Synchronous timing of return to breeding sites in a long-distance migratory seabird with ocean-scale variation in migration schedules

BACKGROUND

Migratory birds generally have tightly scheduled annual cycles, in which delays can have carry-over effects on the timing of later events, ultimately impacting reproductive output. Whether temporal carry-over effects are more pronounced among migrations over larger distances, with tighter schedules, is a largely unexplored question.

METHODS

We tracked individual Arctic Skuas Stercorarius parasiticus, a long-distance migratory seabird, from eight breeding populations between Greenland and Siberia using light-level geolocators. We tested whether migration schedules among breeding populations differ as a function of their use of seven widely divergent wintering areas across the Atlantic Ocean, Mediterranean Sea and Indian Ocean.

RESULTS

Breeding at higher latitudes led not only to later reproduction and migration, but also faster spring migration and shorter time between return to the breeding area and clutch initiation. Wintering area was consistent within individuals among years; and more distant areas were associated with more time spent on migration and less time in the wintering areas. Skuas adjusted the period spent in the wintering area, regardless of migration distance, which buffered the variation in timing of autumn migration. Choice of wintering area had only minor effects on timing of return at the breeding area and timing of breeding and these effects were not consistent between breeding populations.

CONCLUSION

The lack of a consistent effect of wintering area on timing of return between breeding areas indicates that individuals synchronize their arrival with others in their population despite extensive individual differences in migration strategies.

Flight heights obtained from GPS versus altimeters influence estimates of collision risk with offshore wind turbines in Lesser Black-backed Gulls Larus fuscus

The risk posed by offshore wind farms to seabirds through collisions with turbine blades is greatly influenced by species-specific flight behaviour. Bird-borne telemetry devices may provide improved measurement of aspects of bird behaviour, notably individual and behaviour specific flight heights. However, use of data from devices that use the GPS or barometric altimeters in the gathering of flight height data is nevertheless constrained by a current lack of understanding of the error and calibration of these methods. Uncertainty remains regarding the degree to which errors associated with these methods can affect recorded flight heights, which may in turn have a significant influence on estimates of collision risk produced by Collision Risk Models (CRMs), which incorporate flight height distribution as an input. Using GPS/barometric altimeter tagged Lesser Black-backed Gulls Larus fuscus from two breeding colonies in the UK, we examine comparative flight heights produced by these devices, and their associated errors. We present a novel method of calibrating barometric altimeters using behaviour characterised from GPS data and open-source modelled atmospheric pressure. We examine the magnitude of difference between offshore flight heights produced from GPS and altimeters, comparing these measurements across sampling schedules, colonies, and years. We found flight heights produced from altimeter data to be significantly, although not consistently, higher than those produced from GPS data. This relationship was sustained across differing sampling schedules of five minutes and of 10 s, and between study colonies. We found the magnitude of difference between GPS and altimeter derived flight heights to also vary between individuals, potentially related to the robustness of calibration factors used. Collision estimates for theoretical wind farms were consequently significantly higher when using flight height distributions generated from barometric altimeters. Improving confidence in telemetry-obtained flight height distributions, which may then be applied to CRMs, requires sources of errors in these measurements to be identified. Our study improves knowledge of the calibration processes for flight height measurements based on telemetry data, with the aim of increasing confidence in their use in future assessments of collision risk and reducing the uncertainty over predicted mortality associated with wind farms.

Quantifying avian avoidance of offshore wind turbines: Current evidence and key knowledge gaps

The risk of collision between birds and turbines is seen as one of the key issues in the planning process for offshore wind farms. In some cases, predictions of collision risk have led to projects either being withdrawn from the planning process, or refused planning consent. Despite this, the evidence base on which collision risk is assessed is extremely limited and assessments rely on models which can be highly sensitive to assumptions, notably about bird collision avoidance behaviour. We present a synthesis of the current state of knowledge about collision risk and avoidance behaviour in seabirds. Evidence suggests species-specific responses to turbines and that in order to avoid collision, most birds adjust their flight paths at some distance from the turbines, rather than making last-second adjustments. We highlight the key gaps in knowledge and make recommendations for future data collection.

Fine-scale foraging behaviour of a medium-ranging marine predator

1. Movement patterns of predators should allow them to detect and respond to prey patches at different spatial scales, particularly through the adoption of area-restricted search (ARS) behaviour. Here we use fine-scale movement and activity data combined with first-passage time (FPT) analysis to examine the foraging strategy of northern gannets Morus bassanus in the western North Sea, and to test the following hypotheses: (i) birds adopt a hierarchical foraging strategy characterized by nested ARS behaviour; (ii) the locations and characteristics of ARS zones are strongly influenced by physical oceanography; (iii) the initiation of ARS behaviour is triggered by the detection and pursuit of prey; (iv) ARS behaviour is strongly linked to increased foraging effort, particularly within nested ARS areas. 2. Birds on 13 of 15 foraging trips adopted ARS behaviour at a scale of 9.1 +/- 1.9 km, and birds on 10 of these 13 trips adopted a second, nested ARS scale of 1.5 +/- 0.8 km, supporting hypothesis 1 above. ARS zones were located 117 +/- 55 km from the colony and over half were within 5 km of a tidal mixing front ~50 km offshore, supporting hypothesis 2 above. 3. The initiation of ARS behaviour was usually followed after only a short time interval (typically ~5 min) by the commencement of diving. Gannets do not dive until after they have located prey, and so this pattern strongly suggests that ARS behaviour was triggered by prey detection, supporting hypothesis 3 above. However, ~33% of dives in mixed coastal water and 16% of dives in stratified water were not associated with any detectable ARS behaviour. Hence, while ARS behaviour resulted from the detection and pursuit of prey, encounters with prey species did not inevitably induce ARS behaviour. 4. Following the initiation of ARS behaviour, dive rates were almost four times higher within ARS zones than elsewhere and almost three times higher in zones with nested ARS behaviour than in those without, supporting hypothesis 4 above and suggesting that the foraging success of birds was linked to their ability to match the hierarchical distribution of prey.

Interruption of parturition in rats by morphine: a result of inhibition of oxytocin secretion

Oxytocin secretion is inhibited by opioids, and oxytocin is important in parturition. The effects on parturition of morphine, a relatively selective mu-opioid receptor agonist, were studied in the rat. Morphine or vehicle with or without the opiate antagonist naloxone were administered immediately after the birth of the second pup and the subsequent course of parturition was recorded in a total of 80 rats. Both s.c. morphine (10 mg/kg) and intracerebroventricular (i.c.v.) morphine (18 micrograms through a previously implanted cannula) interrupted parturition, delaying the birth of the sixth pup after treatment to 187.3 +/- 35.9 (S.E.M.) min and 195.4 +/- 19.5 min respectively, compared with 46.4 +/- 3.7 and 66.1 +/- 17.5 min after vehicle alone. The dose of morphine given i.c.v. had no effect when given s.c. Naloxone given concurrently prevented the effects of morphine. Eventually the rate of parturition in the morphine-treated groups recovered. Perinatal pup mortality rate was not increased when morphine was given to the mothers, but it did inhibit the expression of normal intrapartum maternal behaviour. Pup mortality was increased 48 h post partum by morphine given during parturition, and it reduced the proportion of rats with normal maternal behaviour 24 h post partum. Morphine did not affect spontaneous or oxytocin-stimulated contractile activity of the parturient uterus in vitro. The concentration of oxytocin in trunk blood plasma was decreased 40 min after i.c.v. morphine (24.3 +/- 3.9 vs 39.3 +/- 6.5 pmol/l in controls), as was vasopressin (7.2 +/- 1.5 vs 19.7 +/- 4.5 pmol/l in controls). Intravenous infusion of oxytocin (2-5 mU/min for 144.3 +/- 8.2 min; total infused 448.5 +/- 61.9 mU) after i.c.v. morphine re-started parturition; all pups were born to these rats (mean time to pup 6, 110.3 +/- 12.7 min) before the i.v. vehicle-infused rats given i.c.v. morphine re-started (mean time to pup 6, 406.3 +/- 125.2 min). It is concluded that morphine given during parturition acts centrally through opioid receptors to inhibit oxytocin secretion, and impairs the expression of maternal behaviour. Reversal of the effects of morphine on parturition by i.v. oxytocin demonstrates the important role of oxytocin in fetus ejection and expulsion.

Relationship between corpora lutea or fetal number and plasma concentrations of progesterone and testosterone in mice

Blastocysts (1-14) were transferred unilaterally into 63 pseudopregnant mice which were killed on Day 17. Plasma progesterone concentrations were significantly (P less than 0.05) lower in animals with one fetus than in those with 2-5 or 9-14 fetuses. Plasma testosterone concentrations were correlated with fetal number in mice with 1-13 fetuses (P less than 0.001). The total placental content of chorionic gonadotrophin in 13 litters varied directly with the number in the litter (1-6), and was 1.67 +/- 0.15 ng/placenta. The number of corpora lutea per mouse was negatively correlated with mean CL volume per mouse (P less than 0.001), and the number of conceptuses was positively correlated with mean CL volume per mouse (P less than 0.001). The effect of conceptuses on the ovary was systemic. The relationship between plasma testosterone concentration and conceptus number may be due to gonadotrophins acting on the ovary, or androgens produced by the placenta or fetus.

The effects of unilateral ovariectomy during pregnancy on placental and fetal growth in mice

A comparison between placental weight and number of fetuses in normal mice and those in mice unilaterally ovariectomized on the sixth day of pregnancy, revealed a relative hypertrophy of the placentae of the latter group, with a predominance of the effect in litter sizes of five or less. The weights of the fetuses in the unilaterally ovariectomized group were not significantly different from those of the controls, thus affording no evidence of a causal connection between fetal weight and gross placental weight.

Gonadotrophic activity of the guinea-pig placenta during pregnancy

A gonadotrophic substance was extracted from placentae and subplacentae of guinea-pigs. Biological and immunological assays of these tissues obtained on Days 10-63 of pregnancy showed the highest mean concentration of the gonadotrophin on Day 18. Extracts chromatographed on Sephadex G200 had components active in the radioimmunoassay system for hCG, hCG-alpha and hCG-beta subunits. The elution profiles of these extracts were similar to those obtained with human term placentae and purified hCG and its subunits. The guinea-pig placental extracts also cross-reacted with an antiserum to the beta subunit of ovine LH, as did hCG. The biological activity of placental and subplacental extracts and of the hCG standard as neutralized by an anti-hCG serum. There is a strong similarity between hCG and the substance extracted from guinea-pig placentae which may therefore have a luteotrophic function similar to that of hCG.

Gastro-esophageal Resection and Total Gastrectomy in the Treatment of Bleeding Varicose Veins in Banti's Syndrome

Images

Degeneration of the adrenal cortex produced by germanin

Images

Glycogen-Storage Disease: Thesaurismosis Glycogenica (von Gierke)

Images