State-dependent incubation behaviour in the zebra finch

State dependence is thought to be an important factor in resource allocation decisions, particularly in those decisions relating to parental care. Incubation behaviour is a costly part of avian parental care, and therefore likely to depend on the parent's body condition. We manipulated the body condition of zebra finches, Taeniopygia guttata, during incubation by using prelaying diets of different protein content, and induced birds to lay a similar number of eggs. We tested the hypothesis that birds in better body condition would invest more in incubation than birds in poorer condition when incubating on the same diet. Females that had received a high-protein prelaying diet lost more body mass than those that had received a low-protein diet. They also increased the length of their incubation bouts between early and middle incubation, whereas females that had received a low-protein prelaying diet increased bout length only between middle and late incubation. There were no differences between males from the two diet groups, and males were responsible for a lesser proportion of incubation than females. These results indicate that incubation behaviour is state dependent in female zebra finches, and that birds of different body condition adopt different incubation strategies. We found no differences in incubation duration and hatching success between the two incubation strategies in captivity, but the potential risk of nest predation in the wild may differ. We suggest that only females in good condition can afford to adopt a strategy of increasing bout length early in incubation; females in poorer condition first have to recover their body condition after having produced a clutch. Copyright 2003 Published by Elsevier Science Ltd on behalf of The Association for the Study of Animal Behaviour       

Travel schedules to the high arctic: barnacle geese trade-off the timing of migration with accumulation of fat deposits

On their way from the wintering area to the breeding grounds in Spitsbergen, barnacle geese Branta leucopsis stage on islands off the coast of Norway. The aim of this study was to describe when the geese migrate in relation to the body stores deposited and explore questions related to the concept of optimal migration schedules and on the possible mechanisms involved. We estimated fat stores by repeated assessments of the abdominal profile index of individually marked females throughout staging. Reproductive success was derived from observations of the same individuals later in the annual cycle. Females arriving late, or with low fat stores at arrival, achieved higher fat deposition rates, probably by spending more time foraging. But they were unable to match final fat scores of birds that arrived earlier or with larger fat stores. Reproductive success was correlated with the timing of migration and individuals departing at intermediate dates achieved highest success. The exact date of peak reproductive success depended on the size of fat stores accumulated, such that low-quality birds (depositing less fat) benefited most from an early departure to the breeding grounds. Observations in the breeding colonies showed that these birds did not initiate a nest earlier but they spent a longer time in Spitsbergen before settling. The length of stay in Norway was close to the prediction derived from an optimisation model relating spring events to eventual breeding success. Poorest performing birds stayed longer than expected, perhaps depositing more fat to avoid the risk of starvation. Two possible mechanisms of the timing of migration were contrasted and it seemed that the geese departed for migration as soon as they were unable to accumulate any more fat stores.     

The reliance on distant resources for egg formation in high Arctic breeding barnacle geese Branta leucopsis

Breeding in the high Arctic is time constrained and animals should therefore start with their annual reproduction as early as possible. To allow for such early reproduction in migratory birds, females arrive at the breeding grounds either with body stores or they try to rapidly develop their eggs after arrival using local resources. Svalbard breeding barnacle geese Branta leucopsis have to fly non‐stop for about 1100 km from their last continental staging site to the archipelago making the transport of body stores costly. However, environmental conditions at the breeding grounds are highly unpredictable favouring residual body stores allowing for egg production after arrival on the breeding grounds. We estimated the reliance on southern continental resources, i.e. body stores for egg formation, in barnacle geese using stable isotope ratios in the geese's forage along the flyway and in their eggs. Females adopted mixed breeding strategies by using southern resources as well as local resources to varying extents for egg formation. Southern capital in lipid‐free yolk averaged 41% (range: 23–65%), early laid eggs containing more southern capital than eggs laid late in the season. Yolk lipids and albumen did not vary over time and averaged a southern capital proportion of 54% (range: 32–73%) and 47% (range: 25–88%), respectively. Our findings indicate that female geese vary the use of southern resources when synthesising their eggs and this allocation also varies among egg tissues. Their mixed and flexible use of distant and local resources potentially allows for adaptive adjustments to environmental conditions encountered at the archipelago just before breeding.     

Genetic consequences of breaking migratory traditions in barnacle geese Branta leucopsis

Cultural transmission of migratory traditions enables species to deal with their environment based on experiences from earlier generations. Also, it allows a more adequate and rapid response to rapidly changing environments. When individuals break with their migratory traditions, new population structures can emerge that may affect gene flow. Recently, the migratory traditions of the Barnacle Goose Branta leucopsis changed, and new populations differing in migratory distance emerged. Here, we investigate the population genetic structure of the Barnacle Goose to evaluate the consequences of altered migratory traditions. We used a set of 358 single nucleotide polymorphism (SNP) markers to genotype 418 individuals from breeding populations in Greenland, Spitsbergen, Russia, Sweden and the Netherlands, the latter two being newly emerged populations. We used discriminant analysis of principal components, F_ST, linkage disequilibrium and a comparison of geneflow models using migrate ‐n to show that there is significant population structure, but that relatively many pairs of SNPs are in linkage disequilibrium, suggesting recent admixture between these populations. Despite the assumed traditions of migration within populations, we also show that genetic exchange occurs between all populations. The newly established nonmigratory population in the Netherlands is characterized by high emigration into other populations, which suggests more exploratory behaviour, possibly as a result of shortened parental care. These results suggest that migratory traditions in populations are subject to change in geese and that such changes have population genetic consequences. We argue that the emergence of nonmigration probably resulted from developmental plasticity.     

The effect of boldness on decision-making in barnacle geese is group-size-dependent

In group-living species, decisions made by individuals may result in collective behaviours. A central question in understanding collective behaviours is how individual variation in phenotype affects collective behaviours. However, how the personality of individuals affects collective decisions in groups remains poorly understood. Here, we investigated the role of boldness on the decision-making process in different-sized groups of barnacle geese. Naive barnacle geese, differing in boldness score, were introduced in a labyrinth in groups with either one or three informed demonstrators. The demonstrators possessed information about the route through the labyrinth. In pairs, the probability of choosing a route prior to the informed demonstrator increased with increasing boldness score: bolder individuals decided more often for themselves where to go compared with shyer individuals, whereas shyer individuals waited more often for the demonstrators to decide and followed this information. In groups of four individuals, however, there was no effect of boldness on decision-making, suggesting that individual differences were less important with increasing group size. Our experimental results show that personality is important in collective decisions in pairs of barnacle geese, and suggest that bolder individuals have a greater influence over the outcome of decisions in groups.     

Lack of competition between barnacle geese Branta leucopsis and pink-footed geese Anser brachyrhynchus during the pre-breeding period in Svalbard

The feeding ecology of barnacle geese and pink-footed geese was studied in Sassendalen, Svalbard during the pre-nesting period (late May) to assess the potential for inter-specific competition. Barnacle geese fed almost exclusively (97%) by grazing above-ground plant material, mostly (79%) along snow edges in moss-mat habitats. Pink-footed geese fed mostly (93%) by excavating below-ground parts of plants, mostly (56%) away from snow and were more evenly distributed between habitat types. Barnacle goose faeces contained mostly (62%) moss, that of pink-footed geese mostly (48%) below-ground plant storage organs (especially Bistorta viviparum L.). Principal components analysis of dropping contents showed no overlap in species diet in allopatry or sympatry. There was little overlap in diet and feeding ecology of the two species at this pre-nesting feeding site. Hence, unless increased goose feeding densities affect future vegetation density and composition, under present circumstances, increasing numbers of either species is unlikely to affect foraging conditions for the other at this important stage in the annual cycle. However, such changes could have local density-dependent intra-specific effects.     

Fitness consequences of long-term pair bonds in barnacle geese: monogamy in the extreme

In barnacle geese Branta leucopsis, pair-bond members generally remain together every day, each year, often for life. Geesethat maintain long-lasting pair bonds during their lifetimeproduce more offspring than those with shorter pair durations.This result was shown while statistically controlling for thebirds' life span and the proportion of life spent without apartner, two variables that also influence lifetime reproductivesuccess. I argue that continuous partnerships are maintainedin highly competitive goose societies because of the constantneed for female—male cooperation, without which acquiringadequate resources for reproduction would be prohibitive forboth sexes.     

Feeding ecology of barnacle geese on their spring staging grounds in northern Iceland

The distribution and abundance of barnacle geese, Branta leucopsis. staging in northern Iceland was determined in May 1987 and 1994 A similar proportion of the total population (70%) was located in the two years The distribution differed between the two years, with a higher proportion of the geese found in more westerly sites in 1994 Over 80% of records of birds feeding were on improved agricultural pasture though this made up only 47% of the available feeding habitat Some geese fed on riverine and coastal grasslands but this was in a much smaller proportion than the availability of these habitats The number of geese using a site was positively correlated with the area of improved pasture Birds fed intensively through the day, suggesting that the area is important for the accumulation of nutrient stores No differences in habitat use or feeding behaviour were found between 1987 and 1994     

Exploratory behaviour of barnacle larvae in field conditions

The aim of this work was to develop techniques for the real time filming of Semibalanus balanoides cyprid larvae in the field in order to describe the exploratory behaviour of S. balanoides cyprids under natural field conditions. The underwater camera system consisted of a high resolution, remotely controlled colour camera attached to a cradle which could be deployed from a pier. A light utilising a battery of far‐red light‐emitting diodes (λ_min = 615 nm) was used for filming at night. Transparent acrylic treated with barnacle settlement factor and smooth green polyester tiles were used as targets. From the films the tracks of the exploring cyprids were digitised from the 30 min trials. During five, 30 min trials a total of 1014 cyprids explored the surface. The numbers of cyprids exploring the surface varied from 49 to 522 cyprids per trial, and a Monte‐Carlo randomisation model showed that larval supply was random or aggregated. The mean exploration time spent on the target was 163 s with a mean distance travelled on the target of 8.5 cm. Exploratory track length was related to water current velocity by a negative curvilinear regression (R² = 0.92, F = 45.65, p < 0.05). There were significant differences in exploratory behaviour between day and night for total distance travelled (p < 0.001), straight line distance (p < 0.001) and velocity (p < 0.001) and the mean heading angle of the exploratory track (p < 0.01). The results are discussed in relation to settlement patterns and the screening of antifouling surfaces.     

Effects of fleas on nest success of Arctic barnacle geese: experimentally testing the mechanism

Parasites have detrimental effects on their hosts’ fitness. Therefore, behavioural adaptations have evolved to avoid parasites or, when an individual is already in contact with a parasite, prevent or minimize infections. Such anti‐parasite behaviours can be very effective, but can also be costly for the host. Specifically, ectoparasites can elicit strong host anti‐parasite behaviours and interactions between fleas (Siphonaptera) and their hosts are one of the best studied. In altricial bird species, nest fleas can negatively affect both parent and offspring fitness components. However, knowledge on the effects of fleas on precocial bird species is scarce. Research on geese in the Canadian Arctic indicated that fleas have a negative impact on reproductive success. One possible hypothesis is that fleas may affect female incubation behaviour. Breeding females with many fleas in their nest may increase the frequency and/or duration of incubation breaks and could even totally desert their nest. The aim of our study was to 1) determine if a similar negative relationship existed between flea abundance and reproductive success in our study colony of Arctic breeding barnacle geese Branta leucopsis and 2) experimentally quantify if such effects could be explained by a negative effect of nest fleas on female behaviour. We compared host anti‐parasite and incubation behaviour between experimentally flea‐reduced and control nests using wildlife cameras and temperature loggers. We found that flea abundance was negatively associated with hatching success. We found little experimental support, however, for changes in behaviour of the breeding female as a possible mechanism to explain this effect.     

Sharing habitat: Effects of migratory barnacle geese density on meadow breeding waders

• 1.Following targeted conservation actions most goose populations have increased. The growing goose populations caused an increase in human-wildlife conflicts and have the potential to affect nature values. As meadow birds, including meadow-breeding waders, were declining throughout Western Europe, the possible negative effect of rising numbers of foraging barnacle geese on their breeding success has been questioned.
• 2.We used GPS-transmitter data to measure the density of foraging barnacle geese during daylight hours. Using dynamic Brownian Bridge Movement Models (dBBMM), we investigated the effect of barnacle goose density on the territory distribution of five wader species, and on nest success of the locally common Northern lapwing. We used model selection methods to identify the importance of barnacle goose density related to other environmental factors.
• 3.Our results showed an insignificant positive association between barnacle goose density and nest territory density of the Northern lapwing and common redshank. Barnacle goose density had no influence on territory selection of godwit, oystercatcher and ringed plover. We did, however, find a negative correlation between barnacle geese density and the nest success of the Northern Lapwing.
• 4.We infer that either barnacle goose foraging leads to improved territory conditions for some wader species, or that both barnacle geese and waders prefer the same type of habitat for foraging and nesting. Higher barnacle goose density was correlated with fewer Northern lapwing nests being successful.
• 5.Synthesis and application: Experimental research is needed to disentangle the causal chain, but based on our observational findings, we suggest to increase water logging that may attract both barnacle geese and wader species. Further investigation on the effects of barnacle geese on wader species is necessary to identify the cause of the negative correlation between barnacle geese density and nest success of lapwings; nest protection experiments could give further insight.

     

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.     

Growth responses of arctic graminoids following grazing by captive lesser snow geese

The effects of grazing by captive goslings of the Lesser Snow Goose on coastal vegetation at La Pérouse By. Manitoba were investigated. Swards of Carex subspathacea, Festuca rubra and Calamagrostis deschampsioides were grazed once for different periods (0–180 min) and regrowth of vegetation determined, based on measurements of standing crop, net above-ground primary production (NAPP) and forage quality (leaf nitrogen content). The amounts of foliage removed from swards of Carex subspathacea increased with the length of the grazing period, but after 44 days of regrowth there were no significant differences in above-ground biomass between control and grazed plots. While the amount of foliage removed by goslings from swards of Festuca rubra increased with the length of the grazing period (except after 150 min of grazing), the increase in biomass following defoliation was similar among treatments. Goslings removed little biomass from swards of Calamagrostis deschampsioides, even when the opportunity for grazing was 180 min. No significant differences in standing-crop or NAPP between grazed and ungrazed plots were detected by the end of summer. Grazing had no significant effect on amounts of nitrogen in leaf tissue of all species, suggesting that faecal nitrogen was not rapidly incorporated into plant biomass within the growing season. Patterns of regrowth of these species are compared to that of Puccinellia phryganodes. An increase in goose numbers in recent years has led to birds foraging on less preferred species, such as Calamagrostis deschampsiodes and Festuca rubra. Their poor nutritional quality and a lack of a rapid growth response following defoliation may explain, in part, the decline in the weight of wild goslings recorded over the last decade.     

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.     

Sward height and bite size affect the functional response of barnacle geese Branta leucopsis

Intake rate, the rate in which herbivores can process their food, is presumed to be an important factor in habitat selection down to the scale of the foraging patch. Much attention has been given to the selection of swards of high nutritional quality, but much less has been given to the influences of sward structure on patch selection in small herbivores. In this study we tested the effects of sward density and height on the functional foraging response of barnacle geese, Branta leucopsis. The functional response curve for herbivores describes how intake rate is affected by food availability. We conducted feeding trials to determine intake rate and bite size of barnacle geese on experimentally manipulated swards. Results indicate that intake rate is mainly dependent on sward height and that there is a strong correlation between bite size and intake rate. Sward density does not influence the rate of food consumption; it is, however, a crucial parameter affecting potential total yield. We conclude that bite size is the crucial parameter influencing intake rate. Bite size is explained both by sward height and individual differences in bill morphology. Furthermore, intake rate seems to be dependent on the physical structure of the grass species consumed.     

Clonal diversity in high arctic ostracodes

It remains unclear why the majority of parthenogenetic lineages persist for only brief periods of evolutionary time. However, by characterizing their patterns of genetic variation, it is possible to gain insights regarding their evolutionary origin and potential. We examined clonal diversity patterns in high arctic populations of freshwater ostracodes with the goal of clarifying the factors promoting genotypic diversity. Allozyme electrophoresis showed that the three dominant ostracode species in high arctic ponds reproduce via apomictic parthenogenesis that two of these species (Prionocypris glacialis, Candona rectangulata) were both highly clonally diverse, and had allozyme phenotypes suggestive of polyploidy. Scanning microdensitometry confirmed that many clones of P. glacialis at Igloolik were polyploid. In contrast to most other polyploids, clones of P. glacialis seem to be autopolyploids. Although clonal variation in P. glacialis may reflect multiple transitions to parthenogenesis in an undetected sexual population, it seems likely that genomic recombination associated with polyploidy has also played a role in generating local diversity following the transition to parthenogenesis.     

Endocrine regulations of reproductive seasonality, follicular development and incubation in Magang geese

This study investigated the regulatory mechanisms of seasonal breeding, developments of ovarian follicles and incubation in Magang geese, a short day breeding bird. Throughout the year, plasma PRL concentrations increased in non-breeding season in spring and summer (from April to early August), and remained low in the rest of the year, while LH concentrations peaked in August and September and remained low in non-breeding season (March to June). Lengthening photoperiod increased PRL and decreased LH secretions, which inhibited follicular development, terminated lay and induced moulting, while shortening photoperiod decreased PRL and increased LH secretion and reinitiated lay. Long photoperiod stimulated PRL secretion occurred with increased gene expressions of PRL in the pituitary gland and VIP in the hypothalamus, but inhibition of LH secretion was without decreases in gene expressions of LH beta subunit and GnRH. Under breeding conditions, terminating incubation decreased PRL but increased LH concentrations and resumed lay in 24 days following recruitment of about 10 large white follicles into hierarchical development. Plasma concentrations of progesterone and inhibin peaked at peak lay, whereas LH concentrations exhibited a bi-phasic pattern with troughs at peak lay and incubation when PRL concentrations were high. Ninety percent geese exhibited incubation behaviour after laying one clutch of approximately eight eggs in approximately 30 days. In conclusion the seasonal reproductive activities in Magang geese is directly inhibited by long photoperiod and directly stimulated by short photoperiod via PRL and LH secretions, whose interplays also cause occurrences of four to five lay and incubation cycles in the breeding season.