Thorsten J. S. Balsby

Seasonal sea ice cover as principal driver of spatial and temporal variation in depth extension and annual production of kelp in Greenland

We studied the depth distribution and production of kelp along the Greenland coast spanning Arctic to sub-Arctic conditions from 78 °N to 64 °N. This covers a wide range of sea ice conditions and water temperatures, with those presently realized in the south likely to move northwards in a warmer future. Kelp forests occurred along the entire latitudinal range, and their depth extension and production increased southwards presumably in response to longer annual ice-free periods and higher water temperature. The depth limit of 10% kelp cover was 9–14 m at the northernmost sites (77–78 °N) with only 94–133 ice-free days per year, but extended to depths of 21–33 m further south (73 °N–64 °N) where >160 days per year were ice-free, and annual production of Saccharina longicruris and S. latissima, measured as the size of the annual blade, ranged up to sevenfold among sites. The duration of the open-water period, which integrates light and temperature conditions on an annual basis, was the best predictor (relative to summer water temperature) of kelp production along the latitude gradient, explaining up to 92% of the variation in depth extension and 80% of the variation in kelp production. In a decadal time series from a high Arctic site (74 °N), inter-annual variation in sea ice cover also explained a major part (up to 47%) of the variation in kelp production. Both spatial and temporal data sets thereby support the prediction that northern kelps will play a larger role in the coastal marine ecosystem in a warmer future as the length of the open-water period increases. As kelps increase carbon-flow and habitat diversity, an expansion of kelp forests may exert cascading effects on the coastal Arctic ecosystem.

Vocal Imitation in Parrots Allows Addressing of Specific Individuals in a Dynamic Communication Network

Parrots in captivity are known for their ability to vocally imitate humans and recently it has been shown that wild-living orange-fronted conures are able to immediately imitate other individuals’ contact calls. The function of this exceptional ability to imitate remains unclear. However, orange–fronted conures live in fission-fusion flocks where they encounter many different individuals every day, and it is possible that their vocal imitation ability is a flexible means to address a specific individual within a flock. We tested this via playback to short-term captive wild conures. Test birds were placed together in pairs in outdoor aviaries to form simple flocks. To simulate imitation of a specific individual these pairs received playback of contact calls that primarily imitate one of the two birds. Overall, individuals that received simulated vocal imitations of its calls responded more frequently and faster than the other individual. This suggests that orange-fronted conures can use imitations of contact calls to address specific individuals of a flock. In the discussion we argue that the fission-fusion flock dynamics of many parrot species has been an important factor in evolving conures’ and other parrots’ exceptional ability to imitate.

Degradation of whitethroat vocalisations: implications for song flight and communication network activities

Transmission of acoustic signals through the habitat modifies the signals and may thus influence their use in communication. We investigated the transmission of five different types of whitethroat (Sylvia communis) vocalisations, three types of song and two calls. Typical examples were broadcast and re-recorded in a whitethroat habitat with hedgerows and open meadow. We used a complete factorial design with speaker and microphone placed in different natural sender and receiver positions including high perches and song flights. Sound degradation was quantified in terms of signal-to-noise ratio, excess attenuation, tail-to-signal ratio and blur ratio. The results suggest that sound degradation generally increased with distance along a hedgerow, which means that birds here potentially may use degradation in assessing the distance to a vocalising individual. This is unlike the open meadow where the change in degradation with distance was negligible. Surprisingly, song flight relative to perched singing seems not to facilitate transmission of own vocalisations or perception of vocalisations from other individuals, and song flight vocalisations do not transmit differently from other types of vocalisations during song flights. One purpose of song flights might therefore be visual location by potential receivers and surveillance by the territory owner. Source level and degradation differed between the five types of vocalisations in accordance with their functions. Motif song and song flight songs used in attraction of females and/or deterrence of males could transmit through neighbouring territories, whereas the calls and the courtship diving song where a specific individual within or near the territory is addressed had relatively short communication ranges.

Exploring the robustness of macrophyte-based classification methods to assess the ecological status of coastal and transitional ecosystems under the Water Framework Directive

Identifying and quantifying the factors that contribute to the potential misclassification of the ecological status of water bodies is a major challenge of the Water Framework Directive (WFD). The present study compiles extensive biomonitoring data from a range of macrophyte-based classification methods developed by several European countries. The data reflect spatial and temporal variation as well as inter-observer variation. Uncertainty analysis identified that factors related to the spatial scale of sampling generally contributed most to the uncertainty in classifying water bodies to their ecological status, reflecting the high horizontal and depth-related heterogeneity displayed by macrophyte communities. In contrast, the uncertainty associated with temporal variation was low. In addition, inter-observer variation, where assessed, did not contribute much to overall uncertainty, indicating that these methods are easily transferable and insensitive to observer error. The study, therefore, suggests that macrophyte-based sampling schemes should prioritize large spatial replication over temporal replication to maximize the effectiveness and reliability of water body classification within the WFD. We encourage conducting similar uncertainty analyses for new/additional ecological indicators to optimize sampling schemes and improve the reliability of classification of ecological status.

Bioremediation of reject water from anaerobically digested waste water sludge with macroalgae (Ulva lactuca, Chlorophyta)☆

Phosphorus and biologically active nitrogen are valuable nutrient resources. Bioremediation with macroalgae is a potential means for recovering nutrients from waste streams. In this study, reject water from anaerobically digested sewage sludge was successfully tested as nutrient source for cultivation of the green macroalgae Ulva lactuca. Maximal growth rates of 54.57±2.16% FW d(-1) were achieved at reject water concentrations equivalent to 50 μM NH4(+). Based on the results, the growth and nutrient removal was parameterised as function of NH4(+) concentration a tool for optimisation of any similar phycoremediation system. Maximal nutrient removal rates of 22.7 mg N g DW(-1) d(-1) and 2.7 mg P g DW(-1) d(-1) were achieved at reject water concentrations equivalent to 80 and 89 μM NH4(+), respectively. A combined and integrated use of the produced biomass in a biorefinery is thought to improve the feasibility of using Ulva for bioremediation of reject water.

The functions of vocal learning in parrots

Given that both sexes of most parrots learn new vocalizations throughout life and produce them in diverse social contexts, whereas few songbird species combine all these traits, why are parrots not a better model for the evolution of human speech than songbirds? We first note the technical constraints that have limited research on wild parrot communication and then review the discoveries that have accumulated in the last two decades as constraints were overcome. Vocal learning in wild parrots appears unrelated to sexual selection and mate competition but is used by parrot pairs to defend nest sites in ways similar to those of songbirds. Where parrots differ from songbirds is in their specialization on toxic and armored foods, the consequences of this diet on foraging and social dynamics, and the use of learned vocalizations to mediate those dynamics. Parrots thus use learned vocalizations for two quite different functions, only one of which they share with songbirds (and hummingbirds). Interestingly, recent neurobiological studies have shown that parrots have dual cortical pathway nuclei for vocal learning, only one of which is present in songbirds. The parallels between the distributions of functions of vocal learning and brain nuclei suggest future research that should clarify both how and why parrots are more extensive vocal learners than songbirds and whether there are in fact parallels with humans.

Vocal similarity and familiarity determine response to potential flockmates in orange-fronted conures (Psittacidae)

In social species with fission–fusion dynamics, individuals have the opportunity to recruit other individuals selectively by calling. An individual’s decision to call to another could be determined by previous interactions with that individual, which would require individuals to be able to discriminate others based on their vocalizations and associate knowledge with their vocal identity. Alternatively, this decision may be determined solely by the current interaction. In a playback experiment, we tested the ability of orange-fronted conures, Aratinga canicularis to discriminate between calls of familiar and unfamiliar females. Males were able to discriminate between familiar and unfamiliar calls from different females. Furthermore, test birds seemed to associate experience from the previous interaction with the vocal characteristics of the familiar call, but this result was marginally nonsignificant. The success of the playback in imitating the test bird’s contact call in the current interaction proved important, as high similarity between playback and the test bird’s contact calls elicited a stronger response from it. The importance of call imitation during current interactions probably reflects the fact that orange-fronted conures live in flocks with fission–fusion dynamics and therefore often interact with unfamiliar individuals.

Could Have Gone Wrong: Effects of Abrupt Changes in Migratory Behaviour on Harvest in a Waterbird Population.

To sustainably exploit a population, it is crucial to understand and reduce uncertainties about population processes and effects of harvest. In migratory species, management is challenged by geographically separated changing environmental conditions, which may cause unexpected changes in species distribution and harvest. We describe the development in the harvest of Svalbard-breeding pink-footed geese (Anser brachyrhynchus) in relation to the observed trajectory and migratory behaviour of the population. In autumn, geese migrate via stopover sites in Norway and Denmark (where they are hunted) to wintering grounds in the Netherlands and Belgium (where they are protected). In Denmark and Norway harvesting increased stepwise during the 2000s. The increase in the population size only partly explained the change. The change corresponded to a simultaneous stepwise increase in numbers of geese staging in Denmark throughout autumn and winter; geese also moved further inland to feed which collectively increased their exposure to hunting. In Norway the increase in harvest reflected greater utilisation of lowland farmland areas by geese, increasing their hunting exposure. The study demonstrates how changes in migratory behaviour can abruptly affect exposure to hunting, which showed a functional response to increased temporal and spatial availability of geese. The harvest has now reached a level likely to cause a population decline. It highlights the need for flexible, internationally coordinated hunting regulations and reliable up-to-date population estimates and hunting bag statistics, which are rare in European management of migratory waterbirds. Without such information decisions are left with judgments based on population estimates, which often have time lags of several years between recording and reporting, hampering possibilities for the timely adjustment of management actions.

Element repertoire: change and development with age in Whitethroat Sylvia communis song

Song repertoires are often important determining factors in sexual selection. In several species, older males have larger repertoires than 1-year-old males. The development of large song repertoires by an individual is, however, poorly understood. We studied song element repertoire changes in five individual male Whitethroats Sylvia communis sampled as 1- and 2-year olds. These males increased the size of their element repertoire between their first and second year, but song length and number of different elements per song did not change. On average, 44.3% of the song elements in the first-year repertoire were also found in the second-year repertoire. Elements shared between years were found earlier in the songs and tended to occur in sequences. Sequences of shared elements also seemed to be conserved between years. The study suggests that the song element repertoire of the second year is partly based on the first-year repertoire, which may explain why large song repertoires are mainly expressed by males at least 2 years of age. It would appear, therefore, that song element repertoire size could be a reliable signal of male age.

Efficacy of non-lead rifle ammunition for hunting in Denmark

Lead has traditionally been used for making hunting ammunition. However, lead from spent hunting bullets has proven to be a health hazard for wildlife, ecosystems, and humans. The transition to use non-lead ammunition for hunting raises several concerns, especially inter alia the question of efficacy. This study examined whether non-lead rifle ammunition fulfills the demands of ethical and humane hunting by causing a rapid kill of hunted animals equivalent to lead rifle ammunition. A field sample of 657 hoofed animals, most red deer (Cervus elaphus) and roe deer (Capreolus capreolus), were hunted under normal Danish conditions by sport hunters using commonly used rifle calibers. The efficiency of copper versus lead bullets was tested using flight distance after being hit as the primary response parameter. For red deer, we were not able to show any statistical significant difference between performance of non-lead and lead bullet. For roe deer, we found a small, statistically significant, relation between flight distances and shooting distance for roe deer struck with non-lead bullets but not with lead bullets. However, this difference was not of such magnitude as to have any practical significance under hunting conditions. We conclude that in terms of lethality and animal welfare, non-lead ammunition within the tested range of bullet calibers can be recommended as an effective alternative to lead-core bullets.