year across all of the Great Lakes combined, whereas none decreased. Twelve species (67%) increased by 5–50% per year in at least 1 of the 5 Great Lakes, whereas only 3 species (17%) decreased by 2–10% per year in at least 1 of the lakes. There were more positive trends among lakes and species (n = 34, 48%) than negative trends (n = 5, 7%). These large increases are welcomed because most of the species are of conservation concern in the Great Lakes. Trends were likely caused by long-term, cyclical fluctuations in Great Lakes water levels. Lake levels increased over most of the study, which inundated vegetation and increased open water-vegetation interspersion and open water extent, all of which are known to positively influence abundance of most of the increasing species and negatively influence abundance of all of the decreasing species. Coastal wetlands may be more important for marsh birds than once thought if they provide high-lake-level-induced population pulses for species of conservation concern. Coastal wetland protection and restoration are of utmost importance to safeguard this process. Future climate projections show increases in lake levels over the coming decades, which will cause “coastal squeeze” of many wetlands if they are unable to migrate landward fast enough to keep pace. If this happens, less habitat will be available to support periodic pulses in marsh bird abundance, which appear to be important for regional population dynamics. Actions that allow landward migration of coastal wetlands during increasing lake levels by removing or preventing barriers to movement, such as shoreline hardening, will be useful for maintaining marsh bird breeding habitat in the Great Lakes.
