Habitat switching by Bewick's swans: Maximization of average long-term energy gain?

1. In a system where depletion drives a habitat shift, the hypothesis was tested that animals switch habitat as soon as the average daily net energy intake (or gain) drops below that attainable in the alternative habitat.

2. The study was performed in the Lauwersmeer area. Upon arrival during the autumn migration, Bewick's swans first feed on below-ground tubers of fennel pondweed on the lake, but subsequently switched to feeding on harvest remains in sugar beet fields.

3. The daily energy intake was estimated by multiplying the average time spent foraging per day with the instantaneous energy intake rate while foraging. In the case of pondweed feeding, the latter was estimated from the functional response and the depletion of tuber biomass. In the case of beet feeding, it was estimated from dropping production rate. Gross energy intake was converted to metabolizable energy intake using the assimilation as determined in digestion trials. The daily energy expenditure was estimated by the time-energy budget method. Energetic costs were determined using heart rate.

4. The daily gain of pondweed feeding at the median date of the habitat switch (i.e. when 50% of the swans had switched) was compared with that of beet feeding. The daily gain of beet feeding was calculated for two strategies depending on the night activity on the lake: additional pondweed feeding (mixed feeding) or sleeping (pure beet feeding).

5. The majority of the swans switched when the daily gain they could achieve by staying on the pondweed bed fell just below the average daily gain of pure beet feeders. However, mixed feeders would attain an average daily gain considerably above that of pondweed feeders. A sensitivity analysis showed that this result was robust.

6. We therefore reject the hypothesis that the habitat switch by swans can be explained by simple long-term energy rate maximization. State-dependency, predation risk, and protein requirements are put forward as explanations for the delay in habitat switch.

Variation at the DRD4 locus is associated with wariness and local site selection in urban black swans

 BACKGROUND: Interactions between wildlife and humans are increasing. Urban animals are often less wary of humans than their non-urban counterparts, which could be explained by habituation, adaptation or local site selection. Under local site selection, individuals that are less tolerant of humans are less likely to settle in urban areas. However, there is little evidence for such temperament-based site selection, and even less is known about its underlying genetic basis. We tested whether site selection in urban and non-urban habitats by black swans (Cygnus atratus) was associated with polymorphisms in two genes linked to fear in animals, the dopamine receptor D4 (DRD4) and serotonin transporter (SERT) genes.

RESULTS: Wariness in swans was highly repeatable between disturbance events (repeatability = 0.61) and non-urban swans initiated escape from humans earlier than urban swans. We found no inter-individual variation in the SERT gene, but identified five DRD4 genotypes and an association between DRD4 genotype and wariness. Individuals possessing the most common DRD4 genotype were less wary than individuals possessing rarer genotypes. As predicted by the local site selection hypothesis, genotypes associated with wary behaviour were over three times more frequent at the non-urban site. This resulted in moderate population differentiation at DRD4 (FST = 0.080), despite the sites being separated by only 30 km, a short distance for this highly-mobile species. Low population differentiation at neutrally-selected microsatellite loci and the likely occasional migration of swans between the populations reduces the likelihood of local site adaptations.

CONCLUSION: Our results suggest that wariness in swans is partly genetically-determined and that wary swans settle in less-disturbed areas. More generally, our findings suggest that site-specific management strategies may be necessary that consider the temperament of local animals.

Population, behavioural and physiological responses of an urban population of black swans to an intense annual noise event

Wild animals in urban environments are exposed to a broad range of human activities that have the potential to disturb their life history and behaviour. Wildlife responses to disturbance can range from emigration to modified behaviour, or elevated stress, but these responses are rarely evaluated in concert. We simultaneously examined population, behavioural and hormonal responses of an urban population of black swans Cygnus atratus before, during and after an annual disturbance event involving large crowds and intense noise, the Australian Formula One Grand Prix. Black swan population numbers were lowest one week before the event and rose gradually over the course of the study, peaking after the event, suggesting that the disturbance does not trigger mass emigration. We also found no difference in the proportion of time spent on key behaviours such as locomotion, foraging, resting or self-maintenance over the course of the study. However, basal and capture stress-induced corticosterone levels showed significant variation, consistent with a modest physiological response. Basal plasma corticosterone levels were highest before the event and decreased over the course of the study. Capture-induced stress levels peaked during the Grand Prix and then also declined over the remainder of the study. Our results suggest that even intensely noisy and apparently disruptive events may have relatively low measurable short-term impact on population numbers, behaviour or physiology in urban populations with apparently high tolerance to anthropogenic disturbance. Nevertheless, the potential long-term impact of such disturbance on reproductive success, individual fitness and population health will need to be carefully evaluated.

Villa of Agrippa Postumus, Egyptianizing scene and a pair of swans: detail

Boscotrecase, Italy; fresco on lime plaster

Hampered performance of migratory swans: intra- and inter-seasonal effects of avian influenza virus

The extent to which animal migrations shape parasite transmission networks is critically dependent on a migrant's ability to tolerate infection and migrate successfully. Yet, sub-lethal effects of parasites can be intensified through periods of increased physiological stress. Long-distance migrants may, therefore, be especially susceptible to negative effects of parasitic infection. Although a handful of studies have investigated the short-term, transmission-relevant behaviors of wild birds infected with low-pathogenic avian influenza viruses (LPAIV), the ecological consequences of LPAIV for the hosts themselves remain largely unknown. Here, we assessed the potential effects of naturally-acquired LPAIV infections in Bewick's swans, a long-distance migratory species that experiences relatively low incidence of LPAIV infection during early winter. We monitored both foraging and movement behavior in the winter of infection, as well as subsequent breeding behavior and inter-annual resighting probability over 3 years. Incorporating data on infection history we hypothesized that any effects would be most apparent in naïve individuals experiencing their first LPAIV infection. Indeed, significant effects of infection were only seen in birds that were infected but lacked antibodies indicative of prior infection. Swans that were infected but had survived a previous infection were indistinguishable from uninfected birds in each of the ecological performance metrics. Despite showing reduced foraging rates, individuals in the naïve-infected category had similar accumulated body stores to re-infected and uninfected individuals prior to departure on spring migration, possibly as a result of having higher scaled mass at the time of infection. And yet individuals in the naïve-infected category were unlikely to be resighted 1 year after infection, with 6 out of 7 individuals that never resighted again compared to 20 out of 63 uninfected individuals and 5 out of 12 individuals in the re-infected category. Collectively, our findings indicate that acute and superficially harmless infection with LPAIV may have indirect effects on individual performance and recruitment in migratory Bewick's swans. Our results also highlight the potential for infection history to play an important role in shaping ecological constraints throughout the annual cycle.

Lumometsän syli : Anni Swanin satusymbolismi 1896-1923

Lumometsän syli, Anni Swanin satusymbolismi 1896-1923 on suomenkielisen satukirjallisuuden poetiikkaa ja 1900-luvun alun modernia naiseutta selvittävä feministiseen tutkimustraditioon liittyvä tutkimus. Sen kohteena ovat lasten- ja nuortenkirjailija Anni Swanin (1875-1958) satukokoelmat vuosilta 1901-1923 ja Uusi Suometar -lehden sadunomaiset novellit vuosilta 1896-1904. Tutkimus tuo uutta tietoa lastenkirjallisuuden osalta 1900-luvun alun modernin ihmisen problematiikasta. Se sisältää naissubjektin kehityskaaren ja sisäisen kasvun kohti naistaiteilijuutta. Yksityiskohtaisen tarkastelun kohteina ovat sadut Veli ja sisar (1917), Ihmekukka (1905), Marjaanan helmikruunu (1912), Aaltojen salaisuus (1901), Jääkukka (1905), Tyttö ja kuolema (1917), Merenkuningatar ja hänen poikansa (1905), Lumolinna (1905) ja Tarina Kultasirkasta (1901). Tutkimuksessa tarkastellaan Swanin satujen poeettista kieltä ja naiseuden tematiikkaa ranskalaisen postmodernin ajan feministisen viitekehyksen valossa. Siinä keskeisiä ovat Julia Kristevan psykoanalyyttispohjaiset näkemykset ja Hélène Cixous´n sekä Luce Irigarayn ajatukset feminiinisestä kirjoituksesta. Sadut kontekstualisoidaan ajankohdan symbolistiseen taidevirtaukseen ja Suomen taiteen kultakauteen. Satuja tulkitaan naiskirjailijan lajina ja erityisenä naisen metaforisen ilmaisun muotona. Satujen feministinen lukutapa purkaa perinteisiä lukemiskonventioita ja merkitsee satutekstin lukemista "toisin". Se avaa varhaista modernia naiseutta ja sille ominaista naisen ilmaisukielen erityisyyttä sekä mykkää ei-kielellistä, melankolian ilmaisua. Tutkimus tuo esiin uudenlaisen naiskirjailijan aistimusvoimaisen kielen. Swanin satusymbolismi on luonnon kauneuden synesteettista ja aistimusvoimaista kerrontaa, jolle on luonteenomaista aistiestetiikka, metaforisuus, metonymisyys ja metamorfoosit. Swan vahvistaa osaltaan naisen sankaruutta, omaa ilmaisukieltä ja ääntä. Tuloksena paljastuu satuperinteeseen verrattuna uudenlaisia tyttöyden, äitiyden, naistaiteilijuuden ja perheen malleja ja niiden representaatioita. Satumallit osoittautuvat aikanaan moderneiksi tyttösankareiksi, osin ambivalenteiksi uudenlaista naiseutta ja suhteessa oloa heijastaviksi ja ovat siten varhaisia feministisen sadun tunnusmerkkejä. Tutkimus selvittää, miten Swan rakentaa omaperäisen satusymboliikan. Satumetsä on luonnonkauniin suomalaismetsän symbolinen mielenmaisema ja samanaikaisesti sadun myyttis-symbolinen topos. Swanin luontokäsitys sisältää luonnonsuojelun ja varhaisen ekokriittisen näkemyksen. Tutkimus osoittaa Swanin satujen kytkeytyvän 1900-luvun alun modernismiin ja Suomen taiteen kultakauteen. Swan on suomenkielisen symbolistisen taidesadun kehittäjä ja feministisen sadun aloittaja.

The avifauna of Laguna Llancanelo (Mendoza, Argentina), a South American wetland of international importance

Laguna Llancanelo is a large (40,000 ha), very shallow (less than 3 m deep), inland saline waterbody, located in southern Mendoza, Argentina. A survey of the avifauna was undertaken during 1983 to 1985; field trips were made mostly to the northeastern and central-western sectors of the lagoon, in the months of April, May, September, October and December. Complementary studies were made by an aerial survey and assessments of terrestrial birds in the surroundings of the lagoon. A total of 64 species in 22 families of birds usually associated with aquatic environments were recorded. The best-represented families of aquatic birds in terms of numbers of species were: Anatidae (13 swans, geese, ducks), Scolopacidae (7 sandpipers and other small waders), Ardeidae (6 herons, bitterns, egrets, Podicipedidae (4 grebes), Rallidae (4 rails, coots) and Charadriidae (4 plovers, lapwings). The most abundant nesting birds on the lagoon were: Black-necked swan Cygnus melancoryphus (824), silvery grebe Podiceps occipitalis (202) and black-crowned night heron Nycticorax nycticorax (100).

Regional Fisheries Advisory Committee 4th February, 1985

This is the report from the Regional Fisheries Advisory Committee meeting, which was held on the 4th February, 1985. The report contains information on fishing licence duties (1986), Lead and Swans, fyke Nets, Grass Carp Field Trials in the Lancaster Canal and the total available residual chlorine (TARC) in the River Lune. The Fisheries Advisory Committee was part of the Regional Water Authorities, in this case the North West Water Authority. This preceded the Environment Agency which came into existence in 1996.

Regional Fisheries Advisory Committee 20th May, 1985

This is the report from the Regional Fisheries Advisory Committee meeting, which was held on the 20th May, 1985. The report contains sections on fishing licence duties in 1986, lead poisoning in swans, Authority investigations into acidity problems in rivers in Cumbria, fishing offences processed, Fish Counter statistics, and the fisheries liaison meeting report. The section on Authority investigations into acidity problems in rivers in Cumbria pays attention on investigations carried out by the University of Lancaster and Freshwater Biological Association about acidity problems, particularly in the Rivers Duddon and Esk since 1980. This section contains biological findings, a chemical sampling programme, results from continuous pH monitors, and catchment liming. The Fisheries Advisory Committee was part of the Regional Water Authorities, in this case the North West Water Authority. This preceded the Environment Agency which came into existence in 1996.

Regional Fisheries Advisory Committee 21st October, 1985

This is the report from the Regional Fisheries Advisory Committee meeting, which was held on the 21st October, 1985. The report contains sections on River Lune Special Byelaws, proposed haaf net limitation order for the Solway Firth and lead poisoning in swans. Also included is information on River Kent fish passes, reservoirs, total available Residual Chlorine (TARC) in the River Lune, fish hatcheries, and Authority investigations into acidity problems in rivers in Cumbria. The Fisheries Advisory Committee was part of the Regional Water Authorities, in this case the North West Water Authority. This preceded the Environment Agency which came into existence in 1996.

Poisoning from lead gunshot: still a threat to wild waterbirds in Britain

Lead is a highly toxic metal known to be an important cause of morbidity and mortality in waterbirds and terrestrial birds worldwide. The risk to birds of poisoning from lead has resulted in the introduction of legislation in many countries, such as UK restrictions on the use of lead in angling weights and lead gunshot. In this study, we examined data on current and historical trends in lead poisoning in British waterbirds and related these to the introduction of legislation restricting the use of lead. Our results indicate that lead poisoning has continued to affect a wide range of British waterbirds long after legal restrictions were introduced. Elevated levels of lead (i.e. > 20.0 mu g/dL) were found in the blood of 34 % (n = 285) of waterbirds tested at four sites in Britain during the 2010/2011 winter and accounted for the deaths of at least 10.6 % (n = 2,365) of waterbirds recovered across Britain between 1971 and 2010 and 8.1 % (n = 1,051) between 2000 and 2010, with lead gunshot being the most likely source of poisoning. The proportion of birds dying from lead poisoning in England did not vary significantly after the introduction of legislation, accounting for 13.7 % of non-infectious causes of death between 1971 and 1987 (n = 204), 20.8 % (n = 360) between 1988 and 1999 and 11.8 % (n = 423) between 2000 and 2010, despite a significant change in lead-related mortality in mute swans found during the same time period, 25 % (n = 12) between 1971 and 1987, 4.6 % (n = 65) between 1988 and 1999 and 2 % (n = 100) between 2000 and 2010. Existing legislation needs review and extension to ensure the delivery of international commitments and a broad-scale transition to the use of non-toxic shot and angling materials in all environments.