To understand better the impact on mist net capture rates of the activity height of birds, light intensity, bird richness and abundance, we compared data from mist nets and point counts at the Jianfengling Forest Area, Hainan Island. Mist-nets were operated for a total of 7135 net-hours. A total of 587 individuals of 45 bird species were captured. The total mean capture rate was 8.6 ± 10.4 per 100 net-hours. A total of 4932 individuals of 107 bird species were recorded by visual observation alone and 7616 individuals of 120 species were recorded in a visual and aural combination. The Grey-cheeked Fulvetta (Alcippe morrisonia) was the most abundant species, accounting for 38.7% of total captures, 27.9% of visual observations and 22.2% of visual + aural observations. The capture number was correlated with the number observed. Thirty-one species were more likely to be captured than observed. Canopy species, such as members of the Corvidae and Dicruridae, were seldom captured. For all ground feeding species, the capture number was greater than that of observation. Some cryptic species, such as the Lesser Wren Babbler (Napothera epilepidota), Spotnecked Babbler (Stachyris striolata) and Cuckoo Owl (Glaucidium cuculoides) also had a higher relative capture rate than that of observations. There was a significant relationship between light intensity and the number of birds captured.
In this study,live fledglings of Nycticorax nycticorax and Ardeola bacchus at the Huangpu District of Guangzhou City were collected,and their primary feather,breast feather,tail feather,liver,chest muscle and egg shell were sampled for mercury determination.The results showed that these two heron species had a very similar distribution pattern of mercury concentration in their tissues and organs,i.e.,tail feather > breast and primary feather > liver > chest muscle > egg shell.Ardeola bacchus had higher levels of mercury in all its tissues than Nycticorax nycticorax.There were significant interspecific differences in mercury level for breast feather and primary feather.Because the collection of breast feather is easier and not harmful to birds,it is better to use it rather than primary or tail feather to monitor environmental pollution.The mercury level in breast feather was ten times higher than that in liver,lower than that in tail feather,but not significantly different to that in primary feather.The mercury concentrations in the tissues of Nycticorax nycticorax and Ardeola bacchus from Huangpu District of Guangzhou were similar to those from the suburbs of Chengdu,Sichuan Province,but lower than those from Taihu Lake,Jiangsu Province and higher than those from Hong Kong.
