Ocean current connectivity propelling the secondary spread of a marine invasive comb jelly across western Eurasia

Publication history: Accepted - 15 February 2018; Published - 16 May 2018.Aim: Invasive species are of increasing global concern. Nevertheless, the mechanisms driving further distribution after the initial establishment of non-native species remain largely unresolved, especially in marine systems. Ocean currents can be a major driver governing range occupancy, but this has not been accounted for in most invasion ecology studies so far. We investigate how well initial establishment areas are interconnected to later occupancy regions to test for the potential role of ocean currents driving secondary spread dynamics in order to infer invasion corridors and the source–sink dynamics of a non-native holoplanktonic biological probe species on a continental scale. Location: Western Eurasia. Time period: 1980s–2016. Major taxa studied: ‘Comb jelly’ Mnemiopsis leidyi. Methods: Based on 12,400 geo-referenced occurrence data, we reconstruct the invasion history of M. leidyi in western Eurasia. We model ocean currents and calculate their stability to match the temporal and spatial spread dynamics with large-scale connectivity patterns via ocean currents. Additionally, genetic markers are used to test the predicted connectivity between subpopulations. Results: Ocean currents can explain secondary spread dynamics, matching observed range expansions and the timing of first occurrence of our holoplanktonic non-native biological probe species, leading to invasion corridors in western Eurasia. In northern Europe, regional extinctions after cold winters were followed by rapid recolonizations at a speed of up to 2,000 km per season. Source areas hosting year-round populations in highly interconnected regions can re-seed genotypes over large distances after local extinctions. Main conclusions: Although the release of ballast water from container ships may contribute to the dispersal of non-native species, our results highlight the importance of ocean currents driving secondary spread dynamics. Highly interconnected areas hosting invasive species are crucial for secondary spread dynamics on a continental scale. Invasion risk assessments should consider large-scale connectivity patterns and the potential source regions of non-native marine species.Danish Council for Independent Research; Grant/Award Number: DFF-1325-00102B; FP7 People: Marie-Curie Actions, Grant/Award Number: MOBILEX, DFF - 1325-00025; EU, BONUS, BMBF, Grant/ Award Number: 03F0682; Excellence Cluster “Future Ocean”, Grant/Award Number: CP153

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.publishedVersio

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

Using re-sighting data to estimate population size of Pink-footed Geese (Anser brachyrhynchus)

In wildlife management, the ability to reliably assess population sizes is a basic prerequisite. When populations are managed specifically to maintain a population target this is even more vital. In this study we apply a mark-resight approach using neck-collared geese to develop and present an alternative method to total counts when estimating the population size of Pink-footed Geese (Anser brachyrhynchus). Estimates of population size from the mark-resight approach showed an increasing trend from 31,000 birds in 1991/ 1992 to 100,700 birds in 2011/2012, and fluctuating numbers around 80,000 in recent years. By exploring the relationship between uncertainty of the population estimate and the monitoring effort, we showed that a minimum of approximately 120 independent flocks greater than 100 birds should be surveyed to derive a ratio estimate of marked to unmarked birds minimizing uncertainty of the overall population estimate

Night-brooding behaviour in provisioning cavity-nesting birds is a trade-off between adult predation risk and nestling thermoregulation needs

Night-brooding of nestlings in cavity-nesting avian species carries predation risks to parents. Anecdotally, several species are known to shift from constant adult night-brooding behaviour to leaving nestlings unattended at night during offspring development but the timing, speed of change and sex-specific differences between parents, and the factors shaping this behaviour have rarely been described. Moreover, the location and nature of night roosts used by adults whilst provisioning nestlings has received little research attention. We studied breeding Common Starlings Sturnus vulgaris and hypothesised that, in such a cavity-nesting species, 1) nestlings would only be night-brooded until they achieved thermal independence, 2) since the species is frequently polygynous, female parents would most likely exclusively night-brood offspring despite provisioning by both sexes and 3) night-brooding would be more likely during nights with lowest temperatures. Nightly video recordings throughout the nestling phase at eight Starling nests together with data from 18 Starlings fitted with GPS-loggers during 26 nights provided support for hypotheses 1) and 2), while we found no support for hypothesis 3). All tagged male Starlings always roosted far from the nesting site (up to 8 km) independent of nestling age; all females brooded nestlings, usually up to the first seven-nine days after hatching (when the nestlings achieve thermoregulation), but roosted with males after day 10, when all tagged Starlings from the same nesting ‘colony’ roosted together. These results confirm differential sex-related parental effort in provisioning Starlings, suggesting females only night-brood until young achieve homeothermy

Spectrograms (A–C) of orange-fronted conure contact calls from three different playback trials to different flocks.

<p>In each spectrogram the first call is the playback call, the second call is a solo contact call of the target bird (imitated bird) and the third call is a solo call of the non-imitated bird. The three playback calls came from three different flocks. The numbers above the solo contact calls are their cross-correlation similarity relative to the playback call. In A and B the playback call came from a male and in C a female. The test birds in A and C were all females and in B the test birds were both males. The three parts of the contact call are marked below the first call in spectrogram C. The spectrogram has been prepared in Avisoft (FFT = 256, Overlap = 75%, Blackman window).</p

Playbacks successfully imitated the targeted birds.

<p>Playback calls (LS mean ± SE) had a higher similarity to the solo calls of imitated than non-imitated test birds. The similarity between the individuals solo contact call and the playback was quantified by spectrographic cross-correlation.</p