白马鸡的天堂

2003年9月上旬,稻城的初秋似乎还没有到来,美丽的山间小城还笼罩在一片葱绿之中。早晨．我隐隐地感到了一丝凉意,拉开窗帘．不觉惊讶地张大了嘴巴．整个稻城已是一片白茫茫,稻城今年的第一场雪,鹅毛大雪．巳经令人猝不及防地下起来了。     

Paradise Bent

Paradise Bent. 1999. 51 minutes, color. video by Heather Croall. For more information, contact Beyond Distribution, PTY LTD, 53-55 Brisbane Street, Surry Hills, NSW 2010, Sydney, Australia; or 1875 Century Park East, Suite 1320, Los Angeles, CA 90067.     

Footnote on Breeding of Paradise Flycatcher

Bird community diversity was assessed in semi-arid savanna in the Northern Cape province of South Africa and related to vegetation diversity and foliage height diversity. As this is an area in which shrub encroachment is common, the effects of shrub or bush encroachment on bird species diversity were specifically addressed. An experiment in which the dominant encroaching species, Acacia mellifera, was removed from ten 1 ha plots was used and compared with ten controls. A strong positive association with foliage height diversity was shown. No effect of experimental removal of the dominant encroacher, A. mellifera, on bird species diversity or species richness was found. However, four species increased in relative abundance in cut plots and two species decreased in relative abundance in these plots.     

A Low Temperature Limit for Life on Earth

There is no generally accepted value for the lower temperature limit for life on Earth. We present empirical evidence that free-living microbial cells cooling in the presence of external ice will undergo freeze-induced desiccation and a glass transition (vitrification) at a temperature between −10°C and −26°C. In contrast to intracellular freezing, vitrification does not result in death and cells may survive very low temperatures once vitrified. The high internal viscosity following vitrification means that diffusion of oxygen and metabolites is slowed to such an extent that cellular metabolism ceases. The temperature range for intracellular vitrification makes this a process of fundamental ecological significance for free-living microbes. It is only where extracellular ice is not present that cells can continue to metabolise below these temperatures, and water droplets in clouds provide an important example of such a habitat. In multicellular organisms the cells are isolated from ice in the environment, and the major factor dictating how they respond to low temperature is the physical state of the extracellular fluid. Where this fluid freezes, then the cells will dehydrate and vitrify in a manner analogous to free-living microbes. Where the extracellular fluid undercools then cells can continue to metabolise, albeit slowly, to temperatures below the vitrification temperature of free-living microbes. Evidence suggests that these cells do also eventually vitrify, but at lower temperatures that may be below −50°C. Since cells must return to a fluid state to resume metabolism and complete their life cycle, and ice is almost universally present in environments at sub-zero temperatures, we propose that the vitrification temperature represents a general lower thermal limit to life on Earth, though its precise value differs between unicellular (typically above −20°C) and multicellular organisms (typically below −20°C). Few multicellular organisms can, however, complete their life cycle at temperatures below ∼−2°C.     

A promiscuous mating system in the Blue Bird of Paradise Paradisaea rudolphi

We studied nesting behaviour, spatial dispersion of display areas and home range dynamics in the Blue Bird of Paradise Paradisaea rudolphi . We found that (1) females carried out nesting duties alone; (2) males displayed from solitary and dispersed sites; (3) female home ranges overlapped, and (4) males had access to and displayed to numerous females. These data suggest a promiscuous mating system in the Blue Bird of Paradise and resolve earlier controversy over this issue.     

A promiscuous mating system in the Blue Bird of Paradise Paradisaea rudolphi

We studied nesting behaviour, spatial dispersion of display areas and home range dynamics in the Blue Bird of Paradise Paradisaea rudolphi. We found that (1) females carried out nesting duties alone; (2) males displayed from solitary and dispersed sites; (3) female home ranges overlapped, and (4) males had access to and displayed to numerous females. These data suggest a promiscuous mating system in the Blue Bird of Paradise and resolve earlier controversy over this issue.