Evaluating the impact of caribou habitat restoration on predator and prey movement

Fragmentation of the boreal forest by linear features, including seismic lines, has destabilized predator-prey dynamics, resulting in the decline of woodland caribou (Rangifer tarandus caribou) populations. Restoration of human-altered habitat has therefore been identified as a critical management tool for achieving self-sustaining woodland caribou populations. However, only recently has testing of the response of caribou and other wildlife to restoration activities been conducted. Early work has centered around assessing changes in wildlife use of restored seismic lines. We evaluated whether restoration reduces the movement rates of predators and their associated prey, which is expected to decrease predator hunting efficiency and ultimately reduce caribou mortality. We developed a new method for using cameras to measure fine-scale movement by measuring speed as animals traveled between cameras in an array. We used our method to quantify speed of caribou, moose (Alces alces), bears (Ursus americanus), and wolves (Canis lupus) on treated (restored) and untreated seismic lines. Restoration treatments reduced travel speeds along seismic lines of wolves by 1.38 km/h, bears by 0.55 km/h, and caribou by 1.57 km/h, but did not reduce moose travel speeds. Reduced predator and caribou speeds on treated seismic lines are predicted to decrease encounter rates between predators and caribou and thus lower caribou kill rates. However, further work is needed to determine whether reduced movement rates result in reduced encounter rates with prey, and ultimately reduced caribou mortality.

Demographic responses of nearly extirpated endangered mountain caribou to recovery actions in Central British Columbia

Recovering endangered species is a difficult and often controversial task that challenges status quo land uses. Southern Mountain caribou are a threatened ecotype of caribou that historically ranged in southwestern Canada and northwestern USA and epitomize the tension between resource extraction, biodiversity conservation, and Indigenous Peoples' treaty rights. Human-induced habitat alteration is considered the ultimate cause of caribou population declines, whereby an increased abundance of primary prey-such as moose and deer-elevates predator populations and creates unsustainable caribou mortality. Here we focus on the Klinse-Za and Quintette subpopulations, part of the endangered Central Group of Southern Mountain caribou in British Columbia. These subpopulations were trending toward immediate extirpation until a collaborative group initiated recovery by implementing two short-term recovery actions. We test the effectiveness of these recovery actions-maternity penning of adult females and their calves, and the reduction of a primary predator, wolves-in increasing vital rates and population growth. Klinse-Za received both recovery actions, whereas Quintette only received wolf reductions, providing an opportunity to test efficacy between recovery actions. Between 1995 and 2021, we followed 162 collared female caribou for 414 animal-years to estimate survival and used aerial counts to estimate population abundance and calf recruitment. We combined these data in an integrated population model to estimate female population growth, total population abundance, and recovery action effectiveness. Results suggest that the subpopulations were declining rapidly (λ = 0.90-0.93) before interventions and would have been functionally extirpated (<10 animals) within 10-15 years. Wolf reduction increased population growth rates by ~0.12 for each subpopulation. Wolf reduction halted the decline of Quintette caribou and allowed them to increase (λ = 1.05), but alone would have only stabilized the Klinse-Za (λ = 1.02). However, maternity penning in the Klinse-Za increased population growth by a further ~0.06, which when combined with wolf reductions, allowed populations to grow (λ = 1.08). Taken together, the recovery actions in these subpopulations increased adult female survival, calf recruitment, and overall population growth, more than doubling abundance. Our results suggest that maternity penning and wolf reductions can be effective at increasing caribou numbers in the short term, while long-term commitments to habitat protection and restoration are made.

A Pragmatic Approach for Developing Landbase Cumulative Effects Assessments with Aggregated Impacts Crossing Multiple Ecological Values

In strategic cumulative effects assessments, significant methodological challenges exist for classifying and aggregating impacts when using multiple indicators to determine relative risks upon ecological values from anthropogenic developments. We present a strategic spatial modeling case study CEA (2012-2112) in a 909,000 ha forested landscape of Southwestern British Columbia. We explore decisions needed to calculate and aggregate modeled indicators of cumulative anthropogenic footprints on landscape conditions by examining the choice of quantitative methods. We compare how aggregated impact conclusions may differ for seven indicators grouped in two ways to represent three ecological values (Forest Ecosystems, Riparian Ecosystems and Species at Risk): four expert-defined policy-driven valued components (VCs) or three analytically derived environmental resource factors (ERFs). By explicitly demonstrating methodological choices at each step of impact estimation and aggregation, we outline a practical systematic approach to customize strategic CEAs of this type and retain transparency for interpreting impacts among values. Aggregated impacts for VCs appeared dominated by those estimated from "condition" indicators describing the degree of expected deviations in indicator states from desired conditions; aggregated impacts of ERFs were dominated by "pressure" indicators linked to underlying causal processes assumed important for describing changes in future ecological conditions. High spatial congruence occurred between impact statements for some VCs compared to ERFs representing the same ecological value; poor congruence between others likely occurred because they represented different ecological processes. Aggregated impact classifications may usefully signal impact severity and risk but are dependent on indicator grouping, hence choices for aggregation are integral to the assessment process.

Corridors or risk? Movement along, and use of, linear features varies predictably among large mammal predator and prey species

Space-use behaviour reflects trade-offs in meeting ecological needs and can have consequences for individual survival and population demographics. The mechanisms underlying space use can be understood by simultaneously evaluating habitat selection and movement patterns, and fine-resolution locational data are increasing our ability to do so. We use high-resolution location data and an integrated step-selection analysis to evaluate caribou, moose, bear, and wolf habitat selection and movement behaviour in response to anthropogenic habitat modification, though caribou data were limited. Space-use response to anthropogenic linear features (LFs) by predators and prey is hypothesized to increase predator hunting efficiency and is thus believed to be a leading factor in woodland caribou declines in western Canada. We found that all species moved faster while on LFs. Wolves and bears were also attracted towards LFs, whereas prey species avoided them. Predators and prey responded less strongly and consistently to natural features such as streams, rivers and lakeshores. These findings are consistent with the hypothesis that LFs facilitate predator movement and increase hunting efficiency, while prey perceive such features as risky. Understanding the behavioural mechanisms underlying space-use patterns is important in understanding how future land-use may impact predator-prey interactions. Explicitly linking behaviour to fitness and demography will be important to fully understand the implications of management strategies.

Specialization by territorial hummingbirds on experimentally enriched patches of flowers: energetic profitability and learning

On unmanipulated hummingbird feeding territories, time spent foraging in patches was directly proportional to the number of flowers they contained. After we added nectar to the flowers in some patches, foraging increased in those patches, decreased in other patches, and decreased overall relative to control conditions. Specialization on enriched patches and reduction in foraging effort quantitatively reflected the energy we added, but the reduced effort had little effect on overall energy expenditure. Nevertheless, rates of net energy intake increased under enrichment, because gross intake rates increased. These experiments provide evidence that hummingbirds allocate effort among patches, using memory of relative patch quality when they initiate bouts of foraging. The strongest evidence is that individuals begin each day of foraging as if it were the previous day. On mornings after control days, birds foraged among patches as they had the day before, even though there was an (undiscovered) bonanza on their territories. On mornings after days of enrichment, however, whether or not a patch was enriched again, birds specialized on it at first. If the patch was enriched again, they continued to exploit it; if not, they reverted to normal patterns of allocation.

Cues for orientation in hummingbird foraging: color and position

In this study we examined the relative influence of the color and position of food sources on the feeding patterns of hummingbirds. We studied ruby-throated hummingbirds (Archilochus colubns) in the field and rufous hummingbirds (Selasphorous rufus) in the laboratory. The field experiments demonstrated that the use of equally profitable feeders in arrays is more strongly influenced by position than by color. This suggests that hummingbirds learn and remember the locations of profitable food sources and return to them preferentially if the reward continues to be adequate. The laboratory experiments demonstrated that although hummingbirds learn quickly to return to a single profitable feeder in a linear array of unprofitable ones if it is marked by a consistent color cue, their learning is strongly influenced by position in the absence of color cues. This suggests that hummingbirds' spatial memory may be limited in resolution and that they may use visible landmarks to improve their performance. These results are consistent with the hypothesis that landmarks facilitate foragers' limited ability to learn and remember profitable locations in their environments.

Nest-site characteristics of the avian community in the dune-ridge forest, Delta Marsh, Manitoba: a multivariate analysis

Nest-site characteristics of nine bird species breeding in high densities in the dune-ridge forest at Delta Marsh, Manitoba, were analyzed using multivariate techniques. Varimax-rotated principal component analysis of the entire set of nest-site variables suggested partitioning of the data into nest-habitat and nest-tree subsets. Discriminant analysis of nest-habitat variables confirmed the ambiguous nature of species relationships in the factor analysis. Discriminant analysis of nest-tree variables identified three distinct groups of species, based primarily on vertical stratification. The existence of these groups and their memberships were supported by similar results derived from discriminant analysis of the entire nest-site data set. Within these groups, pairs of species showed sufficient similarity in nest sites to warrant detailed investigation.

Feeding territoriality in migrant rufous hummingbirds: defense of yellow-bellied sapsucker (Sphyrapicus varius) feeding sites

Postbreeding migrant rufous hummingbirds (Selasphorus rufus) establish feeding territories in several habitats at Grizzly Lake, CA. Here we describe hummingbird territorial defense of tree sap made available by sapsucker feeding activity. Territorial hummingbirds fed almost exclusively on sap obtained on their territories, and they remained on the same territories for up to 6 days. The amount of energy produced on each territory was in excess of our estimates of hummingbird energy expenditures; sapsuckers, other birds, insects and small mammals remove almost all of the surplus. Comparisons of the time budgets of birds defending tree sap with those of territorial individuals in nearby habitats showed that these birds spent less time foraging and more time perching than birds in even high-quality subalpine meadows. Sap is thus a rich, easily defendable resource that may be of general value to temperate-zone hummingbirds. Utilization of sap may allow individuals to avoid critical, unpredictable energy shortages while migrating and may permit populations to exploit habitats that would otherwise be unavailable.