Geology topics
Source-linked reports with geographic coverage including Canada.
Using a geology-based assessment methodology, the U.S. Geological Survey estimated undiscovered, technically recoverable mean resources of 135.4 trillion cubic feet of continuous gas in Devonian–Mississippian shales in the Horn River Basin, Cordova Embayment, and Liard Basin of Canada.
In a polyphenic species, differences in resource use are expected among ecotypes, and homogeneity in resource use is expected within an ecotype. Yet, using a broad resource spectrum has been identified as a strategy for fishes living in unproductive northern environments, where food is patchily distributed and ephemeral. We investigated whether specialization of trophic resources by individuals occurred within the generalist piscivore ecotype of lake trout from Great Bear Lake, Canada, reflective of a form of diversity. Four distinct dietary patterns of resource use within this lake trout ecotype were detected from fatty acid composition, with some variation linked to spatial patterns within Great Bear Lake. Feeding habits of different groups within the ecotype were not associated with detectable morphological or genetic differentiation, suggesting that behavioral plasticity caused the trophic differences. A low level of genetic differentiation was detected between exceptionally large-sized individuals and other piscivore individuals. We demonstrated that individual trophic specialization can occur within an ecotype inhabiting a geologically young system (8,000–10,000 yr BP), a lake that sustains high levels of phenotypic diversity of lake trout overall. The characterization of niche use among individuals, as done in this study, is necessary to understand the role that individual variation can play at the beginning of differentiation processes.
Atlantic brant ( Branta bernicla hrota ) are important game birds in the Atlantic Flyway and several long-term monitoring data sets could assist with harvest management, including a count-based survey and demographic data. Considering their relative strengths and weaknesses, integrated analysis to these data would likely improve harvest management, but tools for integration have not yet been developed. Managers currently use an aerial count survey on the wintering grounds, the mid-winter survey, to set harvest regulations. We developed an integrated population model (IPM) for Atlantic brant that uses multiple data sources to simultaneously estimate population abundance, survival, and productivity. The IPM abundance estimates for data from 1975–2018 were less variable than annual mid-winter survey counts or Lincoln estimates, presumably reflecting better accounting for observer error and incorporation of demographic estimates by the IPM. Posterior estimates of adult survival were high (0.77–0.87), and harvest rates of adults and juveniles were positively correlated with more liberal hunting regulations (i.e., hunting days and the daily bag limit). Productivity was variable, with the percent of juveniles in the winter population ranging from 1% to >40%. We found no evidence for environmental relationships with productivity. Using IPM-predicted population abundances rather than mid-winter survey counts alone would have meant fewer annual changes to hunting regulations since 2004. Use of the IPM could improve harvest management for Atlantic brant by providing the ability to predict abundance before annual hunting regulations are set, and by providing more stable hunting regulations, with fewer annual changes.
Arctic marine mammals are harvested by Indigenous people for subsistence and are socially and culturally important. For ice-dependent species like the polar bear Ursus maritimus , management and conservation require understanding interactions between harvest and sea-ice loss due to climate change. We developed a demographic model to evaluate harvest risk for polar bears in Southern Hudson Bay, Canada, where the annual ice-free season has increased by approximately one month in recent decades. The model was based on the theta-logistic equation and allowed for density-dependent changes (through carrying capacity [ K ]) and density-independent changes (through population growth rate [ r ]). Model parameters were estimated using a Bayesian Monte Carlo method that included capture-recapture, aerial survey, and harvest data. Harvest management followed a state-dependent approach under which new estimates of abundance were used to update the harvest level every five years. Under a middle-of-the-road environmental scenario that assumed K and r would decline in proportion to projected sea-ice declines, annual removal of 0.02–0.03 of females resulted in a 0.8 probability of maintaining subpopulation abundance above maximum net productivity level for three polar bear generations (~34 years), our primary criterion for sustainability. Under more pessimistic and optimistic environmental scenarios, comparable female harvest rates were 0.01 and 0.055, respectively. Our coupled modeling-management framework can be used to inform tradeoffs between protection and sustainable use for wildlife populations experiencing habitat loss.
Unusual channel-amphitheatre landforms are present in Late Pleistocene–early Holocene, subaqueous fan and delta deposits in the glacial Lake Fraser basin, central British Columbia. The lake formed during the decay of the last Cordilleran Ice Sheet and drained ~11,500 years ago during a large outburst flood. The fronts of a delta and two subaqueous fans consisting of silt to fine sand are marked by branching networks of wide, nearly flat channels that terminate upstream in digitate, steep-walled amphitheatres. We propose that these channel-amphitheatre landforms formed by liquefaction flowslides that were induced by the rapid drawdown of glacial Lake Fraser during the outburst flood. Similar geomorphic forms, which we believe also to be associated with rapid drawdowns of large Late Pleistocene–early Holocene lakes, occur elsewhere in North America. A recent tailings dam failure and an intentional breaching of a 100-year-old hydroelectric dam provide insights into the processes responsible for the landforms. By using geomechanical analysis, we show how rapid lake drawdown can trigger liquefaction flowslides in deposits of silt to fine sand. The novelty of our approach lies in combining geomechanical reasoning with geomorphic analogues to understand histories of ancient glacier-dammed lakes and of the glacial lake outburst floods that are sourced from them.
Abundance estimates can be crucial for managing species of economic concern. The accuracy of these estimates can depend on the methods used to track animals and to estimate abundance from tracking data. We tested experimentally if disparate estimates of trapping efficiency calculated for sea lamprey ( Petromyzon marinus ) in the St. Marys River near Sault Ste. Marie, Canada could be explained by effects related to the invasiveness and handling involved in tagging or the tag size used in the marking procedures. Trapping is used to gauge adult abundance, trapping efficiency, and success of a binational sea lamprey control program in the Laurentian Great Lakes, North America. Our experiment compared nightly catches of sea lamprey marked with external fin clips, surgically-implanted passive integrated transponder tags (PIT-only), and surgically-implanted PIT and acoustic tags (PIT+acoustic). We found no evidence that the probability of being trapped was affected by the added invasiveness and handling of internal tagging. Nightly recaptures of PIT-only tagged sea lamprey, relative to fin-clipped sea lamprey, were not different from expectations based on the numbers of individuals released from each treatment group. Conversely, there was evidence of effects related to tag size. Nightly recaptures of PIT+acoustic tagged sea lamprey, relative to PIT-only tagged sea lamprey, were lower than expected based on numbers of individuals released from each treatment group. Effects related to tag size partially explain the disparate estimates in trapping efficiency observed for sea lamprey.
Exploration of the continental slope of the Canadian Beaufort Sea has revealed a remarkable coalescence of slide scars with headwalls between 130 and 1100 m water depth (mwd). With increased depth, the scars widen and merge into one gigantic regional slide scar that is more than 100 km wide below ~1100 mwd. To understand the development of these features, five sites were investigated with an Autonomous Underwater Vehicle, which provided 1-m bathymetric grids and Chirp profiles, and surveyed with a Remotely Operated Vehicle. The morphologies are consistent with retrograde failures that occurred on failure planes located between 30 and 75 m below the modern seafloor. At issue is whether the continental slope in this area is preconditioned for failure. While rapid sedimentation during glacial periods, and the presence of shallow gas cannot be ruled out, given the geological environment, it is unclear that they are primary preconditioning factors. Evidence of widespread flushing of the slope with brackish waters, and observed flows of brackish water within slide scars, suggest fluid venting and overpressure may play a role in the development of the extensive slope failures seen along this margin. The impact of pore water salinity changes at the depth of the failure plane on slope stability has not been considered in marine settings previously.
As climate warming and precipitation increase at high latitudes, permafrost terrains across the circumpolar north are poised for intensified geomorphic activity and sediment mobilization that are expected to persist for millennia. In previously glaciated permafrost terrain, ice-rich deposits are associated with large stores of reactive mineral substrate. Over geological timescales, chemical weathering moderates atmospheric CO 2 levels, raising the prospect that mass wasting driven by terrain consolidation following thaw (thermokarst) may enhance weathering of permafrost sediments and thus climate feedbacks. The nature of these feedbacks depends upon the mineral composition of sediments (weathering sources) and the balance between atmospheric exchange of CO 2 vs. fluvial export of carbonate alkalinity ( Σ [ HCO 3 - "> HCO − 3 , CO 3 2 - "> CO 2 − 3 ]). Working in the fluvially incised, ice-rich glacial deposits of the Peel Plateau in northwestern Canada, we determine the effects of slope thermokarst in the form of retrogressive thaw slump (RTS) activity on mineral weathering sources, CO 2 dynamics, and carbonate alkalinity export and how these effects integrate across watershed scales ( ∼ 2 to 1000 km 2 ). We worked along three transects in nested watersheds with varying connectivity to RTS activity: a 550 m transect along a first-order thaw stream within a large RTS, a 14 km transect along a stream which directly received inputs from several RTSs, and a 70 km transect along a larger stream with headwaters that lay outside of RTS influence. In undisturbed headwaters, stream chemistry reflected CO 2 from soil respiration processes and atmospheric exchange. Within the RTS, rapid sulfuric acid carbonate weathering, prompted by the exposure of sulfide- and carbonate-bearing tills, appeared to increase fluvial CO 2 efflux to the atmosphere and propagate carbonate alkalinity across watershed scales. Despite covering less than 1 % of the landscape, RTS activity drove carbonate alkalinity to increase by 2 orders of magnitude along the largest transect. Amplified export of carbonate alkalinity together with isotopic signals of shifting DIC and CO 2 sources along the downstream transects highlights the dynamic nature of carbon cycling that may typify glaciated permafrost watersheds subject to intensification of hillslope thermokarst. The balance between CO 2 drawdown in regions where carbonic acid weathering predominates and CO 2 release in regions where sulfides are more prevalent will determine the biogeochemical legacy of thermokarst and enhanced weathering in northern permafrost terrains. Effects of RTSs on carbon cycling can be expected to persist for millennia, indicating a need for their integration into predictions of weathering–carbon–climate feedbacks among thermokarst terrains.
Understanding the evolutionary impacts of harvest on fish populations is important for informing fisheries management and conservation and has become a growing research topic over the last decade. However, the dynamics of fish populations are highly complex, and phenotypes can be influenced by many biotic and abiotic factors. Therefore, it is vital to collect robust data and explore multiple alternative hypotheses before concluding that fish populations are influenced by harvest. In their recently published manuscript, Bowles et al, Evolutionary Applications, 13(6):1128 conducted age/growth and genomic analysis of walleye ( Sander vitreus ) populations sampled 13–15 years (1–2.5 generations) apart and hypothesized that observed phenotypic and genomic changes in this time period were likely due to harvest. Specifically, Bowles et al. (2020) documented differential declines in size-at-age in three exploited walleye populations compared to a separate, but presumably less-exploited, reference population. Additionally, they documented population genetic differentiation in one population pair, homogenization in another, and outlier loci putatively under selection across time points. Based on their phenotypic and genetic results, they hypothesized that selective harvest had led to fisheries-induced evolution (referred to as nascent changes) in the exploited populations in as little as 1–2.5 generations. We re-analyzed their data and found that (a) sizes declined across both exploited and reference populations during the time period studied and (b) observed genomic differentiation in their study was the result of inadequate data filtering, including retaining individuals with high amounts of missing data and retaining potentially undersplit and oversplit loci that created false signals of differentiation between time points. This re-analysis did not provide evidence for phenotypic or genetic changes attributable to harvest in any of the study populations, contrasting the hypotheses presented by Bowles et al. (2020). Our comment highlights the potential pitfalls associated with conducting age/growth analyses with low sample sizes and inadequately filtering genomic datasets.
Polar bears ( Ursus maritimus ) rely on annual sea ice as their primary habitat for hunting marine mammal prey. Given their long lifespan, wide geographic distribution, and position at the top of the Arctic marine food web, the diet composition of polar bears can provide insights into temporal and spatial ecosystem dynamics related to climate-mediated sea ice loss. Polar bears with the greatest ecological constraints on diet composition may be most vulnerable to climate-related changes in ice conditions and prey availability. We used quantitative fatty acid signature analysis (QFASA) to estimate the diets of polar bears ( n = 419) in two western Canadian Arctic subpopulations (Northern Beaufort Sea and Southern Beaufort Sea) from 1999 to 2015. Polar bear diets were dominated by ringed seal ( Pusa hispida ), with interannual, seasonal, age- and sex-specific variation. Foraging area and sea ice conditions also affected polar bear diet composition. Most variation in bear diet was explained by longitude, reflecting spatial variation in prey availability. Sea ice conditions (extent, thickness, and seasonal duration) declined throughout the study period, and date of sea ice break-up in the preceding spring was positively correlated with female body condition and consumption of beluga whale ( Delphinapterus leucas ), suggesting that bears foraged on beluga whales during entrapment events. Female body condition was positively correlated with ringed seal consumption, and negatively correlated with bearded seal consumption. This study provides insights into the complex relationships between declining sea ice habitat and the diet composition and foraging success of a wide-ranging apex predator.
Global warming-related changes to freshwater ecosystems in Arctic and Subarctic regions have been magnified by nutrient input from increasing waterfowl populations. To gain insight into how these changes might affect ecosystem function, we conducted a mesocosm experiment in the Subarctic by enriching N and P (1 ×, 10 ×, and 20 × treatments) and increasing mean water temperatures ≤ 3°C. We measured responses of two species of larval amphibians, periphyton, and phytoplankton. Wood frog ( Rana sylvatica ) larvae developed quicker (odds ratio [OR] for 1°C increase = 0.903, 95% CI 0.892–0.912) and were more likely to metamorphose (OR 1.076, 95% CI 0.022–14.73) in warmer waters. Boreal chorus frogs ( Pseudacris maculata ) also developed quicker with warmer temperatures (OR 0.880, 95% CI 0.860–0.900), despite a non-significant trend toward reduced survival (OR 0.853, 95% CI 0.696–1.039). Periphyton and phytoplankton concentrations increased with nutrient additions, as did size of wood frog metamorphs. Periphyton and phytoplankton did not vary with temperature, but periphyton was limited by tadpole abundance. Our results highlight the potential for non-linear responses to ecosystem change, with species-specific consumer and ecosystem responses that depend on the magnitude of changes.
Long‐distance migration presents complex conservation challenges, and migratory species often experience shortfalls in conservation due to the difficulty of identifying important locations and resources throughout the annual cycle. In order to prioritize habitats for conservation of migratory wildlife, it is necessary to understand how habitat needs change throughout the annual cycle, as well as to identify key habitat sites and features that concentrate large numbers of individuals and species. Among long‐distance migrants, sea ducks have particularly complex migratory patterns, which often include distinct post‐breeding molt sites as well as breeding, staging and wintering locations. Using a large set of individual tracking data (n = 476 individuals) from five species of sea ducks in eastern North America, we evaluated multi‐species habitat suitability and partitioning across the breeding, post‐breeding migration and molt, wintering and pre‐breeding migration seasons. During breeding, species generally occupied distinct habitat areas, with the highest levels of multi‐species overlap occurring in the Barrenlands west of Hudson Bay. Species generally preferred flatter areas closer to lakes with lower maximum temperatures relative to average conditions, but varied in distance to shore, elevation and precipitation. During non‐breeding, species overlapped extensively during winter but diverged during migration. All species preferred shallow‐water, nearshore habitats with high productivity, but varied in their relationships to salinity, temperature and bottom slope. Sea ducks selected most strongly for preferred habitats during post‐breeding migration, with high partitioning among species; however, both selection and partitioning were weaker during pre‐breeding migration. The addition of tidal current velocity, aquatic vegetation presence and bottom substrate improved non‐breeding habitat models where available. Our results highlight the utility of multi‐species, annual‐cycle habitat assessments in identifying key habitat features and periods of vulnerability in order to optimize conservation strategies for migratory wildlife.
Estimating population abundance is a challenging task complicated by the amount, type, and quality of available data. Conservationists have relied on design-based estimates from Partners in Flight (PIF), which primarily uses roadside data from the North American Breeding Bird Survey (BBS) to estimate populations sizes. However, the BBS was not designed to estimate population sizes. We developed models incorporating land cover and climate variables based on roadside and off-road point-count surveys. We calculated spatially explicit, model-based population estimates for 81 landbird species in Bird Conservation Region 6 in Alberta, Canada, and compared these to PIF estimates. We also developed a framework to evaluate how the differences between the detection distance, time-of-day, roadside count, and habitat representation adjustments explain discrepancies between the two estimators. We showed that the key assumptions of the PIF population size estimator were commonly violated in this region, and the two approaches provided very different population size estimates for most species. The average differences between estimators were explained by differences in the detection distance and time-of-day components, but these adjustments left much unexplained variation among species. Differences in the roadside count and habitat representation components explained most of the among-species variation. The variation caused by these factors was large enough to change the population size ranking of the species. The roadside count bias needs serious attention when roadside surveys are used to extrapolate over off-road areas. Habitat representation bias is likely prevalent in regions sparsely and non-representatively sampled by roadside surveys, such as the boreal region of North America, and thus population size estimates for these regions need to be treated with caution for certain species. Model-based integration of available data sources and additional sampling can contribute towards more accurate population size estimates for conservation in remote areas of North America.
Cyclic fluctuations in abundance exhibited by some mammalian populations in northern habitats (“population cycles”) are key processes in the functioning of many boreal and tundra ecosystems. Understanding population cycles, essentially demographic processes, necessitates discerning the demographic mechanisms that underlie numerical changes. Using mark–recapture data spanning five population cycles (1977–2017), we examined demographic mechanisms underlying the 9–10‐yr cycles exhibited by snowshoe hares ( Lepus americanus Erxleben) in southwestern Yukon, Canada. Snowshoe hare populations always decreased during winter and increased during summer; the balance between winter declines and summer increases characterized the four, multiyear cyclic phases: increase, peak, decline, and low. Little or no recruitment occurred during winter, but summer recruitment varied markedly across the four phases with the highest and lowest recruitment observed during the increase and decline phase, respectively. Population crashes during the decline were triggered by a substantial decline in winter survival and by a lack of subsequent summer recruitment. In contrast, initiation of the increase phase was triggered by a twofold increase in summer recruitment abetted secondarily by improvements in subsequent winter survival. We show that differences in peak density across cycles are explained by differences in overall population growth rate, amount of time available for population growth to occur, and starting population density. Demographic mechanisms underlying snowshoe hare population cycles were consistent across cycles in our study site but we do not yet know if similar demographic processes underlie population cycles in other northern snowshoe hare populations.
Two catastrophic landslides occurred in quick succession on 13 and 16 May 2019, from the north face of Joffre Peak, Cerise Creek, southern Coast Mountains, British Columbia. With headscarps at 2560 m and 2690 m elevation, both began as rock avalanches, rapidly transforming into debris flows along middle Cerise Creek, and finally into debris floods affecting the fan. Beyond the fan margin, a flood surge on Cayoosh Creek reached bankfull and attenuated rapidly downstream; only fine sediment reached Duffey Lake. The toe of the main debris flow deposit reached 4 km from the headscarp, with a travel angle of 0.28; while the debris flood phase reached the fan margin 5.9 km downstream, with a travel angle of 0.22. Photogrammetry indicates the source volume of each event is 2-3 Mm3, with combined volume of 5 Mm3. Lidar differencing, used to assess deposit volume, yielded a similar total result; although error in the depth estimate introduced large error and masks expected increase due to dilation and entrainment. The average velocity of the rock avalanche-debris flow phases, from seismic analysis, was ~25-30 m/s, and the velocity of the 16 May debris flood on the upper fan, from super-elevation and boulder sizes, was 5-10 m/s. The volume of debris deposited on the fan was ~104 m3, 2-orders of magnitude less than the avalanche/debris flow phases. The 13 May landslide was apparently triggered by rapid snowmelt; with debuttressing triggering the 16 May event. While spring 2019 was warm, it wasn’t unusual. It is likely that progressive glacier retreat and permafrost degradation were the conditioning factors; precursor activity was noted at least 1 yr previous; thus, the mountain was primed to fail and average seasonal snowmelt tipped the balance.
The aqueous speciation and mineralogy of antimony (Sb) in waters and tailings at Beaver Brook antimony deposit have been analyzed to understand Sb mobility during the initial stages of stibnite (Sb2S3) weathering in a near-surface environment. Dissolution of stibnite in oxidizing conditions releases Sb in drainage water and Sb is incorporated into the mineral structures of several secondary minerals. The most abundant Sb host in Beaver Brook tailings is primary stibnite, which dissolves, releasing Sb(III) to the pore water which rapidly oxidizes to Sb¬(V). The maximum concentration of Sb in tailings pore water is 26.4 mg/L and only 0.9% is in form of Sb(III). In all surface water, Sb concentration ranges from 0.01 to 26.1 mg/L (average 9.4 mg/L) and is mostly present in its Sb(V) (98.9 to 99.2 % of total Sb). The secondary minerals containing Sb formed in tailings impoundment, include tripuhyite-like Sb-Fe oxides (FeSbO4) where Sb is an important part of their structure with variable Fe/Sb ratios and Sb concentrations of up to 37.8% by weight (average of 21.7%). These are important Sb host phases in the top 30 cm of tailings. Iron oxides enriched in Sb, such as goethite (FeOOH), where Sb (average of 3.9% by weight) is adsorbed or incorporated in the structure are common but represent less than 1.3 % of the total mass of Sb. The elevated Mg concentrations in tailing ponds and pore water promote the precipitation of brandholzite (Mg[Sb(OH)6]2·6H2O) (in association with gypsum) during dry periods, which is easily dissolved during rainy periods. Brandholzite dissolution may significantly contribute to the concentration of dissolved Sb, together with stibnite dissolution, whereas Sb-Fe oxides are stable in the neutral pH, oxidized surface environment. Arsenic (As) accompanies Sb in all media but its behaviour differs from that of Sb. The source of As is arsenopyrite, which decomposes more slowly than stibnite. This may be due to the formation of oxidation rims on arsenopyrite grains composed of Fe, As, S, Sb and Ca which slow the dissolution, whereas no rims are seen on stibnite. Also, despite similar As and Sb concentration in bulk tailings, the concentration of Sb in drainage water is higher than that of As. In pore water, As(III) is the dominant oxidation state of As suggesting that the oxidation of dissolved As is slower than that of Sb.
The Yukon–Alaska Highway corridor in southern Yukon is subject to geohazards ranging from landslides to floods and earthquakes on faults in the St. Elias Mountains and Shakwak Valley. Here we discuss the late Holocene seismic history of the Denali fault, located at the eastern front of the St. Elias Mountains and one of only a few known seismically active terrestrial faults in Canada. Holocene faulting is indicated by scarps and mounds on late Pleistocene drift and by tectonically deformed Pleistocene and Holocene sediments. Previous work on trenches excavated against the fault scarp near the Duke River reveals paleoseismic sediment disturbance dated to ∼300–1,200, 1,200–1,900, and 3,000 years ago. Re-excavation of the trenches indicates a fourth event dated to 6,000 years ago. The trenches are interpreted to show a negative flower structure produced by extension of sediments by dextral strike-slip fault movement. Nearby Crescent Lake is ponded against the fault scarp. Sediment cores reveal four abrupt sediment and diatom changes reflecting seismic shaking at ∼1,200–1,900, 1,900–5,900, 5,900–6,200, and 6,500–6,800 years ago. At the Duke River, the fault offsets sediments, including two White River tephra layers (∼1,900 and 1,200 years old). Late Pleistocene outwash gravel and overlying Holocene aeolian sediments show in cross section a positive flower structure indicative of post-glacial contraction of the sediments by dextral strike-slip movement. Based on the number of events reflecting ∼M6, we estimate the average recurrence of large earthquakes on the Yukon part of the Denali fault to be about 1,300 years in the past 6,500–6,800 years.
Occupancy patterns can assist with the determination of habitat limitation during breeding or wintering periods and can help guide population and habitat management efforts. American black ducks ( Anas rubripes ; black ducks) are thought to be limited by habitat and food availability during the winter, but breeding sites may also limit the size or growth potential of the population. The Canadian Wildlife Service conducts an annual breeding waterfowl survey that we used to explore the hypothesis that black duck carrying capacity is limited by wetlands available for breeding in Québec, Canada. We applied single‐visit, multi‐species occupancy models to the 1990–2015 population survey data to determine if there was evidence the black duck population was limited by breeding habitat. Using a dynamic (multi‐season) occupancy modeling approach, we estimated latent occupancy (occupancy accounting for imperfect detection) of black ducks and then used latent occupancy estimates to derive occupancy, colonization, and extirpation rates. We jointly modeled the occupancy dynamics of black ducks and other duck species in wetlands where both species were present. Throughout the duration of the survey, 44% of wetlands were never observed to be occupied by black ducks. Occupancy models showed wetland size was positively associated with occupancy at the first time step (initial occupancy) and colonization. All 2‐species models indicated initial black duck occupancy, persistence (continued occupancy), and colonization were positively associated with the presence of a second species. Colonization rate over the 26‐year period ranged from 7% to 27% across all models. Extirpation rates were similar and were constant through time within each model. Low occupancy rates, combined with approximately equal colonization and extirpation rates, suggest there are available wetlands for breeding black ducks in their core breeding area. If breeding habitats are not saturated, this suggests migration or wintering areas may be more limiting to black duck population abundance.