Abstract Desert communities are threatened with species loss due to climate change, and their resistance to such losses is unknown. We constructed a food web of the Mojave Desert terrestrial community (300 nodes, 4080 edges) to empirically examine the potential cascading effects of bird extinctions on this desert network, compared to losses of mammals and lizards. We focused on birds because they are already disappearing from the Mojave, and their relative thermal vulnerabilities are known. We quantified bottom‐up secondary extinctions and evaluated the relative resistance of the community to losses of each vertebrate group. The impact of random bird species loss was relatively low compared to the consequences of mammal (causing the greatest number of cascading losses) or reptile loss, and birds were relatively less likely to be in trophic positions that could drive top‐down effects in apparent competition and tri‐tropic cascade motifs. An avian extinction cascade with year‐long resident birds caused more secondary extinctions than the cascade involving all bird species for randomized ordered extinctions. Notably, we also found that relatively high interconnectivity among avian species has formed a subweb, enhancing network resistance to bird losses.

Parameter approximation is often necessary when calculating species thermal properties, and researchers historically have assumed animals are spherical when estimating volume and density. We hypothesized that a spherical model would result in significantly biased measures of density for birds, which are generally longer than they are tall or wide, and that these inaccuracies would significantly alter the outputs of thermal models. We calculated the densities of 154 bird species using sphere and ellipsoid volume equations and compared these estimates to one another and to published bird densities measured using more exact volume displacement methods. We also calculated evaporative water loss as a percentage of body mass per hour, a variable known to be critical for bird survival, twice for each species, once with the sphere-based density and once with the ellipsoid-based density. We found that volume and density estimates were statistically similar between published densities and those estimated using the ellipsoid volume equation, suggesting that this method is suitable for approximating bird volume and calculating density. In contrast, the spherical model overestimated body volume and therefore underestimated body densities. This resulted in the spherical approach consistently overestimating evaporative water loss as a percent of mass lost per hour than the ellipsoid approach. This outcome would result in mischaracterizing thermal conditions as lethal for a given species, including overestimating vulnerability to increased temperatures due to climate change.

Background & Aims Patients with advanced heart failure needing heart transplant commonly suffer liver dysfunction. However, there is limited data on the impact of liver fibrosis on outcomes for HT candidates. We determine the relationship between liver fibrosis severity and mortality rates for HT patients. Methods A retrospective cohort study of adults listed for HT who underwent a liver biopsy for evaluation of early or advanced liver fibrosis from 08/12/2004-02/16/2022. Trend analysis was performed using Cox proportional hazard model, controlling for MELD-XI. At-risk period starts at the time of waitlist; the end of the follow-up period was mortality on the waitlist, mortality post-HT, or administrative censoring at the end of the study. Results There was no significant difference in the survival of patients with advanced fibrosis and early fibrosis over time (HR 1.54, CI 0.59-4.02, p = 0.5). Similarly, there was also no significant survival difference within groups who did (HR 0.78, CI = 0.26-2.33, p = 0.8) or did not (HR 1.00, CI 0.09-11.43, p = 0.9) receive transplants. However, most transplants were performed in patients with no or early fibrosis. Conclusion There was no significant difference in the survival rates between HT candidates with and without advanced fibrosis on the waitlist and post-HT, challenging the notion that advanced fibrosis should be an absolute contraindication for HT. However, our findings are limited by the small sample size, retrospective design, and focus on patients already deemed suitable for transplantation. These limitations highlight the need for prospective studies involving broader patient populations, including those excluded from transplant candidacy due to severe fibrosis or cirrhosis. Future research should evaluate whether pre-transplant liver biopsy is necessary for all HT candidates or if clinical assessments can adequately stratify risk.

Community viability analysis (CVA) has been put forth as an analogue for population viability analysis (PVA), an accepted conservation tool for evaluating species-specific threat and management scenarios. The original proposal recommended that CVAs examine resistance-based questions. PVAs, however, are broadly applicable to multiple types of viability questions, suggesting that the original CVA definition may be too narrow. In the present article, we advance an expanded framework in which CVA includes any analysis assessing the status, threats, or management options of an ecological community. We discuss viability questions that can be investigated with CVA. We group those inquiries into categories of resistance, resilience, and persistence, and provide case studies for each. Finally, we broadly present the steps in a CVA.

Conservation of predators requires a comprehensive understanding of their life history and ecology, including the delineation of temporal and spatial dietary habits. Gyrfalcons (Falco rusticolus), Willow Ptarmigan (Lagopus lagopus), and Rock Ptarmigan (L. muta) are Arctic specialists, strongly linked in a dynamic predator-prey relationship, and facing similar conservation threats. We studied Gyrfalcon predation of ptarmigan on Alaska's Seward Peninsula and investigated whether species-specific contributions to diet reflected preferential selection or exploitation of the more abundant prey species. Additionally, we examined how the sex ratios of ptarmigan in Gyrfalcon diet varied throughout the breeding season. We collected ptarmigan prey remains from in and around occupied Gyrfalcon nesting sites in 2017, and identified species and sex by molecular techniques. We compared proportions of the two ptarmigan species in Gyrfalcon diet to proportions of the Rock and Willow Ptarmigans' preferred habitat around Gyrfalcon nesting sites (n = 205 skeletal remains from 12 nests), and compared sex ratios of ptarmigan prey remains temporally (n = 252 skeletal remains from 12 nests). We found that prey remains were more likely to be Rock Ptarmigan when areas around Gyrfalcon sites had greater slope and higher elevation (i.e., they better matched the habitat preferences of Rock Ptarmigan), which may suggest Gyrfalcon diet tracked ptarmigan availability without preference for species. Ptarmigan remains were biased toward male birds during June, when most female ptarmigan are incubating on concealed nests. Although we recommend additional analysis of these topics, our findings further our understanding of Gyrfalcon and ptarmigan ecology as the Arctic faces rapid changes to its climate and landscape.

As with many areas in Africa, Kenya has witnessed rapid human development in recent decades, including an increase in urbanization and an intensification of agriculture. The impact of these land use changes on wildlife populations have, however, rarely been examined. The Augur Buzzard is a widespread raptor species, thought to adapt relatively well to human alterations of habitat. In this study, we explore trends in Augur Buzzard ( Buteo augur ) territory occupancy over nearly two decades around Lake Naivasha, Kenya, in relation to land-use changes, particularly expansion in human housing and flower farms. We hypothesized that these changes would cause population declines in this species within our study area. Using remote-sensed satellite imagery, we found that human development (agriculture and human settlement) increased from 9 to 24% of the study area from 1995 to 2014. We found a 47% decline in active territories over this same time period, representing an annualized decline of 3.1%. Based on the length of three generations this would qualify this species to be uplisted to at least Vulnerable in our study area, raising our concerns that the same pattern may be occurring across the species’ range. We then explored whether abandonment of individual territories was associated with either (i) the current amount or (ii) the change in human development within a range of buffer circles of varying radii (0.1–5.0 km). Contrary to our expectations, no associations were found between human development and territorial abandonment, and thus we could not attribute specific territorial abandonment to these broad scale anthropogenic land cover changes. We encourage further research to investigate whether territorial abandonment may be associated with either finer resolution (habitat specific) changes, or sources of direct mortality, for example human persecution or electrocutions. These factors might explain the decline in this population better than broader scale increases in anthropogenic land cover.

In the last decade, poaching of high-profile wildlife species has increased across Africa, particularly threatening the viability of rhinoceros populations. Protection efforts and anti-poaching measures have increased across the continent, but a lack of research on the motivations driving the recruitment of local people by poaching syndicates may limit successful law enforcement. We explore the societal drivers and personal motivations behind individuals' involvement in poaching syndicates in Namibia and how this process is perceived at different levels of decision-making. There was a general consensus across all informant populations that wildlife crime syndicates are divided into five tiers of engagement. Poachers, the lowest tier, are typically recruited by a second tier of local business people via a cycle of dependency and debt. Further, although anti-poaching efforts are generally aimed at apprehending individuals at the lowest tier, the dependency mechanism used by local recruiters supplies syndicates with a consistent source of recruits. We also identified a misalignment of perceptions between local people and socially distant conservation practitioners regarding the personal motivations and societal drivers of commercial poaching. We urge conservation practitioners to invest in developing a more contextual understanding of local perceptions and perspectives prior to establishing rhinoceros protection measures. Such contextual information is critical to ensuring that limited conservation resources are used effectively to achieve the greatest positive impact for both people and rhinoceros.

To stem the ongoing loss of biodiversity, there is an urgent need to distinguish between effective and ineffective approaches for protecting species habitats. Using Google Earth Engine and 30 years of Landsat images, we quantify habitat change for 24 vertebrates on the U.S. Endangered Species List (ESA) and IUCN Red List across different categories of land ownership (e.g., federal, state, and private) that are subject to different conservation-focused legal restrictions. These estimates exclude changes due to agricultural conversion and burned areas. Imperiled species evaluated lost the least habitat (3.6%) on federal lands, while losses on private lands without conservation easements were more than twice as great (8.1%). Differences in annual percent loss before and after species were placed on the Endangered Species List, and between ESA and Red List species suggest that the ESA limited habitat loss and was most effective on federal lands. These results emphasize the importance of federal lands for protecting habitat for imperiled species and highlight the need to improve habitat protection on private lands for long-term conservation.

Nest failure of most pairs of Roseate Terns (Sterna dougallii) at Falkner Island, Connecticut, in 2002-2003 (due mainly to predation by Black-crowned Night-herons [Nycticorax nycticorax]) was followed by the rapid departure of many of the failed individuals in both years. Nine failed pairs (16.7%) stayed while 40 (74.1%) of 54 unsuccessful pairs left within 2 d following nest failure in 2002, and 7 pairs (21.9%) stayed while 25 (78.1%) of 32 unsuccessful pairs left within 2 d in 2003. Individuals that departed this colony site by the end of June likely had time to prospect and renest at another colony site in the same year, and individuals that successfully renested at another colony site could have shown reduced colony-site fidelity to Falkner Island in subsequent years.

We recorded banded Roseate Terns (Sterna dougallii) and unbanded individuals mated to banded individuals in May and the first third of June in 2001 and 2002 to quantify post-spring migration prospecting by this species at Falkner Island, Connecticut. In 2001, more than one quarter: 34/125 (27.2%) of those observed by 19 May and 38/150 (25.3%) of those observed by 25 May did not remain at this colony site and went elsewhere to attempt breeding. In 2002, fewer terns were observed by 19 May, but an even higher percentage: 11/28 (39.3%) of those seen by 19 May and 58/151 (38.4%) of those seen by 25 May did not stay and nest. Our results demonstrate that a substantial proportion of the earliest arriving individuals at this site are prospecting and gathering information about local conditions before making a decision about going elsewhere to nest.