Winter Body Condition Research Articles

Reduction in overwinter body condition and size of Pacific sand lance has implications for piscivorous predators during marine heatwaves

Acute anomalous ocean warming events, including marine heatwaves (MHWs), have significant effects on reproduction and survival of piscivorous seabirds. Additionally, MHWs have negative effects on seabird fish prey, exacerbating these consequences and resulting in population implications for seabirds. We evaluated the relative body condition of Pacific sand lance Ammodytes personatus, an important seabird forage species, in Haro Strait, a highly productive region of southern British Columbia, Canada. We compared body condition and length of fish cohorts that experienced the 2016 MHW year (MHW cohorts) with fish hatched during 3 subsequent post MHW years (2017-2019). Age-0 MHW cohorts had a seasonal decline in body condition in age-0 fish from 100% in the summer to 81% in the winter, while age-1 fish showed a decline from summer-fall highs of 93.5% to wintertime low of 79.5%. In comparison, post MHW cohorts had a winter body condition that was 2-4 times higher than their MHW cohorts. Similar to previous studies in Alaska during the MHW, age-1 fish failed to grow and reach the typical size that distinguishes them from age-0 fish. Poor sand lance condition and growth in winter may explain the ramifications of a warming ocean for top predators, including seabirds and Pacific salmon, which depend on these prey fish in Haro Strait. Our results support the idea that Haro Strait, which is influenced by estuarine circulation resulting in cooler temperatures than surrounding areas, serves as a climate refugium for sand lance populations in summer and provides buffering capacity to ocean climate warming events.

Vertical sexual habitat segregation in a wintering migratory songbird

AbstractSexual habitat segregation during the wintering period is a widespread phenomenon and has important implications for the ecology and conservation of migratory birds. We studied Black-and-white Warblers (Mniotilta varia) wintering in second-growth scrub and old-growth mangrove forest in Jamaica to quantify sexual habitat segregation and explore whether patterns of habitat occupation have consequences on physical condition. We used this information along with a body size analysis and simulated territorial intrusions to assess whether behavioral dominance or habitat specialization was responsible for habitat segregation. Based on standardized capture data, we found that females were more abundant than males in both scrub and mangrove forests. Foraging observations, however, suggested vertical segregation within each habitat, with females foraging primarily near the ground and males in the mid-canopy and canopy, indicating that our sex ratio estimates may be biased. Using 2 measures of body condition, we show that males were in better body condition than females, regardless of habitat. We found that males were on average slightly larger than females, and home range analysis and simulated territorial intrusions indicated that males were more territorial than females. We argue that the observed vertical sexual habitat segregation is likely caused by behavioral dominance rather than habitat specialization. Winter body condition is known to carry over to affect migration timing, reproductive success, and annual survival in other songbirds, and therefore sexual habitat segregation may have important implications for year-round population dynamics in Black-and-white Warblers.

Foraging efficiency, social status and body condition in group-living horses and ponies.

Individual animals experience different costs and benefits associated with group living, which may impact on their foraging efficiency in ways not yet well specified. This study investigated associations between social dominance, body condition and interruptions to foraging behaviour in a cross-sectional study of 116 domestic horses and ponies, kept in 20 discrete herds. Social dominance was measured for each individual alongside observations of winter foraging behaviour. During bouts of foraging, the duration, frequency and category (vigilance, movement, social displacements given and received, scratching and startle responses) of interruptions were recorded, with total interruption time taken as a proxy measure of foraging efficiency. Total foraging time was not influenced by body condition or social dominance. Body condition was associated with social dominance, but more strongly associated with foraging efficiency. Specifically, lower body condition was associated with greater vigilance. This demonstrates that factors other than social dominance can result in stable differences in winter body condition.

Impact of winter fodder beet or kale allocation on body condition score gain and early lactation performance of dairy cows

Forage crops such as fodder beet (FB) and kale are an important feature of dairy farming in Southland and Otago where winter pasture growth is negligible. However, farmers are concerned about poor performance of cows following winter FB feeding. In winter 2017, cows were offered FB or kale both with pasture baleage at two allocation rates: target (crop allocated to achieve a winter body condition score (BCS) gain of 0.7) or high (ad libitum crop). Diets with FB were lower in fibre, phosphorus, sulphur and calcium, but had a higher metabolizable energy, compared with kale diets. Body condition change and early lactation performance were monitored to compare effects of winter FB and kale diets. Average daily BCS gain before calving was similar for FB and kale cows. Crop type had a greater impact on cow performance than allocation rate. Cows wintered on FB had better reproductive performance (3-week pregnancy rate), and greater average milk solids, fat and protein yield (kg/d) than cows wintered on kale. Therefore, winter FB did not reduce cow performance compared with kale. However, the cumulative effects of a FB diet long term are yet to be determined and future research should monitor the impact on animal health.

Nutritional-Landscape Models Link Habitat Use to Condition of Mule Deer (Odocoileus hemionus)

In heterogeneous landscapes, large herbivores employ plastic behavioral strategies to buffer themselves against negative effects of environmental variation on fitness. Yet, the mechanisms by which individual responses to such variation scale up to influence population performance remain uncertain. Analyses of space-use behaviors exemplify this knowledge gap, because such behaviors are often assumed, but rarely demonstrated, to have direct fitness consequences. We combined fine-scale data on forage biomass and quality with movement data and measures of somatic energy reserves to determine whether variation in use (the quantity of resource units, e.g., pixels on a landscape, that receive some level of investment by an animal during a specific sampling period) or selection (use of a resource unit relative to its availability to the animal during the same sampling period) of the nutritional landscape predicted early winter body condition of mule deer (Odocoileus hemionus). At the population level, mule deer exhibited stronger selection for high forage biomass at the landscape scale than at the home-range scale, and during summer than during spring. Use of the nutritional landscape varied among individual deer and had important consequences for early winter condition (an important determinant of survival and reproduction in capital-breeding ungulates). Females that consistently used vegetation communities that provided high biomass of preferred forage plants throughout spring and summer entered winter in better condition than females that used those vegetation communities less frequently. In contrast, selection (i.e., use relative to availability) of the nutritional landscape by individual deer was not significantly related to early winter condition at either the landscape or home-range scales. Our results highlight the value of using mechanistic, nutritional approaches to understand the potential fitness consequences of individual variation in behavior. In addition, our study suggests that patterns of forage use by ungulates may sometimes correlate more strongly with fitness than patterns of forage selection, which are scale-dependent and more vulnerable to biases stemming from the need to accurately quantify availability.

Allocation of body reserves during winter in eider Somateria mollissima as preparation for spring migration and reproduction

Capital breeders, such as the eider duck Somateria mollissima, accumulate resources before the start of breeding. Eiders preferentially feed on blue mussels Mytilus edulis to build up body condition during winter. We explored how body condition and gizzard mass of wintering eiders relate to mussel quality and quantity, winter climate and body condition of females at the breeding grounds. Body condition during winter (defined as scaled body mass index) of eiders increased during winter and the magnitude of the effect depended on age and mussel quality. Gizzard mass of eiders increased during winter with effects of mussel quality, mussel stocks and sex. Body condition in winter of adult females increased from the first half of January to the second half of February on average by 1.5%, equal to c. 96 g. During the same period gizzard mass of adult females increased by 12.2%, i.e., a nearly ten-fold increase compared to that observed in body condition in winter. Body condition of females at the breeding grounds in Finland (defined as body condition at hatching) was significantly positively correlated with gizzard mass in winter, but not significantly correlated with body condition in winter. Thus, eiders allocate body reserves to increase gizzard mass but less so to increase body condition in winter. This can be considered an adaptive migratory strategy of these eiders, whereby large winter (pre-migratory) gizzards increase food processing capacity, making it possible for eiders to arrive at the breeding grounds with superior body condition and a high reproductive potential.

Has winter body condition varied with population size in a long-distance migrant, the Bewick’s Swan (Cygnus columbianus bewickii)?

Assessments of body condition can provide useful information on changes in the state of individuals within a population, which may in turn help to inform conservation efforts. For example, decreases in body condition over time can indicate reduced food resources. Mass and skull length measures recorded for 195 adult and 467 first winter (cygnets) Bewick’s Swans (Cygnus columbianus bewickii) at wintering sites in the UK between winters 1966/1967 and 2017/2018 therefore were analysed to determine whether a ca. 40% decline in numbers in the Northwest European Bewick’s Swan population between 1995 and 2010 corresponded with poorer body condition from the mid-1990s onwards. Parents and siblings were known for all individuals, allowing us to account for shared genetic factors and rearing environment in our analysis. We used linear mixed-effects models and an information-theoretic approach to test different models of temporal variation in scaled body mass index (SBMI). Within our study population, although SBMI values varied both within and between years, we found no evidence of any directional trends in body condition. Of our competing time models of swan SBMI, a model in which age-specific body condition was constant over time received the greatest support in the data. Body condition was greater for adults than cygnets, but did not vary between sexes or wintering sites. Our findings suggest no connection between the recent declines in population size and body condition. Population decline is therefore unlikely to be caused by inadequate food supplies.

Associations between changing climate and body condition over decades in two southern hemisphere passerine birds

BackgroundClimate change presents considerable challenges for endotherms because they must maintain high, relatively constant body temperatures across a range of environmental conditions to ensure survival and optimise performance. Individuals exposed to changing weather must manage energy and water allocation to maintain thermal homeostasis, with consequences for body condition, and hence there is potential for selection because body condition is strongly linked to fitness. Understanding how weather drives changes in body condition is therefore fundamental to understanding how fitness is affected by climate change. Here we test for associations between weather and body condition and how this changes over time, in two co-existing species of small insectivorous passerines, the red-winged fairy-wren, Malurus elegans and white-browed scrubwren, Sericornis frontalis, that have been the subject of a ringing study for 39 years in temperate south-western Australia. The study populations have experienced increases in minimum temperatures in winter and summer as well as decreases in the frequencies of days with thermal minima < 5 °C, but the summer climate remains relatively mild with few days experiencing thermal maxima > 35 °C. Although, warming temperatures may reduce thermoregulatory costs, repeated exposure to hot conditions has been shown to have negative effects on body condition. Thus, we predict that the reduction over time in daily minima < 5 °C, along with the influence of increased maximum and minimum temperatures in summer and winter, will have positive effects on body condition.ResultsIn accordance with thermoregulatory predictions, colder daily minima in the range 1–19 °C prior to capture were associated with reduced body condition in winter in both species. Furthermore, in summer, in fairy-wrens but not scrubwrens, warmer daily maxima were associated with increasing body condition, and repeated exposure to temperatures > 30 °C over consecutive days was negatively associated with body condition. Body condition increased over the 39 years of the study for fairy-wrens but there was no change in scrubwrens, which is consistent with observed within-season associations between body condition and weather, and the change in climate over time.ConclusionsWe show that associations between body condition and weather variables are complex and dynamic, with seasonal trends in body condition resulting from a balance between multiple, competing weather variables. Moreover, temporal trends in body condition over years could be predicted from the relative strength of seasonal trends and the direction and magnitude of changing climate. Because body condition is predicted to be strongly tied to both reproduction and survival, changes in climate may be having complex and far reaching consequences for demography mediated through shifts in body condition. Finally, subtle differences in the sensitivities of the species to weather variables led to different trends in condition over time which may be associated with differences in the capacity for behavioural thermoregulation. Understanding the causes of such sensitivities is vital in improving capacity to predict species responses to climate change.

Effect of herbage allowance on productive and reproductive responses of primiparous beef cows grazing on Campos grassland

The effects of two levels of herbage allowance (HA, kg DM/kg liveweight (LW)) on forage mass and chemical composition, cow body condition score, cow LW, stocking rate, productive and reproductive responses were evaluated during two consecutive years. Eighty primiparous spring-calving beef cows were allocated to a completely randomised block design of two HA that had an annual average of 2.5 (low) and 4.0 kg DM/kg LW (high) from –150 to 195 days postpartum. The grazing system was continuous, and the put-and-take method was employed to adjust HA. At 86 ± 12 days postpartum, all cows were submitted to calf suckling restrictions with nose plates (12 days) and dietary flushing (2 kg/cow.day of whole-rice bran for 22 days), 6 days before bull introduction. Forage mass was affected by HA (P = 0.004) and year (P = 0.014); the high HA had a greater forage mass than the low HA (1474 vs 1212 ± 86 kg DM/ha; P &lt; 0.05), and Year 2 had a greater forage mass than Year 1 (1545 vs 1134 ± 78 kg DM/ha; P &lt; 0.05). Stocking rate was affected by HA and season (P = 0.0004) interaction. The stocking rate during autumn and spring was greater in low than high HA, and no differences were identified in winter and summer. The body condition score was improved in high HA during autumn and resulted in a greater winter (mid-gestation) body condition score than the low HA without differences during spring-summer (postpartum). Cow LW was lower during autumn, winter and early postpartum (16 days postpartum) in low HA in Year 1 than high HA of Year 1 and high and low HA cows in Year 2. Furthermore, the probability of total pregnancies (0.88 vs 0.59 ± 0.07; P = 0.01) and the calf weight adjusted to 205 days (194 vs 175 ± 16 kg; P &lt; 0.05) were greater in high HA. Calf weight adjusted to 205 days (Year 1: 192 vs Year 2: 177 ± 16 kg; P &lt; 0.05) and survival curves of postpartum anoestrus (P = 0.01) were affected by year but did not affect the probability of conception, early or total pregnancies. In conclusion, the reproductive and productive responses of primiparous beef cows grazing Campos grasslands were improved in high HA and could contribute to alleviating adverse climatic conditions effects.

Widespread exposure to lead affects the body condition of free-living whooper swans Cygnus cygnus wintering in Britain

Lead poisoning, through the ingestion of spent lead gunshot, is an established cause of morbidity and mortality in waterbirds globally, but the thresholds at which blood levels begin to affect the physiology of birds in the wild are less well known. Here we determine the prevalence of lead exposure in whooper swans and, for the first time, identify the level of blood lead associated with initial reductions in body condition. Blood lead elevated above background levels (i.e. >20 μg dL−1) was found in 41.7% (125/300) of swans tested. Blood lead was significantly negatively associated with winter body condition when levels were ≥44 μg dL−1 (27/260 = 10%). Our findings indicating that sub-lethal impacts of lead on body condition occur at the lower end of previously established clinical thresholds and that a relatively high proportion of individuals in this population may be affected, reaffirm the importance of reducing contamination of the environment with lead shot.

Asynchronous vegetation phenology enhances winter body condition of a large mobile herbivore.

Understanding how spatial and temporal heterogeneity influence ecological processes forms a central challenge in ecology. Individual responses to heterogeneity shape population dynamics, therefore understanding these responses is central to sustainable population management. Emerging evidence has shown that herbivores track heterogeneity in nutritional quality of vegetation by responding to phenological differences in plants. We quantified the benefits mule deer (Odocoileus hemionus) accrue from accessing habitats with asynchronous plant phenology in northwest Colorado over 3 years. Our analysis examined both the direct physiological and indirect environmental effects of weather and vegetation phenology on mule deer winter body condition. We identified several important effects of annual weather patterns and topographical variables on vegetation phenology in the home ranges of mule deer. Crucially, temporal patterns of vegetation phenology were linked with differences in body condition, with deer tending to show poorer body condition in areas with less asynchronous vegetation green-up and later vegetation onset. The direct physiological effect of previous winter precipitation on mule deer body condition was much less important than the indirect effect mediated by vegetation phenology. Additionally, the influence of vegetation phenology on body fat was much stronger than that of overall vegetation productivity. In summary, changing annual weather patterns, particularly in relation to seasonal precipitation, have the potential to alter body condition of this important ungulate species during the critical winter period. This finding highlights the importance of maintaining large contiguous areas of spatially and temporally variable resources to allow animals to compensate behaviourally for changing climate-driven resource patterns.

Relationships between plumage coloration, diet diversity, and winter body condition in the Lesser Goldfinch

Bright and colorful plumage is thought to be an honest signal of individual quality in birds because consuming high-quality forage results in more colorful plumage. To gain insight into the ecological and evolutionary context of the relationship between color, body condition, and diet, we studied a mostly urban population of Lesser Goldfinches (Spinus psaltria). We collected body measurements and digital photographs of plumage, as well as feathers and blood of goldfinches during three winters (2009–2012) in northern Nevada, USA. We analyzed the body tissues (feathers and blood) for stable isotope values of carbon and nitrogen to infer the diets of individual goldfinches, and quantified CIELAB color space values of chroma, brightness, and hue of plumage from the digital images. We then examined the relationships between color values and body condition, and color and stable isotope values. We found that the brightness (L* value) of the back plumage was correlated with both body condition and with stable isotope values of nitrogen (δ15N) in the winter diet. Furthermore, stable isotope analyses of both feathers and blood showed temporal differences in diet. However, hue and chroma, which are color values that are thought to more directly represent feather carotenoid content, were not related to body condition or diet. Our results suggest that the foraging ecology of Lesser Goldfinches changes over time, and that, in winter, plumage color values that are putatively indicative of carotenoid content do not seem to be an honest signal of individual quality as measured by body condition.

Habitat and herbivore density: Response of mule deer to habitat management

The suite of demands competing for wildlife management funds necessitates direct assessment of management decisions, especially when these decisions have direct costs, as well as tangible opportunity costs. We conducted a mark–resight study that estimated mule deer (Odocoileus hemionus) density across multiple study units in southwest Colorado that had been exposed to different intensities of habitat treatments. Our treatments were comprised of common habitat management techniques including hydro-axe and roller-chopper disturbances as well chemical control of weeds and reseeding with desirable mule deer browse species. Reference study units received no habitat management treatments. Total deer densities varied between 20–84 deer/km2 in southern study units and 4–12 deer/km2 in northern study units. We did not observe a consistent pattern of higher deer density on advanced treatment study units despite it being the primary hypothesis of the study. We observed a wide range of variation in deer density among years. Resighting probabilities (range 0.070–0.567) were best modeled as an interactive function of study unit and year, although sampling method was also influential. We recommend that if population density is to be used as a population response variable, it be used in tandem with other, possibly more sensitive parameters such as overwinter survival or late winter body condition. © 2014 The Wildlife Society.

Winter body condition in the Collared Flycatcher: Determinants and carryover effects on future breeding parameters

ABSTRACT Factors that determine the condition of migratory birds at their wintering sites are poorly known. Age, sex, and morphological characteristics of birds may have an influence on their winter condition by affecting their foraging and competitive abilities. Winter body condition could have long-term consequences on the reproductive success of migratory birds during the subsequent breeding season. Using 3 yr of data from Collared Flycatchers (Ficedula albicollis), we examined the characteristics of winter-grown tail feathers, as indicators of winter body condition, in relation to sex, age, morphological traits, and future breeding variables. Tail feather mass was highly repeatable between years, but feather growth rate was not repeatable, which suggests that the latter trait mainly indicates environmental circumstances during molt, whereas feather mass may more strongly reflect genetic effects. Tail feathers of males and adults showed better quality than those of females and juveniles, possibly becau...

The Flight Feather Molt of Griffon Vultures (Gyps fulvus) and Associated Biological Consequences

Molt patterns are poorly understood in most large bird species; however, they are of paramount importance in the development of surveys in which age is a key parameter. From 2000 to 2011, we studied the body condition and molt patterns of 214 Griffon Vultures (Gyps fulvus) in Spain. Adult Griffon Vultures (“griffons”) demonstrated a poor body condition in winter during the incubation period, which then improved after hatching. Conversely, subadults were fairly uniform throughout the year, with their condition slightly inferior to that of adults throughout the year (except during the incubation period). The molt period lasted from April to December, ending in winter. Juveniles started their first molt in May of their second calendar year, beginning from the innermost primary (pp1) and proceeding outwards. Later, in midsummer, some individuals molted secondaries (only 17% of secondaries were molted in the first molt season) beginning at four foci: from the innermost (ss25) outwards, the outermost (ss1) and ss5 or ss6 inwards, and centrifugally from ss12. In the third calendar year, griffons continued molting primaries outwards in an orderly fashion and two new foci appeared in secondaries, apparently at ss6 and ss15. Most juvenile feathers were completely molted by the fourth calendar year, although some fifth-calendar-year griffons had retained juvenile secondaries. Subsequently, adults did not show a consistent molt pattern, but had a high degree of asymmetry between the two wings. Some quills were molted more often than others and this led us to hypothesize that adult griffons might molt quills on demand.El conocimiento sobre los patrones de muda de la mayoría de las grandes aves es aún escaso, sin embargo resulta de fundamental importancia para desarrollar investigaciones en las que la determinación de la edad es clave. Entre 2000 y 2011 estudiamos la condición corporal y el patrón de muda de 214 individuos de Gyps fulvus en España. Los buitres adultos mostraron una condición corporal baja en invierno, durante el periodo de incubación, la cual mejoró tras el nacimiento de los pollos. Por el contrario los sub-adultos mantuvieron una condición corporal uniforme a lo largo del año, un poco más baja que los adultos a lo largo del año, exceptuando el periodo de incubación. El periodo de muda duró desde abril hasta diciembre, finalizando en el invierno. Los juveniles comenzaron su primera muda en mayo de su segundo año de calendario, iniciándola desde las plumas primarias más internas (pp1) hacia fuera. Después, a mediados del verano, algunos jóvenes mudaron las plumas secundarias (sólo el 17% de las secundarias fueron mudadas en la primera sesión de muda), comenzando en cuatro focos, desde la más interna (ss25) hacia fuera, desde la más externa (ss1), desde la ss5 o ss6 hacia dentro y centrífugamente desde las ss12. En el tercer año calendario, los buitres continuaron la muda de las primarias de forma ordenada hacia fuera y aparecieron dos focos nuevos en las secundarias, en ss6 y ss15. Para el cuarto año calendario la mayoría de las plumas juveniles estuvieron completamente mudadas, aunque algunos buitres del quinto año aún presentaban secundarias juveniles retenidas. Tras esto, los adultos no mostraron un patrón consistente de muda, con un alto grado de asimetría entre ambas alas. Algunas rémiges fueron mudadas más frecuentemente que otras, lo que nos permite hipotetizar que los buitres adultos podrían mudar las rémiges cuando fuera necesario.

Individual quality persists between years: individuals retain body condition from one winter to the next in Teal

Few studies have considered how body condition changes over time in individual birds, and most of these concerned long-lived breeding birds. We used a large database of Common Teal Anas crecca ringed and recaptured while wintering in the Camargue to study inter-annual persistence in wing length and body condition. Winter body condition may be a major determinant of survival during that season, and may further be related to breeding success. Indices of condition were compared for individual Teal between the moments of ringing and of recapture the following winter, analyzing each sex and age class (adult or juvenile) separately. Wing length was highly repeatable between years, though some limited annual variation was also recorded in adult males. Using scaled mass index as an index of body condition, we observed that condition at ringing was the strongest predictor of body condition at recapture for males and juvenile females, although inter- and intra-annual variation was also significant in most cases. The value of the slope for the relationship between individual body condition indices at ringing and recapture did not differ from 1 for males and for adults, whereas, for juvenile females, the slope was significantly greater than 1, indicating that individual differences in condition became more exaggerated over time. When analyses were repeated using crude body mass instead of a condition index, results were generally similar. Birds recaptured the following winter had a greater body condition at ringing that those that were not recaptured, supporting the hypothesis of a link between winter body condition and return probability. Our results demonstrate the importance of a head start in Teal, given persistent effects of obtaining better condition in the first winter, and suggest specific age and sex effects. They also underline the value of condition indices as a long-term predictor of individual quality in birds, even during the non-breeding season and for such a relatively short-lived species.

Reproduction in Steller's Jays (Cyanocitta stelleri): individual characteristics and behavioral strategies

ABSTRACT. We explored the consequences of male and female explorative and risk-taking behaviors that are components of a behavioral syndrome, as well as basic demographic and physical characteristics of three measures of reproductive performance in Steller's Jays (Cyanocitta stelleri). Older individuals of both sexes performed slightly better in measures of annual reproductive performance. Age was also positively correlated within pairs. In some years, males in better winter body condition performed better, whereas higher-performing females were in worse condition. Because winter body condition was negatively correlated within pairs, males in better condition possibly enabled their mates to invest more in reproduction in a given year, losing more body mass than low-performing females. Overall, variation in individual male and female traits, especially behavioral traits, explained little of the variation in annual reproductive performance. That age was identified as the single most consistent factor, which...

Winter body condition in relation to age, sex and plumage ornamentation in a migratory songbird

Winter body condition may play important roles in the life history of migratory birds, but it is difficult to estimate. We used the growth rate of winter‐grown tail feathers of Collared Flycatchers Ficedula albicollis as an indicator of winter body condition, comparing this trait between age classes and sexes and relating it to plumage ornamentation (forehead and wing patch sizes). Adults and males were in better nutritional condition during winter, as indicated by their faster tail feather growth rates, than were yearlings and females, respectively, which could indicate differences in individual quality and foraging ability with age, or age‐ and sex‐related winter habitat segregation. However, feather growth rate was related neither to the size of the winter‐grown forehead patch nor to the size of the summer‐grown wing patch, suggesting weak condition‐dependence for the winter‐grown ornament and complex life‐history consequences for the summer‐grown ornament.

Hunting from motorboats displaces Wadden Sea eiders Somateria mollissima from their favoured feeding distribution

AbstractHunting of eiders Somateria mollissima from motorboats is common in Danish marine waters, and to reduce hunting pressure on eiders and other diving duck species in Denmark, motorboat hunting was banned within 42 marine sites covering an area of 2,934 km2, although the effects of this regulation have to date not been examined. Our case study analyses the effects of excluding motorboat hunting from an area of 682 km2 of the Danish Wadden Sea (hereafter the ‘Study Area’) which also supported a large area of blue mussel beds, the preferred food for eiders. Our study covered the entire Danish Wadden Sea (total area 1,225 km2) during the hunting seasons (October‐February) of 1980–2003 using 85 aerial surveys of eiders and motorboats used by hunters. Eider numbers increased by 56% in the Study Area following the ban on motorboat hunting despite a 50% reduction in the eider flyway population over the same period. There was a significant negative relationship between the density of hunter motorboats and that of eiders on a small geographical scale (1.8–2.5 km). Motorboat hunting in the Study Area also affected eider distribution at larger geographical scales (4–12 km), displacing eiders from the Study Area offshore from the Wadden Sea into the North Sea. Following the ban on motorboat hunting, most eiders occurred in the Study Area. Winter (21 December‐31 January) body condition of eiders was greater in the Study Area than the body condition of eiders in the Offshore Area during autumn (20 October‐20 December). Eider abundance relative to blue mussel biomass significantly increased after motorboat hunting was banned in the Study Area, but there was no such change during winter after the hunting ban. Since the ban on motorboat hunting in the Study Area, eider numbers throughout the entire Danish Wadden Sea seem to be regulated by total blue mussel biomass.

The income–capital breeding dichotomy revisited: late winter body condition is related to breeding success in an income breeder

The income–capital breeding dichotomy revisited : late winter body condition is related to breeding success in an income breeder