Reassessing perennial cover as a driver of duck nest survival in the Prairie Pothole Region

Conservation plans designed to sustain North American duck populations prominently feature a key hypothesis stating that the amount of the landscape in perennial cover surrounding upland duck nests positively influences nest survival rates. Recent conflicting research testing this hypothesis creates ambiguity regarding which management actions to pursue and where to prioritize conservation delivery. We compared existing models and new formulations of existing models explaining spatiotemporal variation in nest survival using independent data documenting the fate of >20,000 duck nests within the Drift Prairie, Missouri Coteau, and Prairie Coteau physiographic regions of the United States Prairie Pothole Region during 2002–2018. Our results suggest an inconsistent relationship between perennial cover and survival of upland duck nests, which depended upon physiographic region and current and time-lagged landscape and environmental conditions. The magnitude and direction of how perennial cover correlated with daily nest survival depended on its dominance as a landcover type. A positive relationship existed when perennial cover was a minor component of landcover in all physiographic regions (<30% of a 10.4-km² area) and, in the Drift Prairie and Prairie Coteau, when perennial cover was the dominant landcover type (>60%). A constant or negative relationship was predicted at locations of about 30–60% perennial cover. Additionally, environmental conditions (i.e., density of wetlands and estimated gross primary productivity in the previous year) moderated or enhanced the effect of perennial cover on nest survival, depending on physiographic region. Our finding of inconsistency in the relationship between perennial cover and nest survival contradicts the conservation premise that nest survival universally increases linearly when uplands are converted to perennial cover. Promoting policies and management actions designed to increase perennial cover can be expected to be situationally but not consistently associated with higher survival of upland duck nests.     

Factors Affecting Wetland Use by Spring Migrating Ducks in the Southern Prairie Pothole Region

There is increasing recognition of the importance of wetlands in the prairie pothole region (PPR) of the northern United States for stopover habitat for spring-migrating waterfowl. The quality and quantity of stopover habitat found near breeding areas can affect speed and success of migration and subsequent breeding events. Conservation and management of wetlands in the region has traditionally focused narrowly on reproductive phases of the life cycle, and little to no research has examined how ducks use a diversity of available wetlands in the region during migration. We conducted weekly surveys on 1,061 wetlands during spring 2018 and 2019 to examine factors affecting duck use of wetlands in the intensively modified southern PPR landscape of Iowa, USA, for wetland restoration and conservation strategies. We compared wetland types, which included farmed, seasonal, and semi-permanent wetlands, and lakes. The highest duck use per unit area occurred on semi-permanent wetlands, followed by seasonal, and then farmed wetlands, and lakes. Ducks were highly clustered in our study, with 75% of all use-days occurring on only 37 wetlands comprising 41% of all wetland area surveyed. We used hurdle models to examine how local and landscape factors measured within and around wetlands influenced duck use during spring migration. Multiple factors related to duck use at local and landscape scales, such as wetland area, vegetation abundance, and number of wetlands in the surrounding landscape. Among semi-permanent wetlands, local factors within wetlands were more important than landscape factors in determining duck use. Collectively, our findings suggest semi-permanent wetlands within the PPR play a key role in transitioning birds from wintering areas to breeding areas and that management of semi-permanent wetlands should promote interspersion of emergent vegetation and open water and growth of submersed aquatic plants to improve their function for migrants. © 2021 The Authors. The Journal of Wildlife Management published by Wiley Periodicals LLC on behalf of The Wildlife Society.     

Waterfowl Nesting in Fall-Seeded and Spring-Seeded Cropland in Saskatchewan

Abstract: Waterfowl nesting in annual croplands has remained a little-known aspect of waterfowl nesting ecology because of the inability of many studies to systematically search this habitat through the nesting season. Where searches have been conducted, they are generally restricted to the period prior to seeding, and many nests found are destroyed by the seeding operation. Consequently, fall-seeded crops have been promoted as an alternative cropping practice that could increase nest survival of waterfowl nesting in croplands. During 1996–1999, we conducted 3–4 complete nest searches on 4,274 ha of cropland, including spring-seeded wheat and barley, winter wheat, and fall rye in southern Saskatchewan, Canada. Using suites of predictive models, we tested hypotheses regarding relative nest abundance and nest survival among crop types and tested the influence of several landscape-scale covariates on these metrics. Apparent nest densities were higher in fall-seeded crops (winter wheat: 0.39 nests/ha, fall rye: 0.25 nests/ha) than in spring-seeded crops (0.03 nests/ha), and nest density in spring-seeded croplands increased with percent cropland and percent wetland habitat in the surrounding landscape. Nest survival was higher in winter wheat (38%) than in either fall rye (18%) or spring-seeded crops (12%), and nest survival in spring-seeded crops increased with relative nest initiation date. Nest survival was unaffected by surrounding landscape characteristics but tended to be higher in years of average wetness. Based on our findings, winter wheat and fall rye have the potential to provide productive nesting habitat for ≥7 species of upland nesting ducks and fall-seeded crops are a conservation tool well suited to highly cropped landscapes.     

Distribution of duck broods relative to habitat characteristics in the Prairie Pothole Region

Conservation programs for breeding ducks in the Prairie Pothole Region (PPR) of the United States and Canada require effective means of evaluating and characterizing breeding habitat across large landscapes. Extensive surveys of the distribution of duck broods in late-summer could help identify wetland basins with greater probabilities of occupancy. Broods are difficult to detect, however, rendering presence–absence data from single-visit surveys difficult to interpret, particularly when probability of detection is related to habitat features. Multiple-visit occupancy surveys offer a potential solution. From 20 July to 5 August 2007–2009, we conducted a 3-visit survey of wetland basins located on 167 10.4-km² study plots in the PPR. Our survey focused on broods of the 5 most common breeding duck species (Anas spp.). Our main objectives were to investigate ecological relationships between occupancy of wetland basins by broods and habitat characteristics and to examine if habitat-specific detection was of enough concern to warrant multi-survey approaches in the future. We surveyed 3,226 wetland basins during the study. Probability of occupancy of a wetland basin by a brood was positively related to the log of wet area for all 5 study species and was greater on wetlands located on plots with a greater proportion of herbaceous perennial cover for 4 of 5 species. For example, the median probability of occupancy for gadwall (Anas strepera) increased from 0.08 (90% Credible Interval [CrI]: 0.07, 0.10) to 0.28 (90% CrI: 0.23, 0.33) as wet area increased from 0.19 ha to 2.12 ha, and increased from 0.12 (90% CrI: 0.09, 0.16) to 0.20 (90% CrI: 0.16, 0.25) as proportion of perennial grass cover on the study plot increased from 0.03 to 0.99. Because occupancy and detection were both related to attributes of wetland basins, we concluded that the multiple-visit survey was a useful approach for identifying habitat relationships of duck broods. Our results indicated that most broods of the study species were found in 10.4-km² landscapes with greater densities of small- to mid-sized wetland basins and a greater proportion of herbaceous perennial vegetation. Our study provided new empirical support that could be used to help target conservation actions to the most productive landscapes for breeding ducks. © 2012 The Wildlife Society.     

Effect of wind energy development on breeding duck densities in the Prairie Pothole Region

Industrial wind energy production is a relatively new phenomenon in the Prairie Pothole Region and given the predicted future development, it has the potential to affect large land areas. The effects of wind energy development on breeding duck pair use of wetlands in proximity to wind turbines were unknown. During springs 2008–2010, we conducted surveys of breeding duck pairs for 5 species of dabbling ducks in 2 wind energy production sites (wind) and 2 paired reference sites (reference) without wind energy development located in the Missouri Coteau of North Dakota and South Dakota, USA. We conducted 10,338 wetland visits and observed 15,760 breeding duck pairs. Estimated densities of duck pairs on wetlands in wind sites were lower for 26 of 30 site, species, and year combinations and of these 16 had 95% credible intervals that did not overlap zero and resulted in a 4–56% reduction in breeding pairs. The negative median displacement observed in this study (21%) may influence the prioritization of grassland and wetland resources for conservation when existing decision support tools based on breeding-pair density are used. However, for the 2 wind study sites, priority was not reduced. We were unable to directly assess the potential for cumulative impacts and recommend long-term, large-scale waterfowl studies to reduce the uncertainty related to effects of broad-scale wind energy development on both abundance and demographic rates of breeding duck populations. In addition, continued dialogue between waterfowl conservation groups and wind energy developers is necessary to develop conservation strategies to mitigate potential negative effects of wind energy development on duck populations. Published 2012. This article is a U.S. Government work and is in the public domain in the USA.     

Evidence for 20th century climate warming and wetland drying in the North American Prairie Pothole Region

The Prairie Pothole Region (PPR) of North America is a globally important resource that provides abundant and valuable ecosystem goods and services in the form of biodiversity, groundwater recharge, water purification, flood attenuation, and water and forage for agriculture. Numerous studies have found these wetlands, which number in the millions, to be highly sensitive to climate variability . Here, we compare wetland conditions between two 30‐year periods (1946–1975; 1976–2005) using a hindcast simulation approach to determine if recent climate warming in the region has already resulted in changes in wetland condition. Simulations using the WETLANDSCAPE model show that 20th century climate change may have been sufficient to have a significant impact on wetland cover cycling. Modeled wetlands in the PPR's western Canadian prairies show the most dramatic effects: a recent trend toward shorter hydroperiods and less dynamic vegetation cycles, which already may have reduced the productivity of hundreds of wetland ‐ dependent species.     

Landscape-level correlates of mallard duckling survival: Implications for conservation programs

Despite recent work, uncertainty remains concerning how abiotic and biotic factors affect duckling survival. Additionally, upland habitat characteristics may affect duckling survival rates but this potential relationship has largely been ignored. We evaluated several unresolved hypotheses about causes of mallard (Anas platyrhynchos) duckling survival variation, with an emphasis on assessing effects of managed and remnant natural upland habitats. During 1993–2000, 617 radio-marked females provided information about brood habitat use and duckling survival on 27 sites in prairie Canada. We contrasted a priori and exploratory models that incorporated effects of upland, wetland, weather, female, and brood-related variables on duckling survival rates. Survival was highest for ducklings when a greater proportion of their surrounding landscape (i.e., within a 500-m radius buffer around the brood) was comprised of wetlands characterized by a central expanse of open water and a peripheral ring of flooded emergent vegetation. Cold and wet weather in the first week of life resulted in lower duckling survival. In a post hoc analysis, duckling survival (of older ducklings) was negatively related to increasing proportions of managed hayland. © 2011 The Wildlife Society.     

Waterfowl Use of Dense Nesting Cover in the Canadian Parklands

ABSTRACT Dense nesting cover (DNC) has been a conspicuous component of habitat management for upland-nesting ducks for >30 years, but its benefits for nesting ducks have been contentious. During 1994–1999 we monitored 3,058 dabbling duck (Anas spp.) nests in 84 DNC fields located throughout the Canadian Parklands to examine sources of among-field variation in nest density and nesting success. Nest density averaged 1.51 (SE=0.15) nests/ha and overall nesting success was 20.4%, but there was pronounced annual variation in both estimates. Nesting success increased with increasing field size (range = 6–111 ha), but nest density remained constant. Nest density increased with percent wetland habitat within DNC fields and declined with percent perennial cover in the surrounding 2.4 × 2.4-km landscape, but these variables were not important for predicting nesting success. Nest abundance and nesting success roughly doubled in fields seeded with alfalfa (Medicago sativa) or sweet clovers (Melilotus spp.), but there was no benefit from using native as opposed to tame grasses. We recommend that waterfowl managers in the Canadian Parklands establish DNC with alfalfa in large fields in landscapes with abundant wetlands but minimal competing cover.     

Correlation Between Nest and Duckling Survival of Mallards Breeding in Saskatchewan

Abstract: Few studies have estimated reproductive and survival parameters of breeding ducks simultaneously, although such efforts can reveal relationships among vital rates. We estimated survival of mallard (Anas platyrhynchos) nests and duckling on 8 study sites in south-central Saskatchewan during spring and summer 2000 and 2001. We observed a strong positive correlation between these parameters (r = 0.914) and through analysis of residual values found 14% of the relationship was explained by a predator-removal treatment, 26% by year effects, 44% by spatial variation, and 16% unexplained. Potential mechanisms include similar environmental factors influencing both parameters (e.g., predators) and positive density dependence. Information regarding covariation among vital rates is important in construction and interpretation of population growth models describing population dynamics of mallards and other upland-nesting ducks.     

Land use and climate influences on waterbirds in the Prairie Potholes

Aim We examined the influences of regional climate and land‐use variables on mallard (Anas platyrhynchos), blue‐winged teal (Anas discors), ruddy duck (Oxyura jamaicensis) and pied‐billed grebe (Podilymbus podiceps) abundances to inform conservation planning in the Prairie Pothole Region of the United States. Location The US portion of Bird Conservation Region 11 (US‐BCR11, the Prairie Potholes), which encompasses six states within the United States: Montana, North Dakota, South Dakota, Nebraska, Minnesota and Iowa. Methods We used data from the North American Breeding Bird Survey (NABBS), the National Land Cover Data Set, and the National Climatic Data Center to model the effects of environmental variables on waterbird abundance. We evaluated land‐use covariates at three logarithmically related spatial scales (1000, 10,000 and 100,000 ha), and constructed hierarchical spatial count models a priori using information from published habitat associations. Model fitting was performed using a hierarchical modelling approach within a Bayesian framework. Results Models with the same variables expressed at different scales were often in the best model subset, indicating that the influence of spatial scale was small. Both land‐use and climate variables contributed strongly to predicting waterbird abundance in US‐BCR11. The strongest positive influences on waterbird abundance were the percentage of wetland area across all three spatial scales, herbaceous vegetation and precipitation variables. Other variables that we included in our models did not appear to influence waterbirds in this study. Main conclusions Understanding the relationships of waterbird abundance to climate and land use may allow us to make predictions of future distribution and abundance as environmental factors change. Additionally, results from this study can suggest locations where conservation and management efforts should be focused.     

Maximizing species conservation in continental Ecuador: a case of systematic conservation planning for biodiverse regions

Ecuador has the largest number of species by area worldwide, but also a low representation of species within its protected areas. Here, we applied systematic conservation planning to identify potential areas for conservation in continental Ecuador, with the aim of increasing the representation of terrestrial species diversity in the protected area network. We selected 809 terrestrial species (amphibians, birds, mammals, and plants), for which distributions were estimated via species distribution models (SDMs), using Maxent. For each species we established conservation goals based on conservation priorities, and estimated new potential protected areas using Marxan conservation planning software. For each selected area, we determined their conservation priority and feasibility of establishment, two important aspects in the decision-making processes. We found that according to our conservation goals, the current protected area network contains large conservation gaps. Potential areas for conservation almost double the surface area of currently protected areas. Most of the newly proposed areas are located in the Coast, a region with large conservation gaps and irreversible changes in land use. The most feasible areas for conservation were found in the Amazon and Andes regions, which encompass more undisturbed habitats, and already harbor most of the current reserves. Our study allows defining a viable strategy for preserving Ecuador''s biodiversity, by combining SDMs, GIS-based decision-support software, and priority and feasibility assessments of the selected areas. This approach is useful for complementing protected area networks in countries with great biodiversity, insufficient biological information, and limited resources for conservation.     

黄淮海地区湿地系统生物多样性保护格局构建

以黄淮海地区为研究对象,首先分析了区域现有湿地保护状况,再基于湿地类型、保护状况和目标保护物种分布,综合考虑GDP、人口密度等社会经济因素,以湿地生物多样性保护为目标,运用系统保护规划的理论和方法,以Marxan作为空间优化模型,进行多目标的湿地系统保护预案设计,构建区域湿地不同保护水平的保护空缺和不可替代性格局,确定合理的湿地系统保护格局。研究结果表明:现有的湿地保护体系仅覆盖了区域17%左右的湿地,尚有许多重要生境游离于现有保护区系统外。为完善黄淮海地区湿地保护体系,需要对黄海海区域内28个保护区进行功能区划调整或者保护等级提升,并在山东(5个县)和河北(4个县),河南、江苏和安徽(各3个县),北京和天津(各1个县)等20个县市内建立新的保护区,与现有湿地保护系统有机整合,最终形成一个黄淮海地区湿地生物保护网络合理格局。结果表明:同其他相关研究方法对比,系统保护规划方法在区域大尺度生物多样性保护方面更具有意义;同时也表明该方法在中国的应用前景广阔。     

A new method for conservation planning for the persistence of multiple species

Although the aim of conservation planning is the persistence of biodiversity, current methods trade-off ecological realism at a species level in favour of including multiple species and landscape features. For conservation planning to be relevant, the impact of landscape configuration on population processes and the viability of species needs to be considered. We present a novel method for selecting reserve systems that maximize persistence across multiple species, subject to a conservation budget. We use a spatially explicit metapopulation model to estimate extinction risk, a function of the ecology of the species and the amount, quality and configuration of habitat. We compare our new method with more traditional, area-based reserve selection methods, using a ten-species case study, and find that the expected loss of species is reduced 20-fold. Unlike previous methods, we avoid designating arbitrary weightings between reserve size and configuration; rather, our method is based on population processes and is grounded in ecological theory.     

Integrating multiple data sources for assessing blue whale abundance and distribution in Chilean Northern Patagonia

Aim

Species distribution models are useful tools for depicting important habitat, assessing abundance and orienting conservation efforts. For small populations in poorly studied ecosystems, available data are often scarce and patchy. To overcome this limitation, we aim to evaluate the use of different data types within a hierarchical Bayesian framework with the goal of modelling the abundance and distribution of a small and highly migratory population of blue whale (BW, Balaenoptera musculus) summering in Chilean Northern Patagonian (CNP).

Location

CNP, Eastern South Pacific (ESP).

Methods

We constructed a Bayesian hierarchical species distribution Model (HSDM), combining a binomial N‐mixture model used to model BW groups counts in line‐transect data (2009, 2012 and 2014) with a logistic regression for modelling presence‐availability data (2009–2016), allowing both models to share covariate parameters for borrowing strength in estimations.

Results

Distance to areas of high chlorophyll‐a concentration during spring before summering season (AHCC‐s) was the most important and consistent explanatory variable for assessing BW abundance and distribution in CNP. Incorporating accessorial presence‐only data reduced uncertainty in parameters estimation when comparing with a model using only line‐transect data, although other covariates of secondary importance failed to be retained in this model.

Main conclusions

Our results remark the capability of HSDM for integrating different data types providing a potential powerful tool when data are limited and heterogeneous. Results indicate that AHCC‐s, and possibly thermal fronts, could modulate BW abundance and distribution patterns in CNP. Preliminary model‐based delimitations of possible priority conservation areas for BW in CNP overlap with highly used vessel navigation routes and areas destined to aquaculture.