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PubMed2000

Thermoregulation in winter swimmers and physiological significance of human catecholamine thermogenesis.

Thermoregulation in control subjects and cold-adapted winter swimmers was examined during 1 h of cold water immersion (13 C). It was found that the thermoregulatory functions of winter swimmers differ from those of non-cold-adapted subjects. As evident from the relationship between rectal temperature and the magnitude of cold thermogenesis, in controls a significant part of cold thermogenesis during the early phase of cooling was induced by changes in peripheral temperature input, while in the late phase of cooling it was the central temperature input which was mainly engaged in induction of cold thermogenesis. In winter swimmers the magnitude of cold thermogenesis was solely related to changes in rectal temperature, indicating the predominance of the central temperature input in activation of heat production mechanisms. The thermoregulatory threshold for induction of cold thermogenesis was lowered (by 0.34 C), but the apparent hypothalamic thermosensitivity was the same as in non-cold-adapted subjects. These differences are indicative of adaptation of thermoregulatory control centres. Additionally, the activity of thermoregulatory effectors was also changed. Shivering was induced later during cooling (after 40 min) in winter swimmers than in controls, which suggests an important participation of non-shivering thermogenesis in the early thermogenic response. Winter swimmers also showed bradycardia and a greater reduction in plasma volume during cooling. The data indirectly indicate restriction of heat loss from the body. Only a non-significant increase in quantity of subcutaneous fat was observed in winter swimmers. Thus, winter swimmers were able to survive a significantly greater temperature gradient between body and environment than non-cold-adapted subjects by modifying the sensory functions of hypothalamic thermoregulatory centres to lower heat loss and produce less heat during cold exposure. Additionally, the capacity of the total cold thermogenesis due to potentiation of non-shivering heat production was also increased. Heat produced due to thermogenic action of adrenaline may represent more than a quarter of the total cold thermogenesis. In conclusion, the data suggest that winter swimmers exhibit metabolic, hypothermic and insulative types of cold adaptation.

Adaptation, Physiological↗

PubMed2001

The effect of season, occupation and repeated winterings on anthropologic and physiological characteristics in Russian antarctic staff.

UNLABELLED: Thirty anthropometric and ten physiological parameters were examined over a 10-month-period in 1985-86, in 66 male polar explorers, aged 25-61 years, at an Antarctic station (Mirny observatory). For 30 of these persons this was their first wintering in Antarctic while the remaining 36 had wintered there at least once before. The mentioned measurements were taken on 3 different occasions in April, September and January corresponding in the Antarctic to the beginning of the polar night and interim season period and the beginning of the polar day. Subjects of the investigation belonged to 3 occupational groups: administrative personnel, scientific staff, and manual laborers. Extended statistical analysis of the data was carried out in an attempt to distinguish the dynamics of the studied parameters in relation to the season of wintering (Climate), the number of previous winterings (Frequency), the type of occupation (Work), and their interactions. Multifactorial statistical analyses were also performed, so as to adjust for age of subjects, which is a requisite for evaluating the factor of repeating winterings, obviously age-related. Changes in a number of characteristics were clearly recognized as connected with the factor of repeating winterings, to wit: 1) Anthropometric parameters such as or subcutaneous fat and relative muscle mass; 2) Parameters pertaining to speed of neuromuscular response such as wrist muscle effort, or time of simple motor response; and 3) Physiological parameters encompassing vascular--blood pressure and respiratory--spirometric measurements. CONCLUSION: Our findings suggest that frequency of repeated winterings is not a leading factor influencing physical status of examinees. Occupational status of examinees alone or in interaction with repeated winterings and seasonal climatic factors have more prominent impact on the well-being of polar explorers.

Acclimatization↗

PubMed2004

Winter excess mortality in intensive care in the UK: an analysis of outcome adjusted for patient case mix and unit workload.

OBJECTIVE: To investigate whether mortality in UK intensive care units is higher in winter than in non-winter and to explore the importance of variations in case mix and increased pressure on ICUs. DESIGN AND SETTING: Cohort study in 115 adult, general ICUs in England, Wales and Northern Ireland. PATIENTS AND PARTICIPANTS: 113,389 admissions from 1995 to 2000. MEASUREMENTS AND RESULTS: Hospital mortality following admission to ICU was compared between winter (December-February) and non-winter (March-November). The causes of any observed differences were explored by adjusting for the case mix of admissions and the workload of the ICUs. Crude hospital mortality was higher in winter. After adjusting for case mix using the APACHE II mortality probability this effect was reduced but still significant. When additional factors reflecting case mix and workload were introduced into the model, the overall effect of winter admission was no longer significant. Factors reflecting both the case mix of the individual patient and of the patients in surrounding beds were found to be significantly associated with outcome. After adjustment for other factors, the occupancy of the unit (proportion of beds occupied) was not significantly associated with mortality. CONCLUSIONS: The excess winter mortality observed in UK ICUs can be explained by variation in the case mix of admissions. Unit occupancy was not associated with mortality.

APACHE↗

PubMed2002

Using weather indices to predict survival of winter wheat in a cool temperate environment.

Seven years of winter survival data for winter wheat ( Triticum aestivum L.) were collected on a loam soil located on the Central Experimental Farm at Ottawa, Ontario (45 degrees 23'N, 75 degrees 43'W). The site was low-lying and subject to frequent winter flooding and ice-sheet formation. Two cultivars, a soft white and a hard red winter wheat, were planted in September. Crop establishment was measured in late fall and the percentage survival was measured in April of the following year. Meteorological data, which were available from the nearby weather site, were used to develop a large set of monthly weather indices that were felt to be important for winter survival. The objective of the study was to use genetic selection algorithms and artificial neural networks to select a subset of critical weather factors and topographic features and to model winter survival. The six weather indices selected were the total rain depth for December (mm), the total rain depth for February (mm), the number of days of the month with snow on the ground for January, the extreme minimum observed daily air temperature for March ( degrees C), the number of days of the month with snow on the ground for March, and the number of days of April with a daily maximum air temperature greater than 0 degrees C. It was found 89% of the variation in winter survival could be explained by these six weather indices, the cultivar, elevation and plot location.

Forecasting↗

PubMed2001

Increased vagal tone during winter in subsyndromal seasonal affective disorder.

BACKGROUND: Seasonal affective disorder (SAD) is characterized by recurrent winter depression with summer remissions and/or hypomania. Further symptoms include hypersomnia, increased appetite, weight gain, fatigue, and social withdrawal, which may indicate autonomic changes during winter. METHODS: Measurements of respiratory sinus arrhythmia, heart rate (HR), and skin conductance level (SCL) were taken from 32 participants in subsyndromal SAD and control groups (eight male and eight female subjects in each group) in autumn and winter to determine any change in autonomic function. Measures were taken at baseline and during two stressor tasks. Single determinations of blood pressure, sublingual temperature, depression, aerobic fitness, and body mass index were also measured at each session. Replication in a second data collection period over subsequent winter and spring periods was conducted with an additional 32 participants to extend the findings and to counterbalance order effects in testing. Data were combined to produce "winter" and "nonwinter" test periods and statistically corrected for testing order. RESULTS: Respiratory sinus arrhythmia differences indicated that SAD subjects have increased vagal tone in winter. Both groups show a decrease for HR and increases for SCL and diastolic blood pressure in winter. CONCLUSIONS: Seasonal affective disorder may show similarities with hibernation, and the results may indicate mechanisms different from those of nonseasonal depression.

Adult↗

PubMed2001

Feeding behavior of newly settled winter flounder (Pseudopleuronectes americanus) on calanoid copepods.

Field and laboratory investigations were conducted to examine feeding by newly settled winter flounder (Pseudopleuronectes americanus) on two co-occurring calanoid copepods, Eurytemora affinis and Acartia hudsonica. During the spring, these prey are present when winter flounder initiate their demersal lifestyle in estuaries of the northeastern United States. Epibenthic zooplankton were collected concurrently with winter flounder in the Navesink River estuary, NJ, in May 1998 and 1999. Although both calanoid species were in the estuary during the 2-year survey, E. affinis was consumed nearly to the exclusion of A. hudsonica by newly settled winter flounder. Annually, E. affinis and A. hudsonica had similar size distributions in field collections, indicating that species choice was not size selective. However, when preying on E. affinis, winter flounder preferred the larger sized organisms. In single species laboratory experiments, E. affinis and A. hudsonica were consumed equally by newly settled winter flounder (19-23 mm TL), but there were more strikes made toward E. affinis. Despite the lower catch efficiency, E. affinis was selected over A. hudsonica when the prey species were offered together in equal numbers. The selection for E. affinis over A. hudsonica by newly settled winter flounder may be the result of behavioral and/or morphological differences in the prey species.

Journal Article↗

PubMed2003

Biological activities of organic compounds adsorbed onto ambient air particles: comparison between the cities of Teplice and Prague during the summer and winter seasons 2000-2001.

The capital of the Czech Republic, Prague, appears today to be one of the most polluted residential areas in the country, whereas air pollution in the Northern Bohemia region (the former "Black Triangle Region") has substantially decreased during the last decade, especially with respect to the gaseous pollutant SO(2). This study evaluated the biological activities of complex mixtures of organic compounds adsorbed onto ambient air particles (PM10) collected during the summer and winter seasons of 2000-2001 at three monitoring sites--Teplice (TP), Prague-Smíchov (PRG-SM) (city centre) and Prague-Libus (PRG-LB) (suburban area). The following short-term in vitro assays with strikingly different endpoints were used: a bacterial mutagenicity test using the Salmonella typhimurium tester strain TA98 and YG1041, an acellular assay (CT DNA) combined with 32P-postlabelling to evaluate DNA adduct-forming potency and the chick embryotoxicity screening test (CHEST). The results of the mutagenicity test with the YG1041 strain, the acellular genotoxicity (DNA adducts) and the embryotoxicity tests responded to the amount of eight carcinogenic polycyclic aromatic hydrocarbons (PAHs) analysed in the EOM (dichloromethane extractable organic matter) samples tested. Nevertheless, the biological effects of the EOM did not differ between locations. The highest biological activity of the ambient air in terms of organic compounds associated with particles (per unit volume of air) was seen in the Prague city centre during both summer and winter seasons. At this location, B[a]P concentration ranged from 0.1 to 8.9 ng/m(3) (mean 0.3 and 3.6 ng/m(3) for summer and winter seasons, respectively), 13 PAHs ranged from 11 to 343 ng/m(3) (mean 52 and 160 ng/m(3) for summer and winter seasons, respectively). Generally, using in vitro tests, higher ambient air activity was found in the winter season as compared with the summer season at all three monitoring sites (TA98 +S9, approximately 4-fold; YG1041 -S9, approximately 5-fold; YG1041 +S9, approximately 8-fold; CT DNA +S9, approximately 10-fold; CHEST, approximately 10-fold; B[a]P, carcinogenic PAHs and total PAHs analysed, more than 10-fold). The different proportions of individual PAHs found in the summer and winter samples suggested traffic as a major emission source in the summer and, additionally, residential heating in the winter season at all three monitoring sites. The DNA adduct patterns resulting from the in vitro acellular assay also demonstrated similar major emission sources at all three locations. The study shows that particle-bound carcinogenic-PAH concentrations may be taken as an index for the biologically active (mutagenic, genotoxic, embryotoxic) components in air particulate samples. Therefore, high-quality monitoring data of carcinogenic PAHs may be useful for epidemiological studies of the impact of air pollution on the health of the population and for helping decision makers to improve our environment.

Adsorption↗

PubMed2003

Impacts of warm winters and extreme rainstorms on the base consumption in a limed lake, southern Norway.

The chemical composition of a limed lake, the two main inlets and the outlet was monitored during a period of 3 years. The winters of 1991-1992 and 1992-1993 were unusually warm while the winter of 1993-1994 was more normal. The lake surface water was wind exposed in the warm winters and as a consequence of frequent turnovers the acid input from the catchment mixed with the whole lake water body. In the winter of 1993-1994, the lake was ice-covered for approximately 4 months. During this period the drainage water from the catchment flowed to the outlet of the lake in the upper 2-3 m of the water column and only some of the acid input was neutralised. This is compared to a complete neutralisation in the winter of 1992-1993. The in-lake loss of alkalinity during this warm winter was approximately 29 microeq/l (November-June) compared to approximately 7 microeq/l lakewater in 1993-1994. Acid drainage from the catchment induced by an extraordinary rainstorm with heavy sea-salt deposition contributed to the in-lake alkalinity consumption in spring 1993. As winter temperatures above 0 degrees C and more frequent rainstorms may be common due to expected global warming, future increased lime consumption in-lakes may be projected in acidified areas as southern Norway.

Journal Article↗

PubMed2001

Varroa destructor reproduction during the winter in Apis mellifera colonies in UK.

The reproductive behaviour of female Varroa destructor mites invading worker brood cells during the winter months (January to mid-March) was investigated in four Apis mellifera colonies in UK. The number of viable offspring produced during a reproductive cycle, per mite, was only 0.5 during winter compared with 1.0 during the summer. This was mainly due to a large increase in the population of non-reproductive mites (winter 20%, summer 8%). This increase can be explained by the high level of male offspring mortality observed in winter (42% vs. 18% in summer), which results in nearly half of the newly reared female mites being unfertilised. Since mites that do reproduce lay a similar number of eggs in winter (X = 4.7) as in summer (X = 4.9), and the level of mortality suffered by the first female offspring is similar in winter (7%) as in summer (6%), it is probably not the internal physiological state of the host which causes the high level of winter non-reproduction, as has been previously suspected.

Animals↗

PubMed2002

Reproduction of the raccoon dog (Nyctereutes procyonoides) after feeding or food deprivation in winter.

The wild raccoon dog (Nyctereutes procyonoides, Canidae, Carnivora) goes through autumn fattening followed by winter sleep. Farmed raccoon dogs also exhibit autumn fattening but not winter sleep, as a result of daily feeding and lack of nests. We studied the effects of food deprivation and winter sleep or active winter feeding on the physiology and reproduction of farm-born raccoon dogs. Eighty-six animals were put on a 2-month fast in November-December. The fast caused no deleterious effects on the health of the raccoon dogs. In the spring the food-deprived animals had slightly more cubs per mated female than the fed animals. There was a significant negative correlation between the number of cubs obtained and the mean body mass of the females at the beginning of the mating season. The highest mean number of cubs was obtained by the females that weighed 5-7 kg. The results indicate that the raccoon dog is finely adapted to a long period of food deprivation in the winter. Furthermore, winter sleep and food deprivation could be introduced to farm conditions by providing the raccoon dogs with nestboxes and withholding food for a period of 6-8 weeks in mid-winter.

Adaptation, Physiological↗

PubMed2004

FRIGIDA-related genes are required for the winter-annual habit in Arabidopsis.

In temperate climates, the prolonged cold temperature of winter serves as a seasonal landmark for winter-annual and biennial plants. In these plants, flowering is blocked before winter. In Arabidopsis thaliana, natural variation in the FRIGIDA (FRI) gene is a major determinate of the rapid-cycling vs. winter-annual flowering habits. In winter-annual accessions of Arabidopsis, FRI activity blocks flowering through the up-regulation of the floral inhibitor FLOWERING LOCUS C (FLC). Most rapid-flowering accessions, in contrast, contain null alleles of FRI. By performing a mutant screen in a winter-annual strain, we have identified a locus, FRIGIDA LIKE 1 (FRL1), that is specifically required for the up-regulation of FLC by FRI. Cloning of FRL1 revealed a gene with a predicted protein sequence that is 23% identical to FRI. Despite sequence similarity, FRI and FRL1 do not have redundant functions. FRI and FRL1 belong to a seven-member gene family in Arabidopsis, and FRI, FRL1, and at least one additional family member, FRIGIDA LIKE 2 (FRL2), are in a clade of this family that is required for the winter-annual habit in Arabidopsis.

Amino Acid Sequence↗

PubMedDate not supplied

Evidence for a proximate influence of winter temperature on metabolism in passerine birds.

The roles of ultimate and proximate factors in regulating basal and summit metabolic rates of passerine birds during winter have received little study, and the extent to which winter temperatures affect these variables is unknown. To address this question, we measured basal and summit (maximum cold-induced) metabolic rates in black-capped chickadees (Poecile atricapillus), dark-eyed juncos (Junco hyemalis), and American tree sparrows (Spizella arborea) during winters from 1991/1992 to 1997 in southeastern South Dakota. Both temperature and these metabolic rates varied within and among winters. Least-squares regression revealed significant negative relationships for normalized basal and summit metabolism against mean winter temperature for all species pooled (R2=0.62 to 0.69, P</=0.001). Simple and multiple regressions were performed to analyze the influence of short-term (0-7 d preceding testing), medium-term (14-30 d before testing), and long-term (100-yr means for mean, minimum, and extreme low temperatures) temperature variables on whole-animal and mass-specific metabolic rates. Simple correlation coefficients for whole-animal metabolic rates were highest (r=-0.48 to -0.75, P<0.01) for 14-30-d temperature variables in chickadees and juncos and for 0-5-d temperature variables (r=-0. 54 to -0.68, P<0.01) in tree sparrows. For mass-specific metabolic rates, simple correlation coefficients were again highest (r=-0.45 to -0.70, P<0.01) for 14-30-d temperature variables in chickadees and juncos. Simple correlations for mass-specific metabolic rates were highest for 7-14-d temperature variables for tree sparrows (r=-0.67 to -0.68, P<0.01). Multiple regressions yielded model R2s ranging from 0.45 to 0.94 using a forward selection procedure and from 0.23 to 0.71 using a stepwise selection procedure. The partial R2 contributed from mass variation was small in all cases, ranging from 0.05 to 0.18, indicating that winter temperature was generally a good predictor of metabolic rate in these species. Metabolism was substantially correlated with short- and medium-term temperature variables for all species (cumulative partial R2=0.31 to 0.70 for forward selection and 0.13 to 0.57 for stepwise selection) but, at most, only weakly so with long-term temperature variables (cumulative partial R2=0-0.11 for forward selection and 0-0.06 for stepwise selection). Thus, short- to medium-term temperatures were better predictors of metabolic rates than long-term temperatures. These data suggest a proximate role for winter temperature in regulating metabolism in these birds.

Adaptation, Physiological↗

PubMed1996

Winter excess mortality: a comparison between Norway and England plus Wales.

Seasonal fluctuations in mortality are associated with age, outdoor temperature, and influenza. The relative excess winter mortality is approximately twice as high in the UK compared with the Scandinavian countries. Using data from Norway and England plus Wales, this study compares the effect of age, temperature and influenza on winter excess mortality in the two countries. Bivariate analyses showed that the excess winter mortality (December-March) in England and Wales was nearly twice as high in old as in middle-aged people, and also markedly higher than in Norway, while the association between excess winter deaths and influenza was of a similar magnitude. In the British data only, a marked and statistically significant negative relationship existed between outdoor temperature and excess winter mortality, corresponding to an increase of approximately 3,500 deaths in England and Wales (approximately 2/10,000 in the population aged 45 years and over) per 1 degree C reduction in winter temperature, after adjustment for age and influenza. Using data from 20 Western European countries, a highly significant positive correlation (R = 0.71, p < 0.001) was found between total mortality rates for the elderly (65 years and over) and relative excess winter mortality.

Age Factors↗

PubMed1991

The decline in winter excess mortality in The Netherlands.

In most countries, numbers of deaths rise considerably during the winter season. This winter excess in mortality has, however, been declining during recent decades. The causes of this decline are hardly known. This paper attempts to derive a number of hypotheses on the basis of a detailed description of trends in winter excess mortality in the Netherlands. Numbers of death by age, cause of death, and month of death for the period 1953-1988 were analysed by log-linear regression. There was a 50% reduction in winter excess mortality between the 1950s and 1970 followed by a much smaller reduction in later years. The decline in winter excess for total mortality can largely be attributed to parallel declines for a number of cardiovascular and respiratory diseases. Excess mortality decreased for winter months without influenza epidemics as well as for those with epidemics. The results suggest that the decline in winter excess mortality in the Netherlands can only partly be explained by decreases in influenza-associated mortality. It is argued that the role of the introduction of central heating is minimal and that a fundamental role is played by factors closely related to socioeconomic progress.

Adolescent↗

PubMed2001

Winter excess morbidity: is it a summer phenomenon?

BACKGROUND: It was hypothesized that winter excess mortality is a feature of ill health produced by exposure to ambient low temperatures, and will be matched by winter excess morbidity. The aim of the study was to test the prediction that winter excess morbidity would be observable and would show a social class gradient with greater excesses in less affluent groups, who are less able to heat their houses or whose lack of a car exposes them more frequently to outdoor cold exposure. METHODS: The study was set in the Metropolitan Borough of Stockport and documented, from routine health services hospital admissions data, winter and summer differences in ACORN-specific, age- and sex-standardized hospital admission rates and ratios, for ischaemic heart disease, directly and indirectly standardized using the Stockport population as the standard. RESULTS: The expected social class gradient in ischaemic heart disease admissions was more clearly observable in the summer than in the winter. Affluent groups showed winter excess morbidity, less affluent groups showed summer excess morbidity. CONCLUSION: The data serendipitously indicate an alternative hypothesis - that winter excess morbidity is a feature of health benefits derived in the summer and differentially available to the more affluent, such as opportunities for outdoor leisure. This hypothesis deserves testing in a study designed for that purpose, although it is not entirely satisfactory as an explanation of existing data.

Cold Temperature↗

PubMed1993

Cold tolerance and water content of current-year red spruce foliage over two winter seasons.

Red spruce (Picea rubens Sarg.) in high elevation forests of northeastern North America suffers from frequent and severe winter injury, leading to apical dieback, decreased growth, and high mortality. To examine the role of winter desiccation and freezing injury in winter damage, weekly assessments of cold tolerance and water content were made on current-year foliage collected from native red spruce trees at a high elevation site over two winter seasons. In both years, foliage maintained high water contents and adequate cold tolerance; nonetheless, slight to moderate injury was observed each year on some trees. Despite brief thaw periods each winter, no mid-winter dehardening sufficient to put foliage at risk of freezing injury was evident. These findings suggest that, at least in some years, winter injury to current-year red spruce foliage is produced by a mechanism other than desiccation or absolute low temperatures.

Journal Article↗

PubMed2003

Development and recovery from winter embolism in silver birch: seasonal patterns and relationships with the phenological cycle in oceanic Scotland.

Silver birch (Betula pendula Roth) is increasingly used in the United Kingdom for reforestation. However, recent evidence indicates that, under some circumstances, planted birch can suffer serious and repeated mortality of the apical leaders and branches, with consequent loss of apical dominance and the formation of a contorted stem. Plants from 37 seed sources of silver birch from Scotland and northern England planted at two sites were compared for several characteristics related to hydraulic architecture, vulnerability to freeze-thaw cycle induced embolism and spring recovery from winter embolism during the period 2000-2002. Phenological rhythms were also monitored in late winter-early spring to document relationships between phenology and water relations parameters. Significant differences were found across seed sources in stage of bud flushing for four dates in spring. Early flushing seed sources differed by about 1 to 2 weeks from late-flushing seed sources across the two sites. Wintertime xylem embolism in stems reached a peak of about 50 to 70% loss of xylem hydraulic conductivity, depending on the size and position of the sample shoots in the canopy. Small apical shoots were significantly more embolized than large basal shoots. Development of winter embolism was coupled to the occurrence of frost events. As percent loss of hydraulic conductivity increased during the winter, wood relative water content declined. Embolism reversal occurred rapidly in spring at the time of development of positive root pressure. No significant differences in the degree of winter embolism in 2001 were found among the three seed sources examined. The investigation was expanded in the winter-spring of 2002 to include 10 seed sources across both sites. Significant differences were found in degree of winter embolism across sites, dates and seed sources. For each date, there was a significant relationship between flushing scores and wood relative water contents across the two sites and all seed sources, suggesting that differences in time of flushing across sites and seed sources were likely caused by differences in the time of occurrence of root pressure, a necessary precondition to flushing.

Betula↗

PubMed2004

Ecological conditions during winter affect sexual selection and breeding in a migratory bird.

Populations of migratory birds have undergone marked declines, although the causes and mechanisms remain unknown. Because environmental effects on population dynamics are mediated by the effects of ecological factors on individuals, understanding changes in individual phenotypes in response to ecological conditions is key to understanding population trends. We show that breeding individuals of a declining population of trans-Saharan migratory barn swallows, Hirundo rustica, were affected by environmental conditions, as estimated from the normalized difference vegetation index (NDVI), reflecting primary production, in their winter quarters. The breeding dates of the same individuals in consecutive breeding seasons were advanced and clutch sizes were larger after winters with high NDVI in the winter quarters. Feather moult was also affected by winter conditions, with consequences for male sexual attractiveness. Length of tail ornament was positively correlated with NDVI during the previous winter, and males with large tail ornaments reproduced earlier and had larger clutches. The mean annual breeding date of the population was earlier and breeding success was increased after favourable winters, but this result was mainly determined by a single winter with very low NDVI. Thus, ecological conditions in Africa influence individual performance and productivity in a barn swallow population.

Africa South of the Sahara↗