The global population and status of Snowy Owls Bubo scandiacus are particularly challenging to assess because individuals are irruptive and nomadic, and the breeding range is restricted to the remote circumpolar Arctic tundra. The International Union for Conservation of Nature (IUCN) uplisted the Snowy Owl to “Vulnerable” in 2017 because the suggested population estimates appeared considerably lower than historical estimates, and it recommended actions to clarify the population size, structure, and trends. Here we present a broad review and status assessment, an effort led by the International Snowy Owl Working Group (ISOWG) and researchers from around the world, to estimate population trends and the current global status of the Snowy Owl. We use long-term breeding data, genetic studies, satellite-GPS tracking, and survival estimates to assess current population trends at several monitoring sites in the Arctic and we review the ecology and threats throughout the Snowy Owl range. An assessment of the available data suggests that current estimates of a worldwide population of 14,000–28,000 breeding adults are plausible. Our assessment of population trends at five long-term monitoring sites suggests that breeding populations of Snowy Owls in the Arctic have decreased by more than 30% over the past three generations and the species should continue to be categorised as Vulnerable under the IUCN Red List Criterion A2. We offer research recommendations to improve our understanding of Snowy Owl biology and future population assessments in a changing world.

Daily sodium intake in England is ∼3.3 g/day(1), with government and scientific advice to reduce intake for cardiovascular health purposes having varying success(2). Eccrine sweat is produced during exercise or exposure to warm environments to maintain body temperature through evaporative cooling. Sweat is primarily water, but also contains appreciable amounts of electrolytes, particularly sodium, meaning sweat sodium losses could reduce daily sodium balance without the need for dietary manipulation. However, the effects of sweat sodium losses on 24-h sodium balance are unclear.

Fourteen active participants (10 males, 4 females; 23±2 years, 45±9 mL/kg/min) completed a preliminary trial and two 24-h randomised, counterbalanced experimental trials. Participants arrived fasted for baseline (0-h) measures (blood/urine samples, blood pressure, nude body mass) followed by breakfast and low-intensity intermittent cycling in the heat (∼36⁰C, ∼50% humidity) to turnover ∼2.5% body mass in sweat (EX), or the same duration of room temperature seated rest (REST). Further blood samples were collected post-EX/REST (1.5-3 h post-baseline). During EX, sweat was collected from 5 sites and water consumed to fully replace sweat losses. During REST, participants drank 100 mL/h. Food intake was individually standardised over the 24-h, with bottled water available ad-libitum. Participants collected all urine produced over the 24-h and returned the following morning to repeat baseline measures fasted (24-h). Sodium balance was estimated over the 24-h using sweat/urine losses and dietary intake. Data were analysed using 2-way ANOVA followed by Shapiro-Wilk and paired t-tests/Wilcoxon signed-rank tests. Data are mean (standard deviation).

Dietary sodium intake was 2.3 (0.3) g and participants lost 2.8 (0.3) % body mass in sweat (containing 2.5 (0.9) g sodium). Sodium balance was lower for EX (-2.0 (1.6) g vs -1.0 (1.6) g; P = 0.022), despite lower 24-h urine sodium losses in EX (1.8 (1.2) g vs 3.3 (1.7) g; P = 0.001). PostEX/REST blood sodium concentration was lower in EX (137.6 (2.3) mmol/L vs 139.9 (1.0) mmol/L; P = 0.002) but did not differ at 0-h (P = 0.906) or 24-h (P = 0.118). There was no difference in plasma volume change (P = 0.423), urine specific gravity (P = 0.495), systolic (P = 0.324) or diastolic (P = 0.274) blood pressure between trials over the 24-h. Body mass change over 24-h was not different between trials (REST +0.25 (1.10) %; EX +0.40 (0.68) %; P = 0.663).

Sweat loss through low-intensity exercise resulted in a lower sodium balance compared to rest. Although urine sodium output reduced with EX, it was not sufficient to offset exercise-induced sodium losses. Despite this, body mass, plasma volume and blood sodium concentration were not different between trials, suggesting sodium may have been lost from non-osmotic sodium stores. This suggests sweat sodium losses could be used to reduce sodium balance, although longer studies are required to confirm this thesis.

Early adversity increases risk for child mental health difficulties. Stressors in the home environment (e.g., parental mental illness, household socioeconomic challenges) may be particularly impactful. Attending out-of-home childcare may buffer or magnify negative effects of such exposures. Using a longitudinal observational design, we leveraged data from the NIH Environmental influences on Child Health Outcomes Program to test whether number of hours in childcare, defined as 1) any type of nonparental care and 2) center-based care specifically, was associated with child mental health, including via buffering or magnifying associations between early exposure to psychosocial and socioeconomic risks (age 0–3 years) and later internalizing and externalizing symptoms (age 3–5.5 years), in a diverse sample of N = 2,024 parent–child dyads. In linear regression models, childcare participation was not associated with mental health outcomes, nor did we observe an impact of childcare attendance on associations between risk exposures and symptoms. Psychosocial and socioeconomic risks had interactive effects on internalizing and externalizing symptoms. Overall, the findings did not indicate that childcare attendance positively or negatively influenced child mental health and suggested that psychosocial and socioeconomic adversity may need to be considered as separate exposures to understand child mental health risk in early life.

Observations of radiocarbon (14C) in Earth’s atmosphere and other carbon reservoirs are important to quantify exchanges of CO2 between reservoirs. The amount of 14C is commonly reported in the so-called Delta notation, i.e., Δ14C, the decay- and fractionation-corrected departure of the ratio of 14C to total C from that ratio in an absolute international standard; this Delta notation permits direct comparison of 14C/C ratios in the several reservoirs. However, as Δ14C of atmospheric CO2, Δ14CO2 is based on the ratio of 14CO2 to total atmospheric CO2, its value can and does change not just because of change in the amount of atmospheric14CO2 but also because of change in the amount of total atmospheric CO2, complicating ascription of change in Δ14CO2 to change in one or the other quantity. Here we suggest that presentation of atmospheric 14CO2 amount as mole fraction relative to dry air (moles of 14CO2 per moles of dry air in Earth’s atmosphere), or as moles or molecules of 14CO2 in Earth’s atmosphere, all readily calculated from Δ14CO2 and the amount of atmospheric CO2 (with slight dependence on δ13CO2), complements presentation only as Δ14CO2, and can provide valuable insight into the evolving budget and distribution of atmospheric 14CO2.

We present and evaluate the prospects for detecting coherent radio counterparts to gravitational wave (GW) events using Murchison Widefield Array (MWA) triggered observations. The MWA rapid-response system, combined with its buffering mode ($\sim$4 min negative latency), enables us to catch any radio signals produced from seconds prior to hours after a binary neutron star (BNS) merger. The large field of view of the MWA ($\sim$$1\,000\,\textrm{deg}^2$ at 120 MHz) and its location under the high sensitivity sky region of the LIGO-Virgo-KAGRA (LVK) detector network, forecast a high chance of being on-target for a GW event. We consider three observing configurations for the MWA to follow up GW BNS merger events, including a single dipole per tile, the full array, and four sub-arrays. We then perform a population synthesis of BNS systems to predict the radio detectable fraction of GW events using these configurations. We find that the configuration with four sub-arrays is the best compromise between sky coverage and sensitivity as it is capable of placing meaningful constraints on the radio emission from 12.6% of GW BNS detections. Based on the timescales of four BNS merger coherent radio emission models, we propose an observing strategy that involves triggering the buffering mode to target coherent signals emitted prior to, during or shortly following the merger, which is then followed by continued recording for up to three hours to target later time post-merger emission. We expect MWA to trigger on $\sim$$5-22$ BNS merger events during the LVK O4 observing run, which could potentially result in two detections of predicted coherent emission.