Ole Roland Therkildsen

Energetics of Feeding on Winter Wheat Versus Pasture Grasses: A Window of Opportunity for Winter Range Expansion in the pink-footed Goose Anser brachyrhynchus

Traditionally, pink-footed geese Anser brachyrhynchus wintering in Denmark, the Netherlands and Belgium have used the Danish sites only during mild winters, rapidly moving southwards in case of cold spells. Since the 1980s, an increasing number of geese have remained on the Danish wintering grounds despite cold spells, foraging on pastures and winter wheat Triticum aestivum fields. We compare the daily time and energy budgets and the food quality in the two habitats during winter. Winter wheat fields were increasingly used by the geese as temperatures dropped. At temperatures around 0°C, the geese foraged in both habitats, spending on average 83.8% and 74.9% of the daytime foraging in pastures and winter wheat, respectively. The estimated daily energy expenditure was slightly higher on pastures than on winter wheat fields (1,076 vs 1,057 kJ). The estimated daily food intake determined using the ‘marker substance’ method was 148 and 157 g ash free dry weight (AFDW) in geese feeding on pastures and winter wheat fields, respectively, equivalent to a daily net energy intake of 1,109 kJ and 1,145 kJ. Daily food intake, estimated on the basis of oesophagus contents of collected birds, was 170 g AFDW in pasture feeding geese and varied within 159–229 g AFDW in winter wheat feeding geese. In the mild winter, the protein content in winter wheat and Poa did not differ, whereas in the severe winter the protein content remained high in winter wheat but decreased in Poa. During the winters of 1994–1996, the abdominal profile index, API, in individually neck-banded geese observed repeatedly, only changed significantly during late January 1996. Neither during cold spells was there any change in API. Since the 1980s, the area covered by winter wheat has increased markedly in Denmark. Because winter wheat represents a reliable and profitable food source even in severe winters, the recent change in agricultural practice has enhanced the development of a new wintering strategy of pink-footed geese, allowing a northward expansion of their winter range. Potentially, this will increase the crop damage conflict and may lead to further population growth.

Assessment of food intake rates in pink-footed geese Anser brachyrhynchus based on examination of oesophagus contents.

An alternative to the so-called ‘marker substance’ method used to estimate daily food intake in geese is presented. Based on the assumption that a grazing bird takes one leaf per peck, the daily food intake rate can be calculated by multiplying mean bite weight, peck rate and total daily foraging time. Wintering pink-footed geese Anser brachyrhynchus feeding on pastures and winter wheat fields were collected and samples of leaves in the oesophagus were measured, dried and weighed individually. We measured leaf lengths in unexploited areas of the same fields upon which geese had been feeding. Peck rates of winter wheat feeding geese were measured. Daily foraging time was obtained from observations of activity budgets of flocks of geese. Daily food intake of winter wheat feeding geese was estimated at 159–229 g ash free dry weight (AFDW) during late winter and at 188–212 g AFDW in early spring. For geese feeding on pastures in early spring food intake was estimated at 170 g AFDW. Averages were generally in accordance with estimates derived by the ‘marker substance’ method. Bite length was positively related to primary leaf length of winter wheat, suggesting that geese adjust bite size to available leaf lengths. There was a negative relationship between peck rate and length of all leaf types, but the relationship was only significant for primary leaves. Based on the assumption that bite length was identical to primary leaf length and the relationship between primary leaf length and peck rate, a quadratic relation between primary leaf length and instantaneous intake rates was derived, yielding a peak intake rate of 0.62 g AFDW min-1 at a primary leaf length of 8.4 cm. In the beginning of the winter, bite lengths were close to this optimal leaf length, but decreased during winter.

A review of the factors causing paralysis in wild birds: Implications for the paralytic syndrome observed in the Baltic Sea

We reviewed paralysis in wild birds with a special focus on the Baltic Sea paralytic syndrome recently described by Balk et al. (2009) by assessing multiple causative factors. The review showed that paralysis may occur in various species and that the aetiology can be divided into biotoxins, nutritional deficiencies, environmental contaminants and infectious diseases. The review also showed that the symptoms are influenced by age, sex and species of the affected individual. It seemed that paralysis may be treated or relieved by e.g. thiamine injections or additives. Due to a lack of extensive diagnostic studies, the potentially negative effects of paralysis at the population level of wild birds remain unsolved. We recommend that when investigating paralysis in wild birds, a holistic study approach including multiple factors are undertaken in order to pinpoint cause-and-effect relationships as well as the potential impacts on wild bird populations including those in the Baltic Sea.

Surveillance for Avian Influenza Viruses in Wild Birds in Denmark and Greenland, 2007–10

SUMMARY. In Denmark and Greenland, extensive surveillance of avian influenza (AI) viruses in wild bird populations has been conducted from 2007 through 2010. In Denmark, the surveillance consisted of passive surveillance of wild birds found dead or sick across Denmark and active surveillance of apparently healthy live birds in waterfowl reservoirs and along migratory flyways, birds living in proximity to domestic poultry, and hunted game birds. Dead birds were sampled by oropharyngeal swabbing. Healthy live wild birds were captured with nets, traps, or by hand and were sampled by swabbing of the oropharyngeal and cloacal tracts, or swabs were collected from fresh fecal droppings. Hunted game birds were delivered to game-handling establishments, where each bird was sampled by oropharyngeal and cloacal swabbing. During the 2007–10 period, a total of 11,055 wild birds were sampled in Denmark, of which 396 were birds that were found dead. In Greenland, samples were collected mainly from fecal droppings in breeding areas. Samples from 3555 live and apparently healthy wild birds were tested. All swab samples were tested by pan-influenza reverse transcriptase–PCR (RT-PCR), and the positive samples were further tested by H5/H7 specific RT-PCRs. H5/H7-positive samples were subjected to hemagglutination cleavage site sequencing for pathotyping. In addition, all RT-PCR–positive samples were subjected to virus isolation, and the virus isolates were subsequently subtyped. In Denmark, low pathogenic (LP) H5 viruses were detected throughout the period, in addition to a few LPAI H7 and several other subtypes. In Greenland, very few samples were positive for AI. None of them were found to be of the H5 or H7 subtypes by RT-PCR. Isolation of these viruses in eggs was unsuccessful; thus, they were not subtyped further. The findings did, however, demonstrate the presence of LPAI viruses in Greenland. For several water bird species overwintering in North America and northwest Europe, respectively, Greenland constitutes a common breeding area. This raises the possibility that viruses could be transmitted to North America via Greenland and vice versa. In Denmark, the screenings for AI showed LPAI viruses to be naturally occurring in the wild bird population, particularly in waterfowl. The occurrence of AI viruses in the wild bird population may pose a risk for AI infections in Danish poultry.

Field methods to assess pectoral muscle mass in moulting geese

In this paper, we report two new simple field methods to assess changes in pectoral muscle mass in live moulting geese. In the first method, transverse chest profiles of Canada geese Branta canadensis and greylag geese Anser anser were recorded using soldering wire. This standard measure of the chest angle showed a highly significant relationship with actual pectoral muscle mass. Chest angle measures showed a highly significant polynomial correlation with an index of moult stage, i.e. length of the ninth primary (p9). This indicated an initial slight decline in pectoral muscle mass as p9 length increased, followed by an increase in muscle mass in preparation for regaining the ability to fly. In the second method, visual pectoral profile scores from 0 (thin pectoral muscles concave) to 3 (convex bulky) recorded at distances using telescope or binoculars also proved to be useful as a field measure of pectoral muscle mass in moulting geese. Hence, the first method provides a non-consumptive means of predicting pectoral muscle mass in moulting geese without the need to dissect birds, and the second method enables field prediction of muscle mass in moulting geese without resort to capture of birds.

Genetic Analysis of Avian Influenza Virus from Wild Birds and Mallards Reared for Shooting in Denmark

Abstract Denmark forms a geographical bottleneck along the migration route of many water birds breeding from northeastern Canada to north Siberia that gather to winter in Europe and Africa. Potentially, the concentration of such large numbers of water birds enhances the risk of avian influenza virus (AIV) introduction to domestic poultry. In 2003, Denmark initiated a nationwide survey of AIV in wild birds and mallards reared for shooting. Partial sequence analysis of the six internal genes from a total of 12 low pathogenic (LP) AIV isolates obtained in 2003 showed that genes from these viruses were closely related with genes from AIV circulating in northern Europe. For the Danish sequences only the PB2 and NS genes differ, so they cluster to more than one cluster in the phylogenetic trees. In spring 2006, highly pathogenic (HP) AIV H5N1 was detected in 44 cases of wild birds in Denmark. Sequence analysis of the HP H5N1 virus genome showed that it was not related to the LPAIV isolated previously, but closely related to the HPAIV H5 (Asian type) detected in the rest of Europe at that time. Even though only partial sequences were applied, this gave the idea for future full-length sequence studies.

Low Pathogenic Avian Influenza (H7N1) Transmission Between Wild Ducks and Domestic Ducks

This article describes a virological investigation in a mixed flock of ducks and geese following detection of avian influenza virus antibodies in domestic geese. Low pathogenic H7N1 was found in both domestic and wild birds, indicating that transmission of virus was likely to have taken place between these. The importance of implementing and maintaining appropriate biosecurity measures is re‐emphasized.