Comparative detection,density, and reproductive performance of Kirtland's warbler in jack and red pine

The formerly endangered Kirtland's warbler (Setophaga kirtlandii) is among a growing number of conservation-reliant species that depend on active management to avoid reverting to endangered status. Because the Kirtland's warbler is a habitat specialist of young, even-aged jack pine (Pinus banksiana), managers of the recovery effort stressed creating new jack pine stands and monitoring numbers of singing males through an annual census using single visits to individual stands. Kirtland's warbler will occupy and breed in red pine (P. resinosa), but red pine has not been surveyed for Kirtland's warblers in the annual population census. Furthermore, the current monitoring approach cannot determine their species detection probability or individual detection probability, which is essential to evaluate both red pine use and the accuracy of the census. From 2016–2018 we estimated density and detection probabilities in jack pine and red pine stands through repeated visits to a limited number of stands rather than single visits to many stands. Estimates of species detection probability indicated that ≥1 male Kirtland's warbler would be detected on most sites when any were present, but individual detection probabilities were less and varied by stand type, indicating that single visits to sites would underestimate numbers and that accurate estimation of detection probability was important for estimation of density in different stand types. We offer quantitative estimates of detection probabilities for determination of Kirtland's warbler population size in jack pine versus red pine stands in the same areas and breeding seasons. Managers of Kirtland's warblers should incorporate detection probabilities into population surveys to achieve more accurate estimates of population size.     

Characteristics of the breeding habitat of Endangered Kirtland's Warblers on a Canadian Military Installation

Kirtland's Warblers (Setophaga kirtlandii) are an endangered species with specialized habitat requirements, and the only documented nesting location in Canada is an Army installation. From 2007 to 2010, I compared habitat characteristics of sites occupied and not occupied by Kirtland's Warblers at Garrison Petawawa located ～200 km northwest of Ottawa, Ontario. Sites occupied by Kirtland's Warblers (N = 11) had greater percent cover of low sweet blueberry (Vaccinium angustifolium; 31.2%), coral lichen (Cladina stellaris; 0.4%), reindeer lichen (Cladonia rangiferina; 8.3%), and wavy‐leaved moss (Dicranum polysetum; 4.3%) than unoccupied sites (N = 6). I found no difference in tree species composition between sites, with jack pine (Pinus banksiana), white pine (Pinus strobus), red pine (Pinus resinosa), poplar (Populus tremuloides), and red maple (Acer rubra) present in both used and unused sites. Forest stands occupied by Kirtland's Warblers were significantly younger (< 20 yr old) than unoccupied sites, and most occupied sites were within former fire zones and sites where jack pines had been planted. Thus, breeding habitat of Kirtland's Warblers in Canada consisted of young pine trees, with more red pine than in their breeding habitat in Michigan, and ground cover including blueberry, lichens, and mosses. These results suggest that Kirtland's Warblers may be less selective in their habitat requirements than previously thought, and should provide guidance for recovery groups and regulatory agencies in accurately delineating suitable habitat for these warblers in Canada.     

FOREST MANAGEMENT ALTERNATIVES AND SONGBIRD BREEDING HABITAT ON THE CHEROKEE NATIONAL FOREST,TENNESSEE

Abstract: We used a 60-yr forest simulation of the Cherokee National Forest, Tennessee, USA, to model the effects of timber harvest and natural disturbance upon habitat availability for 6 songbird species: Acadian flycatcher (Epidonax virescens), blue-headed vireo (Vireo solitarius), chestnut-sided warbler (Dendroica pensylvanica), tufted titmouse (Parus bicolor), yellow-billed cuckoo (Coccyzus americanus), and yellow-throated warbler (Dendroica dominica). Forest simulations, based on expected harvest intensities and historic levels of natural disturbance, were used to update a stand inventory database at 10-yr intervals between 1993 and 2053. Habitat models for the 6 bird species were applied to the updated stand inventory and available habitat quantified for each decade. Late-successional species showed substantial increases in habitat availability over the 60-yr period at most harvest intensities, whereas habitat for early-successional species was stable or declined at most harvest intensities. Acadian flycatcher, yellow-throated warbler, and blue-headed vireo habitat increased by 200%, 213%, and 40%, respectively, whereas tufted titmouse habitat remained relatively constant at expected harvest levels. Chestnut-sided warbler habitat was stable at expected harvest levels but declined at lower harvest intensities, and yellow-billed cuckoo habitat declined by 37% at expected harvest levels. Natural disturbance had little effect on habitat availability for any bird species compared to the effects of timber harvests and increasing forest age. Our models suggest that anthropogenic disturbance, and lack thereof, can play a definitive role determining habitat availability and population viability for forest songbirds.     

Initial Effects of Wildfire on Freshwater Turtle Nesting Habitat

Natural wildfire regimes are important for ecosystem succession but can have negative ecological effects depending on fire characteristics. A portion of a granite rock barrens landscape that extends along the eastern shoreline of Georgian Bay, Lake Huron to eastern Ontario, Canada, burned in 2018 during a wildfire that affected >11,000 ha. This landscape is a biodiversity hotspot providing habitat for many species at risk where freshwater turtles nest in soil deposits in cracks and crevices in the bedrock dominated by moss (Polytrichum spp.) and lichen (Cladonia spp.) cover. To assess the initial effect of wildfire on freshwater turtle nesting habitat, we measured soil depths and estimated moss, lichen, and vascular plant cover at 2 morphology types (crevice, flat) in burned and unburned areas of the landscape. The probability that burned flat plots supported soil was near zero; the burned flat plots had 98% less soil volume compared to unburned flat plots. Although crevices were more resistant to soil loss, burned crevices still had a 15% lower probability of having soil and 35% less soil volume compared to unburned crevice plots. We estimated nest site availability by calculating the number of locations with shallow (5–10 cm), intermediate (10–20 cm), and deep (>20 cm) soils required for a small (5 cm × 5 cm) or medium (10 cm × 10 cm) nest chamber. Overall, the burned open rock barrens had 71–73% fewer sites with suitable soil depth and volume for a nest chamber of either size. Furthermore, burned plots had almost no lichen and moss cover but were dominated by bare soil, forbs, and jack pine (Pinus banksiana) seedlings. Although the loss of tree cover in previously forested areas may increase nest site availability for freshwater turtles in newly open areas, we suggest that organic soil combustion and soil erosion may require restoration activities in the post-fire landscape to support successful nesting of at-risk turtles. © 2020 The Wildlife Society.     

Why Pine Barrens Restoration Should Favor Barrens Over Pine

Pine barrens include an assortment of pyrogenic plant communities occurring on glacial outwash or rocky outcrops scattered along the Atlantic coastal plain from New Jersey to Maine, and inward across New England, New York, Pennsylvania, and the northern Great Lakes region. At least historically, pine barrens provided some of the highest quality terrestrial shrublands and young forests in the eastern North American sub‐boreal and northern temperate region. However, the mosaic open‐canopy, sparse‐shrub, and grassland early successional state is generally lacking in contemporary pine barrens. Many sites in the northeastern United States have converted to overgrown scrub oak (Quercus ilicifolia, Quercus prinoides) thickets and closed canopied pitch pine (Pinus rigida)‐dominated forests. Thinning pitch pine is a contentious issue for the imperiled pitch pine‐scrub oak barrens community type (G2 Global Rarity Rank, 6–20 occurrences). Here we provide a historical, ecological, and resource management rationale for thinning pitch pine forest to restore savanna‐like open barrens with a mosaic of scrub oaks, heath shrubs, and prairie‐like vegetation. We postulate that the contemporary dominance of pitch pine forest is largely of recent anthropogenic origin, limits habitat opportunities for at‐risk shrubland fauna, and poses a serious wildfire hazard. We suggest maintaining pitch pine‐scrub oak barrens at 10–30% average pitch pine cover to simultaneously promote shrubland biodiversity and minimize fire danger.     

The northern limit of Pinus banksiana Lamb. in Canada: explaining the difference between the eastern and western distributions

Aim Present northern distribution limit of jack pine (Pinus banksiana Lamb.) follows the northern limit of continuous open boreal forest in western Canada, but not in eastern Canada where it is located further south. We tested the hypothesis that fire plays a more important role than climate in explaining the present position of the northern distribution limit of jack pine. Location An experimental jack pine plantation was set up in 1992, c. 300 km north of the present distribution limit of the species, in the Boniface river area of northern Québec (57°43′ N, 76°05′ W). Methods Climate and fire data were used to compare sites at and north of the present distribution limit of jack pine. In 2001, surviving individuals from the plantation were measured (total height, annual shoot elongation, basal diameter, and presence/absence of cones). Results Climate data from the ten weather stations used in this study did not show major differences. The northern limit of jack pine distribution is closely associated with the occurrence of fires larger than 200 ha. Survival of the planted jack pines was 31%. About 25% of the surviving pines qualified as normal, single‐stem individuals; the others were slightly uprooted and/or showed marks of erosion or foraging. Cones were produced, although no viable seeds were found. Main conclusions The low number of degree‐days above 5 °C at the plantation site could explain why the seeds were not viable. However, such climate conditions are not sufficient to prevent growth, as was shown by annual shoot elongation measurements. Most of the surviving jack pines from the Boniface river plantation are relatively healthy and follow a normal developmental programme. Low fire frequency and small fire size are amongst the main factors that prevented P. banksiana from migrating further north or east following deglaciation in northern Québec and Labrador.     

Width of riparian buffer and structure of adjacent plantations influence occupancy of conservation priority birds

Conservation of biodiversity on forest landscapes dominated by plantations has become an increasingly important topic, and opportunities to maintain or enhance biodiversity within these forests need to be recognized and applied. Riparian buffers of mature forest retained along streams in managed forest landscapes offer an opportunity to enhance biodiversity across these landscapes. However, influence of buffer width and structure of adjacent plantations on habitat use by birds is not well understood. We modeled probability of occupancy, while accounting for variable detection probabilities, for 16 bird species of regional conservation importance in the Ouachita Mountains of Arkansas, USA. We examined occurrence of breeding birds in streamside management zone (SMZ) buffers embedded in three structural classes of pine plantation: young open-canopy, closed-canopy, and older thinned plantations. Our occupancy models included a positive association with SMZ width for nine bird species associated with mature forests. Models for three early successional species (prairie warbler [Dendroica discolor], white-eyed vireo [Vireo griseus], and northern bobwhite [Colinus virginianus]) included a negative association with SMZ width. Occupancy models for Acadian flycatcher (Empidonax virescens), summer tanager (Piranga rubra), pine warbler (Dendroica pinus), prairie warbler, and northern bobwhite also included structural condition of adjacent plantations, but most species did not appear affected by condition of surrounding plantations. We found diverse responses among species to width of retained SMZs and structure of adjacent plantations; some species apparently benefitted from SMZs >100 m wide, while others benefitted from narrow buffers. Furthermore, most species traditionally associated with mature forests were common in narrow SMZs, regardless of width. Thus, optimal width of SMZs relative to avian conservation depends on the species of greatest conservation interest.     

Net ecosystem productivity of boreal jack pine stands regenerating from clearcutting under current and future climates

Life cycle analysis of climate and disturbance effects on forest net ecosystem productivity (NEP) is necessary to assess changes in forest carbon (C) stocks under current or future climates. Ecosystem models used in such assessments need to undergo well-constrained tests of their hypotheses for climate and disturbance effects on the processes that determine CO₂ exchange between forests and the atmosphere. We tested the ability of the model ecosys to simulate diurnal changes in CO₂ fluxes under changing air temperatures (T_a) and soil water contents during forest regeneration with eddy covariance measurements over boreal jack pine (Pinus banksiana) stands along a postclearcut chronosequence. Model hypotheses for hydraulic and nutrient constraints on CO₂ fixation allowed ecosys to simulate the recovery of C cycling during the transition of boreal jack pine stands from C sources following clearcutting (NEP from −150 to −200 g C m⁻² yr⁻¹) to C sinks at maturity (NEP from 20 to 80 g C m⁻² yr⁻¹) with large interannual variability. Over a 126-year logging cycle, annualized NEP, C harvest, and net biome productivity (NBP=NEP–harvest removals) of boreal jack pine averaged 47, 33 and 14 g C m⁻² yr⁻¹. Under an IPCC SRES climate change scenario, rising T_a exacerbated hydraulic constraints that adversely affected NEP of boreal jack pine after 75 years. These adverse effects were avoided in the model by replacing the boreal jack pine ecotype with one adapted to warmer T_a. This replacement raised annualized NEP, C harvest, and NBP to 81, 56 and 25 g C m⁻² yr⁻¹ during a 126-year logging cycle under the same climate change scenario.     

Large forests enhance songbird nesting success in agricultural‐ dominated landscapes of the Midwestern US

We studied the effects of habitat composition and distance from edges on nesting success and brood parasitism of forest birds in the Kaskaskia River Bottoms, one of the largest remaining tracts of floodplain forest in the agricultural Midwestern United States. Our goal was to help the private landowners, who have maintained this region in forest cover, enhance the value of these forests for nesting birds. We measured nest predation rates and levels of brood parasitism of four species, the indigo bunting Passerina cyanea, Acadian flycatcher Empidonax virescens, northern cardinal Cardinalis cardinalis and prothonotary warbler Protonotaria citrea in relation to distances from natural and anthropogenic edges and proportion of natural and anthropogenic habitats within fixed radii around nests. We predicted that nesting success would increase with increasing distance from anthropogenic habitats and with increasing land cover in natural habitats. Our results showed no strong effect of any of these variables on avian nesting success, although parasitism levels increased slightly with increasing proportion of agricultural land around nests for two of the species. Nevertheless, nesting success for at least three of these species was much higher than in more fragmented forest tracts elsewhere in the agricultural Midwest where most forest tracts appear to be population sinks for most species. These results suggest that forest tracts in the Kaskaskia may be saturated with nest predators and brood parasites, but are not super‐saturated in a way that would cause these tracts to become ‘black hole’ population sinks. Our data further suggest that, as long as landowners maintain their private landholdings in forest cover, the details of how they manage their land may have little effect on songbird nesting success. These results also suggest that reforestation efforts in areas with many openings may still benefit forest birds.     

Accelerated soil CO<Subscript>2</Subscript> efflux after conversion from secondary oak forest to pine plantation in southeastern China

Soil respiration (R _s) is an important component of the carbon cycle in terrestrial ecosystems, and changes in soil respiration with land cover alteration can have important implications for regional carbon balances. In southeastern China (Xiashu Experimental Forest, Jiangsu Province), we used an automated LI-8100 soil CO₂ flux system to quantify diurnal variation of soil respiration in a secondary oak forest and a pine plantation. We found that soil respiration in the pine plantation was significantly higher than that in the secondary oak forest. There were similar patterns of soil respiration throughout the day in both the secondary oak forest and the pine plantation during our 7-month study (March–September 2005). The maximum of R _s occurred between 4:00 pm and 7:00 pm. The diurnal variations of R _s were usually out of phase with soil surface (0.5 cm) temperature (T _g). However, annual variation in R _s correlated with surface soil temperature. Soil respiration reached to a maximum in June, and decreased thereafter. The Q₁₀ of R _s in the secondary oak forest was significantly higher than that in the pine plantation. The higher Q₁₀ value in the secondary oak forest implied that it might release more CO₂ than the pine plantation under a global-warming scenario. Our results indicated that land-use change from secondary forest to plantation may cause a significant increase in CO₂ emission, and reduce the temperature sensitivity of soil respiration in southeastern China.     

Relevance of exotic pine plantations as a surrogate habitat for ground beetles (Carabidae) where native forest is rare

Plantation forests are of increasing importance worldwide for wood and fibre production, and in some areas they are the only forest cover. Here we investigate the potential role of exotic plantations in supporting native forest-dwelling carabid beetles in regions that have experienced extensive deforestation. On the Canterbury Plains of New Zealand, more than 99% of the previous native forest cover has been lost, and today exotic pine (Pinus radiata) plantations are the only forest habitat of substantial area. Carabids were caught with pitfall traps in native kanuka (Kunzea ericoides) forest remnants and in a neighbouring pine plantation, grassland and gorse (Ulex europaeus) shrubland. A total of 2,700 individuals were caught, with significantly greater abundance in traps in young pine, grassland and gorse habitats than in kanuka and older pine. Rarefied species richness was greatest in kanuka, a habitat that supported two forest specialist species not present in other habitat types. A critically endangered species was found only in the exotic plantation forest, which also acts as a surrogate habitat for most carabids associated with kanuka forest. The few remaining native forest patches are of critical importance to conservation on the Canterbury Plains, but in the absence of larger native forest areas plantation forests are more valuable for carabid conservation than the exotic grassland that dominates the region.     

Short-term Effects of Harvest Technique and Mechanical Site Preparation on Arthropod Communities in Jack Pine Plantations

Arthropods play a key role in the functioning of forest ecosystems and contribute to biological diversity. However, the influence of current silvicultural practices on arthropod communities is little known in jack pine (Pinus banksiana) forests, a forest type comprising a major portion of the Canadian boreal forest. In this study, the effects of silvicultural treatments on arthropod communities were compared to identify those treatments that minimize ecological impacts on arthropods. The influence of harvesting techniques and mechanical site preparations on insect family richness and abundance of arthropods (total, by orders and by trophic groups) was examined in young (three-year-old) jack pine plantations of northern Ontario. Each of the following treatments were conducted in three plots: (1) tree length harvest and trenching; (2) full tree harvest and trenching; (3) full tree harvest and blading; and (4) full tree harvest and no site preparation. Arthropods were collected using sweepnets and pitfall traps over two years. Blading significantly reduced insect family richness, the total abundance of arthropods, abundance of Orthoptera, Heteroptera, Hymenoptera, Diptera, insect larvae, and plant feeders when compared to the other treatments. The use of either full tree or tree length harvesting had similar short-term effects on family richness and the abundance of arthropods. Arthropod diversity declined with increasing post-harvest site disturbance. These results suggest that arthropod communities in the understory and on the ground are reduced most on sites mechanically prepared by blading, but are similar under conditions immediately following either full tree or tree length harvesting. The implications for regenerating jack pine in the boreal forest are discussed.     

Simulated long‐term effects of harvest and biomass residue removal on soil carbon and nitrogen content and productivity for two Upper Great Lakes forest ecosystems

We used the ecosystem process model Biome‐BGC to simulate the effects of harvest and residue removal management scenarios on soil carbon (C), available soil nitrogen (N), net primary production (NPP), and net ecosystem production (NEP) in jack pine (Pinus banksiana Lamb.) and sugar maple (Acer saccharum Marsh) ecosystems in northern Wisconsin, USA. To assess harvest effects, we simulated short (50‐year) and long (100‐year) harvest intervals, high (clear‐cut) and low (selective) harvest intensities, and three levels of residue retention (15%, 25%, and 35%) over a 500‐year period. The model simulation of NPP, soil C accumulation, and NEP agreed reasonably well with biometric and eddy‐covariance measurements of these two ecosystems. The more intensive (50‐year rotation clear‐cuts with low residue retention) harvest scenarios tended to have the greatest NEP (420 and 678 t C ha^?1 for the 500‐year interval for jack pine and sugar maple, respectively). All the harvest scenarios decreased mineral soil C and available mineral soil N content relative to the no‐harvest scenario for jack pine and sugar maple. The rate of change in mineral soil C decreased the greatest in the most intensive biomass removal scenarios (?0.012 and ?0.072 t C ha^?1 yr^?1 relative to no‐harvest for jack pine and sugar maple, respectively) and the smallest decrease was observed in the least intensive biomass removal scenarios (?0.002 and ?0.009 t C ha^?1 yr^?1 relative to no‐harvest for jack pine and sugar maple, respectively). The more intensive biomass removal harvest scenarios in sugar maple significantly decreased peak productivity (NPP) in the simulation period.     

Bird Populations in Rustic and Planted Shade Coffee Plantations of Eastern Chiapas, México

Much of the remaining “forest” vegetation in eastern Chiapas, Mexico is managed for coffee production. In this region coffee is grown under either the canopy of natural forest or under a planted canopy dominated by Inga spp. Despite the large differences in diversity of dominant plant species, both planted and rustic shade coffee plantations support a high overall diversity of bird species; we recorded approximately 105 species in each plantation type on fixed radius point counts. We accumulated a combined species list of 180 species on repeatedly surveyed transects through both coffee plantation types. These values are exceeded regionally only by moist tropical forest. Of the habitats surveyed, shade coffee was second only to acacia groves in the abundance and diversity of Nearctic migrants. The two plantation types have similar bird species lists and both are similar in composition to the dominant woodland—mixed pine-oak. Both types of shade coffee plantation habitats differ from other local habitats in supporting highly seasonal bird populations. Survey numbers almost double during the dry season—an increase that is found in omnivorous migrants and omnivorous, frugivorous, and nectarivorous resident species. Particularly large influxes were found for Tennessee warblers (Vermivora peregrina) and northern orioles (Icterus galbula) in Inga dominated plantations.     

Density and habitat associations of Henslow's Sparrows wintering in saline soil barrens in southern Arkansas

ABSTRACT Although the habitat requirements of breeding populations of Henslow's Sparrow (Ammodramus henslowii) have been examined, less is known about their habitat requirements and ecology during the nonbreeding season. We estimated population densities and quantified habitat associations of Henslow's Sparrows wintering in saline soil barrens in southern Arkansas. Densities of Henslow's Sparrows in the saline soil barrens were similar to those in the Longleaf Pine (Pinus palustris) Ecosystem of the southeastern United States, considered by many to be their primary wintering habitat. Henslow's Sparrows were closely associated with open areas with greater cover of Aristida spp. and globe beaksedge (Rhynchospora globularis), greater stem density at 11–20 cm above ground, more lichens, more herbaceous cover, more bare ground, greater occurrence of little bluestem (Schizacyrium scoparium) as the tallest vegetation, less moss, and less shrub cover than randomly selected sites. In contrast to the results of studies conducted in the Longleaf Pine Ecosystem, the presence of Henslow's Sparrows in our study was not correlated with the height of the tallest vegetation. Our results indicate that saline soil barrens of southern Arkansas support a high density of wintering Henslow's Sparrows and do so for longer postdisturbance periods than longleaf pine savanna. We also found that stem density near the ground was similar to that reported from longleaf pine savanna, but only about half that observed on their breeding grounds. Areas used by Henslow's Sparrows had more lichen and less moss cover, suggesting that those areas were drier than random sites within the barrens. Further research is needed to determine if large populations of Henslow's Sparrows winter in other saline soil barrens and if fire influences habitat associations and densities in the barrens.     

Does landscape composition alter the spatiotemporal distribution of the pine processionary moth in a pine plantation forest?

Landscape composition and physiognomy affect community structure and species distribution across space and time. The pine processionary moth (PPM) (Thaumetopoea pityocampa Den. & Schiff., Lepidoptera, Notodontidae) is a common pine defoliator throughout southern Europe and Mediterranean countries. We surveyed the spatiotemporal distribution of the PPM in a pine plantation forest in southwestern France and used the density of the winter nests as a proxy for population density. The study spanned 4 years (2005–2008) and showed a high temporal variability in nest density. We found a strong edge effect with nest densities at stand edges more than twice as large as within-stand densities. At the landscape scale, the spatial distribution of the moth exhibited a significant spatial autocorrelation in 3 out of 4 years of our study. The spatial scales of the autocorrelation ranged from ca. 2 km to more than 22 km. We found a positive correlation between spatial distributions corresponding to certain sampling years, but the relationship was not systematic. Landscape configuration appeared to be an important driver of the PPM spatial pattern. Bivariate Moran’s I correlograms showed that patch richness density as well as the percentage of local landscape covered by various land uses were correlated with population density. The study showed that accounting for landscape characteristics may be important in order to understand forest insect pest distribution, even in cases where the host species is abundant and homogeneously distributed throughout the study area, e.g., pure plantation forests.     

Reducing the conservation reliance of the endangered Kirtland's warbler through adaptive management

Species are considered conservation-reliant when their continued existence is dependent on human assistance. Conservation reliance challenges the conservation community in terms of their ability to sustain the funding and public-private partnerships needed for indefinite management. Although increased funding for conservation is critical, reducing conservation reliance through adaptive management represents an attractive alternative. We used a large-scale ecological experiment as a case study in the use of adaptive management to reduce conservation reliance. For >40 years, the United States Fish and Wildlife Service has trapped and lethally removed an obligate brood parasite, the brown-headed cowbird (Molothrus ater), to protect the Kirtland's warbler (Setophaga kirtlandii) from the negative effects that brood parasitism has on its reproductive success. To determine if the conservation reliance of the Kirtland's warbler could be reduced through optimization of the cowbird control program, we used an adaptive management approach. In collaboration with stakeholders, we experimentally reduced cowbird trapping effort across nearly all of the Kirtland's warbler breeding range. We monitored the resulting cowbird abundance and rate of parasitism, and then adjusted the scale of trap reductions based on the previous year's results. Despite reducing (2015–2017) and eventually eliminating (2018) cowbird trapping, we detected only 20 cowbirds (2015–2017) and found that just 4 of 514 (<1%) nests were parasitized (2015–2018). Our results indicate that the cowbird control program can at least temporarily be suspended, thereby reducing conservation reliance in the Kirtland's warbler and freeing funds for other management. We urge the conservation community to consider the use of adaptive management to reduce conservation reliance in other threatened and endangered taxa. © 2019 The Wildlife Society.     

Sugarcane and Eucalyptus plantation equally limit the movement of two forest‐dependent understory bird species

Habitat fragmentation results in landscape configuration, which affects the species that inhabit it. As a consequence, natural habitat is replaced by different anthropogenic plantation types (e.g. pasture, agriculture, forestry plantations and urban areas). Anthropogenic plantations are important for biodiversity maintenance because some species or functional groups can use it as a complementary habitat. However, depending on plantation permeability, it can act as a barrier to the movement of organisms between habitat patches, such as forest fragments, reducing functional connectivity for many species. Anthropogenic plantations are becoming the most common land use and cover type in the Anthropocene and biodiversity conservation in fragmented landscapes requires information on how different plantation types affect the capacity of the species to move through the landscape. In this study, we evaluated the influence of the type and structure of plantations on the movement of two forest‐dependent understory bird species – plain antvireo (Dysithamnus mentalis) and flavescent warbler (Myiothlyps flaveola) – within a highly fragmented landscape of Atlantic Forest hotspot. Knowing that forestry plantation is assumed to be more permeable to dependent forest bird species than open ones, we selected six study areas containing a forest fragment and surrounding plantation: three with sugarcane plantation and three with Eucalyptus sp. plantation. We used playback calls to stimulate the birds to leave forest fragments and traverse the plantations. Control trials were also carried out inside the forest fragments to compare the distances crossed. We observed that individuals moved longer distances inside forest than between plantation types, which demonstrate that plantations do constrict the movements of both species. The two plantation types equally impeded the movements of the species, suggesting the opposite of the general assumption that forestry plantations are more permeable. Our results indicate that, for generalist species, plantation type does not matter, but its presence negatively impacts movement of these bird species. We highlight that plantations have negative influences on the movements of common bird species, and discuss why this is important when setting conservation priorities.     

Evaluating different harvest intensities over understory plant diversity and pine seedlings,in a <Emphasis Type="Italic">Pinus pinaster</Emphasis> Ait. natural stand of Spain

Although modern forestry takes into consideration the analysis of the effects of forest management on plant structure, diversity and seedlings, little is known about how those parameters respond to harvest techniques in the Mediterranean region. We investigated the effect of three different harvest intensities, respect to uncut controls, on understory plant species functional groups, richness, diversity and pine seedlings in a natural Maritime pine stand in Spain, three years after harvesting. The harvest treatments produced a reduction of the number of Pinus pinaster seedlings and woody species cover, and an increase of species richness (total and of annual species) and plant cover of annual species respect to control plots (CO). The Shannon diversity values showed no differences between treatments. These results emphasize that the tree harvest treatments analyzed are not suitable for the management of this P. pinaster stand. Otherwise, the reduction of pine seedling density by harvest treatments and the changes in richness and cover of functional groups would not induce the natural regeneration of this stand maintaining the understory plant layer.     

INFLUENCE OF NEIGHBORS ON TREE FORM: EFFECTS OF LATERAL SHADE AND PREVENTION OF SWAY ON THE ALLOMETRY OF LIQUIDAMBAR STYRACIFLUA (SWEET GUM)

Liquidambar styraciflua (sweet gum) saplings were open grown (control), guy-wired to prevent wind-induced sway (constrained), or guy-wired within open-topped shade cloth cylinders to simulate shading by neighboring trees (shaded). Mechanical stability was assessed after 2 years of growth by field measurement of whole-tree flexibility and with the critical buckling height predictions of five allometrical models. Data from this experiment are supplemented with measurements of sweet gum trees growing in a 9-year-old pine plantation; individuals crowded but not overtopped by pines are compared with similar-aged trees growing in openings within the plantation. Changes in aboveground architecture were stimulated by both prevention of sway and lateral shade but the effect of the latter was most pronounced; shaded saplings approached or exceeded their calculated critical height and buckled under their own weight when the shade cloth cylinders were removed. Rates of aboveground biomass acquisition, total leaf area, wood density, and wood elastic moduli did not differ among the three treatments; changes in stem allometry accounted for most of the observed differences in tree stability. Sweet gum trees growing in a pine plantation responded similarly to neighbors; crowded trees had larger height: diameter ratios and more closely approached their calculated critical heights than did trees growing in the open. Sweet gum saplings growing in dense stands of similar-sized plants may surmount their neighbors by allocating relatively more wood to height growth than to girth increment.