Changes in nutrient dynamics of midcontinent greater white-fronted geese during spring migration

Waterfowl and other migratory birds commonly store nutrients at traditional staging areas during spring for later use during migration and reproduction. We investigated nutrient-storage dynamics in the midcontinent population of greater white-fronted geese (Anser albifrons; hereafter white-fronted geese) at spring staging sites in the Rainwater Basin of Nebraska during February–April and in southern Saskatchewan during April–May, 1998 and 1999. In Nebraska, lipid content of white-fronted geese did not increase, and protein content changed little over time for most age and sex categories. In Saskatchewan, lipids increased 11.4 g/day (SE = 1.7) and protein content increased 1.6 g/day (SE = 0.6) in the sample of adult geese collected over a 3-week period. A study conducted during 1979–1980 in the Rainwater Basin reported that white-fronted geese gained 8.8–17.7 g of lipids per day during spring, differing greatly from our results 2 decades later. In addition, lipid levels were less in the 1990s compared to spring 1980 for adult geese nearing departure from staging sites in Saskatchewan. This shift in where geese acquired nutrient stores from Nebraska to more northern staging sites coincided with a decrease in availability of waste corn in Nebraska, their primary food source while staging at that stopover site, and an increase in cultivation of high-energy pulse crops in Saskatchewan. White-fronted geese exhibited flexibility in nutrient dynamics during spring migration, likely in response to landscape-level variation in food availability caused by changes in agricultural trends and practices. Maintaining a wide distribution of wetlands in the Great Plains may allow spring-staging waterfowl to disperse across the region and facilitate access to high-energy foods over a larger cropland base. © 2011 The Wildlife Society.     

Seasonal variation in nutritional characteristics of the diet of greater white-fronted geese

We studied diet and habitat use of greater white-fronted geese (Anser albifrons) from autumn through spring on their primary staging and wintering areas in the Pacific Flyway, 1979–1982. There have been few previous studies of resource use and forage quality of wintering greater white-fronted geese in North America, and as a consequence there has been little empirical support for management practices pertaining to habitat conservation of this broadly distributed species. Observations of >2,500 flocks of geese and collections of foraging birds revealed seasonal and geographic variation in resource use reflective of changes in habitat availability, selection, and fluctuating physiological demands. Autumn migrants from Alaska arrived first in the Klamath Basin of California and southern Oregon, where they fed on barley, oats, wheat, and potatoes. Geese migrated from the Klamath Basin into the Central Valley of California in late autumn where they exploited agricultural crops rich in soluble carbohydrates, with geese in the Sacramento Valley feeding almost exclusively on rice and birds on the Sacramento–San Joaquin Delta primarily utilizing corn. White-fronted geese began their northward migration in late winter, and by early spring most had returned to the Klamath Basin where 37% of flocks were found in fields of new growth cultivated and wild grasses. Cereal grains and potatoes ingested by geese were low in protein (7–14%) and high in soluble nutrients (17–47% neutral detergent fiber [NDF]), whereas grasses were low in available energy (47–49% NDF) but high in protein (26–42%). Greater white-fronted geese are generalist herbivores and can exploit a variety of carbohydrate-rich cultivated crops, likely making these geese less susceptible to winter food shortages than prior to the agriculturalization of the North American landscape. However, agricultural landscapes can be extremely dynamic and may be less predictable in the long-term than the historic environments to which geese are adapted. Thus far greater white-fronted geese have proved resilient to changes in land cover in the Pacific Flyway and by altering their migration regime have even been able to adapt to changes in the availability of suitable forage crops. © 2010 The Wildlife Society.     

Spring snow goose hunting influences body composition of waterfowl staging in Nebraska

A spring hunt was instituted in North America to reduce abundance of snow geese (Chen caerulescens) by increasing mortality of adults directly, yet disturbance from hunting activities can indirectly influence body condition and ultimately, reproductive success. We estimated effects of hunting disturbance by comparing body composition of snow geese and non-target species, greater white-fronted geese (Anser albifrons) and northern pintails (Anas acuta) collected in portions of south-central Nebraska that were open (eastern Rainwater Basin, ERB) and closed (western Rainwater Basin, WRB; and central Platte River Valley, CPRV) to snow goose hunting during springs 1998 and 1999. Lipid content of 170 snow geese was 25% (57 g) less in areas open to hunting compared to areas closed during hunting season but similar in all areas after hunting was concluded in the ERB. Protein content of snow geese was 3% (14 g) less in the region open to hunting. Greater white-fronted geese had 24% (76 g; n = 129) less lipids in the hunted portion of the study area during hunting season, and this difference persisted after conclusion of hunting season. We found little difference in lipid or protein content of northern pintails in relation to spring hunting. Indirect effects of spring hunting may be considered a collateral benefit regarding efforts to reduce overabundant snow goose populations. Disrupted nutrient storage observed in greater white-fronted geese represents an unintended consequence of spring hunting that has potential to adversely affect reproduction for this and other species of waterbirds staging in the region. © 2012 The Wildlife Society.     

Seasonal changes in condition, reproduction and fecundity in the wild European rabbit (Oryctolagus cuniculus)

A total of 1248 rabbits ( Oryctolagus amiculus ) were shot on farmland in Cambridgeshire, UK over a period of three years. This provided pooled estimates of changes in reproductive and body condition and of fecundity during the annual cycle. Both males and females showed a significant annual cycle in reproductive condition as indicated by changes in the size of the gonads and accessory glands of reproduction. No females were pregnant during October, November and December, but males with active spermatogenesis were found during every month of the year. The distribution of pregnancies through the year showed that the reproductive season varied greatly between individuals. Peak fecundity occurred during April, May and June. On average, each female conceived 23.9 and suckled 17.2 young per breeding season. Proportionately more young died during the early stages of the reproductive season. The body weight of adult males, but not of females, varied seasonally. Body condition (kidney fat index) in adults was maximal at the start of the breeding season and minimal at the end.     

Lifetime individual plasticity in body condition of a migratory bird

Body condition is an important trait that reflects the capacity of individuals to acquire food or resist disease, eventually allowing successful reproduction and survival. We first quantified the effects of condition on life history and a secondary sexual trait using long‐term lifetime data on condition in a migratory bird species, the barn swallow, Hirundo rustica. Second, we quantified sources of individual variation in condition by separating the within‐individual from the between‐individual components of variation of environmental condition and age on body condition. Therefore, we were able to partition variation as a result of selection and phenotypic plasticity. Within‐individual variation in body condition increased in early life until middle age (i.e. 3–4 years of age) in the two sexes followed by only a slight decrease in body condition during senescence in males but not in females. After accounting for age‐dependent variation, condition could be partitioned into a within‐individual plastic response to environmental conditions during migration and a nonplastic response (i.e. a between‐individual difference) to environmental conditions experienced in the African winter quarters. Specifically, there was a within‐individual increase in body condition as environmental conditions during migration improved in both males and females, independent of age. There was a between‐individual effect of condition found in the winter quarter in body condition of females, but not in males, which was attributed to the disappearance of females in poor body condition from the study population as a result of the higher natal dispersal of low‐quality females compared to high‐quality ones during years with favourable environmental conditions in the African winter quarters. Males and females also tended to be in better body condition during the warmer springs upon arrival at the breeding grounds. There was a temporal decline in female body condition during 1991–2007, whereas no significant trend was detected in males. Therefore, both intrinsic (e.g. age and sex) and extrinsic factors (e.g. climate) affected body condition. © 2011 The Linnean Society of London, Biological Journal of the Linnean Society, 2012, 105 , 420–434.     

A preliminary analysis of the diet composition of overwintering Bean geese (Anser fabalis) and greater white-fronted geese (A. albifrons) in Korea using PCR on fecal samples

Bean geese (Anser fabalis) and Greater white-fronted geese (Anser albifrons) are the dominant wintering waterfowl in South Korea. Although they are commonly observed in estuaries and rice fields during the winter, the diet composition of the geese during the winter has rarely been studied. In this study, we provide the results from preliminary analyses on the diet of these two geese species overwintering in Daebu Island of South Korea. We used a total of 13 fecal samples from Bean geese (n?=?4) and Greater white-fronted geese (n?=?9), and performed a BLAST search for the sequences obtained from 87 clones (n?=?36 for Bean geese and n?=?51 for Greater white-fronted geese). The diet of Bean geese consisted of five families of plants: Caryophyllaceae (75.0%), Poaceae (13.9%), Asteraceae (5.5%), Polygonaceae (2.8%) and Cucurbitacea (2.8%). On the other hand, the diet of Greater white-fronted geese consisted of 6 families of plants: Poaceae (74.5%), Caryophyllaceae (9.8%), Solanacea (5.9%), Portulacaceae (3.9%), Lamiaceae (3.9%) and Brassicaceae (2.0%). We found that plants of the rice family (Poaceae) are important in the diet of wintering geese, especially for Greater white-fronted geese. This knowledge can be used to establish conservation strategies of the geese overwintering in South Korea.     

Hermaphroditism in two populations of Chiton articulatus (Mollusca: Polyplacophora) from the eastern tropical coast of México

Through histological analyses, this study reveals an unusually high incidence of hermaphroditism in Chiton articulatus. Specimens were sampled every 30?days between September 2010 and September 2011 at two locations (Las Brisas and Jaramillo beaches, Acapulco) on the tropical eastern Pacific coast of Mexico. At both sites, hermaphroditism was found throughout the year, although in varying proportions. Higher percentages of hermaphroditism were found during the pre-spawning summer months (Las Brisas Beach 63%, Jaramillo Beach 68%). Two different kinds of hermaphroditic gonads were found, showing a preponderance of either male or female tissues but, commonly, female tissues occupied the greatest part of the gonad cross sections. Similar to other species of polyplacophorans, there was a predominance of males, although M:F sex ratios ranged from 0.7 to 4.5: 1 at Las Brisas Beach and 0.3–8: 1 at Jaramillo Beach.     

Changes in Agriculture and Abundance of Snow Geese Affect Carrying Capacity of Sandhill Cranes in Nebraska

ABSTRACT The central Platte River valley (CPRV) in Nebraska, USA, is a key spring-staging area for approximately 80% of the midcontinent population of sandhill cranes (Grus canadensis; hereafter cranes). Evidence that staging cranes acquired less lipid reserves during the 1990s compared to the late 1970s and increases in use of the CPRV by snow geese (Chen caerulescens) prompted us to investigate availability of waste corn and quantify spatial and temporal patterns of crane and waterfowl use of the region. We developed a predictive model to assess impacts of changes in availability of corn and snow goose abundance under past, present, and potential future conditions. Over a hypothetical 60-day staging period, predicted energy demand of cranes and waterfowl increased 87% between the late 1970s and 1998–2007, primarily because peak abundances of snow geese increased by 650,000 and cranes by 110,000. Compared to spring 1979, corn available when cranes arrived was 20% less in 1998 and 68% less in 1999; consequently, the area of cornfields required to meet crane needs increased from 14,464 ha in 1979 to 32,751 ha in 1998 and 90,559 ha in 1999. Using a pooled estimate of 88 kg/ha from springs 1998–1999 and 2005–2007, the area of cornfields needed to supply food requirements of cranes and waterfowl increased to 65,587 ha and was greatest in the eastern region of the CPRV, where an estimated 54% of cranes, 47% of Canada geese (Branta canadensis), 45% of greater white-fronted geese (Anser albifrons), and 46% of snow geese occurred during ground surveys. We estimated that a future reduction of 25% in available corn or cornfields would increase daily foraging flight distances of cranes by 27–38%. Crane use and ability of cranes to store lipid reserves in the CPRV could be reduced substantially if flight distance required to locate adequate corn exceeded a physiological maximum distance cranes could fly in search of food. Options to increase carrying capacity for cranes include increasing accessibility of cornfields by restoring degraded river channels to disperse roosting cranes and increasing wetland availability in the Rainwater Basin to attract snow geese using the CPRV.     

Physical growth of northern fur seals (Callorhinus ursinus): seasonal fluctuations and migratory influences

Growth curves are described for males, pregnant females, and non-pregnant females using morphometric measurements collected from over 18000 northern fur seals ( Callorhinus ursinus ) shot at sea between California and the Bering Sea from 1958 to 1974. Seals of all ages experience seasonal increases and decreases in body mass and length. Seasonal fluctuations of body length may be an artefact of mass displacement caused by seasonal changes in mass. Rapid growth and gain in mass occur during a brief one to three month period as the population migrates northward through the coastal waters of northern British Columbia and Alaska on their way to the Pribilof Islands. Body mass of females and immature males is gradually lost while fasting on land and wintering along the coasts of Washington, Oregon, and California. Pregnant females are both heavier and longer than non-pregnant females of the same age. Body mass in pregnant females levels off with age in contrast with the increasing mass of non-pregnant females. Growth of northern fur seals does not appear to stop at an upper asymptote, but continues throughout their life spans.     

Thermal relations of dwarf caiman, Paleosuchus palpebrosus, in a hillside stream: Evidence for an unusual thermal niche among crocodilians

Body temperatures of 13 Paleosuchus palpebrosus, 7 males and 6 females, were monitored by radio-telemetry during cold periods (dry season) and warm periods (wet and dry seasons) in a stream draining into the Brazilian Pantanal. The mass of the caimans varied from 2.5 to 20.0 kg, and snout–vent length from 47.5 to 95.0 cm. Mean monthly body temperature was 21.6 °C, and varied from 20.1 to 25.6 °C throughout the year. Body temperature was correlated with air and water temperature but did not differ between males and females. Unlike all other crocodilians investigated in detail to date, the caimans did not show evidence of attempts to obtain higher body temperatures when ambient temperatures were low, and had low and generally constant temperatures in relation to the surrounding air and water throughout the year. The caimans remained in burrows during cold periods in the dry season, which may explain why they did not seek higher temperatures. Tolerance of relatively low and constant body temperatures may be a key adaptation of species of Paleosuchus, allowing them to occupy environments inhospitable to other crocodilians.     

Growth of Greater White-Fronted Goose Goslings Relates to Population Dynamics at Multiple Scales

The abundance of greater white-fronted geese (Anser albifrons frontalis) on the Arctic Coastal Plain (ACP) of northern Alaska, USA, has more than tripled since the late 1990s; however, recent rate of annual population growth has declined as population size increased, which may indicate white-fronted geese on the ACP are approaching carrying capacity. We examined rates of gosling growth in greater white-fronted geese at 3 sites on the ACP during 2012–2014 to assist with predictions of future population trends and assess evidence for density-dependent constraints on recruitment. We marked goslings at hatch with individually coded webtags and conducted brood drives during early August to capture, measure, and weigh goslings. Annual estimates of gosling mass at 32 days old (range = 1,190–1,685) indicate that goslings had obtained >60% of asymptotic size. This rate of growth corresponds with that of other goose species and populations with access to high-quality forage and no limitations on forage availability, and is consistent with the overall increase in abundance of white-fronted geese at the ACP scale. Contrary to most previous investigations, age-adjusted mass of goslings did not decline with hatch date. Goslings grew faster in coastal areas than at inland freshwater sites. Taken together, these findings suggest forage was not limiting gosling growth rates in either ecosystem, but forage was of greater quality in coastal areas where goose foraging habitat is expanding because of permafrost subsidence. Spatial patterns of gosling growth corresponded with local-scale patterns of population density and population change; the areas with greatest rates of gosling growth were those with the greatest population density and rates of population increase. We found little evidence to suggest forage during brood rearing was limiting population increase of white-fronted geese on the ACP. Factors responsible for the apparent slowing of ACP-wide population growth are likely those that occur in stages of the annual cycle outside of the breeding grounds. Published 2021. This article is a U.S. Government work and is in the public domain in the USA.     

Dynamics and ecological consequences of avian influenza virus infection in greater white-fronted geese in their winter staging areas

Recent outbreaks of highly pathogenic avian influenza (HPAI) in poultry have raised interest in the interplay between avian influenza (AI) viruses and their wild hosts. Studies linking virus ecology to host ecology are still scarce, particularly for non-duck species. Here, we link capture–resighting data of greater white-fronted geese Anser albifrons albifrons with the AI virus infection data collected during capture in The Netherlands in four consecutive winters. We ask what factors are related to AI virus prevalence and whether there are ecological consequences associated with AI virus infection in staging white-fronted geese. Mean seasonal (low pathogenic) AI virus prevalence ranged between 2.5 and 10.7 per cent, among the highest reported values for non-duck species, and occurred in distinct peaks with near-zero prevalence before and after. Throat samples had a 2.4 times higher detection frequency than cloacal samples. AI virus infection was significantly related to age and body mass in some but not other winters. AI virus infection was not related to resighting probability, nor to maximum distance travelled, which was at least 191 km during the short infectious lifespan of an AI virus. Our results suggest that transmission via the respiratory route could be an important transmission route of AI virus in this species. Near-zero prevalence upon arrival on their wintering grounds, in combination with the epidemic nature of AI virus infections in white-fronted geese, suggests that white-fronted geese are not likely to disperse Asian AI viruses from their Siberian breeding grounds to their European wintering areas.     

Regional and interannual variations in spawning activity of Pacific saury Cololabis saira during northward migration in spring in the north-western Pacific

Regional and interannual variations in spawning activity of Pacific saury Cololabis saira during the northward migration in spring were investigated for 1995–1997 in the north-western Pacific. Only females with a large body size (≥270–290 mm knob length) appeared to spawn. Almost all females in this cohort were actively spawning in a region of sea surface temperature ( T _SS) >18° C, the proportion of active spawners appeared positively related to T _SS in a region of 13° C < T _SS≤ 18° C, and no females were spawning in the region of T _SS≤13° C. Although this relationship between spawning activity and T _SS was common in all years, the distribution of females in the large-size cohort among the regions varied interannually. Consequently, the proportion of active spawners among adult females showed considerable interannual variations.     

Sexual selection on male body size and mating behaviour in American toads,Bufo americanus

Mating behaviour of B. americanus was observed from 1985 to 1987. The population contained 38–45 males and 11–26 females, depending on the year. The breeding season of this ‘explosive breeder’ usually encompassed less than 48 h. Male reproductive success varied from zero to two matings per season and zero to an estimated 15 126 zygotes per season. All females mated once per season and variation in their zygote production was estimated to be 4017–11 624 zygotes per season. Body length explained 76% of the variation in zygote production of females. However, male body length was only weakly correlated with mating success in two of three seasons, and with zygote production in one of three seasons. Male arm length was predicted to correlate with male mating success because longer arms should facilitate remaining clasped to females when challenged by rival males. However, mating males did not differ from non-mating males in arm length, and the relationship between arm length and body length was the same for the sexes. Various male behaviours were measured using focal-animal sampling but only call rate correlated with male mating success. The pattern of size dimorphism (females larger than males) is consistent with the observed sex-specific relationships between reproductive success and body size.     

Egg fertility among vasectomized and non‐vasectomized male resident Canada geese at the Wildlife Conservation Park/Bronx Zoo

In 1991, a vasectomy program was initiated at the Wildlife Conservation Park/Bronx Zoo to minimize the population growth of resident Canada geese (Branta canadensis). Sixty‐nine males were vasectomized over a 6‐year period. From 1994 to 1998, egg fertility was examined in females paired with vasectomized and non‐vasectomized geese. Of the 340 eggs laid by females paired with vasectomized males, 12% were fertile. In comparsion, of the 526 eggs laid by females paired with non‐vasectomized males, 90% were fertile. The vasectomy procedure was easier to perform on males captured during the breeding season than on those captured during molt owing to the enlarged size of the vas deferens. Where resident Canada goose populations are small and resources available, the implementation of a vasectomy program can be effective in reducing population growth. Zoo Biol 19:35–40, 2000. © 2000 Wiley‐Liss, Inc.     

Seasonal changes in energy and the energy cost of spawning in Gulf of Alaska Pacific cod

In the Gulf of Alaska, adult Pacific cod exhibited an annual cycle of condition, gonad index and liver index in which maximum values occurred in ripe fish in March and minima in July. About 30–31 % of prespawning stored energy was expended during the spawning effort. The energy associated with spawning derived from liver (24% and 18%), somatic tissue (22% and 33%) and gonad (53% and 48%) for females and males, respectively. Liver index and gonad index at the time of sampling were directly related in females, but in males gonad index was best related to liver index 1–3 months earlier.
The Pacific cod is very similar to the Atlantic cod in terms of energy cycling, maximum gonad sizes, energy expended during spawning and gonadal contribution to energy expenditure. However, in Pacific cod, somatic tissue contributes markedly to energy expended during reproduction. The Pacific cod cod differs from the walleye pollock with respect to gonad index (13% and 20%ν. 20% and 8% for females and males, respectively), spawning weight loss (25%ν. 38%), liver energy loss during spawning (71%ν. 55%) and energy cost of spawning.     

How does environmental variation influence body mass,body size,and body condition? Roe deer as a case study

We tested the influence of population density and of drought intensity (measured as the Gaussen Index in spring and summer of the year of birth) on winter body mass, hind foot length, and body condition of roe deer fawns. Body mass decreased with increasing density and increased with increasing Gaussen Index in summer, in a similar way for both males and females. Hind foot length of males showed the same response. On the other hand, hind foot length of females decreased with increasing density only after dry summers, hence when environmental conditions were very harsh. Body condition was affected neither by density nor by drought intensity. Our results indicate that body mass and size are much better indicators of phenotypic quality than body condition in roe deer. The sex-specific responses of body size to environmental conditions could correspond to a differential allocation in favour of daughters by heavier than average roe deer mothers.     

Short and chubby or long and slim? Food intake,growth and body condition in free‐ranging pythons

Abstract An animal's sex and body size can influence not only its rate of food consumption, but also the way in which it allocates the resultant energy among the competing demands of maintenance, growth, reproduction and storage. A 13‐year mark–recapture study of pythons (Liasis fuscus) in tropical Australia provides extensive data on these topics. Rates of food intake and growth were highest in small pythons, and decreased more rapidly with body size in males than in females. Allocation to storage (as measured by the snake's mass relative to its body length) showed a more complex pattern. Body condition was high at hatching, but dropped rapidly as energy was allocated to growth rather than storage. Condition then increased through juvenile life, was at a maximum close to maturation, and was higher in females than in conspecific males. Body condition thereafter decreased with increasing body length. These allocation ‘decisions’ reflect the relative advantages of growth versus energy storage at different body sizes. Hatchling snakes grow rapidly (and hence become thin) because greater body size enables the snake to ingest larger prey items. Adult females amass larger energy reserves than males, because they need reserves to produce the clutch. Large snakes become thinner because their feeding rates are low, and they cannot compensate with increased prey size because large‐bodied mammalian prey are rare in our study area.     

Spatial distribution and features of biology of Pacific sleeper shark Somniosus pacificus in the North Pacific

The results of the investigations of spatial and vertical distribution of Pacific sleeper shark Somniosus pacificus in the North Pacific Ocean conducted for many years are presented. In addition, the size distribution and features of biology of the species are studied. The largest abundance of the species is registered in the Bering Sea, western Gulf of Alaska, eastern Aleutian Islands, and Pacific waters of northern Kuril Islands and southeastern Kamchatka. The species is the most abundant near the bottom at the depth from 200 to 700 m and in the pelagic waters at a depth of 100–200 m. The average depths of the catches of Pacific sleeper shark substantially change over the year reaching minimum values in June and maximum values in December. Vertical daily migrations (to the water column at night and to the bottom during the day) are registered. The catches are represented by fish 26–352 cm in length, and sharks 100–200 cm in length prevail. The males are noticeably smaller than the females. In general, condition of the fishes decreases and feeding intensity increases with growth. Food composition substantially changes with the increase of body length: consumption of squids decreases and consumption of crustaceans, fishes, and fishery wastes increases. The food composition is slightly different in the females and males.     

Latitudinal variation in population structure of wintering Pacific Black Brant

ABSTRACT.   Latitudinal variation in population structure during the winter has been reported in many migratory birds, but has been documented in few species of waterfowl. Variation in environmental and social conditions at wintering sites can potentially influence the population dynamics of differential migrants. We examined latitudinal variation in sex and age classes of wintering Pacific Black Brant ( Branta bernicla nigricans ). Brant are distributed along a wide latitudinal gradient from Alaska to Mexico during the winter. Accordingly, migration distances for brant using different wintering locations are highly variable and winter settlement patterns are likely associated with a spatially variable food resource. We used resightings of brant banded in southwestern Alaska to examine sex and age ratios of birds wintering at Boundary Bay in British Columbia, and at San Quintin Bay, Ojo de Liebre Lagoon, and San Ignacio Lagoon in Baja California from 1998 to 2000. Sex ratios were similar among wintering locations for adults and were consistent with the mating strategy of geese. The distribution of juveniles varied among wintering areas, with greater proportions of juveniles observed at northern (San Quintin Bay and Ojo de Liebre Lagoon) than at southern (San Ignacio Lagoon) locations in Baja California. We suggest that age-related variation in the winter distribution of Pacific Black Brant is mediated by variation in productivity among individuals at different wintering locations and by social interactions among wintering family groups.