The role of phenolic compounds and other plant constituents in feeding by Canada geese in a coastal marsh

Summary We have assessed the relative importance of phenolic compounds, other secondary metabolites, and gross nutrient levels as feeding cues to Canada geese. Phenolic content was the most significant constituent influencing feeding selection by geese. Nutrient content had little or no effect on feeding selection.Correlative data showing the negative influence of plant phenolics on food choices by wild geese were supported by feeding preference tests. Extracts of unpalatable plants inhibited feeding by captive geese relative to extracts of palatable plants. In high phenolic plants, the phenolic containing methanol extract was more inhibitory than extractions made with petroleum ether. In a relatively low phenolic, unpalatable plant, an inhibitory factor was extractable in petroleum ether, indicating that for this species, another class of deterrents was involved. Preference tests with individual secondary metabolites showed that tannic acid and quebracho tannin were very effective in inhibiting feeding by geese and phenolic acids were slightly inhibitory, but a sesquiterpene lactone was not deterrent. These results point out the primacy of some secondary metabolites in determining food choices by geese.     

Feeding Preferences in Greylag Geese and the Effect of Activated Charcoal

ABSTRACT Greylag geese (Anser anser) can cause serious damage to agricultural fields near wetlands that are attractive for resting and nesting but not for feeding. Alternative plantings or spraying fields may prevent goose damage. We randomly designed 64 plots in spring 2004 and prepared plantings of white clover (Trifolium repens), white clover with perennial ryegrass (Lolium perenne; mixture), fertilized perennial ryegrass (grass), or unfertilized perennial ryegrass. We measured goose-dropping densities in plots as a measure of feeding preference in autumn 2004 (7 weeks), spring 2005 (6 weeks), and autumn 2005 (7 weeks) following removal of a protective fence and vegetation sampling for content analysis in 2004. We also sprayed activated charcoal (20 kg/ha) in a suspension on 32 plots (8/planting) to deter geese in autumn 2004 only. In a second experiment we examined pairs of greylag geese in cages for preferences between grass treated with or without activated charcoal. Charcoal did not deter geese in either experiment. However, dropping density averaged highest for clover (1.01/m²), followed by the mixture (0.65/m²), then fertilized (0.23/m²) and unfertilized grass (0.16/m²). Preferences were consistent in all 3 experimental periods. Fertilized grass reached 31.8 cm in height on average in spring, whereas clover measured 15.4 cm. Crude protein and water-soluble carbohydrate content (g/kg dry matter) was 294 and 49, respectively, in white clover and 183 and 139, respectively, in fertilized grass. We found a positive partial correlation independent of vegetation type between dropping densities and crude protein and a negative correlation with water-soluble carbohydrate content. Thus, to prevent grazing damage to agricultural fields, we recommend planting white clover, strongly preferred by feeding geese, in areas (fallow agricultural or nonagricultural) adjacent to their habitat and not in agricultural fields under production.     

Goose grazing selectivity along a depletion gradient

The micro-habilat food selectivity along a gradient of increasing grazing intensity of wintering pink-footed geese Anser brachyrhynchus and barnacle geese Branta leucopsis foraging on winter wheat Triticum aestivum and smooth meadow grass Poa pratensis was investigated. Protein content of ungrazed primary and secondary leaves of winter wheat did not differ, whereas the protein content of tertiary leaves was significantly lower. Secondary leaves were significantly longer than both primary and tertiary leaves, whereas tertiary leaves were significantly longer than primary leaves. Protein content of primary and secondary leaves of Poa pratensis did not differ, whereas the protein content of tertiary leaves was significantly lower. Primary leaves were significantly shorter than both secondary and tertiary leaves, which did not differ significantly.
For all leaf categories, there was an increase in the removal with increasing goose grazing intensity. The geese showed a sequential selection of winter wheat leaves according to the protein content, initially preferring primary and secondary leaves, but increasingly selecting tertiary leaves of poorer quality as high-quality leaves became depleted. Foraging on Poa pratensis. geese selected secondary leaves according to the protein content, whereas tertiary leaves were preferred to primary leaves, although these had a protein content equal to secondary leaves. This, however, may be explained by the primary leaves being too short to maintain intake rates.
It is concluded that feeding preferences cannot be established on the basis of protein contents of food plants alone and that green biomass estimates not necessarily reflect resource availability.     

Foraging preferences of Canada geese among turfgrasses: Implications for reducing human–goose conflicts

Canada geese (Branta canadensis) can cause serious damage to turfgrass areas and create human health and safety concerns (e.g., collisions with aircraft, disease transmission). We conducted a study during 2005–2007 to determine if Canada geese exhibit a feeding preference among various commercially available turfgrasses. Behavioral responses of captive geese to 9 turfgrasses, bare ground, and litter were observed over 6 4-week trials during July–September following the installation of selected turfgrasses into experimental arenas. Captive geese preferred to forage on Kentucky bluegrass, creeping bentgrass, and fine fescue sods compared to centipedegrass, St. Augustinegrass, and zoysiagrass. Forage qualities and macronutrient levels varied among the turfgrasses and might explain the foraging preferences geese exhibited during this study. Canada goose feeding rate was positively correlated with crude protein, nitrogen content, and calcium, but negatively correlated with acid detergent fiber content, within various turfgrasses. Our findings suggest careful selection of turfgrasses could be an effective method for reducing Canada goose conflicts in urban and suburban areas. © 2011 The Wildlife Society.     

Foraging behaviour of brent geese, Branta b. bernicla, on grasslands: effects of sward length and nitrogen content

Feeding behaviour and preferences of brent geese, Branta b. bernicla were observed on pastures of different sward lengths and nitrogen contents. On swards of 2.0-6.0 cm captive geese took larger bites and had a higher intake rate when feeding on 6-cm swards than when feeding on shorter ones. In the field wild geese chose 6-cm swards in preference to both shorter and longer ones. For unfertilized pastures there was a strong negative relationship between nitrogen content and sward height: 11-cm swards contained 2.8% nitrogen, 3.5-cm swards 4.2% nitrogen. Application of 75 kg N ha^-1 organically based fertilizer at the end of October eliminated this relationship between nitrogen content and sward height, swards of all heights then having a mean content of 4.1% N. On fertilized plots the geese preferred swards longer than 6 cm with no indication of a decrease in preference up to the maximum height investigated, 16 cm. Breaking strain of grass laminae was measured to give an indication of the proportion of strengthening tissues in the leaves and hence their digestibility. Apical laminae from longer swards had a higher breaking strain than those from shorter swards. Unfertilized swards had a higher breaking strain than fertilized swards but the difference in breaking strain between long and short swards was the same on fertilized and control treatments. These results are discussed in relation to the forage maturation hypothesis and are interpreted as indicating that the primary constraint on maximizing energy intake rates is not the reduced energy digestibility of older foliage but the reduced nitrogen content in the higher-biomass swards. We conclude that it is the balance between maximizing energy intake and nitrogen absorption rates which results in the observed preference for intermediate-height swards.     

Pre-nesting feeding selectivity of Pink-footed Geese Anser brachyrhynchus in artificial grasslands

The pre-nesting feeding ecology of Pink-footed Geese Anser brachyrhynchus was studied in southern Iceland in April and May 1989–1992. Extensive surveys showed that prior to movement to their nesting areas in the interior, Pink-footed Geese fed mainly on intensively managed grasslands of the southern lowlands. Faecal analysis showed that geese feeding in hayfields foraged almost exclusively on the most commonly reseeded species, Timothy grass Phleum pratense , which made up the majority (41% by number of green shoots) of new growth in studied hayfields. Dropping counts, as an indicator of goose use, were highly significantly correlated in all years with density of growing Phleum shoots in individual field units. Geese showed a response in feeding patterns to changes in Phleum density as a result of reseeding patterns. Analysis of forage quality in 1991 showed that Phleum shoots had a higher protein content than all other grasses present in hayfields, with the exception of Deschampsia caespitosa. The latter species showed similar levels of protein, but its tussocky nature precluded effective grazing by the geese. Phleum was similar in fibre content to other common grasses. Based on removal of tagged plants, geese grazed predominantly on the youngest leaves of Phleum , which also had higher protein content and lower fibre than older leaves and attached dead leaves, which were rarely taken by geese. Geese grazed shorter length classes of youngest leaves, which showed higher protein content than longer, older terminal leaves. Recently created grassland habitat has increased the opportunities for female geese to supplement their reserves during the crucial prelude to clutch initiation by selecting the highest quality plant species and the most nutritious parts of that forage.     

The relationship between feeding preferences and consumption rates in grass carp and grass carp × bighead carp hybrids

The relationship between food preference hierarchy and consumption rate was examined for the grass carp, Ctenopharygodon idella , and its Fl hybrid (grass carp × bighead carp). Preferences of both types of fish were similar, although hybrids consumed vegetation at a much lower rate. For both, relative preference in feeding trials with mixed plant species was significantly correlated with consumption rate in monospecific feeding experiments. No correlations were found between preference and caloric content, protein content or relative water content. The hypothesis is proposed that preference hierarchies reflect relative handling times of different food types and that these fish maximize 'through-put' by preferentially consuming plant species which can be most rapidly ingested.     

Habitat switching by dark-bellied brent geese Branta b. bernicla (L.) in relation to food depletion

Seasonal changes in the distribution and feeding behaviour of dark-bellied brent geese Branta b. bernicla (L.) and the biomass of their food plants were studied in three successive winters on the Norfolk coast. The data was used, in conjunction with published information, to show how depletion, productivity and mortality of food plants drive the pattern of habitat switching in this species. It is then possible to explain the habitat shifts observed over the last 35 years and predict future changes. On arrival, geese fed first on algal beds and then on salt marsh, grass and arable fields before returning to feed entirely on the salt marsh in spring. The biomass of green algae, and subsequently the salt marsh vegetation, declined during the autumn and this could be attributed to depletion through goose grazing and natural mortality. As depletion occurred the geese fed more intensively, for a greater percentage of time and with an increasing pace rate, the net result, however, was a declining intake rate (as measured by defaecation rate). The algal biomass at which the geese switched from the algal beds to salt marsh was consistent between years, with heavy storm-induced loss of algae in one year resulting in an earlier switch. That the timing of habitat switches may be explained by depletion of food plants was further supported by historical data: the number of brent geese wintering at the site has increased dramatically over the last 30–35 years and the time of switching from algal beds to salt marsh and from salt marsh to salt marsh and fields has become progressively earlier, as expected from the increased depletion. The expected further increase in brent goose numbers will increase the rate of depletion of intertidal vegetation so that the switches between habitats will be more rapid and the geese will move inland earlier and remain inland longer. The expected increase in the brent goose population will thus result in a disproportionate increase in the levels of conflict between brent geese and agriculture.     

The palatability of Arctic willow for greater snow geese: the role of nutrients and deterring factors

Temporary feeding on willow buds and leaves by nesting greater snow geese provided us with an opportunity to test the relative importance of nutrients and deterrents in affecting the palatability for geese of a food plant with a high phenol content. Protein, total phenol and fiber (neutral and acid detergent fiber, and lignin) were analyzed in closed and open buds and in rolled and open leaves. Geese feed on willows at the open-buds and rolled-leaf stages but not at the closed-bud and open-leaf stages. Protein content was higher in open buds and rolled leaves (25–27%) than in closed buds and open leaves (19–21%). Phenol content increased during leaf emergence but was already high (14%) in rolled leaves. All plant fibers were very high in closed buds but declined rapidly during leaf emergence. The increase in phenol: protein ratio appeared to be more important than phenol concentration alone in explaining the cessation of feeding by geese on willow leaves whereas the high fiber content of closed buds may explain why they were not eaten. Our results illustrate the value of a multifactorial approach in the study of the food selection process in herbivores.     

Development of feeding selectivity and consistency in food choice over 5 years in fallow deer

In order to better understand the development and maintenance of feeding selectivity, several feeding experiments were performed with fallow deer (Dama dama L.). In experiments performed when the fawns were between ten and 27 days old, it was found that all fawns showed preferences for sucrose but aversions towards tannic acid and ascorbic acid. However, differences in selectivity towards tannic acid were present already before the fawns became functional ruminants and these individual differences lasted 5 years. Moreover, individuals that ingested overall less tannic acid, searched more thoroughly between food sources. When the foraging behaviour was compared with age (11–41 days old and 65–97 days old), it was found that the time a fawn spent eating, increased with age, and the time spent on exploration, smelling and tasting plants decreased with age. Furthermore, the fawns increased their intake of grass and herbs, while the intake of soil and dead plant material decreased with age.     

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.     

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.     

Feeding patch selection by herbivorous Anatidae: the influence of body size, and of plant quantity and quality

Recent findings suggest that herbivores select feeding sites of intermediate biomass in order to maximise their digestible nutrient intake as the result of the trade-off between forage quality and quantity ('forage maturation hypothesis'). We propose a reformulation of this hypothesis which recognises this trade-off, but also underlines that constraints due to body mass (i.e. metabolism and digestive constraints, size of the feeding apparatus) can lead to variations in grazing patterns. We tested this latter hypothesis experimentally in three species of herbivorous Anatidae of different body mass: the wigeon Anas penelope (in our study c. 620 g), the barnacle goose Branta leucopsis (c. 2000 g), and the greylag goose Anser anser (c. 3500 g). Each species was tested separately from 0600 to 0930 hours, in an enclosure with a mosaic of patches of grass of three different heights: short, medium and tall. The behaviour, and the location (i.e. patch) of each individual were recorded every 5 minutes. Our results show important interspecific differences in intake rates resulting in different feeding site selection: wigeon and barnacle goose fed fastest on the shortest swards, and selected short grass which was also of higher quality. Tall grass provided the highest dry matter intake rate and digestible protein intake for greylag geese, and they preferred these swards. These choices allowed the birds to maximise their digestible nitrogen intake rate rather than dry matter intake rate and our results thus underline the importance of nitrogen as a major currency for foraging decisions in herbivorous Anatidae. Since the birds selected the two extreme sward heights (instead of the medium one), the results give support to our hypothesis and underline the role of body size as an important cause of variations in patch selection in herbivorous Anatidae.     

Spatial and temporal feeding segregation of two Icelandic goose species during the spring pre-nesting period

The pre-nesting feeding behaviour of greylag Anser anser and pink-footed geese A brachyrhynchus was studied on agricultural land at low altitude in southern Iceland from 10 April to 8 May 1990 Greylag geese were already present on 12 April increased to 4580 birds by 24 April, but declined to 1300 by 3 May Pink-footed geese arrived around 20 April and numbers continued to increase to a peak count of 11340 on 3 May Over 60% of greylag geese initially used stubble fields on the coast where this habitat was most frequent, but increasingly resorted to grassland and wetland habitats during late April Later-arriving pink-feet predominantly used managed grassland, away from coastal areas At inland grassland sites, greylag numbers peaked on 20 April, pink-feet m early May The early exploitation by greylags was associated with grass growth initiated under protective snow-patches Greylags spent 90 times more time feeding within 1 m of snow patches with enhanced grass growth than expected by chance and their feeding rates near snow patches were faster and their step rates slower than further away By early May, grass growth was uniform and, although snow-patches persisted, no difference in forage quality, goose feeding rates or step rates could be detected It is concluded that, in spring 1990 at least, habitat segregation during spring migration in southern Iceland minimised competition between these two closely related goose species within the same geographical area In areas where both species exploit the same habitat, a two week difference m timing of breeding (and hence phenology of migration) further assures minimal overlap in feeding exploitation     

蛋白质,纤维素和单宁酸对东方田鼠摄食的影响

食物选择性是动物对取食生境中现存的食物种类做出的选择,是一个复杂的生态适应过程,与动物自身生理状及环境中食物的可利用量密切相关。单宁酸、蛋白质和纤维素是影响植食性动物食物选择的重要因素。在控制其它营养因子的条件下,设置10%蛋白质+2.25%纤维素+3%单宁酸(食物1)/6%单宁酸(食物2)和20%蛋白质+4.51%纤维素+3%单宁酸(食物3)/6%单宁酸(食物4)4个处理组,通过自助餐式选择笼内的喂养实验,测定单宁酸、蛋白质和纤维素对东方田鼠食物选择的影响。结果表明,东方田鼠对3%单宁酸处理组食物摄食量显著高于对6%单宁酸处理组(P0.001);但东方田鼠对6%单宁酸食物摄食量依蛋白质浓度变化,在20%蛋白质处理组的摄食量显著高于10%蛋白质处理组(P0.05);在含3%单宁酸处理组中,纤维素成为影响东方田鼠摄食的主要因素,而当单宁酸浓度增加到6%时,纤维素和蛋白质对东方田鼠摄食影响差异不显著;总之,单宁酸、蛋白质和纤维素对东方田鼠的摄食都产生重要影响,单宁酸对东方田鼠食物选择的影响程度最大,纤维素次之,蛋白质对东方田鼠摄食的影响会随单宁酸浓度的升高而增大。     

Hydrology‐driven responses of herbivorous geese in relation to changes in food quantity and quality

East Dongting Lake is a Ramsar site and a particularly important wintering ground for herbivorous geese along the East Asian‐Australasian Flyway. The operation of the Three Gorges Dam has changed the water regime and has a significant impact on wetland ecosystems downstream. We studied the responses of two sympatric herbivorous goose species, the Lesser white‐fronted goose Anser erythropus and Bean goose Anser fabalis, to habitat change by investigating their food conditions, habitat selection, and diet composition in the wintering periods of 2016/2017 and 2017/2018, which had early and late water recession, respectively. It was expected that the contrasting water regimes would result in different food conditions and geese responses. The results showed that the food quality and quantity differed significantly between winters. As responses to the high‐quantity/low‐quality food during 2016/2017, more geese switched to feeding on mudflat and exploited plants such as dicotyledons and moss. The tall swards of Carex spp. (dominant plants in the meadow) that developed during the first growing season decreased the food accessibility during the second growing season and hindered the exploitation of newly generated shoots by the geese, which was further confirmed by our clipping control experiment. Nearly all the geese chose to feed on meadow, and Carex spp. made up the majority of their diet in 2017/2018 when there was more low‐quantity/high‐quality food. Compared with the globally vulnerable Lesser white‐fronted geese, the larger‐sized Bean geese seemed to be less susceptible to winter food shortages and exhibited more stable responses. We concluded that the food quality–quantity condition was the external factor influencing the geese responses, while morphological and physiological traits could be the internal factors causing different responses between the two species. This study enhanced the understanding of the influence that habitat change exerts on herbivorous geese in their wintering site in the context of the Three Gorges Dam operation. We suggested that regulating hydrological regime was important in terms of wetland management and species conservation.     

Feeding by geese on the Filsø Farmland, Denmark, and the effect of grazing on yield structure of spring barley

From the end of August to early May on average 506400 goose days were spent on the farmland of Filsø, 92% by pink-footed geese, 7% by greylag geese and 1% by bean geese. 36% of the goose days were spent on stubbles (autumn), 38% on stubbles with undersown seed grass (autumn-spring), and 21% on new-sown barley fields (spring).
Geese feeding on spring barley consume kernels left on the surface or in the upper surface layers. In 1982 and 1983 trials were set up to quantify the effect of grazing. The effect on yield and plant structure was measured by comparing ungrazed (exclosures) and grazed plots. Grazing by geese significantly reduced the grain yield (7-20%), but the reduction was not proportional to goose usage. The maximum reduction in sprout density was observed in 1982 in an area with heavy goose usage; sprout density was reduced by 72%, but the subsequent yield in the same area was only reduced by 8%. Plants on grazed plots compensated for the reduced sprout density by having more tillers with ears and grains of higher weight. The effect of grazing on stubble, seed grass, and winter cereals on Filsø is discussed.     

Patch choice of avian herbivores along a migration trajectory–From Temperate to Arctic

Migratory waterfowl species seem to track temporal and spatial pulses of optimal forage availability on their way from temperate wintering to arctic breeding sites. In order to unravel the relative contribution of forage quality and forage biomass to foraging choices in avian herbivores, we experimentally manipulated biomass and quality of main forage plants through fertilisation and grazing exclusion at three sites along the flyway of barnacle geese, Branta leucopsis. Fertilisation increased the nitrogen content of the forage and grazing exclusion increased biomass levels. Manipulated plots were offered to wild geese in a random block experimental design and goose visitation was measured through dropping counts. At all sites there was a trend towards a higher preference of plots with increased quality and average biomass above plots with an average quality and increased biomass. Generally, geese preferred plots with highest standing crop of nitrogen. The numerical response of the geese to forage changes was supported by behavioural observations at the Baltic site. We conclude that for migrating barnacle geese the bottlenecks in the standing crop of nitrogen appear to lie in the limited biomass availability at the Baltic stopover site and the limited nutrient content of food in the Arctic breeding site, restricting the potential nutrient intake on these sites.     

Recovery of tall cotton–grass following real and simulated feeding by snow geese

Lesser snow geese Anser caerulescens caeruteseens from the western Canadian Arctic feed on underground parts of tall cotton–grass Eriophorum angustifolium during autumn staging on the coastal plain of the Beaufort Sea in Canada and Alaska. We studied revegetation of sites where cotton–grass had been removed either by human–imprinted snow geese or by hand to simulate snow goose feeding. Aerial cover of cotton–grass at sites (n = 4) exploited by human–imprinted snow geese averaged 60 and 39 Mi lower than in undisturbed control plots during the first and second year after feeding, respectively. Underground biomass of cotton–grass stembases and rhizomes in hand–treated plots was 80 and 62% less than in control plots 2 and 4 yr after removal, respectively (n = 10 yr^-1). Aerial cover and biomass of common non-forage species such as Carex aquatilis did not increase on treated areas. Removal of cotton-grass by geese likely reduces forage availability at exploited sites for at least 2–4 yr after feeding but probably does not affect long-term community composition. Temporal heterogeneity in forage abundance likely contributes to the large spatial requirement of snow geese during staging.     

Interspecific Mate Choice Following Cross-fostering in a Mixed Colony of Greylag Geese (Anser anser) and Canada Geese (Branta canadensis). A Study on Development and Persistence of Species Preferences1

The role of early experience in mate choice and species preference of geese was studied in an experiment where young greylag geese (Anser anser) were cross-fostered by Canada geese (Branta canadensis). In two successive years, all eggs from 9 nests of wild Canada geese were removed and replaced by greylag goose eggs. The young greylag geese then followed their Canada goose foster parents on their southward migration in autumn, to return with them in spring. Of 35 returning birds, all 16 females paired with greylag goose males (100%) whereas of 19 males 5 paired with Canada goose females (14%) and the remaining 14 with greylag goose females (74%). The pair bonds generally persisted as long as both birds were present, but after loss of a partner, the remaining bird usually re-mated. Even when this happened several times during the lifetime of a male, the new mate was always a Canada goose female, showing that the males were sexually imprinted to this species. The Canada goose females which had mated with the greylag ganders also remated when widowed, but their new mate could be either a Canada goose or a greylag goose.