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.     

The role of phenolic compounds and nutrients in determining food preference in greater snow geese

Summary We tested Buchsbaum's hypothesis that food palatability in geese is determined by a hierarchy of feeding cues among which deterrent secondary metabolites (mostly phenols) have a primary role (Buchsbaum et al. 1984). In preference tests, greater snow goose feeding was slightly depressed when grass was sprayed with ferulic acid but not when grass was sprayed with p-coumaric and tannic acids. Extracts of Timothy grass, red clover or alfalfa sprayed on grass also failed to depress goose feeding. In a multifactor experiment, phenol and protein content and height of grass were manipulated simultaneously. When ferulic acid was sprayed, protein and phenol content interacted in determining goose feeding preferences; protein content had no effect in the absence of phenol but did have an effect when phenol was added. When tannic acid was used in a similar experiment, results were inconclusive because of a significant and complex interaction between protein content and height of grass. Our results generally failed to support Buchsbaum's hypothesis that phenol content of plants has a primary role in determining food preference in geese. Protein content of plants seemed to be a more important factor.     

Breeding dispersal in a heterogeneous landscape: the influence of habitat and nesting success in greater snow geese

Despite numerous studies on breeding dispersal, it is still unclear how habitat heterogeneity and previous nesting success interact to determine nest-site fidelity at various spatial scales. In this context, we investigated factors affecting breeding dispersal in greater snow geese (Anser caerulescens atlanticus), an Arctic breeding species nesting in two contrasting habitats (wetlands and mesic tundra) with variable pattern of snowmelt at the time of settlement in spring. From 1994 to 2005, we monitored the nesting success and breeding dispersal of individually marked females. We found that snow geese showed a moderate amount of nest-site fidelity and considerable individual variability in dispersal distance over consecutive nesting attempts. This variability can be partly accounted for by the annual timing of snowmelt. Despite this environmental constraint, habitat differences at the colony level consistently affected nesting success and settlement patterns. Females nesting in wetlands had higher nesting success than those nesting in mesic tundra. Moreover, geese responded adaptively to spatial heterogeneity by showing fidelity to their nesting habitat, independently of snowmelt pattern. From year to year, geese were more likely to move from mesic to high-quality wetland habitat, regardless of previous nesting success and without cost on their subsequent nesting performance. The unpredictability of snowmelt and the low cost of changing site apparently favour breeding-site dispersal although habitat quality promotes fidelity at the scale of habitat patches.     

Physicochemical environments and tolerances of cyprinodontoid fishes found in estuaries and salt marshes of eastern North America

Individuals of 28 species of cyprinodontoid fishes have been reported from estuaries/salt marshes of the Atlantic and Gulf coasts of North America. Some species show limited latitudinal distributions and/or occupy a limited range of habitats; others are widely distributed and/or occupy a wide range of habitats.A literature survey was made of conditions of water temperature, dissolved-oxygen (DO) concentrations, and salinities at sites where individuals of each species had been collected, and of laboratory-determined tolerances or lethal limits and other responses to those abiotic conditions. Individuals of Cyprinodon variegatus showed the widest overall range of tolerance of environmental temperatures, −1.9–45.4°C, with Gambusia rhizophorae showing the highest lower temperature-tolerance limit, 17°C. The only species highly sensitive to hypoxia was Floridichthys carpio, which showed “stress” at DO levels of 6–8 mg kg⁻¹. All showed use of aquatic surface respiration, except for Kryptolebias marmoratus, which uses aerial respiration in the presence of H₂S, and/or under hypoxic conditions. Individuals of C. variegatus were found to tolerate ambient salinities ranging from < 0.5 to 125.2, or higher, and several species of the genus Fundulus were found to tolerate concentrations ranging from <0.5 to ≥100. However, some of the species discussed cannot tolerate salinities beyond those of dilute brackish waters. In most instances, laboratory-determined tolerance limits of temperature and salinity were wider than conditions under which individuals of these species had been found in nature. The majority of available information related to adult individuals, with few studies focused on immature stages; however, existing information permitted a brief review of spawning, incubation, and early development features in Fundulus heteroclitus.Suggestions were made, based on existing information, as to species that would be most likely to show altered population distributions resulting from continued global warming. These included five species that have tropical/subtropical, or subtropical/temperate distributions. Also, a few others were included that show extensive latitudinal distributions, most extending northward into cooler temperate regions of the Atlantic coast. At present, none of these species has shown a range alteration that can be attributed to global warming.     

Connecting seas: western Palaearctic continental flyway for water birds in the perspective of changing land use and climate

The western Palaearctic continental flyway that connects the tundra and taiga belts of Russia with north‐west Europe is the major migratory avenue for an estimated 9.3 million herbivorous water birds (swans, geese and ducks). Agricultural practices together with protection measures subsidize the carrying capacity of winter habitats of the birds. Densities of these birds are highest in the Netherlands, where nitrogen (N) inputs to farmland have increased during the last 70 years and became the highest in Europe (>250 kg manure and fertilizer ha^?1 yr^?1). A comparison of population trends of 13 species of avian herbivores reveals generally expanding populations in the past 50 years, with the greatest increases from 1970 to 1990. Populations of the smallest avian herbivores, such as ducks, are either stable or have peaked and are now in decline, whereas numbers of larger herbivores (geese and swans) continue to increase and barnacle and greylag geese now breed in the Netherlands, in addition to northern sites. During the northerly spring migration, stop‐over sites, mostly in the agricultural regions of eastern Europe and Scandinavia, lie between the 3 and 6°C mean daily temperature isotherms in April, temperatures at which grasses start to grow, where flooding of riparian wetlands frequently occurs and fertilizers are applied to farmland. However, the restructuring of agricultural practices in an enlarged EU is likely to affect water bird populations and their migration routes. The reduced use of N in the Netherlands is predicted to constrain population growth, especially of the smallest avian herbivores with their high basal metabolic rates, because of the declining food quality of grass leaves. The introduction of large‐scale farming of oilseed rape, winter cereals, sugar beet and potatoes at the expense of grassland also will adversely affect these birds, whereas larger species are likely to continue exploiting these crops.     

The legacy of past climate and landscape change on species' current experienced climate and elevation ranges across latitude: a multispecies study utilizing mammals in western North America

Aim Elevation and climate ranges across latitude experienced by 21 wide‐ranging mammal species in western North America were summarized to examine two questions: (1) do populations in the northern and southern portions of a species’ range experience different climates or are environments selected to remain similar to climates at the core of ranges; and (2) how do species’ elevational ranges, experienced temperature seasonality and temperature ranges change across latitude? Given the larger effects of climate oscillations in the north vs. the south, a predicted outcome is for species to conserve climate niches across latitude and to show reduced climate and elevation ranges in the north. An alternative outcome is latitudinal niche diversification and increased climate variation in the north. Location Western North America. Methods The questions above were examined using a combination of species occurrence data bases, climate data bases, simple summaries of means and standard deviations and by testing summaries against random distributions across latitude for 21 mammal species from a variety of orders. Results The results showed that: (i) most species conserve their niche strongly or weakly given overall temperature gradients from north to south; (ii) seasonality experienced by species is relatively static until the highest latitudes despite directional trends across the region; and (iii) the elevation range and temperature variation that species experience decreases from south to north. Main conclusions Populations at range edges appear to partition environments to remain closer to temperature values similar to those at the core of the range. In addition, seasonality is not a likely explanatory factor of genetic diversity in latitudinal gradients. The data are instead more consistent with predictions that a combination of higher gene‐flow, increasing environmental instability and decreasing elevation gradients in the north compared to the south may lead to negative correlations between latitude and species’ climate variation. The results corroborate risks faced by northern mammal populations to global climate changes.     

The effects of NaCl on growth,water relations,osmolytes and ion content in <Emphasis Type="Italic">Kochia prostrata</Emphasis>

The effects of NaCl (0, 50, 100, 150 and 200 mM) on growth, water relations, glycinebetaine, free proline, ion contents, stomata number and size of Kochia prostrata (L.) Schard were determined. Shoot and root fresh and dry matter, root and shoot length, relative growth rate, net assimilation rate, relative water content, water use efficiency, soluble sugars and glycinebetaine contents were not changed at low NaCl concentrations, but they were significantly decreased at 200 mM NaCl. The K⁺, Mg²⁺ and Ca²⁺ contents, water potential, chlorophyll a+b and carotenoides contents, and stomata number and size were reduced already at low concentrations of NaCl. In contrast, the Na⁺, Cl^– and proline contents increased several times with increasing NaCl concentration. Kochia prostrata is a salt tolerant species, the optimal growth of this plant occurred up to 150 mM NaCl. The mechanisms of salt tolerance in the plant may be balance among ion accumulation and production of glycinebetaine, proline, soluble sugars for maintenance of pressure potential.