SHOREBIRD HABITAT USE AND NEST-SITE SELECTION IN THE PLAYA LAKES REGION

Abstract: Wetlands in the Playa Lakes Region (PLR) provide important habitats for wintering waterfowl, cranes, and both migrant and breeding shorebirds. Playa Lakes Region wetlands experience naturally fluctuating hydroperiods but are exposed to anthropogenic stresses, which are exacerbated during summer and may influence PLR wetland occupancy and selection by breeding shorebirds. We examined wetland-scale habitat use and nest-site selection of the 4 dominant shorebirds (American avocets [Recurvirostra americana], black-necked stilts [Himantopus mexicanus], killdeer [Charadrius vociferus], snowy plovers [C. alexandrinus]) nesting in playas, saline lakes, and in both created and riparian wetlands in the PLR of Texas, USA. All 4 species nested in saline lakes. Only avocets and killdeer nested in playas, and snowy plovers nested in riparian wetlands. No nests were found in created wetlands. Wetland habitat changed (P < 0.001) during the breeding season, while water habitats generally decreased. Used (i.e., shorebirds found nesting) wetlands had more (P < 0.05) mudflats than non-used (i.e., shorebirds not found nesting) wetlands, which had more (P < 0.05) dry habitats. Used and non-used wetlands had similar (P > 0.05) amounts of water habitats. Nests were located close to vegetation on bare dry ground and dry ground with vegetation. Because water is ephemeral in PLR wetlands, shorebirds must select—in a somewhat predictive manner upon arrival—wetlands with suitable nest-site and brood-rearing habitat. Although surface water is necessary for nesting, its presence is not adequate for delineating suitable PLR wetland habitat for breeding shorebirds. Our findings that created wetlands cannot compensate for regional wetland losses in habitat or function highlights the need for conservation of natural PLR wetlands     

Detecting soil and plant community changes in restored wetlands using a chronosequence approach

Wetland restoration aims to recreate or enhance valuable ecosystem services lost during wetland destruction. Regaining wetland ecosystem services depends on restarting basic wetland functions, like carbon (C) storage, which are unmeasured in many Wetlands Reserve Program (WRP) restoration sites. We collected soil and plant data from 17 WRP sites in western New York that were used for tillage or non-tillage agriculture and then actively restored as isolated depressional wetlands by excavating basins and disabling drainage systems. Sites had been restored for 0–15 years when sampled in August-October 2010. We analyzed data as chronosequences and tested whether soil and vegetation parameters in restored wetlands, over time, (1) departed from pre-restoration baselines, estimated using active agricultural fields paired to each WRP site, and (2) converged towards “natural” benchmarks, estimated from four naturally-occurring wetlands. Restored WRP soils remained similar to agricultural soils in organic matter, density, moisture, and belowground plant biomass across chronosequences, indicating negligible C storage and belowground development for 15 years following restoration. Soil changes were limited in sites restored after both tillage and non-tillage agriculture and throughout the upland meadow, emergent shoreline, and open-water habitat zones that characterize these sites. Many plant metrics like aboveground biomass matched natural wetlands within 15 years, but recovered inconsistently among tilled and untilled sites and across all habitat zones, suggesting land-use history impacts and/or zonation effects. Disparities in recovery times exists between vegetation, which can respond quickly to wetland restoration, and underlying soils, which show limited signs of recovery 15 years after being restored.     

Conservation prioritization through combined approach of umbrella species selection,occupancy estimation,habitat suitability and connectivity analysis of kingfisher: A study from an internationally important wetland complex (Ramsar site) in India

Assessment of occupancy status, as well as projection of suitable habitats and connectivity of wetland indicator species, and thereby identification of potential conservation umbrella and projection of conservation priority areas are often considered important for wetland conservation. Kingfishers are wetland indicators and suffer from habitat degradation due to world-wide destruction of wetlands. Therefore, they can be considered potential candidates for conservation intervention. The present knowledge about the spatial distribution of suitable areas and habitat connectivity of kingfishers at a landscape level is non-existent. We conducted extensive surveys and recorded four kingfisher species in East Kolkata Wetlands (EKW; Ramsar site No. 1208; ∼125 km²). The occupancy estimates were highest for White-throated kingfisher (Halcyon smyrnensis, WTK), followed by common kingfisher (Alcedo atthis, CK), stork-billed kingfisher (Pelargopsis capensis, SBK) and lowest for pied kingfisher (Ceryle rudis, PK). WTK has the highest amount of suitable areas followed by CK, PK and SBK. The spatial overlap of suitable habitats showed that SBK is the potential umbrella species and therefore provides conservation benefits to other kingfisher species and eventually to the EKW. In addition to water areas, emergent vegetation, crop lands and tree cover are other important habitats for kingfishers. The connectivity analyses revealed that suitable habitats were disjunct and are under various anthropogenic threats. Therefore, we need to protect suitable habitats and connectivity between them. Finally, we identified conservation priority areas. Conservation intervention on these high priority zones will not only be beneficial for kingfishers, but also for other avifauna having similar resource requirements as well as the wetland parse.     

Black tern (<Emphasis Type="Italic">Chlidonias niger</Emphasis>) breeding site abandonment in U.S. Great Lakes coastal wetlands is predicted by historical abundance and patterns of emergent vegetation

Breeding colonies of black terns (Chlidonias niger) have become increasingly rare in U.S. Great Lakes coastal wetlands since the mid-twentieth century, with an almost 90% decline in the number of active colony sites since 1991. Although the specific causes of this wetland species’ decline are unknown, habitat loss and degradation are thought to be a major barrier to conservation. Using data from the Great Lakes Colonial Waterbird Survey, we took a unique regional and historical approach to investigate the relationship between black tern colony site abandonment and a suite of local and landscape-scale habitat features in U.S. Great Lakes coastal wetlands. We employed logistic regression models and a combination of stepwise selection procedures to identify the best predictive model for black tern colony abandonment. According to the selected model, breeding colonies with fewer nests were more likely to be abandoned over the following decadal observation period than breeding colonies with more nests. Colony sites were also more likely to be abandoned when vegetation within the wetland shifted towards larger, denser clusters. We performed a simulation study that showed that failing to account for association between observations from the same site affected model selection results, but that cross-validation error for the selected model remained low unless site effects were very strong. Results of this study suggest that focus on protection of sites harboring large numbers of black terns and vegetation management will help limit further colony abandonments.     

Occupancy Patterns of Breeding American Black Ducks

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. © 2019 The Wildlife Society.     

Integrating aspects of ecology and predictive modelling: implications for the conservation of the leopard cat (Prionailurus bengalensis) in the Eastern Himalaya

An understanding of species ecology is vital for effective conservation, particularly if the species forms an important constituent of the lesser mammal guild and regulates small mammal and bird populations. As the ecological role of the leopard cat (Prionailurus bengalensis) in the intricate eastern Himalayan habitats is not known, we assessed the site occupancy, detection probability and activity pattern of leopard cats in Khangchendzonga Biosphere Reserve, India, based on sign surveys and camera trapping. The estimated site occupancy was 0.352?±?0.061 and detection probability was 0.143?±?0.0484. Occupancy modelling indicated low elevation, high rodent abundance and tree cover as best predictors for the occupancy of leopard cat. Diet based on analysed scats revealed murids as the most dominant prey (89.2 %). Information based on photographic captures indicated that the leopard cat exhibited a nocturnal activity pattern (peak activity between 0200–0300 hours), which coincided with its principal prey (revealed through diet analysis), but mainly contradicted with other sympatric competitors, hence indicating a temporal partitioning of resources among them. Ecological niche factor analysis indicated that the leopard cat exhibits high global marginality (1.32) and low global tolerance (0.275). The habitat suitability map for leopard cats showed majority of the habitat as unsuitable (1,959.44 km²) and predicted only 164.54 km² areas of lower temperate forests as moderate to highly suitable. As highly suitable habitats of the leopard cat are in close proximity to villages, conflict issues are a major threat and therefore need to be addressed in conservation program for this felid.     

Identifying the ecological causes of long-term declines of wetland-dependent birds in an urbanizing landscape

Many wetland-dependent birds are thought to be experiencing significant population declines, although population trend data for this suite of birds are rare and the causes of declines poorly understood. We used a 26-year dataset (1980–2005) of wetland bird abundance and distribution among 196 wetlands in northeastern Illinois (i.e., Chicago and its suburbs) to evaluate population trends and identify underlying ecological causes. We used aerial photography and GIS to quantify wetland habitat structure (i.e., the extent of emergent vegetation) and changes in surrounding land use. We then evaluated how changes in land use affected the structure of wetlands and ultimately wetland bird populations. Of the 12 species analyzed, seven experienced significant declines, three showed non-significant declines, and two experienced significant increases. Population declines could not be attributed to wetland loss because none of our wetlands were destroyed. Concurrent research at these wetlands also suggests that neither low adult survival nor poor reproductive success were responsible for the declines. Increased development within 2 km of wetlands, however, was associated with extreme changes in the structure of wetlands. Wetlands tended either to lose much of their vegetation and become open ponds, or become rank stands of dense vegetation. Both changes made wetlands less suitable for many wetland birds. While “no net loss” legislation may protect wetlands from being filled or drained, development near wetlands appears to be altering hydrology, resulting in habitat degradation and population declines of several wetland-dependent bird species.     

2010-2019年不同海湾迁徙水鸟栖息地适宜性变化对比研究

滨海湿地是迁徙水鸟的重要迁飞通道和主要栖息地,评估沿海迁徙水鸟栖息地适宜性及变化态势能为栖息地的合理规划与管理提供科学参考,对迁徙水鸟的保护有重要意义。选择紧邻城市和乡村的深圳湾和雷州湾为研究区,在水鸟栖息地生态系统类型分类的基础上,通过层次分析法确定水鸟栖息地适宜性评价因子,设计栖息地、食物、水分、人类干扰条件及其子类的权重,对栖息地适宜性进行等级划分,分析比较2010-2019年迁徙水鸟栖息地适宜性的时空分布差异,探索适宜性变化差异的原因并给出合理化建议。结果表明：（1）2010-2019年深圳湾有193.4 hm²强干扰区域转变化为中等及弱干扰;雷州湾有16.36 hm²的中等干扰转化为弱、无干扰;（2）深圳湾栖息地适宜性以中等适宜类型为主,2010年和2019年面积占比分别为83.74%和88.71%;雷州湾栖息地适宜性主要以较适宜和中等适宜类型为主,2010年面积占比为86.72%,2010-2019年面积占比基本不变,总体适宜性高于深圳湾。（3）2010-2019年,深圳湾不适宜和较适宜面积分别减少245.54 hm²和26.37 hm²,均转化为中等适宜类型;雷州湾有24.31 hm²的中等和较适宜栖息地转化为适宜类型。     

Selection of nest-site habitat by interior least terns in relation to sandbar construction

Federally endangered interior least terns (Sternula antillarum) nest on bare or sparsely vegetated sandbars on midcontinent river systems. Loss of nesting habitat has been implicated as a cause of population declines, and managing these habitats is a major initiative in population recovery. One such initiative involves construction of mid-channel sandbars on the Missouri River, where natural sandbar habitat has declined in quantity and quality since the late 1990s. We evaluated nest-site habitat selection by least terns on constructed and natural sandbars by comparing vegetation, substrate, and debris variables at nest sites (n = 798) and random points (n = 1,113) in bare or sparsely vegetated habitats. Our logistic regression models revealed that a broader suite of habitat features was important in nest-site selection on constructed than on natural sandbars. Odds ratios for habitat variables indicated that avoidance of habitat features was the dominant nest-site selection process on both sandbar types, with nesting terns being attracted to nest-site habitat features (gravel and debris) and avoiding vegetation only on constructed sandbars, and avoiding silt and leaf litter on both sandbar types. Despite the seemingly uniform nature of these habitats, our results suggest that a complex suite of habitat features influences nest-site choice by least terns. However, nest-site selection in this social, colonially nesting species may be influenced by other factors, including spatial arrangement of bare sand habitat, proximity to other least terns, and prior habitat occupancy by piping plovers (Charadrius melodus). We found that nest-site selection was sensitive to subtle variation in habitat features, suggesting that rigor in maintaining habitat condition will be necessary in managing sandbars for the benefit of least terns. Further, management strategies that reduce habitat features that are avoided by least terns may be the most beneficial to nesting least terns. © 2011 The Wildlife Society.     

辽河三角洲滨海湿地景观规划各预案对指示物种生境适宜性的影响

运用景观生态决策与评价支持系统（LEDESS）对辽河三角洲的3个景观规划预案,即湿地调整,生境管理和农业开发可能导致的地表覆盖物,自然生态单元等立地环境以及保护物种生境适宜性等区域生态后果进行了评估,并与现状进行了对比,模拟结果表明,预案A通过湿地调整措施不仅补偿了芦苇湿地的损失,还将部分不适宜生境和边境生境转变核心生境,相当程度上优化了保护物种丹顶鹤和黑嘴鸥的生境质量,预案B通过一系列生境管理措施,减轻了生境破碎化因素的影响,从而也显著改善了丹顶鹤生境质量,对黑嘴鸥生境质量也有一定改善,预宁C大规模农业开发如能控制一定规模（8000hm2)并采取一定合理模式（滚动开发）,能相当程度上减轻农业开发对物种生境的影响,即使不采取生境补偿措施,对丹顶鹤,黑嘴鸥核心生境也不会有破坏性的影响,模拟结果还表明,区域人类活动导致的生境破碎化是对丹顶鹤生境质量重要的干扰因子,而滩涂农业开发和水产养殖强烈地干扰了涂植被正常的演替过程,从而影响着黑嘴鸥等滩涂鸟类的生境适宜性。     

Habitat and History Influence Abundance of Bog Turtles

Conservation of rare and endangered species requires assessment of factors that influence the current habitat associations of a species and the role of past habitat degradation in limiting occupancy or abundance. The objective of our 2011–2014 study was to determine how habitat characteristics and wetland history can predict occupancy and abundance patterns of bog turtles (Glyptemys muhlenbergii) at the fringe of their range in the southeastern United States. We used a hurdle model to examine occupancy and abundance patterns while addressing problems associated with zero-inflated data. Occupancy patterns were weakly related to percent of the wetland containing emergent vegetation, whereas abundance patterns were predicted by the percent silt in the wetland substrate, percent forest cover, amount of habitat degradation, and recovery time since past habitat degradation. The effect of historical habitat degradation on abundance rather than occupancy patterns has rarely been documented and its effect is rarely studied in vertebrate populations. Identification of predictors of occupancy and abundance patterns will aid discovery of new populations of bog turtles and improve management of occupied wetlands. © 2019 The Wildlife Society.     

Use of Restored Riparian Habitat by the Endangered Least Bell's Vireo (Vireo bellii pusillus)

A primary objective of riparian restoration in California is the creation of habitat for endangered species. Four restoration sites in San Diego County were monitored between 1989 and 1993 and evaluated for their suitability as nesting habitat for Vireo bellii pusillus (Least Bell's Vireo), a state and federally endangered obligate riparian breeder. Vegetation structure at each site was quantified annually and compared to a model of canopy architecture derived from Least Bell's Vireo territories in natural habitat. Vireo use of restored habitat was documented through systematic surveys and nest monitoring. By 1993, only one site in its entirety met the habitat suitability criteria of the model, but portions of each site during all years did so. Differences between sites in the time required to develop suitable habitat—well-developed layered vegetation from the ground to under 8m in height)—were attributable largely to variation in annual rainfall. Vireos visited restoration sites to forage as early as the first growing season, but they did not establish territories or nest there until at least part of the site supported suitable habitat as determined from the model. Placement of territories and nests coincided with patches of dense vegetation characteristic of natural nesting areas. Occupation of restored sites was accelerated by the presence of adjacent mature riparian habitat, which afforded birds nest sites and/or foraging habitat lacking in the planted vegetation. Vireos nesting in restored habitat achieved success comparable to that of vireos nesting in surrounding natural habitat, and there was no evidence that productivity was reduced in created areas. These findings indicate that creating nesting habitat for this target species is feasible and suggest that the critical components of vireo nesting habitat have been captured in both the design and quantitative assessment of restoration sites.     

A geospatial assessment on the distribution,condition, and vulnerability of Wyoming's wetlands

Wetlands serve critical functions including natural flood control and providing wildlife habitat, yet despite these values they remain highly threatened systems. Here we present a landscape-scale geospatial assessment of wetlands in Wyoming. Areas containing high densities of wetlands were identified and mapped, and wetland complexes were quantified as a function of their biological diversity, protection status, susceptibility to climate change, and proximity to sources of impairment. Our results indicate there are 280591 wetlands in Wyoming, totaling 371758 surface hectares, and 222 wetland complexes. The majority (67%) of wetlands are classified as temporary. Low elevation wetland complexes are the least protected, in the poorest current condition, and the most vulnerable to future land use changes. This fundamental information will provide a tool decision-makers can use to more effectively allocate limited resources to conserve, manage, and restore Wyoming's wetlands.     

Predicting changes in the abundance of African wetland birds by incorporating abundance–occupancy relationships into habitat association models

Aim To map changes in the abundance of African wetland birds using remotely derived habitat data. We show that abundance–occupancy relationships can be coupled with habitat association models to map changes in abundance. As conservation resources are more easily allocated when spatial and temporal patterns of abundance are known, our method provides guidance for conservation planning. Location Papyrus, Cyperus papyrus, swamps in east central Africa. Methods Presence/absence surveys of six bird species in 93 wetlands were used to construct models predicting probability of occurrence from habitat characteristics. Densities were then determined from surveys in 23 additional wetlands and modelled as functions of occurrence probability. We then used satellite imagery to derive habitat characteristics remotely in two time periods (1984–87 and 2000–03) and used the modelled relationships between (1) habitat and occupancy and (2) occupancy and density, to infer changes in abundance in all c. 30,000 wetlands within the study area. Results Wetlands within the region declined by 8.6% between the two time periods, but by > 75% in regions of high human population density. Bird densities were also highest in these regions, which comprised wetlands subject to high levels of disturbance. The geographical coincidence of high densities and habitat loss and the existence of positive associations between bird density and occurrence meant that birds declined by much more than the average rate of their habitat. Main conclusions Targeting conservation efforts in areas with high drainage would protect a high proportion of the bird populations. Encouraging people to derive income from disturbance to which the birds are tolerant, rather than drainage, is likely to be an effective strategy. Because habitat characteristics are a key driver of abundance–occupancy relationships, we conclude that there is wide‐scale scope to couple abundance–occupancy relationships with remote habitat mapping to efficiently inform conservation planning.     

Agro-climatic zoning of Jatropha curcas as a subside for crop planning and implementation in Brazil

As jatropha (Jatropha curcas L.) is a recent crop in Brazil, the studies for defining its suitability for different regions are not yet available, even considering the promises about this plant as of high potential for marginal zones where poor soils and dry climate occur. Based on that, the present study had as objective to characterize the climatic conditions of jatropha’s center of origin in Central America for establishing its climatic requirements and to develop the agro-climatic zoning for this crop for some Brazilian regions where, according to the literature, it would be suitable. For classifying the climatic conditions of the jatropha’s center of origin, climate data from 123 weather stations located in Mexico (93) and in Guatemala (30) were used. These data were input for Thornthwaite and Mather’s climatological water balance for determining the annual water deficiency (WD) and water surplus (WS) of each location, considering a soil water-holding capacity (SWHC) of 100 mm. Mean annual temperature (T _m), WD, and WS data were organized in histograms for defining the limits of suitability for jatropha cultivation. The results showed that the suitable range of T _m for jatropha cultivation is between 23 and 27 °C. T _m between 15 and 22.9 °C and between 27.1 and 28 °C were classified as marginal by thermal deficiency and excess, respectively. T _m below 15 °C and above 28 °C were considered as unsuitable for jatropha cultivation, respectively, by risk of frosts and physiological disturbs. For WD, suitability for rain-fed jatropha cultivation was considered when its value is below 360 mm, while between 361 and 720 mm is considered as marginal and over 720 mm unsuitable. The same order of suitability was also defined for WS, with the following limits: suitable for WS up to 1,200 mm; marginal for WS between 1,201 and 2,400 mm, and unsuitable for WS above 2,400 mm. For the crop zoning, the criteria previously defined were applied to 1,814 climate stations in the following Brazilian regions: Northeast (NE) region and the states of Goiás (GO), Tocantins (TO), and Minas Gerais (MG). The suitability maps were generated by crossing the crop climate requirements with the interpolated climate conditions of the selected regions. The maps showed that only 22.65 % of the areas in the NE region are suitable for jatropha as a rain-fed crop. The other areas of the region are classified as marginal (62.61 %) and unsuitable (14.74 %). In the states of GO and TO, the majority of the areas (47.78 %) is classified as suitable, and in the state of MG, 33.92 % of the territory has suitability for the crop. These results prove that jatropha cannot be cultivated everywhere and will require, as any other crop, minimum climatic conditions to have sustainable performance and high yields.     

Mapping ephemeral wetlands: manual digitisation and logistic regression modelling in Nelson Mandela Bay Municipality,South Africa

Until recently, little research has been conducted on the distribution and structure of ephemeral systems in semi-arid areas. This information is critical for appropriate wetland management and conservation. The Nelson Mandela Bay Municipality is a semi-arid area along the south-eastern coastline of the Eastern Cape Province of South Africa. The Municipality encapsulates a wide range of geological and geomorphological features as well as vegetation types within an area of some 1950 km², providing an ideal area for such research. The distribution and abundance of wetlands were defined, and a logistic regression (LR) model was used to establish whether this modelling technique is viable in semi-arid areas with highly variable rainfall patterns. Wetlands were delineated manually using geographical information systems, high-resolution aerial photographs and environmental data. More than 1700 wetland polygons were identified, with 80% of the systems being categorised as depressions, seeps and wetland flats. Unchannelled (8%) and channelled (7%) valley bottom wetlands and floodplain wetlands (5%) were also identified. The wetland database was then used to create a wetland occurrence probability model. There were 19 environmental variables used to develop the LR model, with eight variables used in the final model output. The predictive capacity of the model was good, with an area under curve value of 0.68 and an overall accuracy of 66%. This indicates that probabilistic wetland models are useful in highly variable environments with high numbers of small (<1 ha) wetlands. Such predictive models provide a tool to assist in improving the accuracy of land cover datasets in semi-arid areas, and can be used to inform management decisions on flood risk areas and key conservation zones. In addition, abiotic variables that are significant in the model output provide an indication of the factors influencing wetland functioning in the region.     

Breeding dispersal in a heterogeneous landscape: the influence of habitat and nesting success in greater snow geese

Despite numerous studies on breeding dispersal, it is still unclear how habitat heterogeneity and previous nesting success interact to determine nest-site fidelity at various spatial scales. In this context, we investigated factors affecting breeding dispersal in greater snow geese (Anser caerulescens atlanticus), an Arctic breeding species nesting in two contrasting habitats (wetlands and mesic tundra) with variable pattern of snowmelt at the time of settlement in spring. From 1994 to 2005, we monitored the nesting success and breeding dispersal of individually marked females. We found that snow geese showed a moderate amount of nest-site fidelity and considerable individual variability in dispersal distance over consecutive nesting attempts. This variability can be partly accounted for by the annual timing of snowmelt. Despite this environmental constraint, habitat differences at the colony level consistently affected nesting success and settlement patterns. Females nesting in wetlands had higher nesting success than those nesting in mesic tundra. Moreover, geese responded adaptively to spatial heterogeneity by showing fidelity to their nesting habitat, independently of snowmelt pattern. From year to year, geese were more likely to move from mesic to high-quality wetland habitat, regardless of previous nesting success and without cost on their subsequent nesting performance. The unpredictability of snowmelt and the low cost of changing site apparently favour breeding-site dispersal although habitat quality promotes fidelity at the scale of habitat patches.     

Distribution and Habitat Use of King Rails in the Illinois and Upper Mississippi River Valleys

ABSTRACT The migratory population of the king rail (Rallus elegans) has declined dramatically during the past 40 years, emphasizing the need to identify habitat requirements of this species to help guide conservation efforts. To assess distribution and habitat use of king rails along the Illinois and Upper Mississippi valleys, USA, we conducted repeated call-broadcast surveys at 83 locations in 2006 and 114 locations in 2007 distributed among 21 study sites. We detected king rails at 12 survey locations in 2006 and 14 locations in 2007, illustrating the limited distribution of king rails in this region. We found king rails concentrated at Clarence Cannon National Wildlife Refuge, an adjacent private Wetlands Reserve program site, and B. K. Leach Conservation Area, which were located in the Mississippi River floodplain in northeast Missouri. Using Program PRESENCE, we estimated detection probabilities and built models to identify habitat covariates that were important in king rail site occupancy. Habitat covariates included percentage of cover by tall (>1 m) and short (>1 m) emergent vegetation, percentage of cover of woody vegetation, and interspersion of water and vegetation (2007 only) within 50 m of the survey location. Detection probability was 0.43 (SE = 0.12) in 2006 and 0.35 (SE = 0.03) in 2007 and was influenced by observer identity and percentage of cover by tall herbaceous vegetation. Site occupancy was 0.11 (SE = 0.04) in 2006 and 0.14 (SE = 0.04) in 2007 and was negatively influenced most by percentage of cover by woody vegetation. In addition, we found that interspersion of vegetation and water was positively related to occupancy in 2007. Thus, nesting king rails used wetlands that were characterized by high water-vegetation interspersion and little or no cover by woody vegetation. Our results suggest that biologists can improve king rail habitat by implementing management techniques that reduce woody cover and increase vegetation-water interspersion in wetlands.     

Colonisation by Dreissena of Great Lakes coastal ecosystems: how suitable are wetlands?

1.  Invasive zebra ( Dreissena polymorpha ) and quagga mussels ( Dreissena bugensis ) have become widespread throughout the Great Lakes basin. However, some types of Great Lakes coastal wetlands may be unsuitable for Dreissena invasion.
2.  To test this observation, artificial substrata were placed in wetlands (with emergent vegetation) and in adjacent open water (without emergent vegetation) habitats in two types of Great Lakes coastal ecosystems: drowned river mouth (DRM) and coastal fringing systems. Wetlands in DRM systems generally have deep organic sediment and limited water movement, whereas coastal fringing wetlands generally have low to moderate amounts of organic sediment and intense wind and wave action.
3.  We did not find a significant difference in Dreissena colonisation between wetlands and adjacent open water habitat in fringing systems. However, Dreissena colonisation was significantly lower in DRM wetlands than in the adjacent open water. We also found significantly lower survival in DRM wetlands than adjacent open water habitats, whereas survival did not differ significantly in coastal fringing wetlands and the adjacent open water.
4.  Our results suggest that vulnerability to Dreissena invasion varied among wetland types with DRM wetlands being less suitable than fringing wetlands. We suggest that colonisation and survival of Dreissena is lower in wetlands with deep organic sediment and less turbulent water.