Seabird metapopulations: searching for alternative breeding habitats

Today, many seabird species nest in port areas, which are also necessary for human economic activity. In this paper, we evaluate, using a metapopulation model, the possibilities for creating alternative breeding sites for the Common Tern (Sterna hirundo) in the Rhine¿Meuse¿Scheldt estuary. We explore 22 scenarios that differ with respect to (1) loss of breeding habitat in port areas, (2) location and size of newly created habitat, and (3) coexistence of old and new habitat. Results indicate that loss of port area habitats results in a serious 41% decline in the breeding population. When the loss in ports is compensated for within the ports, the decline was negligible. Fourteen scenarios result in an increase of the Common Tern metapopulation. In these, extra breeding habitat is created outside the ports in fish-rich waters, resulting in a potential metapopulation increase of 25%. However, the period of overlap between lost and newly created habitat strongly affects the results. A gap between the removal of old and the creation of new breeding areas might cause a drop in the metapopulation level of 30%. The population recovery from this drop might take more than 100 years due to slow recolonization. Our results suggest that conservation of seabird species should be evaluated on a metapopulation scale and that the creation of new habitat may help to compensate for habitat loss in other areas. Furthermore, the results indicate that overlap between the existence of old and newly created breeding habitats is crucial for the success of compensation efforts. However, new locations should be carefully selected, because not only is the suitability of the breeding grounds important, but ample fish availability nearby is also ke

Dispersie na het broedseizoen, trek en overwintering van Grote Sterns <i>Thalasseus sandvicensis</i> uit de Voordelta = Post-breeding dispersal, migration and wintering of Sandwich Terns <i>Thalasseus sandvicensis</i> from the southwestern part of the Netherlands

The Sandwich Tern Sterna sandvicensis is a Dutch Red List species with a population of 19,000 pairs in the Dutch coastal zone. It winters off the coasts of Africa and a small populations migrates into the Mediterranean or stays even more north.. In the Netherlands, breeding takes places in a small number of colonies in the Delta area and the Waddensea. In this study, Sandwich Terns from the Delta colony on the Scheelhoek (Natura 2000 SPA ‘Haringvliet’) were investigated which forage during the breeding season in Natura 2000 SPA ‘Voordelta’. In total 30 adult Sandwich Terns were equipped with radio transmitters, a colourring and a plumage colour (picrinic acid or silver nitrate solution). Thanks to these markings birds could be followed in the colonies, from airplanes and from the coast. Several birds used the sand banks off the coast of their breeding colonies to rest after the breeding season. After a short while they dispersed in western and northern direction with sightings in the northern part of the Netherlands (outside and within other colonies). These were always failed breeders, possibly scouting other colonies for future breeding places. Some of these birds even left the Dutch coasts and appeared in Scotland and Denmark. Adults with young probably dispersed into the North Sea after a short stay around the sand banks off the coast near the colonies. They probably head to more nutrient rich areas in the North Sea and adjacent areas where the young birds can practice their fishing techniques before they move south. The adults can build-up here good fat reserves before the start of migration. In September, most of the marked Sandwich Terns were south of their breeding places and during their southward migration birds were seen along the coast of France and on Lanzarote (Canary Islands). Our results showed that using markers on birds could yield good data with a resighting percentage of 20% within only one year. Furthermore, the use of plumage colouring proved to be a good method for obtaining information of individual birds as these colourings attract the attention of observers and are ‘readable’ over large distances

Broedresultaten van kokmeeuwen in Nederland in 1997 = Reproductive success of Black-Headed gulls in the Netherlands in 1997

The Black-headed Gull population in The Netherlands, as in other parts of Europe, has seriously declined since the 1980s. The decline has been noted both at coastal and mainland breeding sites. The reasons for the general decline are not known. Therefore a monitoring programme was established to measure breeding results of Black-headed Gulls in six Dutch colonies in 1997. Remarkable differences were found in hatching success and breeding success. Hatching success was high (75- 90%) in the three northern colonies situated in or near the Wadden Sea, whereas in all other colonies hatching success was extremely low (0-43%). Most eggs were lost through flooding, trampling by geese, depredation or nest desertion. Only in the colony at Griend, fledging success was high (66%) and some young fledged in Julianapolder. In all other colonies, most chicks died of starvation or depredation. In those colonies the food mainly consisted of marine prey (e.g. fish, shrimps and lugworms), whereas in the other colonies the chicks were fed with a large proportion of insects and other invertebrates

Seabirds in Belgian marine waters: implications for policy and management (poster)

In 1992, the Institute of Nature Conservation (INC) started ship-based surveys on the Belgian Continental Shelf (BCS) to study the spatial and temporal distribution of seabirds. Among other things, the study showed that the Belgian marine waters hold internationally important numbers (> 1% of the biogeographical populations) of several coastal and marine bird species. Also the area proved to be of major importance for several species of migratory birds. Out of the 121 bird species encountered at sea during the period 1992-98, 23 were selected as being true marine species that occur in relatively high densities within the Belgian waters. Of these 23 species six were so-called ‘focal species’, being seabirds which are included in the highest priority lists of international conservation instruments (EC-Birds Directive, Bern Convention or Bonn Convention) and which attain at least 1% of the flyway population in Belgian marine waters in a particular season. Based on the distribution patterns, conservation value, and sensitivity for disturbance or oil pollution of the six focal seabirds several areas of high ornithological importance as well as areas sensitive for disturbance or pollution could be distinguished at the BCS. The avian hotspots at the Westkustbanken and Vlaamse Banken turned out to be the most sensitive areas for disturbance and oil pollution throughout the year, while the sensitivity of other areas varies with the seasons

Beach bird surveys in Belgium (poster)

Oil contamination is still a major cause of mortality in many coastal and seabird species around Europe. In a comparison with other North Sea areas, oil rates of most Belgian beached bird species are significantly higher than in northern areas such as the Shetlands and Norway, and more or less in line with oil rates at other European continental coasts. Wrecks of starved unoiled guillemots (and other species) became an almost annual event at the North Sea coasts from the first half of the ‘80s onwards, also in Belgium.Oil rates of beached bird corpses are an appropriate condition indicator of oil pollution at sea. Oil rate of most bird species/taxa in Belgium indicate a decline in oil pollution for the period 1962-99, though only Laridae, guillemot and razorbill show significant reductions. For the other taxa no significant decrease in proportion of oiled birds could be demonstrated, often due to the relatively small study area and hence insufficient number of birds collected. Assuming that a sample of at least ten complete corpses is required to calculate reliable oil rates, only the guillemot (as species) and auks (as taxon) can provide the necessary data in Belgium these days.Long-term oil pollution monitoring in Belgium should be continued with a major focus on a set of abundant bird taxa, sensitive to oil pollution and occurring in various marine habitats and the collection of additional data during the rest of the winter. Most appropriate for this set of limited bird taxa to focus on are grebes (inshore), Laridae, guillemot and razorbill (midshore) and kittiwake and fulmar (offshore).Birds dying at sea may eventually wash ashore. As such, beached bird surveys can be an important source of information concerning mortality of seabirds in the marine environment. However, there has been a lot of debate on the question how numbers of casualties on beaches relate to the actual mortality at sea and which factors affect this relationship. The temporal patterns of beached birds usually follow those of seabirds at sea with a time lag of at least one month. Considering the short Belgian shoreline and the prevailing frequency distribution of winds, probably only 10% of all birds washing ashore died in Belgian marine waters. With a dominant SSW circulation and a net residual current in northeastern direction, many birds must end up on Dutch, German or Scandinavian beaches. Accordingly, there is a higher probability that Belgian beaches receive birds that died in northern France or south England than from other North Sea border states. Based on the number of birds found on the beach and brought in at the MEC, and taking into account that 50-80 % of the corpses have disappeared already within the first 9 days (the mean interval between succeeding weekly surveys), we estimate that the total number of bird corpses beaching on the Belgian coast each winter might be as high as 5,000-10,000 birds

Seabirds & offshore wind farms: Monitoring results 2011

‘Seabirds at sea’ count data exhibit extreme spatial and temporal variation, impeding the assessment of the impact of wind turbines on seabird abundance and distribution. We designed a BACI monitoring program to assess the effect of wind farm presence on seabird displacement and used the results of ship-based surveys to simulate a broad range of empirical scenarios. Based upon these, we investigated how the power of detecting a change in seabird numbers is affected by survey length, monitoring intensity and data characteristics. The methodology used for the assessment was revised as compared to the previous reports. The most crucial difference is the application of zero-inflated estimation. Data on 13 seabird species regularly occurring in the assessment of displacement effects caused by wind turbines. The impact modelling at the Thorntonbank study area so far only reveals attraction effects, i.e. for Little Gull, Great Black-backed Gull, Black-legged Kittiwake, Sandwich and Common Tern. These findings are highly provisory since at the time of the study, one line of wind mills was present. Nevertheless, this poses some serious conservation concerns, given the high protection status and the fragility of the populations of both tern species and of Little Gull, combined with the raised threat of collision-mortality. After the turbines were built at the Bligh Bank, numbers of Common Guillemot and Northern Gannet significantly decreased in the wind farm area. In contrast, numbers of Common Gull significantly increased, and the BACI-graphs suggest attraction of Herring Gull as well. Gulls are probably attracted by the wind farm from a sheer physical point of view, with the farm functioning as a stepping stone, a resting place or a reference feature in the wide open sea. During recent surveys in 2012, good numbers of auks and even Harbour porpoises were encountered inside the wind farm. From an ecological point of view, the presence of auks is very interesting, and we wonder if these self-fishing species are already habituating to the presence of the turbines, and if they will profit from a (hypothetical) increase in food availability

Association of Medical Comorbidities With Objective Functional Impairment in Lumbar Degenerative Disc Disease

STUDY DESIGN Analysis of a prospective 2-center database. OBJECTIVES Medical comorbidities co-determine clinical outcome. Objective functional impairment (OFI) provides a supplementary dimension of patient assessment. We set out to study whether comorbidities are associated with the presence and degree of OFI in this patient population. METHODS Patients with degenerative diseases of the spine preoperatively performed the timed-up-and-go (TUG) test and a battery of questionnaires. Comorbidities were quantified using the Charlson Comorbidity Index (CCI) and the American Society of Anesthesiology (ASA) grading. Crude and adjusted linear regression models were fitted. RESULTS Of 375 included patients, 97 (25.9%) presented at least some degree of medical comorbidity according to the CCI, and 312 (83.2%) according to ASA grading. In the univariate analysis, the CCI was inconsistently associated with OFI. Only patients with low-grade CCI comorbidity displayed significantly higher TUG test times (p = 0.004). In the multivariable analysis, this effect persisted for patients with CCI = 1 (p = 0.030). Regarding ASA grade, patients with ASA = 3 exhibited significantly increased TUG test times (p = 0.003) and t-scores (p = 0.015). This effect disappeared after multivariable adjustment (p = 0.786 and p = 0.969). In addition, subjective functional impairment according to ODI, and EQ5D index was moderately associated with comorbidities according to ASA (all p < 0.05). CONCLUSION The degree of medical comorbidities appears only weakly and inconsistently associated with OFI in patients scheduled for degenerative lumbar spine surgery, especially after controlling for potential confounders. TUG testing may be valid even in patients with relatively severe comorbidities who are able to complete the test

Lower Extremity Motor Impairments in Ambulatory Chronic Hemiparetic Stroke: Evidence for Lower Extremity Weakness and Abnormal Muscle and Joint Torque Coupling Patterns

Although global movement abnormalities in the lower extremity poststroke have been studied, the expression of specific motor impairments such as weakness and abnormal muscle and joint torque coupling patterns have received less attention. We characterized changes in strength, muscle coactivation and associated joint torque couples in the paretic and nonparetic extremity of 15 participants with chronic poststroke hemiparesis (age 59.6 ± 15.2 years) compared with 8 age-matched controls. Participants performed isometric maximum torques in hip abduction, adduction, flexion and extension, knee flexion and extension, ankle dorsi- and plantarflexion and submaximal torques in hip extension and ankle plantarflexion. Surface electromyograms (EMGs) of 10 lower extremity muscles were measured. Relative weakness (paretic extremity compared with the nonparetic extremity) was measured in poststroke participants. Differences in EMGs and joint torques associated with maximum voluntary torques were tested using linear mixed effects models. Results indicate significant poststroke torque weakness in all degrees of freedom except hip extension and adduction, adductor coactivation during extensor tasks, in addition to synergistic muscle coactivation patterns. This was more pronounced in the paretic extremity compared with the nonparetic extremity and with controls. Results also indicated significant interjoint torque couples during maximum and submaximal hip extension in both extremities of poststroke participants and in controls only during maximal hip extension. Additionally, significant interjoint torque couples were identified only in the paretic extremity during ankle plantarflexion. A better understanding of these motor impairments is expected to lead to more effective interventions for poststroke gait and posture