Variation In Activity Patterns Research Articles

Increased default-mode variability is related to reduced task-performance and is evident in adults with ADHD.

Insufficient suppression and connectivity of the default mode network (DMN) is a potential mediator of cognitive dysfunctions across various disorders, including attention deficit/hyperactivity disorder (ADHD). However, it remains unclear if alterations in sustained DMN suppression, variability and connectivity during prolonged cognitive engagement are implicated in adult ADHD pathophysiology, and to which degree methylphenidate (MPH) remediates any DMN abnormalities. This randomized, double-blinded, placebo-controlled, cross-over clinical trial of MPH (clinicaltrials.gov/ct2/show/NCT01831622) explored large-scale brain network dynamics in 20 adults with ADHD on and off MPH, compared to 27 healthy controls, while performing a reward based decision-making task. DMN task-related activation, variability, and connectivity were estimated and compared between groups and conditions using independent component analysis, dual regression, and Bayesian linear mixed models. The results show that the DMN exhibited more variable activation patterns in unmedicated patients compared to healthy controls. Group differences in functional connectivity both between and within functional networks were evident. Further, functional connectivity between and within attention and DMN networks was sensitive both to task performance and case-control status. MPH altered within-network connectivity of the DMN and visual networks, but not between-network connectivity or temporal variability. This study thus provides novel fMRI evidence of reduced sustained DMN suppression in adults with ADHD during value-based decision-making, a pattern that was not alleviated by MPH. We infer from multiple analytical approaches further support to the default mode interference hypothesis, in that higher DMN activation variability is evident in adult ADHD and associated with lower task performance.

Hunting in Bioluminescent Light: Vision in the Nocturnal Box Jellyfish Copula sivickisi.

Cubomedusae all have a similar set of six eyes on each of their four rhopalia. Still, there is a great variation in activity patterns with some species being strictly day active while others are strictly night active. Here we have examined the visual ecology of the medusa of the night active Copula sivickisi from Okinawa using optics, morphology, electrophysiology, and behavioral experiments. We found the lenses of both the upper and the lower lens eyes to be image forming but under-focused, resulting in low spatial resolution in the order of 10–15°. The photoreceptor physiology is similar in the two lens eyes and they have a single opsin peaking around 460 nm and low temporal resolution with a flicker fusion frequency (fff) of 2.5 Hz indicating adaptions to vision in low light intensities. Further, the outer segments have fluid filled swellings, which may concentrate the light in the photoreceptor membrane by total internal reflections, and thus enhance the signal to noise ratio in the eyes. Finally our behavioral experiments confirmed that the animals use vision when hunting. When they are active at night they seek out high prey-concentration by visual attraction to areas with abundant bioluminescent flashes triggered by their prey.

Activity patterns, socioeconomic status and urban spatial structure: what can social media data tell us?

ABSTRACTIndividual activity patterns are influenced by a wide variety of factors. The more important ones include socioeconomic status (SES) and urban spatial structure. While most previous studies relied heavily on the expensive travel-diary type data, the feasibility of using social media data to support activity pattern analysis has not been evaluated. Despite the various appealing aspects of social media data, including low acquisition cost and relatively wide geographical and international coverage, these data also have many limitations, including the lack of background information of users, such as home locations and SES. A major objective of this study is to explore the extent that Twitter data can be used to support activity pattern analysis. We introduce an approach to determine users’ home and work locations in order to examine the activity patterns of individuals. To infer the SES of individuals, we incorporate the American Community Survey (ACS) data. Using Twitter data for Washington, DC, we analyzed the activity patterns of Twitter users with different SESs. The study clearly demonstrates that while SES is highly important, the urban spatial structure, particularly where jobs are mainly found and the geographical layout of the region, plays a critical role in affecting the variation in activity patterns between users from different communities.

Combined Use of GPS and Accelerometry Reveals Fine Scale Three-Dimensional Foraging Behaviour in the Short-Tailed Shearwater.

Determining the foraging behaviour of free-ranging marine animals is fundamental for assessing their habitat use and how they may respond to changes in the environment. However, despite recent advances in bio-logging technology, collecting information on both at-sea movement patterns and activity budgets still remains difficult in small pelagic seabird species due to the constraints of instrument size. The short-tailed shearwater, the most abundant seabird species in Australia (ca 23 million individuals), is a highly pelagic procellariiform. Despite its ecological importance to the region, almost nothing is known about its at-sea behaviour, in particular, its foraging activity. Using a combination of GPS and tri-axial accelerometer data-loggers, the fine scale three-dimensional foraging behaviour of 10 breeding individuals from two colonies was investigated. Five at-sea behaviours were identified: (1) resting on water, (2) flapping flight, (3) gliding flight, (4) foraging (i.e., surface foraging and diving events), and (5) taking-off. There were substantial intra- and inter- individual variations in activity patterns, with individuals spending on average 45.8% (range: 17.1–70.0%) of time at sea resting on water and 18.2% (range: 2.3–49.6%) foraging. Individuals made 76.4 ± 65.3 dives (range: 8–237) per foraging trip (mean duration 9.0 ± 1.9 s), with dives also recorded during night-time. With the continued miniaturisation of recording devices, the use of combined data-loggers could provide us with further insights into the foraging behaviour of small procellariiforms, helping to better understand interactions with their prey.

Seasonal changes of locomotor activity patterns in the desert isopod Hemilepistus reaumuri

The locomotor activity rhythm of the desert woodlouse Hemilepistus reaumurii was monitored as individuals over the four seasons, under entraining and constant darkness conditions. Results indicated that individuals exhibited an endogenous rhythm of locomotor activity with a circadian period longer in spring than the other seasons whatever the regimen. Due to the important inter-individual variability, no significant difference in period was found between seasons as well as between regimens. Periodogram analysis revealed also an ultradian period around 12 h. Activity was mostly confined to the hours of the photophase or to those of subjective day. The activity pattern showed two main peaks. This bimodal circadian rhythm persisted for as long as the experiments were run, and was clearer in summer and autumn than in winter. The most clearly defined rhythms were found in spring and summer recordings, respectively, under entraining and free running conditions. The variation of activity patterns according to the seasons will be discussed.

Effects of food availability and climate on activity patterns of western black-crested gibbons in an isolated forest fragment in southern Yunnan, China.

The critically endangered western black-crested gibbon (Nomascus concolor) is distributed in isolated habitat fragments in northern Vietnam, northwestern Laos, and southwestern China. To assess the behavioral adaptation of this species to forest fragments and its response to seasonal variation in food availability and climate, we present activity patterns of a group inhabiting an isolated forest based on two year-long studies in southern Yunnan, China. Annually, the gibbons spent nearly half of their active time resting, followed by moving and feeding. In both study periods, the time allocated to activities varied significantly between months, and was affected by food availability and climate factors. The group delayed retirement when tree fruit was abundant, and they decreased time spent moving and playing during periods of low fruit availability. In the cold months, the gibbons decreased time spent moving, and they decreased active time and resting time when rainfall was high. The results suggest that the group may seek to maximize net energy intake like energy maximizers when high quality food is most available, and adopt an energy-conserving strategy during periods of lower food availability and temperature. The gibbons showed similar diurnal variation in activity patterns to a group inhabiting a continuous forest at Dazhaizi, Mt. Wuliang, central Yunnan. However, they had a longer active period, and devoted more time to resting but less time to feeding. The individuals also spent lower percentages of time engaged in social behavior than those at Dazhaizi. These differences may be due to their smaller home range and unusual group composition caused by habitat fragmentation.

The use of wearable technology to measure energy expenditure, physical activity, and sleep patterns in dementia

Project Description Unexplained weight loss is frequently observed in dementia leading to further cognitive decline, frailty and disability. Apparent mechanisms that could lead to weight loss (lower energy intake and/or higher expenditure) remain unresolved and may be different in the various stages and types of dementia. During the progression of the illness, the extent to which altered sleep duration and variable physical activity patterns (intermittent or constant pacing/lying down) could affect weight loss is unknown. We have used an innovative light weight physical activity monitor (Sensewear TM Armband, Body Media, Pittsburgh, PA) to objectively determine total energy expenditure (TEE), sleep duration, physical activity and number of steps in people with dementia living in care homes. The armband was placed around the left upper triceps for up to 7 days. The device measures tri-axial acceleration, skin temperature, galvanic skin response and heat flux and has been shown to be valid in resting, exercise and free-living conditions in older people. The mean age of the residents (n=20) was 78.5 (58-99) years, 50% were women with confirmed diagnosis of a range of dementia types. Body Mass Index (BMI) was 23.0 (range 13.7-30.0) kg/m2 with 40% classified as underweight, 50% normal range, 10% overweight. Duration of sleeping ranged from 0.4-12.5 (mean 5.9) hrs/d and time spent lying down was 1.0-16.0 (8.1) hrs/d. On average residents spent 17.4 (6.0-23.7) hrs/d undertaking sedentary activity. Sleeping duration was inversely related to body weight (r= -0.46, p<0.05) and TEE (r= -0.59, P<0.01). There was an inverse association between time lying down for both body weight (r= -0.45, p<0.05) and TEE (r= -0.62, p<0.01).TEE was positively correlated with number of steps per day (r= 0.45, p<0.05). There was no relationship between TEE or BMI and the amount of physical activity. Variable patterns of physical activity and sleep duration demonstrates the need to recognise the influence of these factors on meeting energy requirements and the challenge of providing appropriate food and nutrition within the care home environment. Thus wearable technology has the potential to offer real-time feedback to support better nutritional management and improve efforts to prevent weight loss in dementia.

Use of an exposure model to explore the impact of residential proximity to a highway on exposures to air pollutants of an ambient origin

Air pollutant exposure models are generally applied to large populations living across wide urban areas, and most do not account for daily variation in activity patterns, which can result in exposure misclassification. Far fewer studies exist where exposure is modeled for specific individuals using detailed time-activity data. We employed a novel application of the US-EPA’s Air Pollution Exposure Model (APEX) to simulate exposure levels for 51 residents living within a small study area (1.5 km2) bisected by a heavily trafficked highway in South Auckland, New Zealand. The model produced daily exposure estimates of nitrogen oxides (NO x ), carbon monoxide (CO), and particulate matter (PM10) for the month of July, 2010. Inputs included pollutant and meteorological data monitored at sites positioned both upwind and downwind of the highway, as well as city monitoring sites north of the study area to represent work locations. A local resident survey provided time-activity diary input. The simulation was run once using the residents’ home locations and four times with the population artificially placed 50 and 150 m downwind, as well as 50 and 150 m upwind, relative to the highway. For NO x and CO, the population was 31–36 % more exposed when positioned 50 m downwind and 17–18 % less exposed at the upwind side (p < 0.001), compared to their actual home locations. An additional 100 m separation downwind resulted in a 56–71 % drop in total mean exposure (p < 0.001) and the difference in exposure levels for certain occupations varied by up to a factor of eight (p < 0.05). PM10 exposure was comparatively stable across the area. The effect of residential proximity and position, occupation and work location, were assessed using generalized linear models (GLMs), followed by post hoc testing. This unique application of APEX shows good promise as a planning tool for assessing the potential benefits of a buffer zone between major roads and residential homes, for particular population groups.

Revisiting osteoarthritis in the Cis-Baikal: Understanding behavioral variability and adaptation among middle Holocene foragers

This examination of osteoarthritis (OA) focuses on better understanding behavioral variability among the middle Holocene foragers of the Cis-Baikal, Siberia, particularly as it pertains to a unique period of diachronic cultural change in the region. The three cemetery populations considered lie on either side of an 800–1000 year biocultural ‘hiatus’—characterized by a cessation in the use of formal cemeteries—and are located in two of the Cis-Baikal's four main micro-regions. Two of the cemetery samples, Lokomotiv and Shamanka II, represent the pre-hiatus early Neolithic (EN) Kitoi culture (8000–7000/6800 cal. BP), while the third, Ust'-Ida I, represents the post-hiatus late Neolithic–early Bronze Age (LN–EBA) Isakovo–Serovo–Glazkovo (or ISG) cultural complex (6000/5800–4000 cal. BP). Results reveal a dynamic pattern of variability across both time and space. Of particular interest is an apparent dichotomy between the two pre-hiatus EN sites, namely considerably higher OA severity at Lokomotiv compared to Shamanka II. This disparity suggests fundamental behavioral differences between the populations despite their contemporaneity and cultural continuity, possibly reflecting distinct residential mobility patterns and population densities in their respective micro-regions. In addition, intra-site analyses reveal that activity may have differed considerably between the sexes, whether in type, intensity, and/or duration. Male-dominated logistical foraging on both sides of the hiatus may explain, at least in part, these discrepancies. Finally, results of intra-joint component analyses of the elbow and knee were similar across age, sex, and cemetery groups, and largely consistent with those of epidemiological studies. Taken together, these results add to our growing understanding of pre- and post-hiatus adaptive strategies in the Cis-Baikal by providing a more detailed picture of the complex and highly variable behavioral and activity patterns employed by the region's middle Holocene foragers.

Nocturnal, diurnal, crepuscular: activity assessments of Pisauridae and Lycosidae

Animals are commonly categorized as diurnal, nocturnal, or crepuscular depending on the times of day when they are most active. These categories, although convenient, would be more useful if we knew more about how closely animal activity conformed to the labels. Similarly, if we knew more about the degree of nocturnality or diurnality of a particular species, we would have increased understanding of the selective forces acting on it. To clarify the intensity of nocturnality or diurnality in lycosoid spiders, we measured activity in 46 spiders divided among three congeneric species of fishing spiders (Pisauridae) and five species of wolf spiders (Lycosidae), in an austere laboratory setting. Overall, the three pisaurid species, pooled, were less than half as active as the five lycosid species, also pooled. All three species of fishing spiders and four of the five species of wolf spiders were strongly nocturnal in their activity. Only one species, the wolf spider Piratula minuta (Emerton 1885), was diurnal. None of the individual spiders that showed statistically significant nocturnal or diurnal activity (31 of 31 lycosids, 14 of 15 pisaurids) was purely nocturnal or diurnal. In all individual cases except for a single ambivalent Dolomedes tenebrosus Hentz 1844 (Pisauridae), statistically strong nocturnality was accompanied by substantial activity during the light hours, and statistically strong diurnality was accompanied by substantial activity during the dark hours. We discuss the overall low variability in activity patterns among the fishing spiders in comparison to the much higher variability among the activity patterns of the wolf spiders, the common but not ubiquitous presence of ultradian periodicities in individual spiders, and the significance of the fact that none of the individual spiders was strictly nocturnal or strictly diurnal.

Do ecologically close species shift their daily activities when in sympatry? A test on chamois in the presence of mouflon

Temporal partitioning of daily activities between species may promote coexistence within animal communities by reducing behavioural interference, particularly when species highly overlap in the use of space and resources. Such a strategy may be used by Alpine chamois (Rupicapra rupicapra rupicapra) when in the presence of mouflon (Ovis gmelini musimon × Ovis sp.), an introduced highly gregarious species with a broader ecological niche, overlapping with that of chamois. Using simultaneous monitoring of 29 Global Positioning System-collared chamois and 12 mouflon, we assessed the temporal variation in activity patterns of chamois amongst two subpopulations: one without mouflon and one with mouflon, during January and August, which are the two most extreme periods of spatial overlap of mouflon with chamois distribution. Substantial differences in activity patterns between chamois and mouflon were observed (mean 13.8 ± 10.5% in January and 10.6 ± 11.6% in August). More subtle differences appeared between both subpopulations of chamois and persisted, regardless of the spatial overlap with mouflon (3.2 ± 1.8% in January and 2.6 ± 1.5% in August), thus highlighting that there is no behavioural interference from mouflon on chamois. Our findings suggest that the temporal partitioning of daily activities between chamois and mouflon, although probably a result of species-specific adaptations to environmental conditions, may contribute to their coexistence. © 2014 The Linnean Society of London, Biological Journal of the Linnean Society, 2014, 111, 621–626.

Association between Sleep Disturbances and Leisure Activities in the Elderly: A Comparison between Men and Women

It has been suggested that physical or social activity is associated with fewer sleep disturbances among elderly people. Women report more sleep disturbances than men, which could indicate a variation in activity patterns between the genders. The aim of this study was to investigate associations between sleep disturbances and leisure activities in men and women (n = 945) aged ≥60 years in a Swedish population. Sleep disturbances were measured using eight dichotomous questions and seventeen variables, covering a wide range of leisure activities. Few leisure activities were found to be associated with sleep disturbances and their importance decreased when the models were adjusted for confounders and gender interactions. After clustering the leisure activities and investigating individual activities, sociointellectual activities were shown to be significant for sleep. However, following adjustment for confounders and gender interactions, home maintenance was the only activity significant for sleep. Being a female increased the effect of home maintenance. Besides those leisure activities, poor/fair self-rated health (OR 7.50, CI: 4.27–11.81) and being female (OR 4.86, CI: 2.75–8.61) were found to have the highest association with poor sleep. Leisure activities pursued by elderly people should focus on activities of a sociointellectual nature, especially among women, to promote sleep.

Individual variability of wild juvenile Atlantic salmon activity patterns: effect of flow stage, temperature, and habitat use

The magnitude of variation of diel activity patterns and habitat use of wild Atlantic salmon (Salmo salar) parr was examined during the summer and autumn through a gradient of declining temperature. Fish were marked with passive integrated transponders and tracked using a large network of flatbed antennas. High interindividual variability was observed, as some individuals were predominantly nocturnal whereas others frequently changed their daily activity pattern. Overall fish activity decreased with decreasing temperature and increasing flow stage, but most of these changes in daily activity were observed in crepuscular periods. Parr used habitats with lower velocity at night than in the day during the summer, but not in the autumn. Furthermore, there was no difference between day and night habitats for fish that were cathemeral (active both day and night during a given day), so differences between day and night habitats were the result of individuals adopting different activity patterns. These results suggest that habitat interacts with activity pattern, as individuals using suboptimal habitats seem to increase daytime foraging to secure sufficient energy. Temporal and among-fish variability of activity patterns illustrate the dynamic nature of foraging decisions that may partly result from trade-offs experienced at the microhabitat scale.

A methodological analysis of behavioural observation in social African mole rats (Bathyergidae, Rodentia)

This study evaluates a number of methodological aspects regarding the recording and analysis of social behaviour in mole rat colonies (Bathyergidae, Rodentia). Behavioural observations were carried out on a colony of wild-caught Fukomys micklemi, in order to define an efficient, standardised method for future research. First, durations of work behaviour were scored and compared with data expressed as frequencies (recording method used in previous research). Second, a comparison was made between a terrarium set-up and a set-up with a perspex tunnel system, including a digging unit. Third, observations were carried out at different times of the day in order to map daily activity patterns. Our results show that the set-up with the tunnel system evokes more work activity and increases behavioural resolution. Using frequencies showed to be a better proxy for activity than the labour-intensive scoring of durations. Interindividual variation in activity patterns over a 24-h period were shown to be highly variable, and the moment of peak activity was not consistent. Observations should thus be carried out randomly during the day to avoid any temporal bias.

Differential limb loading in miniature pigs (Sus scrofa domesticus): a test of chondral modeling theory.

Variation in mechanical loading is known to influence chondrogenesis during joint formation. However, the interaction among chondrocyte behavior and variation in activity patterns is incompletely understood, hindering our knowledge of limb ontogeny and function. Here, the role of endurance exercise in the development of articular and physeal cartilage in the humeral head was examined in 14 miniature swine (Sus scrofa domesticus). One group was subjected to graded treadmill running over a period of 17 weeks. A matched sedentary group was confined to individual pens. Hematoxylin and eosin staining was performed for histomorphometry of cartilage zone thickness, chondrocyte count and cell area, with these parameters compared multivariately between exercised and sedentary groups. Comparisons were also made with femora from the same sample, focusing on humerus-femur differences between exercised and sedentary groups, within-cohort comparisons of humerus-femur responses and correlated changes within and across joints. This study shows conflicting support for the chondral modeling theory. The humeral articular cartilage of exercised pigs was thinner than that of sedentary pigs, but their physeal cartilage was thicker. While articular and physeal cartilage demonstrated between-cohort differences, humeral physeal cartilage exhibited load-induced responses of greater magnitude than humeral articular cartilage. Controlling for cohort, the humerus showed increased chondrocyte mitosis and cell area, presumably due to relatively greater loading than the femur. This represents the first known effort to evaluate chondral modeling across multiple joints from the same individuals. Our findings suggest the chondral response to elevated loading is complex, varying within and among joints. This has important implications for understanding joint biomechanics and development.

Weighted phase lag index stability as an artifact resistant measure to detect cognitive EEG activity during locomotion

BackgroundHigh-density electroencephalography (EEG) with active electrodes allows for monitoring of electrocortical dynamics during human walking but movement artifacts have the potential to dominate the signal. One potential method for recovering cognitive brain dynamics in the presence of gait-related artifact is the Weighted Phase Lag Index.MethodsWe tested the ability of Weighted Phase Lag Index to recover event-related potentials during locomotion. Weighted Phase Lag Index is a functional connectivity measure that quantified how consistently 90° (or 270°) phase ‘lagging’ one EEG signal was compared to another. 248-channel EEG was recorded as eight subjects performed a visual oddball discrimination and response task during standing and walking (0.8 or 1.2 m/s) on a treadmill.ResultsApplying Weighted Phase Lag Index across channels we were able to recover a p300-like cognitive response during walking. This response was similar to the classic amplitude-based p300 we also recovered during standing. We also showed that the Weighted Phase Lag Index detects more complex and variable activity patterns than traditional voltage-amplitude measures. This variability makes it challenging to compare brain activity over time and across subjects. In contrast, a statistical metric of the index’s variability, calculated over a moving time window, provided a more generalized measure of behavior. Weighted Phase Lag Index Stability returned a peak change of 1.8% + −0.5% from baseline for the walking case and 3.9% + −1.3% for the standing case.ConclusionsThese findings suggest that both Weighted Phase Lag Index and Weighted Phase Lag Index Stability have potential for the on-line analysis of cognitive dynamics within EEG during human movement. The latter may be more useful from extracting general principles of neural behavior across subjects and conditions.

The functional magnetic resonance imaging-based verbal fluency test in obsessive–compulsive disorder

Clinical use of functional magnetic resonance imaging (fMRI) in obsessive–compulsive disorder (OCD) is limited by a relative absence of fMRI task development, standardization, and normative performance databases. We investigated the fMRI-based verbal fluency test (f-VFT) by quantitatively evaluating brain activation patterns in OCD participants (8 females and 4 males) compared with a normative database (16 females and 16 males). At the group level, OCD participants and references had highly similar activation in left-hemisphere language regions, including the precentral/premotor cortex, thalamus, basal ganglia, and inferior frontal gyrus/frontal operculum. At the interindividual level, however, the OCD group had highly variable activation patterns in the dorsal and ventral regions of the pre-supplementary motor area (pre-SMA) that may correspond with differences in demographic and clinical variables. Further, there were significant correlations in the OCD participants between pre-SMA dorsal and ventral activation and between dorsal pre-SMA activation and perfectionism. Our findings suggest considerable functional anatomical overlap in left-hemisphere language regions between OCD participants and references but significantly higher pre-SMA interindividual variability in OCD compared to the reference group that may be relevant in clinical fMRI application and the theoretical understanding of OCD.

Nocturnal Activity Patterns of Northern Myotis (Myotis septentrionalis) during the Maternity Season in West Virginia (USA)

Nocturnal activity patterns of northern myotis (Myotis septentrionalis) at diurnal roost trees remain largely uninvestigated. For example, the influence of reproductive status, weather, and roost tree and surrounding habitat characteristics on timing of emergence, intra-night activity, and entrance at their roost trees is poorly known. We examined nocturnal activity patterns of northern myotis maternity colonies during pregnancy and lactation at diurnal roost trees situated in areas that were and were not subjected to recent prescribed fires at the Fernow Experimental Forest, West Virginia from 2007 to 2009. According to exit counts and acoustic data, northern myotis colony sizes were similar between reproductive periods and roost tree settings. However, intra-night activity patterns differed slightly between reproductive periods and roost trees in burned and non-burned areas. Weather variables poorly explained variation in activity patterns during pregnancy, but precipitation and temperature were negatively associated with activity patterns during lactation.

Prediction of hip contact forces and muscle activations during walking at different speeds

The validation of musculoskeletal models is a challenging task necessary to obtain confidence in the numerical predictions they can provide. In this paper, a musculoskeletal model of the lower limb is used to predict the hip contact forces and muscle activations resulting from walking at different speeds for three total hip replacement patients implanted with instrumented prostheses (Bergmann et al., J. Biomech. 34:859–871, 2001). The developed model is shown to estimate the magnitude of hip contact forces with encouraging accuracy in terms of relative peak error (on average within 22% of the experimental value) and global prediction error measurements. Hip contact force predictions were found to be generally more accurate for a slow walking speed. The static optimization technique adopted to estimate muscle activation profiles reproduced for the majority of muscles the modulation and variation in activation patterns documented in the literature for different walking speeds.

Different Means to the Same End: Long-Distance Migrant Seabirds from Two Colonies Differ in Behaviour, Despite Common Wintering Grounds

Although seabirds that are trans-equatorial migrants show apparently broad overlap among populations in the non-breeding season, such large-scale pattern may conceal subtle but nevertheless key differences in migratory behaviour. These specializations could reflect adaptation to different environments during the breeding season, carry-over effects from the breeding to the nonbreeding period, or asymmetries in competitive ability of birds of different origin. We compared the migratory and wintering behaviour of Cory's shearwaters Calonectris diomedea nesting in Berlengas and in the Selvagens, two colonies in contrasting oceanographic environments, separated by ca. 1200 km. Although no differences were found in winter distribution, there was a marked divergence in timing, route and the use of staging areas during the postbreeding (autumn) migration. Birds from Berlengas typically travelled to oceanic waters in the North Atlantic for an extended stopover, whereas those from Selvagens rarely did so. In the South Atlantic, birds from Selvagens spent more time in flight, perhaps because they had higher energy and nutrient requirements for feather replacement compared to birds from Berlengas, which moult more flight feathers during breeding. Stable isotope analyses of feathers suggested that this variation in activity patterns was unrelated to trophic ecology. Differences in migration routes and stopovers may expose populations to distinct threats, and should be taken into consideration when defining units for conservation purposes and developing appropriate management strategies.