Females alter their song when challenged in a sex-role reversed bird species

Birdsong serves to attract mates and to deter territorial rivals. Even though song is not restricted to males, this dual function has almost exclusively been demonstrated for male song. To test the generality of hypotheses on birdsong, we investigated female song in the sex-role reversed, classically polyandrous African black coucal (Centropus grillii) in the context of female–female competition. We compared spontaneously vocalizing females with females vocally responding to a playback simulating a conspecific intruder. Females changed vocal parameters in response to playbacks: They lowered the pitch of their vocalizations and enhanced the duration of song elements when being challenged. Also, the composition of the vocalizations was altered. There was no significant correlation between pitch and body size parameters in spontaneous song, but there was for response songs, with larger females having a lower pitch. These changes in vocal properties suggest that the vocalizations are important for mutual assessment of competitive abilities in females. Our findings confirm the general role of intrasexual competition in vocal communication of birds.     

Avian magnetic compass: fast adjustment to intensities outside the normal functional window

To determine how fast birds can adapt to magnetic intensities outside the normal functional window of their magnetic compass, we tested migratory birds in a magnetic field of 92,000 nT, twice the intensity of the local geomagnetic field at the test site in Frankfurt a.M., Germany. In the local field, robins showed a significant preference of their southerly migratory direction, whereas in the 92,000-nT field, they were initially disoriented. However, when the birds were preexposed to 92,000 nT for 1 h before being tested, they were able to orient under this intensity, and their behavior did not differ from that in the geomagnetic field. These data show that birds require only a short time to adjust to magnetic intensities, which they cannot spontaneously use for orientation. Interpreting these findings in view of the radical pair model (Ritz et al. 2000), this means that they can learn rather quickly to interpret novel activation patterns on their retina.     

Urban riverbank residents' evaluation of flood evacuation policies in Winnipeg,Manitoba, Canada

The results of a discrete choice experiment (DCE) as a part of a survey among the urban riverbank residents on the Red River in Winnipeg, Manitoba, Canada, indicated that the risk of over-dike flooding, set at 2ft above the 1997 flood water level, was a significant determinant of both voluntary and mandatory evacuation, compared to those set at the 1996 or 1997 levels. Mandatory evacuation was more preferred over voluntary evacuation when the likelihood of flooding was at its most severe, and the opposite relationship was the case when the likelihood was low. The notification time for evacuation, suggested as 1, 2, and 4 days, proved to be an insignificant attribute, whereas the respondents indicated significant preference for full flood compensation over an offer of either 80% or 90% flood relief, irrespective of the alternatives of voluntary or mandatory evacuation.     

Mechanisms of arsenic removal from water

In this review paper, various methods for arsenic removal from water have been described by explaining the related mechanisms of each methods. Advantages and drawbacks were discussed. Membrane methods were suggested as reliable methods for elimination of arsenic from water in addition to other conventional separation methods.