The occurrence and performance of leucistic Barnacle Geese Branta leucopsis

The paper reports the occurrence of whitish 'leucistic' forms in populations of Barnacle Geese Branta leucopsis. A total of 15 (including 11 in the last 21 years) have been reported in the population breeding in Svalbard and wintering in the Solway Firth, northern Britain, whereas the two other populations, though much larger, have produced only one bird of the same type between them in the last 30 years. Leucism is controlled by a single, recessive allele.
The median lifespan of leucistic birds is 2–3 years, compared to 8–10 years for normal plumaged birds. This is because they are sought out by (illegal) hunters. There is no evidence that there is any difference in pairing or breeding performance between white and normal birds, though one male, which is still alive aged 18 years, has produced 13 young; this performance is matched fay less than 2% of normal geese.
It is suggested that the Svalbard population was established recently, from a few founders from the Siberian population; if one or two of these carried the allele controlling leucism, this would explain its much higher prevalence in this population than in the other discrete groups of Barnacle Geese.     

The population structure of Greenland Barnacle Geese Branta leucopsis on the wintering grounds on Islay

The population structure of the Greenland Barnacle Goose Branta leucopsis at its main winter haunt, the island of Islay, Scotland, was studied using marked individuals caught at three sites on their breeding grounds in east Greenland and on the wintering grounds on Islay. The distribution of individual geese on Islay was found to be non-random. Birds were generally faithful to restricted groups of sites on the island, both within a winter and between consecutive winters. These groups of sites on Islay held different proportions of the individuals from the three catch sites in Greenland. Birds caught together in Greenland were associating in winter more than would be expected if their distribution were random.     

Environmentally induced morphological variation in the Barnacle Goose,Branta leucopsis

The environmental conditions to which juvenile barnacle geese (Branta leucopsis) were exposed during growth were found to affect their body size at fledging as well as their final adult body size. Small juveniles showed compensatory growth from the time of fledging up to one year of age, but this did not fully compensate the differences in body size that were established before fledging. The variation in protein content in plants eaten during growth could probably explain the observed body size differences, sometimes of more than 10%, between different categories of adult geese. Our results imply that one cannot infer selection on morphological characters from differences between samples of adult birds from different localities or from different cohorts within a population, without first showing that environmental conditions during growth do not affect the development of the characters under study.     

Possible effects of local enrichment by gulls on feeding-site selection by wintering Barnacle Geese Branta leucopsis

The selection of salt-marsh feeding sites by wintering Barnacle Geese Branta leucopsis was investigated on Schiermonnikoog, The Netherlands. Use of sites by geese was estimated by counts of goose droppings. Geese spent significantly more time grazing in sites with evidence of Herring Gull Larus argentatus and Lesser Black-backed Gull Lfuscus breeding activity than in nearby non-gull sites. The nitrogen content of red fescue grass Festuca rubra was significantly greater in gull sites. We suggest that the geese preferred to feed in these locations because of the improved nutritional value of the grass. The higher nitrogen content of F. rubra in gull sites was most likely the result of nutrient inputs from gull droppings rather than goose droppings.     

Intraclutch egg-size variation in the Barnacle Goose Branta leucopsis: an egg-removal experiment

We carried out an egg-removal experiment on Barnacle Geese Branta leucopsis to test the hypothesis that tactile contact between the brood patch and eggs accumulating in the nest during laying was causally related to intraclutch egg-size variation, acting through the development of incubation behaviour. Egg removal had no effect on mean egg mass, relaying interval or clutch size: mean (±s.e.) clutch sizes for first clutches were 4.9 ± 0.9 and 4.7 ± 0.9 eggs for control and experimental females, respectively. We therefore conclude that Barnacle Geese have a determinate pattern of egg laying. Daily removal of all eggs from the first-laid egg did not affect the within-clutch pattern of egg-size variation: in both control and experimental clutches the first egg was relatively small, the second or third egg was largest and there was a linear decline in egg size to the smallest, last-laid egg. There was no significant difference in either the absolute or relative size of the last-laid eggs in control and experimental clutches. Tactile contact with eggs in the nest, therefore, is not required for the expression of intraclutch egg-size variation in Barnacle Geese. In this respect, determinate-laying Barnacle Geese differ from species with indeterminate laying patterns (e.g. gulls) where egg removal does affect the normal pattern of within-clutch egg-size variation. If hormonal changes (e.g. prolactin) associated with onset of incubation are causally related to the intraclutch decrease in egg size, then the stimuli involved appear to differ between determinate and indeterminate layers.     

The development of a genome wide SNP set for the Barnacle goose Branta leucopsis

Migratory birds are of particular interest for population genetics because of the high connectivity between habitats and populations. A high degree of connectivity requires using many genetic markers to achieve the required statistical power, and a genome wide SNP set can fit this purpose. Here we present the development of a genome wide SNP set for the Barnacle Goose Branta leucopsis, a model species for the study of bird migration. We used the genome of a different waterfowl species, Mallard Anas platyrhynchos, as a reference to align Barnacle Goose second generation sequence reads from an RRL library and detected 2188 SNPs genome wide. Furthermore, we used chimeric flanking sequences, merged from both Mallard and Barnacle Goose DNA sequence information, to create primers for validation by genotyping. Validation with a 384 SNP genotyping set resulted in 374 (97%) successfully typed SNPs in the assay, of which 358 (96%) were polymorphic. Additionally, we validated our SNPs on relatively old (30 years) museum samples, which resulted in a success rate of at least 80%. This shows that museum samples could be used in standard SNP genotyping assays. Our study also shows that the genome of a related species can be used as reference to detect genome wide SNPs in birds, because genomes of birds are highly conserved. This is illustrated by the use of chimeric flanking sequences, which showed that the incorporation of flanking nucleotides from Mallard into Barnacle Goose sequences lead to equal genotyping performance when compared to flanking sequences solely composed of Barnacle Goose sequence.     

Body size, performance and fitness in galapagos marine iguanas

Complex organismal traits such as body size are influenced byinnumerable selective pressures, making the prediction of evolutionarytrajectories for those traits difficult. A potentially powerfulway to predict fitness in natural systems is to study the compositeresponse of individuals in terms of performance measures, suchas foraging or reproductive performance. Once key performancemeasures are identified in this top-down approach, we can determinethe underlying physiological mechanisms and gain predictivepower over long-term evolutionary processes. Here we use marineiguanas as a model system where body size differs by more thanone order of magnitude between island populations. We identifiedforaging efficiency as the main performance measure that constrainsbody size. Mechanistically, foraging performance is determinedby food pasture height and the thermal environment, influencingintake and digestion. Stress hormones may be a flexible wayof influencing an individual's response to low-food situationsthat may be caused by high population density, famines, or anthropogenicdisturbances like oil spills. Reproductive performance, on theother hand, increases with body size and is mediated by highersurvival of larger hatchlings from larger females and increasedmating success of larger males. Reproductive performance ofmales may be adjusted via plastic hormonal feedback mechanismsthat allow individuals to assess their social rank annuallywithin the current population size structure. When integrated,these data suggest that reproductive performance favors increasedbody size (influenced by reproductive hormones), with an overalllimit imposed by foraging performance (influenced by stresshormones). Based on our mechanistic understanding of individualperformances we predicted an evolutionary increase in maximumbody size caused by global warming trends. We support this predictionusing specimens collected during 1905. We also show in a common-gardenexperiment that body size may have a genetic component in iguanids.This ‘performance paradigm’ allows predictions aboutadaptive evolution in natural populations.     

Barnacle Goose (Branta leucopsis) feeding ecology and trophic relationships on Kolguev Island: The usage patterns of nutritional resources in tundra and seashore habitats

Insight into colonization of new areas by invasive species and their relationships with aboriginal species is a major challenge in ecology, allowing for prediction of the outcome of biological invasions. In this context, the current expansion of the Barnacle Goose (Branta leucopsis) is of great interest. The seasonal dynamics of Barnacle Goose feeding and the structure of its diet on Kolguev Island during the nesting and postnesting periods (May 27–July 29) have been examined. The diet structures of the invasive Barnacle Goose and the aboriginal species White-fronted goose (Anser albifrons) and Bean goose (A. fabalis) have been compared. The probability of interspecific competition and the ecological advantages in the diet patterns of these species have been estimated. If the Barnacle Goose population on Kolguev Island continues to increase, this may led to a decline in the population of aboriginal species of geese on the island.     

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.     

Factors affecting nest defence in female Canada Geese Branta canadensis

The effect of various characteristics of Canada Goose Branta canadensis females and clutch size on their nest defence intensity during incubation was studied in the field during five nesting seasons. Nests were approached by a human, and the leaving distance was measured. Risk-taking in post-encounter behaviour was categorized at three levels. Nesting success was significantly associated with nest tenacity, a variable derived from leaving distance, but not with post-encounter behaviour. Nest tenacity, as well as post-encounter behaviour, differed significantly between individuals. Intensity of post-encounter behaviour, but not nest tenacity, increased with increasing age of the female. Nest tenacity, standardized over the incubation period, increased with increasing clutch size, but post-encounter behaviour intensity did not. None of the nest defence variables was correlated with the structural size of the female. Nest tenacity, but not post-encounter behaviour intensity, increased during incubation. Nest tenacity did not differ between early and late breeders, but post-encounter behaviour was more intense in late breeders. There was no evidence of positive reinforcement of nest defence through repeated visits. Nest defence did not differ between lakes, lake types or nest site types, nor was it affected by the distance to the nearest neighbouring nest. The results supported several of the predictions extracted from parental investment theory.     

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.     

Bryophyte DNA sequences from faeces of an arctic herbivore, barnacle goose (Branta leucopsis)

We tested DNA extraction methods and PCR conditions for the amplification of bryophyte DNA from barnacle goose (Branta leucopsis) faeces collected from Spitsbergen (Svalbard). Both the Qiagen stool kit and a silica-based extraction method received sufficient DNA from fresh and older droppings, as indicated by successful amplification of the plastid psbA-trnH spacer. Standard Taq polymerase outperformed two hot start polymerases. Sequencing of cloned PCR products revealed at least ten moss and two angiosperm sequences. This first example of identifying bryophyte DNA from faeces will allow analysing moss diets of arctic herbivores with a DNA barcoding approach.     

Host-Adapted Cryptosporidium spp. in Canada Geese (Branta canadensis)

The prevalence and distribution of Cryptosporidium spp. in the fecal droppings of the free-living waterfowl Canada geese were examined at 13 sites in Ohio and Illinois. On the basis of the analysis of the small-subunit rRNA gene by PCR, followed by restriction fragment length polymorphism analysis and DNA sequencing, 49 (23.4%) of 209 fecal specimens collected from 10 sites (76.9%) were positive for Cryptosporidium spp. The following five Cryptosporidium species and genotypes were identified: Cryptosporidium goose genotype I (in 36 specimens), Cryptosporidium goose genotype II (in 9 specimens), Cryptosporidium duck genotype (in 1 specimen), Cryptosporidium parvum (in 4 specimens), and C. hominis (in 2 specimens). Cryptosporidium goose genotype I was the most prevalent parasite and was found at all five Cryptosporidium-positive sites in Ohio and at four of five positive sites in Illinois, followed by Cryptosporidium goose genotype II, which was found at two of five positive sites in Ohio and at four of five positive sites in Illinois. Cryptosporidium goose genotype II was detected for the first time, and it is phylogenetically related to goose genotype I and the duck genotype. All three genotypes have not so far been reported in humans, and their pathogenicity in geese has not been determined. Only 10.2% of the Cryptosporidium-positive specimens had C. parvum and C. hominis. The results of this study indicate that Canada geese might only serve as accidental carriers of cryptosporidia infectious to humans and probably play a minor role in the animal-to-human transmission cycle of the pathogen.     

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]     

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.     

A multifactorial explanation for variation in breeding performance of Brent Geese Branta bernicla

The dramatic differences in annual breeding success of Dark-bellied Brent Geese Branta b. bernicla are generally interpreted as being caused by variable conditions on the arctic breeding grounds. The recently revived discussion on this issue mentions, in particular, the cyclic variation in abundance of lemmings, resulting in cyclic variation of predation pressure on bird nests by arctic foxes, as the main factor determining whether Brent Geese are able to breed successfully or not. New data on the spring condition of Brent Geese in Western Europe and wind conditions during migration from the spring staging areas to the breeding grounds show that these factors also influence breeding output.     

Shared or Unshared Parental Care in Overwintering Brent Geese (Branta bernicla hrota)

We examine brood size effects on the behaviour of wintering parent and juvenile brent geese (Branta bernicla hrota) to test predictions of shared and unshared parental care models. The behaviour of both parents and offspring appear to be influenced by declining food availability over the winter. Parental vigilance increased with brood size and may be explained by vigilance having functions in addition to antipredator behaviour where the benefits are shared among the brood. There was no increase in parental aggression with brood size and this does not fit the prediction of shared care. Nevertheless, large families are able to monopolize better feeding areas compared with smaller families and large families static feed more but walk feed less than do small families, the former apparently being the preferred mode. The presence of additional young, rather than increasing the amount of parental aggression, seems to enhance the family's competitive ability. Because parents with large broods benefit from enhanced access to resources there is likely to be no additional significant cost in the parental care of larger broods (sensu Trivers 1972 ).