Survival of Svalbard pink-footed geese Anser brachyrhynchus in relation to winter climate, density and land-use

1. Global change may strongly affect population dynamics, but mechanisms remain elusive. Several Arctic goose species have increased considerably during the last decades. Climate, and land-use changes outside the breeding area have been invoked as causes but have not been tested. We analysed the relationships between conditions on wintering and migration staging areas, and survival in Svalbard pink-footed geese Anser brachyrhynchus. Using mark-recapture data from 14 winters (1989-2002) we estimated survival rates and tested for time trends, and effects of climate, goose density and land-use. 2. Resighting rates differed for males and females, were higher for birds recorded during the previous winter and changed smoothly over time. Survival rates did not differ between sexes, varied over time with a nonsignificant negative trend, and were higher for the first interval after marking (0.88-0.97) than afterwards (0.74-0.93). Average survival estimates were 0.967 (SE 0.026) for the first and 0.861 (SE 0.023) for all later survival intervals. 3. We combined 16 winter and spring climate covariates into two principal components axes. F1 was related to warm/wet winters and an early spring on the Norwegian staging areas and F2 to dry/cold winters. We expected that F1 would be positively related to survival and F2 negatively. F1 explained 23% of survival variation (F1,10=3.24; one-sided P=0.051) when alone in a model and 28% (F1,9=4.50; one-sided P=0.031) in a model that assumed a trend for survival. In contrast, neither F2 nor density, land-use, or scaring practices on important Norwegian spring staging areas had discernible effects on survival. 4. Climate change may thus affect goose population dynamics, with warmer winters and earlier springs enhancing survival and fecundity. A possible mechanism is increased food availability on Danish wintering and Norwegian staging areas. As geese are among the main herbivores in Arctic ecosystems, climate change, by increasing goose populations, may have important indirect effects on Arctic vegetation. Our study also highlights the importance of events outside the breeding area for the population dynamics of migrant species.     

The energetics of barnacle geese (Branta leucopsis) flying in captive and wild conditions

Experimental data on the relationship between mean heart rate (f(H)) and mean rate of oxygen consumption (VO(2)) of captive barnacle geese during flights in a wind tunnel are assessed in terms of their capacity to predict the typical VO(2) of wild barnacle geese, based on the recordings of their f(H), while undertaking autumn migratory flights between Spitsbergen (78 degrees N) and Caerlaverock, Scotland (55 degrees N). A significant linear relationship has been demonstrated between the f(H) and simultaneously recorded VO(2) of a single barnacle goose (B-B) flying in the wind tunnel (VO(2)=1.42 f(H)-304, r(2)=0.82, P<0.001, N=12 flights). Data recorded from three additional geese (N=4 flights), lay within the 95% prediction intervals of the relationship for goose B-B. When these geese (mean body mass=2.06 kg, n=4) were flown in the wind tunnel (WT) without the mask, they had a mean f(H) of 451+/-23 beats min(-1), yielding an estimate for VO(2) of 336+/-33 ml min(-1). However, f(H) has also been recorded from wild barnacle geese (mean migratory f(H) of 253 beats min(-1)), and substitution of this value into the above calibration equation results in an unrealistically low value for mean migratory VO(2) of only 55 ml min(-1). Various factors, such as differences in heart mass, selective tissue perfusion, environmental temperature and flock formation, which might account for some of the difference in f(H) between the captive and wild geese are discussed. Comparison with other WT studies shows that inter-species minimum mass-specific VO(2) declines with increasing body mass (M(b); range 0.035-2.8 kg) as 173 M(b)(-0.224), r(2)=0.848.     

Assessing body condition and energy budget components by scoring abdominal profiles in free-ranging pink-footed geese Anser brachyrhynchus

An abdominal profile index (API) was developed for pink-footed geese Anser brachyrhynchus as a measure of body condition. On basis of carcass analysis of 56 adult geese with known API prior to collection, we found significant linear relationships between API against body mass, abdominal fat and total energy content. Hence, changes in API reflect net energy intake rates. As an example of the applicability of the calibration, we compared APIs of individually marked geese before and after long migration episodes and estimated the cost of flight at 8.9 kJ/km. In addition we estimated gain rates at three major staging sites along the spring flyway indicating an increase in fueling rates with latitude. Calibration of APIs and energy contents offers new opportunities for field studies of waterfowl energetics.     

Minimal intra-seasonal dietary overlap of barnacle and pink-footed geese on their breeding grounds in Svalbard

We analysed barnacle Branta leucopsis and pink-footed goose Anser brachyrhynchus summer diets (May–July 2003) based on the proportions of different plant constituents in the faecal material of adult breeding birds in Sassendalen, Svalbard to assess potential inter-specific competition. Diets were highly restricted and overlapped little during pre-nesting and post hatch. During incubation both species showed greatest variety in their diet, reflecting site-specific differences in local food abundance. However, locally the diets of pink-footed and barnacle geese resembled each other most at this time (although still differing significantly). The conflicting needs of nest defence and maintenance of body condition constrains the extent of the feeding resource utilised by nesting pairs and explains slightly greater dietary overlap at this time. Hence, there is little evidence of inter-specific competition (interference or depletion) at present, but this is most likely to be manifest during the incubation period in the future if goose numbers continue to increase. More detailed investigations of the degree of spatial overlap of the two species and their effects on plant structure, quality and community composition are necessary to predict likely outcomes of expected increases in numbers of both goose species.     

Heart rate and rate of oxygen consumption during flight of the barnacle goose, Branta leucopsis

We report the first measurements of heart rate (f(H)) and the rate of oxygen consumption (V(O(2))) during flights from a species of bird larger than 500 g. V(O(2))was obtained from nine forward flapping flights of 8.9 min mean duration at a mean speed of 13.2 m s(-1) performed by three barnacle geese of mean mass 1.68 kg. Mean V(O(2))was 332 ml min(-1)or 201 ml min(-1) kg(-1). Sixteen flights were obtained from two of these birds equipped with heart rate data loggers, both when they were wearing a V(O(2)) mask and when they were not. During flights with the mask (mean duration 7.4 min), mean f(H) was 472 beats per min and during flights without the mask (mean duration 8.0 min) it was 391 beats per min. Heart rate was also measured in another goose flying without a respiratory mask and mean f(H) for all the three birds (mean mass 1.7 kg) flying without a mask for an average of 7.9 min at 13 m s(-1) was 378 beats per min. Resting f(H) for these three birds was 79 beats per min. The values of f(H) during flight are greater than those obtained from the same species during their autumn migration from Spitsbergen to southern Scotland. The possible reasons for this are discussed.     

Variation in daily and seasonal foraging routines of non-breeding barnacle geese (Branta leucopsis): working harder does not overcome environmental constraints

This study describes the changes in stored body fat in Svalbard barnacle geese Branta leucopsis over the non-breeding period, and uses behavioural patterns to explain the variation in body fat stores. It was predicted that foraging effort would: (1) increase at low food densities; (2) increase when days were short; (3) decrease in smaller flocks; (4) be bimodally distributed throughout the day for long days, but constant for short days. Time constraints were found to be the major driving force behind foraging decisions during the shortest days of mid-winter, whereas food density was found to drive decisions during longer days. Field observations of fat stores showed that fat was rapidly accumulated at the start and end of the non-breeding period, but that fat stores remained constant during mid-winter. It is suggested that day length prevented a positive fat storage rate in mid-winter through the limitation of foraging time, even though foraging effort was high during this period. During a single day, evidence for a bimodal foraging routine was found, where feeding activity was concentrated in the early morning and late afternoon periods. This pattern was found in the full range of day lengths, which suggests that even for short days, feeding must be interrupted so that other essential activities can be conducted. It is concluded that the behavioural choices of barnacle geese were constrained by environmental conditions, and that these behavioural patterns allow the variation in fat stores to be explained.     

Vegetation growth and a seasonal habitat shift of the barnacle goose (Branta leucopsis)

Summary Barnacle geese (Branta leucopsis) wintering on the island of Schiermonnikoog in the Netherlands abruptly switch all their foraging activities from a dairy pasture (a polder) to an adjacent salt-marsh during the early spring. We present evidence to show that this shift is related to changes in the quality of the diet available in these different habitats. Barnacle geese shift from polder to salt-marsh at the precise time that these are equal in dietary protein availability, which occurs as the food plants on the salt-marsh undergo a sudden spring growth. The dairy pasture undergoes its own spring growth shortly afterwards, and more dietary protein is available there for the rest of the year. We suggest that the salt-marsh is a more preferred habitat, but that low dietary protein during the winter prevents its use by barnacle geese. We hypothesize that the salt-marsh may be more preferred due to a lower level of disturbance which permits geese to graze more slowly, improving the utilization of food plants.     

Finding food in a highly seasonal landscape: where and how pink footed geese Anser brachyrhynchus forage during the Arctic spring

Food accessibility and availability in the highly seasonal Arctic landscape can be restricted by snow cover and frozen substrate, particularly in early spring. Therefore, to determine how a long distance migratory herbivore forages in such a landscape, pink‐footed geese Anser brachyrhynchus at an early spring feeding area in Svalbard were studied. Birds arrived in mid May when extensive snow cover restricted habitat availability. Geese fed in all habitats, but the highest densities occurred in wet tundra. However, prolonged snow lie restricted access to wet areas compared to dry and mesic habitats. Above ground biomass was very low in all habitats; yet sizeable amounts occurred below ground. In line with this, the majority of birds (86%) grubbed for below ground plant storage organs such as stem bases and rhizomes. Wet habitat contained greater quantities of edible and lower amounts of inedible below ground material (ratio 1:0.3) than dry (ratio 1:9) or mesic (ratio 1:4) areas. Although foraging in wet habitat prevented geese from encountering high proportions of inedible plant parts, forage species characteristic of this habitat, such as Dupontia grasses and the rush Eriophorum scheuchzeri, were more difficult to extract than food plants typical of drier habitats such as the forb Bistorta vivipara. Hence, we suggest that wet areas are preferred by pink‐footed geese, but the prolonged snow lie there made it necessary to use less preferred but much more abundant drier habitats, which experienced earlier snowmelt and indeed accommodated more than half of all goose foraging recordings.     

The effect of mate change and new partner's age on reproductive success in the barnacle goose, Branta leucopsis

Mate retention frequencies and correlations between mate changeand reproductive performance were estimated in a populationof barnacle geese, Branta leucopsis, breeding on the islandof Gotland in the Baltic. About 90% of the pairs remained togetherfrom one breeding season to the next. Only 2.4% of the pairsdivorced, most mate changes being consequences of the deathof one partner. Divorces were not forecast by low reproductivesuccess, and seemed to be accidental. In the season before matechange, there was no difference in reproductive performance,measured as clutch size, hatching date, and number of fledgedyoung, between faithful pairs and pairs where one partner wassubsequently changed. However, in the first season with a newpartner, clutch size and number of fledged young decreased onaverage. Hence, because mate change led to a reduction in reproductivesuccess, it was concluded that mate retention is advantageous.Our results suggest that this reduction is more likely due tothe lower average age or breeding experience of new partnersthan to the benefits of breeding experience with one particularpartner. [Behav Ecol 1991 ;2:116–122]     

Modelling pink-footed goose (Anser brachyrhynchus) wintering distributions for the year 2050: potential effects of land-use change in Europe

Feeding on farmland by overwintering populations of pink-footed geese ( Anser brachyrhynchus ) conflicts with agricultural interests in Northern Europe. In order to forecast the potential future of this conflict, we used generalized linear models to relate the presence and absence of pink-footed geese to variables describing the contemporary landscape, and predicted their future distributions in relation to two land-use scenarios for the year 2050. One future scenario represented a global, economically orientated world (A1) and the other represented a regional, environmentally concerned world (B2). The probability of goose occurrence increased within cropland and grassland, and could be explained by their proximity to coast, elevation, and the degree of habitat closure. Predictions to future scenarios revealed noticeable shifts in the suitability of goose habitat evident at the local and regional scale in response to future shifts in land use. In particular, as grasslands and croplands give way to unsuitable land-use types (e.g. woody biofuel crops, increased urbanization, and forest) under both future scenarios, our models predicted a decrease in habitat suitability for geese. If coupled with continued goose population expansion, we expect that the agricultural conflict will intensify under the A1 and particularly the B2 scenarios.     

Causes of the redistribution of Pink-footed Geese Anser brachyrhynchus in Britain

The numbers of Pink-footed Geese Anser brachyrhynchus wintering in Britain have been increasing exponentially since the 1950s. The numbers of geese at virtually all roost sites have increased, but the most dramatic increase has been in Norfolk, the southernmost region occupied in Britain. This redistribution was most likely caused either by the increase in the population forcing greater numbers of geese towards more southerly sites as the result of a buffer effect, by a decrease in the quality of sites elsewhere in the range or by an increase in the attractiveness of Norfolk. Co-ordinated counts of geese around Britain and historical data of changes in agricultural practice in Norfolk were used to examine these possibilities. No evidence was found for buffer effects, degradation of sites elsewhere or an increase in food availability in Norfolk. The major difference between Norfolk and other Pink-footed Goose sites is in the food type available in Norfolk, namely harvested Sugar Beet Beta vulgaris remains. This food is of high quality and the geese are not disturbed whilst feeding on it because of its limited commercial value. The pattern of redistribution of Pink-footed Geese may therefore be the result of cultural learning of the benefits of feeding on Sugar Beet.     

Trends in annual and seasonal survival of Pink-footed Geese Anser brachyrhynchus

Adult Pink-footed Geese Anser brachyrhynchus from the Svalbard breeding population were neck-banded and resighted in staging and wintering areas outside the breeding season 1990–1999. We estimated annual and seasonal survival using capture–recapture statistical models. Mean annual survival was 0.829, declining over the study period from 0.90 to 0.79. The annual cycle was partitioned into three periods: summer (1 April–30 September), including both spring and autumn migration, autumn (1 October–31 December), including most shooting, and winter (1 January–31 March). The parsimonious model selected to describe seasonal survival included a declining trend in summer survival, constant autumn and winter survival with lower survival in the severe winter of 1996, and an additive effect of sex on summer and winter survival. Monthly survival was highest during winter. Decreasing summer survival was the main contributor to the overall decline in annual survival, and was attributed mainly to increasing natural mortality on the breeding grounds. Mean annual survival based on the seasonal survival probabilities was 0.835 for females and 0.805 for males. The effect of sex was most pronounced during summer and remains to be explained.     

印度Ladakh地区斑头雁的数量、种群结构和栖息地利用

于 1998、 2 0 0 0和 2 0 0 2年在印度的Ladakh地区进行了野外考察以研究斑头雁的繁殖行为和种群大小。Ladakh地区的斑头雁集小群在淡水湖泊中的小岛上进行繁殖 ,不在树上和悬崖上繁殖。 5月份开始产卵。群内孵化的同步性较低。盐水湖岸上没有观察到进行繁殖或带有幼雏的斑头雁。作者所调查的Ladakh地区有 35 0 - 10 0 0只斑头雁 ,该物种的数量满足了Ramsar公约的有关规定 ,建议将该地区列为国际重要地区     

Insect ectoparasites on wild birds in the Czech Republic during the pre-breeding period

Wild passerine birds (Passeriformes) from the northeastern part of the Czech Republic were examined for ectoparasites during the pre-breeding period in 2007. Two species of fleas of the genera Ceratophyllus and Dasypsyllus (Siphonaptera: Ceratophyllidae), and 23 species of chewing lice belonging to the genera Ricinus, Myrsidea, Menacanthus (Phthiraptera: Menoponidae), Brueelia, Penenirmus, and Philopterus (Phthiraptera: Philopteridae) were found on 108 birds of 16 species. Distribution of insect ectoparasites found on wild birds during pre-breeding was compared with previous data from the post-breeding period. There was no difference in total prevalence of chewing lice in pre-breeding and post-breeding periods. Higher prevalence of fleas and slightly higher mean intensity of chewing lice were found on birds during the pre-breeding period. There was a significant difference in total prevalence but equal mean intensity of chewing lice on resident and migrating birds.     

Energy limitations for spring migration and breeding: the case of brent geese Branta bernicla tracked by satellite telemetry to Svalbard and Greenland

Brent geese were tracked by satellite telemetry from spring staging areas in Denmark to Arctic breeding areas in Svalbard and Greenland in 1997 and 2001. From estimated departure masses and carcass analysis we used flight mechnical theory to estimate maximum flight ranges of both sexes, and remaining stores of fat and protein upon arrival in females. Model predictions suggested that all birds but one exceptionally thin male could easily reach Svalbard, but that approximately one third of the males and half of the females would have problems with flying to Greenland. Nevertheless, some birds even flew longer than the models predicted. In addition, females predicted to be capable of making the flight to Greenland, were predicted to arrive almost lean of fat. This contradicts our expectation that these birds are capital breeders – that they depend on endogenous stores of fat and protein when initiating and incubating their eggs. We discuss how the Greenland breeding sub-population during 1985–1998 has been able to grow at the same rate as the sub-population breeding in Svalbard, despite the added flight distance of 700–1000 km, and despite the birds predicted shortage of fat stores on arrival. We suggest four hypotheses that alone or in combination could explain the discrepancy between model predictions and observations. These are that most birds: (1) refuel on stop-overs in Spitsbergen en route to Greenland; (2) pick favourable tail-winds enabling them to reduce flight costs; (3) fly in formation and thereby save energy; and/or (4) undergo gut atrophy immediately prior to departure, and use the nutrients mobilised by catabolism of the digestive system to build larger pectoral muscles. The latter option would both reduce their airframe fraction, and increase their fat and flight-muscle fractions, enabling them to fly longer. We conclude that the latter option seems less likely to operate in brent geese.     

西藏夯错水鸟多样性及斑头雁繁殖活动区的变化

于2009年4-11月,对西藏夯错的水鸟资源状况进行了调查,旨在了解该地区水鸟资源状况的了解,并为禽流感的防控提供了科学依据.在夯错全年共记录到水鸟26种,隶属于6目10科.夯错也是斑头雁和棕头鸥重要的繁殖地.水鸟春秋季迁徙高峰期在4月份和10月份,这也是水鸟多样性较高的2个月,其主要原因是由于迁徙鸭类数量和种类的增加.卫星跟踪研究表明,在繁殖前期,斑头雁活动区面积较大,主要在夯错及其周围的湿地取食;进入繁殖中期,斑头雁的活动范围减少了许多;繁殖后期,随着幼鸟陆续出壳.父母随即带领幼鸟离开夯错,到其它湿地取食和育雏,因此此期的活动区面积较大.由于夯错面积较小,不能满足斑头雁对食物的需求,因此部分斑头雁选择其它湿地作为主要的取食地,但部分扩散到其它湿地的斑头雁在迁徙前期重新返回夯错,使得该时期斑头雁的数量有呈上升趋势.通过与青海湖水鸟资源状况的比较发现,夯错水鸟种类较少.这可能主要是由于两个湖泊所处地理区划的不同,并由此带来的气候环境的差异,以及植被条件的不同所造成的.这种差异主要是由于夯错海拔较高.紫外线很强,气候干燥,植被单一,栖息地类型多样性较低,因此水鸟的种数也相对较少一些.     

Effects of snow cover on the timing and success of reproduction in high-Arctic pink-footed geese <Emphasis Type="Italic">Anser brachyrhynchus</Emphasis>

During four breeding seasons, 2003–2006, we studied the relationship between snow cover and nesting performance in pink-footed geese (Anser brachyrhynchus) in a key breeding site on Svalbard. Snow cover in late May, i.e., at the time of egg laying of geese, was derived from MODIS satellite images. Snow cover had a profound cascading effect on reproductive output via the number of nesting pairs and timing of nesting, which affected nest success, while there was only a tendency for a negative effect on clutch size. Hence, we estimated a five-fold difference in the number of young produced (to post-hatching) between years with little snow and years with high snow cover. The results from the study area correlated with whole-population productivity estimates recorded in autumn. Thus, snow cover derived from MODIS satellite images appears to provide a useful indicator of the breeding conditions in the Arctic.     

Changes in body mass and organ size during wing moult in non-breeding greylag geese Anser anser

The "cost-benefit" hypothesis states that specific body organs show mass changes consistent with a trade-off between the importance of their function and cost of their maintenance. We tested four predictions from this hypothesis using data on non-breeding greylag geese Anser anser during the course of remigial moult: namely that (i) pectoral muscles and heart would atrophy followed by hypertrophy, (ii) leg muscles would hypertrophy followed by atrophy, (iii) that digestive organs and liver would atrophy followed by hypertrophy and (iv) fat depots be depleted. Dissection of geese captured on three different dates during wing moult on the Danish island of Saltholm provided data on locomotory muscles and digestive organ size that confirmed these predictions. Locomotory organs associated with flight showed initial atrophy (a maximum loss of 23% of the initial pectoral muscle mass and 37% heart tissue) followed by hypertrophy as birds regained the powers of flight. Locomotory organs associated with running (leg muscles, since geese habitually run to the safety of water from predator-type stimuli) showed initial hypertrophy (a maximum gain of 37% over initial mass) followed by atrophy. The intestines and liver showed initial atrophy (41% and 37% respectively), consistent with observed reductions in daily time spent feeding during moult, followed by hypertrophy. The majority of the 22% loss in overall body mass (mean 760 g) during the flightless period involved fat utilisation, apparently consumed to meet shortfalls between daily energetic needs and observed rates of exogenous intake. The results support the hypothesis that such phenotypic plasticity in size of fat stores, locomotor and digestive organs can be interpreted as an evolutionary adaptation to meet the conflicting needs of the wing moult.