Repeated grazing of a salt marsh grass by moulting greylag geese Anser anser– does sequential harvesting optimise biomass or protein gain?

The effects of simulated goose grazing on common saltmarsh-grass Puccinellia maritima plants were tested on a Danish salt marsh during the flightless moulting period of greylag geese Anser anser (3–21 June 1998). Plants in an area exclosed from the influence of grazing and the nutrient effects of goose faeces were subject to removal of youngest lamina at 3-, 6-, 9- and 18-day intervals during this period. Average biomass and protein accumulation between harvests was highest at defoliation intervals of 9 days or more. Field observations from two separate study areas demonstrated geese returned to regraze the Puccinellia sward after 6–8 days and oesophageal contents from feeding geese showed selection for lamina lengths consistent with the results of clipping every 6 days. Geese therefore regrazed Puccinellia patches at shorter intervals than expected were they to maximise their intake of biomass or protein at each visit. However, total cumulative lamina elongation, equivalent to the long term gain during the entire moult period, showed no significant difference between the three most intensive defoliation treatments, which were significantly greater than those of plants defoliated at 18 day intervals. Highest overall lamina protein levels were maintained at 6- and 9-day defoliation intervals. This suggests geese regrazed Puccinellia patches at a rate that maximised their number of harvests during the flightless period, but maintained highest protein levels and overall biomass in the sward. This suggests, in line with earlier studies, that moulting greylag geese combine dietary selection, reduced nitrogen excretion and regrazing patterns to meet protein demands during regrowth of flight feathers.     

Movements of wintering diving ducks: new insights from nasal saddled individuals

Flightless moulting Greylag Geese on the Danish island of Saltholm fed on Puccinellia maritima almost exclusively within 150 m of the coastline, despite abundant equivalent food further away. This distribution pattern could theoretically be explained by two alternative (but not necessarily mutually exclusive) explanations: predation risk (since birds take to open water when disturbed) or variation in food quantity/quality. Above ground green parts of this plant showed consistently higher protein and lower fibre content inland than on the coast, hence differences in food quality could not account for the difference in foraging distribution. However, in grazed plots, shoot density was greater at the coast than inland, resulting in an increase of 1.2–2.8 times the available green above-ground biomass. Hence, the greater abundance of Puccinellia at the coast may contribute to the explanation. However, within exclosures at the coast, Puccinellia shoot density was no different to inland areas, suggesting that some function of goose grazing at the coast was involved in enhancing biomass there. It therefore seems likely that the greater food biomass at the coast is a consequence of geese feeding to within 150 m of the coast, though not necessarily the cause. The fact that the Greylag Geese fed throughout the island whilst able to fly but fed exclusively on the coast during flightlessness suggests that a predator escape mechanism could be the most important factor constraining the feeding distribution of moulting geese.     

Habitat exploitation and interspecific competition of moulting geese in East Greenland

Jameson Land, East Greenland is a moulting area of c. 5000 non-breeding Pink-footed Geese and 5000 Barnacle Geese. Breeding populations of both species in the area are small and scattered. The moulting Pinkfeet originate from Iceland, and the Barnacle Geese from other parts of East Greenland. Both species arrive in the area at the end of June and moult their remiges in July. Moulting flocks of the two species seldom mix. Pinkfoot flocks are common along coastlines, in wide rivers and on lakes with open views to all sides, while Barnacle Geese predominate in smaller rivers and on lakes with surrounding hills. During moult the geese, and especially the Pinkfeet, are extremely wary and depend on a safe area of water serving as a refuge with nearby food supplies (sedge-dominated marshes). Barnacle Geese graze in a zone 0–100 m from the refuge, Pinkfeet up to 200–250 m from the refuge. The moulting sites fill up with geese according to available marsh areas, and the grazing pressure on average amounts to 594 goose-days per ha during the moulting period. Food intake is estimated at 149 g and 138 g organic material per 24 h by Pinkfeet and Barnacle Geese, respectively, [n 1984, which was sunny and warm, net above-ground primary production of a Carex subspathacea marsh (the prime feeding ground during moult) from the beginning of growth to the end of July was 13–15 g dw m², and it is estimated that the geese consumed 60–69% of the production. In 1983, which was cold, geese probably consumed the entire production. Goose grazing did not affect productivity, but nutrient levels were high in grazed compared with ungrazed shoots, and peaked in early July. When separate, the diet of both species comprises sedges and grasses. Where the species co-exist the amount of mosses in the diet increases, especially in Barnacle Geese. With respect to nutrient and fibre contents, moss is a suboptimal food compared to sedges and grasses. When separate, the geese spend 41–46% of the 24 hr grazing. Where they co-exist, Barnacle Geese spend 62% of the time grazing, while Pinkfeet seem unaffected by the presence of Barnacle Geese. It is argued that carrying capacity for moulting geese is reached. Geese compete for resources, the Barnacle Goose suffering from the presence of the other. The observed distribution pattern is suggested to result from (1) Pinkfeet being limited to certain sites due to extreme wariness, and (2) Barnacle Geese trying to avoid competition by utilizing sites which Pinkfeet are reluctant to use. The experience of older Barnacle Geese of stress when settling with Pinkfeet may be the segregation mechanism. Moult coincides with the onset of growth and peak nutrient levels in the vegetation. It is suggested that the geese undertake moult migrations to Jameson Land both to avoid competition for resources with breeding geese and because they gain advantage from a growing, nutritious vegetation.     

The constraint on habitat use in wing-moulting Greylag Geese Anser anser caused by anti-predator displacements

During the flightless period of wing-moult, terrestrial feeding waterbirds tend to forage close to water. Wing-moulting Greylag Geese Anser anser feeding in a Danish saltmarsh were no exception to this pattern as none fed more than 175 m from the sea. An individual-based stochastic model of goose feeding distribution derived from empirical data showed that requirements for drinking water could not explain the coastal feeding distribution as the model predicted that 57% of all goose observations would be more than 175 m from the sea. The availability of Common Saltmarsh Grass Puccinellia maritima , the preferred food item, could partly explain the exploitation pattern of geese but not the absence of geese from inland feeding areas. Furthermore, the results did not support the hypothesis that geese actively avoided inland feeding areas because of elevated costs from vigilance. The frequency of anti-predator displacement to the sea was the most likely explanation of the feeding pattern. A model that included such displacements predicted that 99% of all geese would feed less than 175 m from the sea. As anti-predator displacement put the most severe constraints on the feeding distribution, predation risk and level of disturbance were suggested to be the overall factors, which determine the choice of moult site in wing-moulting geese.     

Adjustments to nitrogen metabolism during wing moult in Greylag Geese, Anser anser

1. This study examined the nitrogen balance of free-living flightless moulting Greylag Geese, Anser anser , in relation to food quality, nitrogen absorption, food retention time and nitrogen excretion rates.
2. Food intake rates during moult were the same as those before and after the flightless period, but total daily time spent foraging fell by 58% from 9·45 h to 3·96 h. Dropping production during moult was 43%, and mean dropping mass 42% of that before and after moult, suggesting a considerable increase in food passage time through the gut during moult. Nitrogen absorption increased from 25% prior to moult to 47% during moult.
3. At the same time, excreted dry mass uric acid in faecal material fell by 68%, such that the proportion of nitrogen absorbed and retained in the body as a proportion of the nitrogen ingested in food rose from 16% prior to moult to 42% during moult.
4. Based on these significant increases in nitrogen absorption and decreases in nitrogen excretion, geese were able to compensate for reduced food intake and derive sufficient nitrogen from their diet to re-grow flight feathers.     

Pre‐moult patterns of habitat use and moult site selection by Brent Geese Branta bernicla nigricans: individuals prospect for moult sites

In environments where habitat quality varies, the mechanism by which individuals assess and select habitats has significant consequences on their spatial distribution and ability to respond to environmental change. Each year, thousands of Black Brent Geese Branta bernicla nigricans migrate to the Teshekpuk Lake Special Area (TLSA), Alaska, to undergo a flightless wing‐moult. Over the last three decades, moulting Brent Geese have changed their distribution within the TLSA, redistributing from inland, freshwater wetlands towards coastal, brackish wetlands. To understand better the mechanism by which Brent Geese select a moult site, as well as reasons behind the long‐term shift of moulting distributions, we examined movements and habitat use of birds marked with GPS‐transmitters during the pre‐moult period. Brent Geese did not generally migrate directly to their moulting site during the pre‐moult period, defined as the time from arrival at the moulting grounds to the onset of flightlessness. Rather, individuals used an average of 3.7 ± 0.6 (se) wetland complexes and travelled a minimum of 95.14 ± 15.84 km during the pre‐moult period. Moreover, 69% of Brent Geese visited their final moult site only to leave and visit other sites before returning for the flightless moult. Brent Geese spent significant time in both inland freshwater and coastal estuarine habitats during the pre‐moult, irrespective of the habitat in which they ultimately moulted. Whereas previous research suggested that Brent Geese choose moult sites based largely upon the experience of previous years, our observations suggest a mechanism of moult site selection whereby Brent Geese ‘prospect’ for moult sites, visiting multiple potential moult sites across varied habitat types, presumably gathering information from each site and correspondingly using this information to choose an appropriate moult site. By allowing individuals to adjust their distributions in response to habitat quality cues that may change annually, such as forage type and availability, prospecting may have influenced the long‐term shift in moulting distributions of Brent Geese in the TLSA.     

Central European Greylag Geese Anser anser show a shortening of migration distance and earlier spring arrival over 60 years

Global climate change can cause pronounced changes in species? migratory behaviour. Numerous recent studies have demonstrated climate‐driven changes in migration distance and spring arrival date in waterbirds, but detailed studies based on long‐term records of individual recapture or re‐sighting events are scarce. Using re‐sighting data from 430 marked individuals spanning a 60‐year period (winters 1956/1957 to 2015/2016), we assessed patterns in migration distance and spring arrival date, wintering‐site fidelity and survival in the increasing central European breeding population of Greylag Geese Anser anser. We demonstrate a long‐term decrease in migration distance, changes in the wintering range caused by winter partial short‐stopping, and the earlier arrival of geese on their breeding grounds. Greylag Geese marked on central Europe moulting grounds have not been recorded wintering in Spain since 1986 or in Tunisia and Algeria since 2004. The migration distance and spring arrival of geese indicated an effect of temperature at the breeding site and values of the NAO index. Greylag Geese migrate shorter distances and arrive earlier in milder winters. We suggest that shifts in the migratory behaviour of Central European Greylag Geese are individual temperature‐dependent decisions to take advantage of wintering grounds becoming more favourable closer to their breeding grounds, allowing birds to acquire breeding territories earlier.     

Non‐breeding Cackling,Ross's and Snow Geese on Baffin Island show no loss of body mass during wing moult

Non‐breeding Cackling Branta hutchinsii, Ross's Anser rossii and Lesser Snow Geese Anser caerulescens caerulescens captured during remigial moult on Baffin Island in 2015 showed no loss of body mass with moult stage, and individual variation in mass was largely explained by sex and measures of body size (tarsus length). Exceptional conditions in 2015 resulted in almost no reproductive effort or success in that year, so captured geese of all three species were likely to have been non‐breeding individuals that initiated moult early, whereas there were almost no failed or successful breeders, which would normally moult later. This suggests that in a non‐breeding year (i.e. in the absence of competition from large numbers of goslings), locally moulting geese can obtain sufficient exogenous energy to meet their needs during the flightless wing moult period without losing body mass. This also is consistent with the hypothesis that in other species of geese, accumulation of fat stores prior to, and depletion of such stores during, wing moult is adaptive and likely to be a feature of individual plasticity to meet particular needs, such as undertaking moult migration to remote sites where precise foraging and predation conditions cannot be anticipated, or where competition from more dominant individuals may restrict their access to a reliable food supply.     

Utilization, diet and diet selection by brent geese Branta bernicla bernicla on salt-marshes in Norfolk

The diet and utilization by brent geese of two plant communities ( Limonium/Armeria marsh—a short sward community in the upper mid salt-marsh and composed of several species, and Salicornia marsh—a community of the lower salt-marsh dominated by Salicornia europuea agg. and Aster tripolium ) were studied on the north Norfolk coast. The biomass on these communities was highest in autumn and declined markedly in November owing to the senescence and die-off of the succulent species. This decline was not significantly precipitated by the grazing of the geese but coincided with their switch to inland habitats where the biomass m^-2 and total food available on fields of winter wheat and grassland within the population's home range was 20–30 times greater. Brent geese continued to graze salt-marsh at a low intensity through the winter, feeding largely on Puccinellia maritima. In spring they returned largely to Limonium/Armeria marsh where they significantly reduced the regrowth of Puccinellia maritima.
The main plant species ealen was Puccinellia maritima , especially in mid winter. Salicornia maritima agg. leaves and seeds formed much of the diet in autumn, whereas Triglochin maritima, Plantago maritima and Aster tripolium were important foods on Limonium/Armeria marsh in spring. All these species were selected at some part of the year. Selection was related to the proline (an imino acid used by salt-marsh plants as an osmoregulator) and chloride content and avoidance related to tannins. Two species which contained condensed tannins. Limonium vulgare and Armeria maritima , were rarely eaten. As well as being a nutrient, proline may help to neutralize the effects of tannins in the diet if incorporated into proline-rich proteins.     

Factors affecting escape behaviour in moulting Greylag Geese Anser anser

The escape behaviour of flightless greylag geese Anser anser has been studied at a Danish moult site. In more than 40% of escapes, a stimulus could not be discerned, suggesting some importance of inaccurate risk assessment among the geese. Quasi-predator stimuli, for example gull alarms and helicopters, were also important and caused 31–43 and 5–13% of escapes, respectively. Geese were, however, displaced in less than 5% of encounters with these stimuli. Each escape prevented geese from feeding for 19 min on average, and hence, the cost of escapes was high. This, the low in-situ predation risk, and the partly distant and not directly threatening nature of the stimuli may have weakened the response of the geese. During the main moult period the geese were, nevertheless, more susceptible to quasi-predator stimuli than before moult—the probability of escape per 15 min period was 0.16–0.22 during moult and 0 before moult. The probability of escapes among moulting geese, which formed large cohesive flocks, was, furthermore, significantly enhanced with increasing flock size. It is possible large flocks were better at detecting quasi-predator stimuli, or simply that there was a greater risk of signals from flock members being misinterpreted. Thus in terms of maintaining uninterrupted foraging it was concluded that an individual would incur extra cost by joining large flocks during the moult period.     

Variation in body mass dynamics among sites in Black Brant Branta bernicla nigricans supports adaptivity of mass loss during moult

Birds employ varying strategies to accommodate the energetic demands of moult, one important example being changes in body mass. To understand better their physiological and ecological significance, we tested three hypotheses concerning body mass dynamics during moult. We studied Black Brant in 2006 and 2007 moulting at three sites in Alaska which varied in food availability, breeding status and whether geese undertook a moult migration. First we predicted that if mass loss during moult were simply the result of inadequate food resources then mass loss would be highest where food was least available. Secondly, we predicted that if mass loss during moult were adaptive, allowing birds to reduce activity during moult, then birds would gain mass prior to moult where feeding conditions allowed and mass loss would be positively related to mass at moult initiation. Thirdly, we predicted that if mass loss during moult were adaptive, allowing birds to regain flight sooner, then across sites and groups, mass at the end of the flightless period would converge on a theoretical optimum, i.e. the mass that permits the earliest possible return to flight. Mass loss was greatest where food was most available and thus our results did not support the prediction that mass loss resulted from inadequate food availability. Mass at moult initiation was positively related to both food availability and mass loss. In addition, among sites and years, variation in mass was high at moult initiation but greatly reduced at the end of the flightless period, appearing to converge. Thus, our results supported multiple predictions that mass loss during moult was adaptive and that the optimal moulting strategy was to gain mass prior to the flightless period, then through behavioural modifications use these body reserves to reduce activity and in so doing also reduce wing loading. Geese that undertook a moult migration initiated moult at the highest mass, indicating that they were more than able to compensate for the energetic cost of the migration. Because Brant frequently change moult sites between years in relation to breeding success, the site‐specific variation in body mass dynamics we observed suggests individual plasticity in moult body mass dynamics.     

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.     

An approach to the assessment of change in the numbers of Canada Geese Branta canadensis and Greylag Geese Anser anser in southern Britain

Capsule Population change in geese was assessed using an approach that requires a relatively small sampling effort.

Aims During the 1999 breeding season a survey was carried out to determine if the numbers of introduced Canada and re-established Greylag Geese in southern Britain had changed since 1988–91 and whether any change had occurred in areas with previously high or low Canada Goose densities.

Methods A randomized stratified sample of 246 tetrads from the 24 156 tetrads covered between 1988–91 in this area, as part of the New Atlas of Breeding Birds, were resurveyed. Eight habitat categories were used in the stratification and were based on 1-km-square summary data obtained from the CEH Land Cover Map of Great Britain (water cover and urbanization) and LANDCLASS stratification (upland/lowland). The five habitat categories with the highest densities of Canada Geese and the greatest variance in numbers were sampled.

Results Between 1989 and 1999, the number of Canada Geese on land with over 5% water cover and on lowland with some water cover increased by on average 156%, an average rate of increase of 9.9% per annum. Southern Britain probably now holds a minimum of 82 000 Canada Geese. Between 1989 and 1999, the number of Greylag Geese on land with over 5% water cover and on lowland with some water cover increased by on average 214%, an average rate of increase of 12% per annum. Southern Britain probably now holds a minimum of 30 000 Greylag Geese.

Conclusion Maximum densities of Canada Geese may have been reached in high-density habitats but their numbers are still increasing very rapidly. Greylag Geese are increasing even more rapidly.     

Phenotypic flexibility of a southern African duck Alopochen aegyptiaca during moult: do northern hemisphere paradigms apply?

Phenotypic flexibility during moult has never been explored in austral nomadic ducks. We investigated whether the body condition, organ (pectoral muscle, gizzard, liver and heart) mass and flight‐feather growth Egyptian geese Alopochen aegyptiaca in southern Africa show phenotypic flexibility over their 53‐day period of flightless moult. Changes in body mass and condition were examined in Egyptian geese caught at Barberspan and Strandfontein in South Africa. Mean daily change in primary feather length was calculated for moulting geese and birds were dissected for pectoral muscle and internal organ assessment. Mean body mass and condition varied significantly during moult. Body mass and condition started to decrease soon after flight feathers were dropped and continued to do so until the new feathers were at least two‐thirds grown, after which birds started to regain body mass and condition. Non‐moulting geese had large pectoral muscles, accounting for at least 26% of total body mass. Once moult started, pectoral muscle mass decreased and continued to do so until the flight feathers were at least one‐third grown, after which pectoral muscle mass started to increase. The regeneration of pectoral muscles during moult started before birds started to gain overall body mass. Gizzard mass started to increase soon after the onset of moult, reaching a maximum when the flight feathers were two‐thirds grown, after which gizzard mass again decreased. Liver mass increased significantly as moult progressed, but heart mass remained constant throughout moult. Flight feather growth was initially rapid, but slowed towards the completion of moult. Our results show that Egyptian geese exhibit a significant level of phenotypic flexibility when they moult. We interpret the phenotypic changes that we observed as an adaptive strategy to minimize the duration of the flightless period. Moulting Egyptian geese in South Africa undergo more substantial phenotypic changes than those reported for ducks in the northern hemisphere.     

Grey and fawn variant plumages

Canada Geese in Yorkshire have extended their breeding range and habitat from traditional aquatic sites to include high-ground heather moorland. Many adults remain on the moors (with their goslings) to moult, and young reared here are an important source of unringed birds in the Yorkshire population and in the moulting flock on the Beauly Firth (Inverness-shire). Adaptations to moorland breeding are discussed; there is an absence of competition for nesting space such as characterises Canada Geese breeding in lowland aquatic sites.     

Actual numbers and effects of recreational disturbance on the distribution and behaviour of Greylag Geese (Anser Anser) in the Neusiedler See – Seewinkel National Park Area

The Neusiedler See – Seewinkel National Park area is confronted with a remarkable increase in tourism and recreational activities during the last years. The “Koppel” area, situated on the eastern shore of the lake, is one of the most important breeding sites for Greylag Geese. Behaviour and distribution of the geese on the breeding site as well as touristic activities on the adjacent road leading along the Koppel were examined to investigate relations and interactions between the Greylag Goose population and tourism. Taking into account the excellent weather and breeding conditions in the year 2000 the results of the survey indicate a stable or even rising Greylag population, increasing numbers of visitors and high disturbance frequencies in the vicinity of the study area. The number of disturbances on the adjacent road seems to affect the suitability of the site in general, leading to a specific temporal and spatial distribution of the birds, whereas different disturbance qualities result in changes of the birds behaviour.     

Leapfrog migration and residents: New migratory habits in Swedish Greylag geese

Knowledge about intraspecific and individual variation in bird migration behavior is important to predict spatiotemporal distribution, patterns of phenology, breeding success, and interactions with the surrounding environment (e.g., human livelihoods). Such variation is key to adaptive, evolutionary responses, i.e., how individuals respond spatiotemporally to the environment to maximize fitness. In this study we used GPS location data from one to three full annual cycles from 76 Greylag geese (Anser anser) to test the hypothesis that geese originating at five latitudinally separated capture sites in Sweden have different migration strategies. We also assessed individual consistency in movement strategy over consecutive annual cycles. We used the scale‐independent net squared displacement modeling framework to quantify variables of autumn and spring migration for geese from each capture site: distance, timing, and duration. Our results demonstrate a positive correlation between migration distance and latitudinal origin. Geese from the northernmost site on average migrated farther south and about 15 times as far as the short‐moving or resident geese from the two southernmost sites. Movement strategies of individual geese varied considerably both within and among capture sites. Individual consistency in movement strategy from one annual cycle to the consecutive was high in geese from the northern sites moving the farthest, whereas the resident or short‐moving geese from the southernmost sites generally showed lower or no individual consistency. These changes have come about during a time span so short (i.e., ca. 35 years or 8–10 generations) that it can unlikely be explained by classical Darwinian between‐generation adaptation. Consequently, and given that young geese follow their parents during their first migration, we presume an important role of within‐family, inter‐generation change as a driver behind the large‐scale changed migration habits in Swedish Greylag geese.     

ACTIVITY BUDGETS OF SPURWINGED AND EGYPTIAN GEESE AT BARBERSPAN DURING WINTER

Halse, S. A. 1985. Activity budgets of Spurwinged and Egyptian Geese at Barberspan during winter. Ostrich 56:104-110.

Daily behaviour of Spurwinged and Egyptian Geese was studied during winter at Barbers an, a large lake in the Transvaal. Non-moulting Spurwinged and Egyptian Geese spend about 2 h and 1,5h, respectively, feeding in farmland surrounding the lake in the early morning and about 20 min and 30 min, respectively, feeding there in the evening. They return to Barberspan during the day.

Activity budgets were calculated for all Spurwinged and all Egyptian Geese, including both moulting and non-moulting birds, at the lake during the day. Both species spend most of the day sleeping on the shore and relatively little time feeding. Both species spend a large proportion of this limited feeding time on open water picking at floating Potamogeton pectinatus. Closer to the shore the feeding habits of the species differ, Egyptian Geese feeding mostly along the shoreline in water a few centimetres deep, immersing only the bill, while Spurwinged Geese upend or submerge their heads and necks in deeper water.

An energy budget was calculated for Spurwinged Geese using the activity budget data. An averag-sized non-moulting goose (5,2 kg) requires about 2000 kJ/day for maintenance. During moult energy requirements increase 30 per cent to 2500 kJ/day because of the extra energy required for feather growth.     

Isotopic evidence for endogenous protein contributions to greylag goose Anser anser flight feathers

Feather stable isotope composition may not reflect local isoscapes in which they were grown if supplemented with protein of endogenous origin. Thus, feather isotope analysis, combined with knowledge of local isoscapes can be used to infer endogenous nutrient composition to feathers in cases where birds travel to moult. We investigated this possibility in a study of flightless moulting greylag geese Anser anser on the Danish island of Saltholm, which are known to mobilise endogenous protein stores (acquired at previous terrestrial staging locations in Sweden) to reconstitute muscle blocks and organs whilst feeding on a saltmarsh (i.e. marine-influenced) diet with contrasting stable isotope ratios. We used stable isotope (δ¹³C, δ¹⁵N) measurements to test the prediction that new-grown flight feathers would have stable isotope values intermediate between those derived from a purely terrestrial C₃ diet and one composed purely of saltmarsh plants. Feather δ¹³C and δ¹⁵N values were intermediate between those expected for feather material derived from local saltmarsh (i.e. exogenous) food items and Swedish terrestrial (endogenous muscle) sources, suggesting a mixing of endogenous and exogenous sources. These results confirm that moult migrant Anatidae exploit body stores to meet specific protein needs during the flightless period of remige regrowth and caution against the use of feather stable isotope ratios as direct indicators of the isotopic environment in which they were regrown, where endogenous contributions may occur.     

Dietary and microtopographical selectivity of Greenland white-fronted geese feeding on Icelandic hayfields

The feeding ecology of Greenland white-fronted geese Anser albifrons flavirostris was studied during .spring staging in Iceland 1997. Geese feeding on Poa pratense dominated hayfields (> 80% cover) were highly selective, selecting for Deschampsia caespitosa which comprised only 10% of the sward. Geese fed most on the south-facing fringes of Deschampsia tussocks. Subsequent analysis showed that the southern fringes of Deschampsia tussocks supported significantly greater biomass (27% greater mass of green material) and that leaves growing on the southern faces had significantly higher protein content than those on the northern faces (33.9% vs 30.5%)_- It appears that the geese maximise their nutritional intake in spring by selecting the grass species of highest quality and taking the most nutritious parts of the plants.