查看完整版本: 漁護署香港物種探索22期 AFCD HK Biodiversity Issue 22

漁護署香港物種探索22期 AFCD HK Biodiversity Issue 22

[size=3]有文章介紹大草鶯及小葵花鳳頭鸚鵡
Articles talking about Chinese Grassbird and Yellow-crested Cockatoo[/size]

[url]http://www.afcd.gov.hk/tc_chi/publications/publications_con/files/IssueNo22.pdf[/url]

The article on the distribution and habitat preferences of Chinese Grassbird in HK is very good. The authors conclude that most sites at which grassbirds have occurred in the past continue to support the species. The overall density of birds in appropriate habitat is estimated at 0.13 birds/ha, while the HK population is estimated at 490. Both these are higher, and no doubt more accurate, than the back of envelope calculations that Paul Leader and I made in our paper. It occurs in grassland dominated by Miscanthus sp. at altitudes from 200m up; as the authors point out, that leaves local populations vulnerable to hill fires, as was vividly shown in recent years at Robin's Nest, one of the strongholds of the species.

If the paper has any drawbacks, it is these. Firstly, I'm not sure how valid it is to estimate the HK population by extrapolating across all grassland above 200m, as grassbirds appear to prefer 'rich grassland'. Not all grassland in HK is of this quality, and for this reason I feel the population estimate may be a little high. Secondly, while the paper rightly points out that almost all sites with records of the species are inside protected country parks, there is no mention of the (in my opinion) significant threat posed by vegetation succession, whereby grassland turns to shrubland. It seems to me that there is a need to assess the practicality of preserving via habitat management swathes of grassland in different areas of HK in order to conserve the populations of this and other grassland-specialists such as Lesser Coucal, the locally-breeding taxon of Richard's Pipit [i]A.r. sinensis[/i], Upland Pipit, Chinese Francolin, Savannah Nightjar and Eagle Owl.

A very good and interesting paper though, and well worth reading.

I share the same concern on the population estimation and sent a feedback to the authors yesterday.

I think this is a very good initiative by AFCD as is of good value for discussion when BirdLife launches the discussion on the status of Chinese Grassbird. It also provide useful information on potential habitat monitoring and management. But i share geoff and captain's concern on the potential over-estimation of population number.

I have been always wondering whether conservation plans for the HK population of Yellow-crested Cockatoo should be set up. It seems that AFCD does recognize the conservation value of this population. As said in the article, we might help to look for the remaining roosting habitats.