Annual variation in waterbird clutch initiation date in relation to spring thaw in Arctic Russia.

To test for the degree of species-specific variation in clutch initiation date in relation to spring thaw, we recorded first egg dates in 1433 nests of seven large bodied long-distance migratory waterbird species breeding on Ayopechan Island in the Chaun Delta, Chukotka, in the Russian Arctic during 2002-2020. Pacific Loon Gavia pacifica, Sandhill Crane Grus canadensis and Glaucous Gull Larus hyperboreus all adjusted timing of clutch initiation completely to annual variation in first frost-free dates. First egg dates of Spectacled Eider Somateria fischeri also significantly advanced in warmer springs, but the rate of change was significantly less than unity, implying a reduced capacity to accommodate change in vernal thaw that may not be able to keep up with greater change in the future. Long-tailed Duck Clangula hyemalis and Vega Gull Larus vegae showed a tendency for earlier first egg dates in years with earlier first frost-free date, but for both species, the relationship failed to reach statistical significance. Bewick's Swan Cygnus columbianus showed almost no change in mean first egg date across the observed variation in first frost-free dates. Based on these data, we suggest that while all seven species showed signs of plasticity in their timing of onset of breeding, Pacific Loon, Sandhill Crane and Glaucous Gull showed greater adaptability to adjust the timing of their breeding season to recent variation in spring thaw than the other four species studied here over this period.

A Relationship between the Characteristics of the Oval Nucleus of the Mesopallium and Parrot Vocal Response to Playback.

Correlations between differences in animal behavior and brain structures have been used to infer function of those structures. Brain region size has especially been suggested to be important for an animal's behavioral capability, controlled by specific brain regions. The oval nucleus of the mesopallium (MO) is part of the anterior forebrain vocal learning pathway in the parrot brain. Here, we compare brain volume and total number of neurons in MO of three parrot species (the peach-fronted conure, Eupsittula aurea, the peach-faced lovebird, Agapornis roseicollis, and the budgerigar, Melopsittacus undulatus), relating the total neuron numbers with the vocal response to playbacks of each species. We find that individuals with the highest number of neurons in MO had the shortest vocal latency. The peach-fronted conures showed the shortest vocal latency and largest number of MO neurons, the peach-faced lovebird had intermediary levels of both, and the budgerigar had the longest latency and least number of neurons. These findings indicate the MO nucleus as one candidate region that may be part of what controls the vocal capacity of parrots.

Follow the leader? Orange-fronted conures eavesdrop on conspecific vocal performance and utilise it in social decisions.

Animals regularly use social information to make fitness-relevant decisions. Particularly in social interactions, social information can reduce uncertainty about the relative quality of conspecifics, thus optimising decisions on with whom and how to interact. One important resource for individuals living in social environments is the production of information by signalling conspecifics. Recent research has suggested that some species of parrots engage in affiliative contact call matching and that these interactions may be available to conspecific unintended receivers. However, it remains unclear what information third parties may gain from contact call matching and how it can be utilised during flock decisions. Here, using a combined choice and playback experiment, we investigated the flock fusion choices and vocal behaviour of a social parrot species, the orange-fronted conure (Eupsittula canicularis), to a contact call matching interaction between two individuals of different sexes and with different vocal roles. Our results revealed that orange-fronted conures chose to follow vocal leaders more often than vocal followers during fusions. Furthermore, flocks responded with higher call rates and matched the stimulus calls closer when subsequently choosing a vocal leader. Interestingly, orange-fronted conures also showed higher contact call rates and closer matches when choosing males over females. These results suggest that paying attention to conspecific contact call interactions can provide individuals with social information that can be utilised during fission and fusion events, significantly influencing the social dynamics of orange-fronted conures.

Changes in flight paths of large-bodied birds after construction of large terrestrial wind turbines.

The proliferation of ever-larger wind turbines poses risks to wildlife, especially from avian collision, yet avoidance behaviour of large-bodied, long-lived bird species in relation to wind turbines remains little studied away from collision "black spots" and offshore marine environments. Here, three-dimensional flight trajectory data are reported from a laser range-finder study of local movements of large-bodied birds (e.g. swans, geese, gulls, cormorants, raptors and cranes, whose populations are relatively more demographically sensitive to collision mortality) in relation to seven terrestrial 150-222 m high (mean 182 m) wind turbines constructed in Denmark in a N-S line. Comparisons of two-dimensional flight passages between turbines pre- (n = 287) and post-construction (n = 1210) showed significant (P < 0.0001) reductions from 48% to 35% within 150 m of each turbine, with corresponding increase 200-300 m from turbines. Results also showed a significant (P < 0.001) 50% reduction in the percentage of avian passages (from 21% to 10%) through the maximum turbine sweep area after construction and that the proportion of birds that passed between turbines at heights below (0-45 m) and above the turbine sweep area (> 182 m) were significantly greater (P < 0.0001) post-construction than prior to construction. These are the first results from tracking large-bodied bird flight trajectories to show the magnitude of their vertical and horizontal adjustments to the presence of turbines, which have implications for assumptions of even flight densities made by collision risk models currently used to predict avian turbine collision rates.

Managing geese with recreational hunters?

As many goose populations across the northern Hemisphere continue to rise, the role of hunters to manage these populations is increasingly being considered. We studied recreational goose hunters in Denmark to assess their behavioural and motivational characteristics, willingness to alter their hunting effort, as well as their ability to act as stewards of a rapidly increasing goose population. We identified several behavioural characteristics that typify effective goose hunting practices. We suggest a degree of specialization is necessary to increase goose harvests, as well as mitigating animal welfare issues (e.g. wounding). However, the majority of Danish goose hunters can be considered to be casual participants in this form of hunting. This poses a challenge for wildlife managers wishing to engage recreational hunters to manage highly dynamic wildlife populations, such as geese. If recreational hunters are to be used as a management tool, wildlife managers and hunting organizations will need to consider how best to facilitate skill development, hunting practices and socially legitimate hunting ethics to foster the stewardship role of hunting. We conclude that it is incumbent on wildlife managers to recognize and deal with both internal factors (e.g. skill development) and external influences (e.g. animal welfare concerns). In doing so, potential tensions in the multi-functionality of hunting can be alleviated, maintain hunting as a legitimate and accepted recreational past-time and management tool.

Plastic litter from shotgun ammunition on Danish coastlines - Amounts and provenance.

Plastic litter in the marine environment is a major global issue. Discarded plastic shotgun ammunition shells and discharged wads are an unwelcome addition and feature among the top ten litter items found on reference beaches in Denmark. To understand this problem, its scale and origins, collections were made by volunteers along Danish coastal shorelines. In all 3669 plastic ammunition items were collected at 68 sites along 44.6 km of shoreline. The collected items were scored for characteristic variables such as gauge and length, shot type, and the legibility of text, the erosion, and the presence of metallic components. Scores for characteristics were related to the site, area, and season and possible influences discussed. The prevalence of collected plastic shotgun litter ranges from zero to 41 items per 100 m with an average of 3.7 items per 100 m. Most ammunition litter on Danish coasts originates from hunting on Danish coastal waterbodies, but a small amount may come from further afield. North Sea coasts are the most distinctive suggesting the possible contribution of long distance drift as well as the likelihood that such litter can persist in marine habitats for decades. The pathway from initial discard to eventual wash-up and collection depends on the physical properties of plastic components, marine tides and currents, coastal topography and shoreline vegetation. Judging from the disintegration of the cartridge and the wear and decomposition of components, we conclude that there is a substantial supply of polluting plastic ammunition materials that has and will accumulate. These plastic items pose a hazard to marine ecosystems and wash up on coasts for many years to come. We recommend that responsible managers, hunters and ammunition manufacturers will take action now to reduce the problem and, thereby, protect ecosystems, wildlife and the sustainability of hunting.

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.

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.

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.

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 ºN to 64 ºN. 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 ºN) with only 94-133 ice-free days per year, but extended to depths of 21-33 m further south (73 ºN-64 ºN) 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 ºN), 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 matching by orange-fronted conures (Aratinga canicularis).

The functions of vocal matching have been clarified in territorial songbirds, compositionally stable groups of birds and mammals, and species with multiple alarm or assembly signals. The functions of vocal matching are less well understood in fission/fusion species that are non-territorial, live in groups with variable composition, and lack multiple alarm signals. Here we present the results of interactive playbacks in a fission/fusion parrot species, the orange-fronted conjure (Aratinga canicularis), that provide evidence of vocal matching. A randomly selected loud contact call (chee) per trial was played to passing wild flocks and short-term captives in Costa Rica. Of the trials where subjects interacted, 30% of wild flocks and 21% of captive trials showed significantly linear or curvilinear changes in similarity between the stimulus and response chees over the course of the trial. Surprisingly, both convergent and divergent sequences were observed, and many trials lacking a single trend showed disjunct changes in stimulus-response similarity. These results suggest that chee exchanges prior to flock fusions are not simply an exchange of greetings but are more likely some form of negotiation. This would explain the presence of convergent, divergent, and variable patterns of stimulus-response similarity seen in our experiments.

Sex-specific responses to vocal convergence and divergence of contact calls in orange-fronted conures (Aratinga canicularis).

We investigated the signal function of vocal imitation of contact calls in orange-fronted conures (OFCs; Aratinga canicularis) in Costa Rica. OFCs live in dynamic social systems with frequent flock fusions and fissions. Exchanges of contact calls precede these flock changes. During call exchanges, the similarity between the contact calls of different individuals may either increase (converge) or decrease (diverge). We conducted a playback experiment on wild-caught captive birds in which we simulated convergent, divergent and no-change interaction series with male and female contact calls. OFCs responded differently to convergent and divergent series of contact calls, but only when we considered the sex of the test birds. Males called most in response to convergent series, whereas females demonstrated high calling rates in response to both convergent and divergent interactions. Both sexes responded most to contact calls from the opposite sex, but overall females produced more calls and had shorter latencies to calling than males. These results demonstrate that OFCs can discriminate between male and female contact calls and that subtle changes in contact call structure during interactions have signal function. The stronger overall response to convergent series suggests that convergence of contact calls is an affiliative signal.

Male calling between courtship sequences in whitethroats: a way to counter intrusions from neighbouring rivals.

In whitethroats (Sylvia communis) unmated and recently mated males often emit a specific call, the woid-call, after a sequence of courtship diving songs when the female is still present. In the experiments we tested the deterring function of the woid-calls.A simple playback experiment showed that unmated males react to woid-calls played at their territory border by initially increasing their distance to the speaker in an escape-like manner before they approached in the same way as to territorial song. In another experiment we simulated a courtship event at a neighbour by playing back sequences of courtship songs from the territory border until the territory owner started to approach the speaker. We then either continued with one sequence of courtship song or switched to woid-calls. The results showed that the woid-calls delayed approaches from the territory owner. Together, the two experiments suggest a deterring effect of woid-calls. The implications of this for their use in courtship contexts where courting males often suffer intrusions from neighbouring males are discussed. We believe that woid-calls are used both preventively and defensively to avoid intrusions when other males have obtained information about female presence and courtship.

The meaning of song repertoire size and song length to male whitethroats Sylvia communis.

The importance of intrasexual differences in repertoire size was investigated in a playback experiment with whitethroats, Sylvia communis. Fourteen unmated territorial males received three treatments: a small repertoire, a large repertoire, and a small-elongated repertoire where the last couple of elements had been repeated to give songs of about the length of large repertoire playback. Besides responding to the intruder's absolute repertoire size or song length, males might also take their own singing ability into consideration. Therefore, the playback was considered relative to the repertoire size and song length of the territory defending males. However, this seems not to have had an important effect on the response. There was a stronger response to large than to small repertoire playback and a stronger response to small-elongated than to small repertoire playback, whereas there was no difference between large and small-elongated repertoire playback. In general, the strongest response was given to playback of long song (large and small-elongated song repertoire), suggesting that males responded to song length rather than repertoire size in short-term interactions with an intruder. This agrees with the idea that song length indicates the degree of arousal of the singer. The lack of response to repertoire size suggests that the evolution of the complex song repertoire in whitethroats' motif song is not a result of intrasexual selection.