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The contribution of interspecific competition to structuring population and community dynamics remains controversial and poorly tested. Interspecific competition has long been thought to influence the structure of migrant–resident bird communities in winter, yet experimental evidence remains elusive. The arrival of billions of songbirds into Neotropical habitats, where they co-exist with residents, provides a unique opportunity to assess interspecific competition and its consequences. Working in 15 ha of Jamaican black mangrove forest, we used removal experiments to test whether dominant resident Yellow Warblers compete interspecifically with subordinate wintering American Redstarts; we also used observational evidence (interspecific territorial overlap) to understand whether this coexistence influences physical condition, spring departure dates or annual return rates. Consistent with interspecific competition, after experimental removal of the resident, yearling male Redstarts (but not females or adult males) immediately moved into vacated Yellow Warbler territories, increasing their overlap with the space by 7.3%. Yearling Redstarts also appeared to adjust their territorial space use by actively avoiding Yellow Warblers; for example, Redstarts departing the wintering grounds as yearlings and returning the following winter shifted such that their territories overlapped 32% less with those of Yellow Warblers. Adult Redstarts showed no such territorial flexibility. Adult male Redstarts also showed evidence supporting the consequences of coexistence: territorial overlap with Yellow Warblers was negatively correlated with body condition and annual return rates. Adult male Redstarts with < 25% territorial overlap with Yellow Warblers were more than three times as likely to return between seasons than those with 100% overlap. We propose that the territorial inflexibility of adult male Redstarts produces these consequences, which may be due to their years-long investment in that particular territory. More generally, the temporary nature of migrant–resident interspecific competition is likely what allows coexistence during winter, the most resource-poor time of year. Interspecific competition and the consequences of coexistence are likely age- and sex-specific and the product of intraspecific dominance hierarchy in Redstarts. Our observations suggest that interspecific coexistence has measurable consequences, and our experiments support the long-held, but previously untested belief that resident birds compete interspecifically with wintering migrants.

Management of wildlife populations often requires reliable estimates of population size or distribution. Estimating abundance can be logistically difficult, and occupancy models have been used as a less expensive proxy for abundance estimation. Another alternative is to use independent estimates of home-range size and mean group size to directly scale occupancy estimates up to abundance. We used simulations to explore when scaling occupancy up to abundance is reliable, and as an example we applied an occupancy approach to estimate abundance of wolves (Canis lupus) from roadside snow-tracking surveys in northern Wisconsin, USA, in 2016 and 2018. Estimates of wolf abundance were plausible and compared favorably with independent estimates produced by territory mapping, and snow-tracking data requirements were lower than for territory mapping. Simulation results suggested that reasonable abundance estimates could be obtained under some conditions but also that severe positive bias could result under other conditions, especially when populations were small and dispersed, home range size was small, and areal sampling units were large. Positive bias in abundance estimates occurs because of closure assumption violations when tracks from a single wolf or pack are detected in >1 sample unit, and the sum of the sample unit areas where tracks were detected exceed the sum of the home range areas. Bias was minimized when sampling units were small relative to home range size or when sampling units were route segments that approximate point sample units, and when home ranges were highly aggregated. We conclude that, although caution is warranted when scaling occupancy estimates up to abundance, scaled occupancy models can provide feasible and reliable estimates of abundance, assuming home range size and mean group size are accurately known or estimated, sampling units are appropriately chosen, and covariates that aggregate home ranges can be used to accurately predict occupancy probability.

Introduction This descriptive study explores typical patterns of vascular territory mapping (VTM) in ischaemic stroke patients with proximal vessel occlusion. VTM is a novel process using CT perfusion that can identify the source and extent of collateral blood flow in patients with vessel occlusion. It functions by determining which vessel provides dominant blood flow to a brain voxel. Methods A total of 167 consecutive patients were analysed from INSPIRE (International Stroke Perfusion Imaging Registry) with their CT perfusion reprocessed through VTM software. We explored the typical territory maps generated by this software relating to common large vessel occlusion location sites (ACA/MCA/PCA). Results/Conclusion In the presence of occlusion, VTM demonstrated a reciprocal increase in collateral vessel territories.

Woodpeckers as cavity excavators are crucial in forest ecosystems, therefore, it is important to study their ecological needs, specifically at the territory scale, using mapping methodologies, of which there are uncertainties considering detection probabilities and the distances of the territory centres in different species and habitats. We studied the effects of the number of visits and isolation distance on detected woodpecker territories in the 1,000 ha forest mosaic of the Peszér forest in Central Hungary. We made territory mapping in 2020 along existing trails and forest roads on the present woodpecker species as Black, Eurasian Green, Great Spotted, Middle Spotted, Lesser Spotted Woodpecker and Eurasian Wryneck. We found a very low detection probability for single territories during one visit, while with the increasing number of visits it is more unlikely to overlook territories. Considering the isolation distances, by lowering the distance, more territories can be registered, which suggests that researchers should take great care choosing the proper distance for a given species whilst avoiding the over- or underestimation of territories. This paper has an actuality as BirdLife Hungary announced the Eurasian Green Woodpecker as the Bird of the Year in 2022, for drawing attention to this species’ habitat preferences and conservation.

ObjectivesArterial spin labelling (ASL) is a method of non-contrast-enhanced perfusion imaging that is generally based on the acquisition of two images which must be subtracted in order to obtain perfusion-weighted images. This is also the case for some flow territory mapping approaches that require the acquisition of two images for each artery of interest, thereby prolonging scan time and yielding largely redundant information. The aim of this study is to accelerate flow territory mapping using ASL by eliminating the acquisition of a control condition.MethodsUsing super-selective ASL, only one artery of interest is tagged, while the contralateral arteries are in a state similar to the control condition. By using an arithmetic combination of the label images of all territories, selective images of flow territories can be obtained without the need to acquire an additional control condition. This approach for obtaining artery-selective perfusion-weighted images without acquiring a control condition is presented in this study and is referred to as \"self-controlled super-selective ASL\".ResultsQuantitative perfusion measurements were similar to conventional super-selective and non-selective perfusion imaging across all subjects.ConclusionSuper-selective arterial spin labelling can be performed without acquiring a control image.Key Points• An accelerated method of flow territory mapping is presented.• Super-selective arterial spin labelling is performed without a control condition.• A new approach for calculating individual flow territories is presented.• The presented technique is compared to established approaches.• The outcome is similar to that using conventional techniques.

Documenting space-use patterns of animals is important for understanding their ecology and providing for their conservation. The concept of territory refers to a defended area, whereas the concept of home range refers to any area used by an animal during its normal activities. Few studies have explored quantitatively how these areas differ, and the use of these terms in the literature has, at times, been inconsistent. Many studies attempt to estimate territory size of a bird by territory mapping, which involves using locations obtained by following a singing bird. This is often assumed to be an effective measure of territory size, but few studies have examined the efficacy of this technique. Here, we used radiotelemetry to estimate breeding home-range and territory sizes of Swainson's Warbler (Limnothlypis swainsonii), a Neotropical migrant songbird. We found that territories were much larger than had been estimated by territory-mapping methods and suggest that researchers use caution when assuming that territory mapping accounts for all areas used by a bird. We also found that home ranges were significantly larger than territories, and these relatively large home ranges necessitate protection of large areas of habitat for Swainson's Warblers. We emphasize the importance of precise terminology when referring to areas of space use and suggest that radiotracking may uncover previously unknown use patterns and important ecological information in species that have not been radiotracked.

Golden-cheeked Warblers (Setophaga chrysoparia) are endangered songbirds that breed exclusively in the Ashe juniper (Juniperus ashei) and oak (Quercus spp.) woodlands of central Texas. Despite being the focus of numerous studies, we still know little about the size of the range-wide breeding population and how density varies across the spectrum of juniper co-dominated woodlands. Models that have been tested and shown to be accurate are needed to help develop management and conservation guidelines. We evaluated the accuracy and bias of density estimates from binomial mixture models, the dependent double-observer method, and distance sampling by comparing them to actual densities determined by intensive territory monitoring on plots in the Balcones Canyonlands Preserve, Austin, Texas. We found that the binomial mixture models consistently overestimated density by 1.1–3.2 times (actual density = 0.07–0.46 males/ha), and the other two models overestimated by 1.129.8 times at low density and underestimated by 0.5–0.9 times at high density plots (actual density = 0.01–0.46 males/ha). The magnitude of error for all models was greatest at sites with few or no birds (<0.15 males/ha), with model performance improving as actual density increased. These non-linear relationships indicate a lack of sensitivity with respect to true changes in density. Until systematic evaluation demonstrates that models such as those we tested provide accurate and unbiased density estimates for a given species over space and time, we recommend additional field tests to validate model-based estimates. Continued model validation and refinement of point-count methods are needed until accurate estimates are obtained across the density spectrum for Golden-cheeked Warblers and other songbird species. Setophaga chrysoparia es una especie de ave paseriforme amenazada, que se reproduce exclusivamente en bosques de Juniperus ashei y Quercus spp. en la región central de Texas. A pesar de ser el foco de numerosos estudios, aun conocemos poco acerca del tamano de las poblaciones a lo largo de su raneo y sobre como varia la densidad a través del espectro de bosques co-dominados por Juniperus ashei. Los modelos que han sido evaluados y que han mostrado que son precisos, son necesarios para desarrollar estrategias de manejo y conservation de la especie. Evaluamos la precisión y el sesgo de los estimativos de densidad a partir de modelos mixtos binomiales, el método dependiente de doble observador y muestreo distancia, comparándolos con densidades determinadas que los modelos mixtos binomiales consistentemente sobrestimaron la densidad entre 1.1 y 3.2 veces (densidad real = 0.07–0.46 machos/ha) y que los otros dos modelos sobreestimaron la densidad entre 1.1 y 29.8 veces a densidades bajas y subestimaron entre 0.5 y 0.9 veces en las parcelas con densidad alta (densidad real = 0.01–0.46 machos/ha). La magnitud del error para todos los modelos fue mayor en sitios donde encontramos pocas o ningun ave (<0.15 machos/ha), incrementando el rendimiento del modelo a medida que la densidad real incrementaba. Estas relaciones no lineales indican una falta de sensibilidad relacionada con cambios reaies en la densidad. Solo hasta que una evaluatión sistemâtica demuestre que los modelos, similares a los que evaluamos en este estudio, provean estimativos precisos y no sesgados de densidad para una especie determinada a través del tiempo y del espacio, recomendamos que se realicen pruebas adicionales en el campo con el fin de validar los estimadores basados en modelos. La continuación de la validación de los modelos y el refinamiento de los métodos de puntos de conteo serân necesarios hasta que se obtengan estimadores precisos a lo largo del espectro de densidades para Setophaga chrysoparia y otras especies de aves paseriformes.

Estimating population abundance for territorial species is challenging because individuals often differ in behavior (e.g., transience, multiterritoriality), and thus in detectability. How well prevailing methods detect and quantify individuals using multiple strategies is rarely addressed. In our effort to efficiently quantify avian abundance and transience among diverse nonbreeding habitats, we combined ‘unmarked' (distance sampling) with traditional ‘marked' (territory mapping) survey methods using a migratory passerine, the American Redstart (Setophaga ruticilla), wintering in 3 habitats in Jamaica from 2010 to 2012. We predicted that the ‘unmarked' survey method would detect not only all known (marked) territorial individuals, but also individuals that were transient or nonterritorial in the same habitats. Comparisons of abundance estimates generated by our best distance sampling (unmarked) model with territory mapping data identified high proportions of transient individuals (up to 50%) in 2 habitats, coastal dry scrub and mangrove, and virtually none in the third habitat, higher-elevation wet limestone forest. Documenting so many nonterritorial individuals, disproportionately weighted toward females and yearlings, in some habitat–year combinations prompts questions of what conditions favor transience and what role these individuals play in population processes. Our results illustrate how unmarked and marked survey methods can be used jointly to establish the number and identity of transients from neighboring areas. The unmarked survey method was sufficient for estimating population size among different habitats, but marked survey methods were necessary to identify and quantify transient individuals. Combined, these methods provide a powerful tool for assessing the range and variation of space-use strategies deployed by nonbreeding individuals.

The retention forestry approach is considered as one of the potentially effective tools for sustainable forest management for conservation of biodiversity in managed temperate and boreal forests. Retention of old-growth forest structures (e.g., very large old living trees) in forest stands during clear-cutting provides maintenance of key habitats for many old-growth forest interior-species. Most of ecological studies on green tree retention (GTR) consequences for biodiversity have been focused on birds. However, the long-term studies of GTR impacts on forest birds are very poor. In this paper, we focused on assessment of the long-term consequences of leaving legacy oak trees on the cut areas for bird diversity 18–22 years after clear-cutting in managed temperate European hardwood floodplain forests. Results based on bird counting using mapping of bird nesting territories revealed a key importance of legacy oak trees for maintaining bird diversity in the study area. These results are widely applicable for managed temperate hardwood forests with serious dominance of oak (Quercus sp.) in forest stands. Legacy oak trees in this habitat type are keystone structures for bird diversity. Retention approach focused on these trees is potentially an important conservation tool for preserving forest bird diversity and other associated species in temperate hardwood forests managed by clear-cutting.

Projected global growth in wind energy development has the potential to negatively affect wildlife populations, and yet the indirect effects of wind turbines on wildlife (e.g., displacement from otherwise suitable habitat) remain largely understudied, compared with investigations of direct effects (e.g., collision mortality). Thus, over a 3-yr period (2009–2011), we used 2 alternative survey methods to study displacement in breeding grassland songbirds at an operational wind facility in the southern Great Plains, USA. Using a line transect method in 2009 and 2010, we estimated the densities of Dickcissels (Spiza americana), Eastern Meadowlarks (Sturnella magna), and Grasshopper Sparrows (Ammodramus savannarum) within 500 m of wind turbines. Dickcissel density was positively related to vegetation structure and was highest 301–400 m from wind turbines in both years; however, this relationship was confounded by fence lines bisecting transects within this single distance bin. By contrast, we found no such relationships in Eastern Meadowlarks or Grasshopper Sparrows. Using a plot-based method in 2011, we estimated Dickcissel and Grasshopper Sparrow densities within 750 m of wind turbines. Again, we found a strong positive relationship between Dickcissel density and vegetation structure. With the change in survey method, however, the confounding effect of fence lines was removed and the relationship between distance to turbine and Dickcissel density disappeared. Variation in Grasshopper Sparrow density in 2011 was not explained by any variable we measured. In summary, we found no evidence of displacement within 500–750 m of wind turbines in the 3 most abundant breeding grassland songbirds at our site. We caution that it may be difficult to isolate the effect of distance to turbine from other factors that covary with distance (e.g., presence of fence lines) when using a line transect method to study displacement at operational wind facilities.