我国的城市发展与大气污染

为了表明我国城市发展与大气污染的关系,以翔实的统计数据,采用两种分类的方法,研究和讨论了不同人口规模、不同功能类型的城市大气污染特点,并从防治大气污染的角度阐明了城市应定性质、定规模、定方向地协调发展。      

Orientation of the pied flycatcher Ficedula hypoleuca: cue-conflict experiments during spring migration

Hierarchical relationships among different compass systems in long-distance migrants are still a matter for discussion because different studies have led to highly variable and apparently contradictory results. We carried out cue-conflict experiments during spring migration on pied flycatchers Ficedula hypoleuca (Passeriformes, Muscicapidae). Birds were exposed to a conflict between celestial and magnetic information by altering the polarized light pattern or magnetic field. The polarization pattern was shifted (±90°) with filters, whereas the magnetic field was altered (+90°) through Helmholtz coils. Birds were tested in modified Emlen funnels both before and after the cue conflict; during the tests, only the natural magnetic field was available. This protocol was designed to test whether the experimental birds recalibrated their magnetic compass on the directional information derived from the light polarization pattern when the region near the horizon was visible during the conflict. Contrary to this expectation, we did not record any significant shift in magnetic orientation after one or repeated exposures to the cue conflict. Our results support earlier studies, which suggest that the magnetic field is the primary compass cue during the migratory period.     

Orientation experiments with displaced juvenile barn swallows (Hirundo rustica) during autumn migratory season

In a previous paper, we reported that juvenile barn swallows (Hirundo rustica) trapped during the autumn migratory season and tested in modified Emlen funnels under overcast conditions can use magnetic information for compass orientation, although they did not orient toward the expected migratory direction. To further investigate this behaviour, in the present paper, we report the results of two series of displacement experiments performed on juvenile barn swallows belonging to two different roost sites [Massaciuccoli Lake (ML) and Terzo Cavone (TC)] and tested using the same protocol as that previously adopted. On the whole, the outcome of the ML and TC experiments was quite different with respect to (a) the degree of bird activity within the funnel (substantially lower for TC) and (b) the effect of the experimental displacement on the directional preferences of the tested subjects (not detectable in TC, while evident in ML swallows). Taken together, these results suggest that migrating swallows could react differently to the experimental tests depending on the roost site where they were caught. Indeed, TC swallows, trapped in southern Italy, close to the seacoast, and characterized by fairly large amounts of fat stores, mainly broke off their migratory activity or reoriented their directional preferences toward inland sites, possibly in search of more profitable habitats. On the other hand, ML swallows, trapped about 660 km to the north and characterized by lower amounts of fat stores, apparently tried to compensate for the experimental displacement.