MF magnitude does not affect body condition, pro-oxidants and anti-oxidants in Eurasian kestrel (Falco tinnunculus) nestlings

Clutch size and egg volume in great tits (Parus major) increase under low intensity electromagnetic fields: a long-term field study

Exposure to electromagnetic fields (EMFs) can affect a wide range of biological processes, including reproduction, growth and development. Experiments aimed at investigating the biological effects of EMFs, focused on potential harmful effects on humans, have been mostly carried out in vitro or with animal models in laboratory conditions. By contrast, studies performed on wild animals are scarce. The effects of EMFs created by an electric power line on reproductive traits of a wild great tit (Parus major) population were explored by analysing data gathered during nine breeding seasons. EMF exposure significantly increased clutch size (7%) and egg volume (3%), implying a 10% increase in clutch volume. This indicates an increase in reproductive investment from parent birds exposed to EMFs as compared to the adjacent reference area. These results cannot be attributed to habitat or adult quality differences between the exposed and reference group. Nevertheless, no differences in hatching success or final productivity (fledging and reproductive success or nestling body mass) could be detected. Our study clearly shows that EMFs created by power lines can have biological consequences in wild organisms that live intimately with them. To our knowledge, this is the first study showing an increase in clutch size, and one of the few reporting an increase in egg size, associated with EMF exposure. The possible mechanisms by which great tits invest more under EMF exposure are discussed, and future research directions to evaluate the effect of EMFs on avian reproduction in the wild are suggested.

Differential magnetic field effects on heart rate and nociception in anosmic pigeons

Several studies have shown that exposure to altered magnetic fields affects nociception by suppressing stress-induced hypoalgesia, and that this effect is reduced or abolished if the treatment is performed in the absence of light. This raises the question as to whether other sources of sensory stimuli may also modulate these magnetic effects. We investigated the possible role of olfaction in the magnetically induced effects on sensitivity to nociceptive stimuli and heart rate (HR) in restraint-stressed homing pigeons exposed to an Earth-strength, irregularly varying (<1 Hz) magnetic field. The magnetic treatment decreased the nociceptive threshold in normally smelling birds and an opposite effect was observed in birds made anosmic by nostril plugging. Conversely, no differential effect of olfactory deprivation was observed on HR, which was reduced by the magnetic treatment both in smelling and anosmic pigeons. The findings highlight an important role of olfactory environmental information in the mediation of magnetic effects on nociception, although the data cannot be interpreted unambiguously because of the lack of an additional control group of olfactory-deprived, non-magnetically exposed pigeons. The differential effects on a pigeon's sensitivity to nociceptive stimulus and HR additionally indicate that the magnetic stimuli affect nociception and the cardiovascular system in different ways.

Blood parasitaemia in a high latitude flexible breeder, the white-winged crossbill,Loxia leucoptera: contribution of seasonal relapse versus new inoculations

We measured seasonal changes in the prevalence of haematozoa (Leucocytozoon fringillinarum, Haemoproteus fringillae, andTrypanosoma avium) in free-ranging White-winged Crossbills,Loxia leucoptera, over 1·5 year in Fairbanks, Alaska, USA. This prevalence was low during early winter.L. fringillinarumprevalence increased in late winter/early spring, in the absence of vectors, suggesting relapse of latent infection. By contrast, the prevalence ofT. aviumandH. fringillaedid not increase until mid-spring, coincident with the emergence of putative vectors and suggestive of new inoculations. The winter breeding period was not associated with lower body condition or elevated blood heterophil/lymphocyte ratios than the summer post-breeding period. Thus, birds unlikely perceived their breeding effort as particularly stressful. Adult males in May and June had low plasma testosterone and their blood prevalence ofL. fringillinarum, but not other haemoparasites, was higher than in adult females. This difference may have resulted from sex differences in behaviour and/or plumage colouration – bright red in males, dull green/yellow in females. Species in which reproduction and vector abundance are seasonally dissociated may constitute important models for investigating the respective contribution of reproductive hormones, breeding effort, and vector abundance to patent and latent hemoparasitic infections and to new inoculations.

Magnetic fields produced by power lines do not affect growth, serum melatonin, leukocytes and fledging success in wild kestrels

Nesting on high voltage transmission line towers exposes birds to electric and magnetic fields for long periods. Nestlings are exposed from their development in ovo until fledging. This is a critical period for them because the quality of the developmental environment may affect their fitness at adulthood. We carried out a field study on Eurasian kestrels, Falco tinnunculus, to compare chicks from pairs nesting on high voltage power lines vs. those nesting in control sites in similar habitats. The magnetic field (MF) was measured in each nest-box and analysed in relation to growth curves, melatonin levels, leukocyte counts, and fledging success. None of the variables differed between exposed and control nestlings. Wing length (proxy of age) showed a negative covariation with serum melatonin concentration. Our findings suggest that exposure to MFs produced by high voltage power lines during the embryonic and post-hatching period (until fledging) does not have significant short-term physiological effects on kestrel nestlings.