changes-1995/2015:(1)exTinctions

Common Shelducks at Mai Po, March 2 2012

The (excellent) Hong Kong  Bird Report for 2015 has just been published. To while away the wet summer afternoons,  I thought it might be of interest to look at the most obvious changes that had taken place in the avifauna at Mai Po/Deep Bay over the past twenty years.  I’ve taken an unscientific,  snapshot approach, comparing the entries on a handful of  species in the 2015 report with the 1995 report.  I begin with four species that seem, unfortunately, to have disappeared from Deep Bay for good.

Note that “the AWC surveys” in my comments refers to The Asian Waterbird Census 2008-2015 - results of coordinated counts in Asia and Australasia  (Mundkur et al., 2017).

COMMON SHELDUCK Tadorna tadorna
2015: No records.
1995: Waterfowl counts  for Deep Bay in the early part of the year were 980 in January, 1012 in February and 491 in March, though 850 were still present on 28 February.
 
Notes: The highest count was 4,011 on 17 January 1988. There was a massive decline at the turn of the century from 1320 in Jan 2000 to 279 in 2001, then it was more or less downhill all the way to the last record of a single bird in the first-winter period in 2013.
 
Comment: In terms of numbers, this is the most dramatic loss to the Hong Kong avifauna so far this century. The question with this species, as with other species that have become extinct or declined in Hong Kong, is: Are birds simply wintering elsewhere in East Asia or does the HK situation mirror a general decline? In terms of the Common Shelduck, there is no evidence of a decline elsewhere in East Asia. The AWC survey, in fact, shows that numbers have increased in Japan, for example,  from 2,070 in 2008 to 6,104 in 2015. It seems likely that the ex-Hong Kong birds are now wintering further to the northeast. This may be a result of climate change, but perhaps there is a more localised reason for the disappearance of the species. One specualtion  is that a change in the nature of the food supply in Deep Bay caused by the exponential growth of Shenzhen in recent years has impacted negatively on this species.

RED-BREASTED MERGANSER Mergus serrator
2015: No records
1995: All March records: one at Mai Po on 4th, four at Tsim Bei Tsui on 18th, 27 at Mai Po on 19th and 22 off Cape D’Aguilar on 20th.
 
Notes: Although never common, this species used to be a regular winter visitor and passage migrant to Deep Bay with a high count of 97 near Lau Fau Shan in January 1990. There has been a strong decline in numbers since the turn of the century so that now it is a scarce spring passage through southern waters and is no longer annual. There have been no records in Deep Bay since 2012.
 
Comment: The decline in Hong Kong may reflect a general decline in the region. The total number in the AWC surveys (which includes most of Asia and Australasia) show a rise from 6,869 in 2008 to 11,288 in 2012, followed by a decline to 3,235 in 2015. The surveys show a decline in Japan from 6,075 in 2009 to 1,755 in 2015. Numbers in Korea vary annually e.g. from 1,890 in 2008, up to 10,136 in 2012 and down to 1,475 in 2015. The East Asian population is said to be 25,000-100,000 (Reeber 2015); however, the AWC surveys indicate that this assessment may be too high.

BLACK-HEADED IBIS Threskiornis melanocephalus
2015: No records
1995: One in Deep Bay 18 March to 25 April, one at Kam Tin on 4 October and one in Deep Bay 14 October to 25 December.
 
Notes: The highest count was 25 in January 1974. There was a significant decline in the last quarter of the 20th century. There have been no records in Hong Kong since 1999.
 
Comment: Present in south and southeast Asia – population 20,000. There used to be a small population in East Asia (c.100 birds in 2002) and breeding was considered – although not proven - to occur in Heilongjiang. Presumably the records in Japan, Hong Kong and elsewhere in eastern and southern China derived from this breeding population.  The last record in China was one in Zhejiang province in November 2005. The east Asian population is now believed to be extinct.

DALMATIAN PELICAN Pelecanus crispus
2015: No records
1995:Peak count of 19 on 3 February and ten on 25 December.
 
Notes: The Dalmatian Pelican used to be a regular winter visitor to Deep Bay although there was a significant decline after the late 1970s when the flock was of 70-85 birds. Between 18 and 24 birds were present in the 1990s. This further declined to 15 in 2005, after which there were two in 2006, no more than one until 2010 and with no records since.
 
Comment: A small eastern population breeds in Mongolia and winters in southeast China. The size of this population was considered to  number c.50 birds in 2007 (Shi et al, 2008) but there was a recent count of 112 at Dongtai, Jiangsu in November 2013 (China Coastal Waterbird Census Group, 2015). The ex-Hong Kong birds are considered to be wintering further to the north. The comment about Common Shelduck above may also be relevant to this species.

There are two more species that might be included in this section. One is Indian Spot-billed Duck Anas haringtoni and the other is the critically endangered Baer's Pochard Aythya baeri. Neither of  these have been recorded in the territory since 2012.