The ability of an animal to acquire enough food to meet its caloric needs is key to its survival and fitness. Understanding the composition of that animal's diet is a crucial element to consider when assessing the species' health and overall role in its ecosystem. We conducted a dietary study of Northern River Otter (Lontra canadensis) at 18 sites across 12 different watersheds in Wisconsin, U.S.A., from summer 2017 through winter 2018. We report the frequency of prey remains found in river otter scats (n = 190) collected at these sites. Fish of any kind appeared in 86% (n = 163) of all scat samples, while crayfish (Cambaridae) were the most commonly occurring individual prey item, appearing in 62% (n = 117) of all scat samples. The second most common prey groups were the bottom feeder fish (Catostomidae and Cyprinidae) group and the panfish (Centrarchidae) group, which both occurred in 45% of all scats. While identifying prey species, we found small, spherical objects that did not appear to be of biological origin in 48% (n = 92) of all scats. After testing the objects using multiple approaches, we confirmed the objects as microbeads, defined as small beads of plastic composition no larger than 5mm in size. This is the first recorded observation of plastic microbeads associated with river otters in North America, and may indicate bioaccumulation of these objects in inland waterways.
Myotis bats have experienced significant population losses due to white-nose syndrome (WNS) throughout large portions of their distributions in eastern North America. As closed-space foragers, these species comprise an important feeding guild within eastern forests. An understanding of where summer populations remain and how their ecology has changed following impact from WNS is needed to assess fully the recovery potential of Myotis bats. We used acoustic sampling, capture surveys, radiotelemetry and roost surveys from 2015 to 2018 to evaluate the status of northern long-eared bat (Myotis septentrionalis) in an eastern Kentucky forest following region-wide impacts from WNS to this species. Acoustic activity of Myotis remained unchanged over the 4 y of sampling, with activity of these bats greatest in mid- to late July. Northern long-eared bats represented 97% of the Myotis captured, indicating activity levels likely reflected patterns for this species. We located 18 roost trees of northern long-eared bats in five tree species, including both live and dead trees. All roost trees were on upper slopes within 100 m of ridge top roads. Maximum exit counts, 24 and 21, at two roosts occurred in late May and early June, suggesting these dates represented the summer maternity period of northern long-eared bats in this forest. Our results demonstrated that post-WNS populations of northern long-eared bats on Robinson Forest formed small colonies, day-roosted in trees near roads on forested ridge tops, were reproductively active, and maintained steady levels of activity across the 4 y of sampling. These data suggest that local populations of northern long-eared bats are surviving WNS and continue to persist during summer months in forests of the Appalachian Mountain region. We hypothesize presence of ridge top roads, often associated with forest logging operations, may be important habitat elements for increasing availability of preferred roosting habitat for summer populations of northern long-eared bats in actively managed forests.
Bird-window collisions (BWCs) constitute a significant source of mortality for both resident and migratory birds. Because windows reflect surrounding landscape components, such as vegetation or sky, birds do not always perceive glass as a barrier. Here we demonstrate a novel technique to classify and quantify reflections in windows on the Radford University campus in southwest Virginia, U.S.A. We deployed a consumer-grade Unmanned Aerial Vehicle, i.e., drone, to photograph 14 contiguous or near-contiguous window columns across five campus buildings in August 2020. For each study aspect, the drone (equipped with an RGB camera) captured images at ca. 5 m altitudinal increments from the ground floor to the roof of each building (three to six images/vertical column). We then manually classified each image in ImageJ to calculate approximate proportions of reflected: (1) vegetation, (2) sky, (3) and artificial structures or impervious surfaces, plus (4) nonreflective glass. We used a generalized linear model to determine how proportional reflections of vegetation, sky, buildings, and nonreflective glass varied across vertical increments. We found the proportion of sky significantly decreased with increasing photo heights, whereas proportion of nonreflective glass significantly increased with increasing heights. This supports previous findings that because birds are drawn to sky reflections, they may collide at relatively lower positions on buildings. Inconsistency in landscape design and building positioning on the campus precluded trends in vegetative or building reflections by height. Our pilot study demonstrates the applicability of a consumer-grade drone for investigating visual characteristics of reflections that influence BWCs from variable observation angles. We suggest the expanded use of drone images as a straightforward technique to measure changes in reflection characteristics from varying degrees of observation. They are a novel method in developing a BWC risk assessment as well as potential mitigation strategies in a suburban or campus environment with buildings of intermediate heights.
Abstract. I describe the phenology of territorial Greater Sandhill Cranes (Grus canadensis tabida) from a long-term (20+ y) marked population near Briggsville, Wisconsin. Territorial adults typically arrived in mid-March (average = 27 Mar., median = 25 Mar.) and egg-laying commenced a median date of 2 wk post-arrival. Chicks typically hatched in mid-May (average and median = 12 May). Renesting occurred from 3-14 d after the first clutch failed and renests hatched from late May to early July (95% CI: 23 May–8 Jul.). Known territorial birds began congregating in mid-Sept, and fall migration typically occurred in late Nov. Territory use by adults occurred at all stages of the annual cycle and may be a way to ensure reclamation of the territory in subsequent years.
Species richness and abundances of fluvial specialist fishes often decrease within waters impounded by dams, but mechanisms underlying these decreases are poorly understood. Purpose of this study was to assess the effects of impounded water on fluvial specialist Greenthroat Darter Etheostoma lepidum by quantifying differences in life history (i.e., age structure, life span), reproduction (i.e., gonadosomatic index [GSI], stages of ovarian development), and stomach contents (i.e., diet items and parasites) between a population taken from a lentic environment (Lake Site) and a lotic environment (River Site). Among fishes taken from both sites, Greenthroat Darters lived up to 1.5 y, spawned for 11 mo, and consumed primarily aquatic insects and crustaceans. Differences in reproduction were not detected between populations at the Lake Site and at the River Site. Greenthroat Darters taken from Lake Site consumed fewer diet items, fewer aquatic insects, and greater number of crustaceans than those taken from River Site; however, diet weight, percent stomach fullness, and percent empty stomachs were similar between sites. Greenthroat Darters taken from Lake Site exhibited lower condition factors than those taken from River Site, which corresponded with a greater number of parasites (i.e., Acanthocephala and Nematoda) in individuals taken from Lake Site. Differences quantified herein were not sufficient to cause extirpation of Greenthroat Darters in the impounded waters, given the species has persisted in the impounded water at least since the late 1800s; however, differences in diets and parasites might explain the lower abundance of Greenthroat Darters in Lake Site compared to River Site.
