Effects of weather on avian migration at proposed ridgeline wind energy sites

With the popularity of wind energy increasing globally, concerns surfaced in the 1980s as to the potential adverse effects of wind turbines on migrating birds. Understanding how weather conditions influence passage rates can help determine the potential for increased avian–turbine collisions. Using vertical and horizontal mounted marine radars, raptor stand watch observations, and portable handheld weather stations, we studied how temperature, cloud cover, barometric pressure, wind direction, and wind speed affected avian passage rates and height of migrants over 3 ridges (Wartenbe, North Dokie, and South Dokie) being developed for wind energy in northern British Columbia. Using an Akaike's Information Criterion (AIC), we determined that a reduced model combining wind speed, barometric pressure, and cloud cover was best at explaining and predicting higher passage rates (expressed as no. birds/hr) in the fall migration for both diurnal and nocturnal migrants. Wind speed proved the most important predictor of passage rates for spring nocturnal migrants and a combination of cloud cover, temperature, and wind direction for diurnal spring migrants. Wind speed also predicted decreases in flight altitude among nocturnal migrants but increased altitude in diurnal migrants. This information coupled with migration timing and topographical areas of higher migrant activity can be useful to wind energy proponents who wish to mitigate collision risk with migrating birds. © 2011 The Wildlife Society.     

Cardiac responses to exercise in the dog before and after destruction of the sinoatrial node

Chronotropic and dromotropic responses to treadmill exercise were compared in conscious dogs prior to and following excision of the sinoatrial node (SAN). The initial junctional rhythm accompanying removal of the SAN region was replaced within hours to days by subsidiary atrial pacemaker (SAP) foci located in the inferior right atrium along the sulcus terminalis. With SAN intact, cardiac acceleration was immediate at onset of exercise and the tachycardia was directly proportional to work intensity. Atrioventricular (AV) conduction concurrently accelerated during exercise as manifest by shortening in P-R and atrioventricular (A-V) intervals. Following SAN excision, subsidiary atrial pacemaker foci likewise demonstrated prompt tachycardias during exercise, although heart rate was significantly reduced at rest and during steady state exercise. In the SAP state, tachycardia during exercise was related to work intensity and was mediated by changes in cardiac autonomic nerve activity. Combined propranolol-atropine blockade increased heart rate at rest in the SAP state, and significantly attenuated the tachycardia accompanying treadmill exercise. Following SAN excision the P-R (A-V) interval was significantly reduced in the resting animal. In response to exercise, AV conduction time decreased in the SAP state, though the absolute levels during steady state exercise were not significantly different from prior control runs with SAN intact. Blood pressure response to exercise was similar during both SAN and SAP states. We conclude that following an initial unstable period, SAP foci maintain adequate heart rate increases in response to dynamic exercise, primarily mediated via autonomic nerve regulation.     

Adjustment of juvenile tuatara to a cooler,southern climate: operative temperatures,emergence behaviour and growth rate

Translocations for conservation often involve species limited to relict distributions. However, uncertainty can exist regarding the ability of source individuals to acclimatise following a shift to a distant location. We investigated the ability of captive-reared juvenile tuatara (Sphenodon punctatus) of Cook Strait stock (41°S) to adjust to outdoor, predator-protected pens within Orokonui Ecosanctuary (45 °S). We examined potential basking and within burrow temperatures, the influence of temperature on emergence, and growth rates in comparison with other locations. Tuatara at Orokonui reached their preferred temperature when basking over summer, and burrows provided protection from freezing over winter. Emergence was temperature-dependent and essentially ceased during winter. Growth rates of Orokonui-held juveniles were within the range for four other captive-rearing facilities and faster than for wild juveniles from a Cook Strait population. As all Orokonui-held juveniles have survived and grown we conclude that the climate at this southern location is suitable to consider a free-release.     

Assessment of flipper tag site healing in gray seal pups using thermography

Infrared thermography was used to monitor the healing process at flipper tag sites in gray seal (Halichoerus grypus) pups. We tested the hypothesis that tagging would result in a rise in surface temperature associated with tag site healing processes compared with adjacent untagged areas of the flipper. Prior to tagging thermal images were recorded of the dorsal side of hind flippers of pups tagged in early lactation (n= 20) and at weaning (n= 19) on the Isle of May, Scotland (56°11′N, 02°33′W) from October to December 2008. Pups tagged in early lactation were sampled again at late lactation, at weaning and then every 3 d for an average of 29 d post‐tagging while pups tagged at weaning were sampled every 3 d for an average of 17 d post‐tagging. Tag sites were also scored for signs of infection or swelling at each sampling. Results showed that (1) small temperature increases associated with wound healing processes around the tag site returned to pre‐tagging levels before animals leave the island and (2) there was little evidence of tagging‐related infections or tag loss irrespective of age at tagging.     

Impact of variance components on reliability of absolute quantification using digital PCR

Background

Digital polymerase chain reaction (dPCR) is an increasingly popular technology for detecting and quantifying target nucleic acids. Its advertised strength is high precision absolute quantification without needing reference curves. The standard data analytic approach follows a seemingly straightforward theoretical framework but ignores sources of variation in the data generating process. These stem from both technical and biological factors, where we distinguish features that are 1) hard-wired in the equipment, 2) user-dependent and 3) provided by manufacturers but may be adapted by the user. The impact of the corresponding variance components on the accuracy and precision of target concentration estimators presented in the literature is studied through simulation.

Results

We reveal how system-specific technical factors influence accuracy as well as precision of concentration estimates. We find that a well-chosen sample dilution level and modifiable settings such as the fluorescence cut-off for target copy detection have a substantial impact on reliability and can be adapted to the sample analysed in ways that matter. User-dependent technical variation, including pipette inaccuracy and specific sources of sample heterogeneity, leads to a steep increase in uncertainty of estimated concentrations. Users can discover this through replicate experiments and derived variance estimation. Finally, the detection performance can be improved by optimizing the fluorescence intensity cut point as suboptimal thresholds reduce the accuracy of concentration estimates considerably.

Conclusions

Like any other technology, dPCR is subject to variation induced by natural perturbations, systematic settings as well as user-dependent protocols. Corresponding uncertainty may be controlled with an adapted experimental design. Our findings point to modifiable key sources of uncertainty that form an important starting point for the development of guidelines on dPCR design and data analysis with correct precision bounds. Besides clever choices of sample dilution levels, experiment-specific tuning of machine settings can greatly improve results. Well-chosen data-driven fluorescence intensity thresholds in particular result in major improvements in target presence detection. We call on manufacturers to provide sufficiently detailed output data that allows users to maximize the potential of the method in their setting and obtain high precision and accuracy for their experiments.

Electronic supplementary material

The online version of this article (doi:10.1186/1471-2105-15-283) contains supplementary material, which is available to authorized users.