IDENTIFICATION

VOCALISATIONS

The commonly heard call is a harsh ‘chwee’ or, more often, a churr.

When uttered in alarm it is louder and more frequent.

Sings infrequently, often from cover, uttering a medley of moderately sweet notes lacking any noticeable grace.

DISTRIBUTION & HABITAT PREFERENCE

In addition to the Tai Mo Shan massif, which has been considered the stronghold since the species was first found in HK, Chinese Grassbird occurs at other upland grassland sites including Robin’s Nest in the north New Territories, Pat Sin Leng in the northeast, Tai To Yan, Grassy Hill, Ma On Shan and Fei Ngo Shan in the central New Territories and Lantau and Sunset Peaks on Lantau.

It was recorded from 1.1% of squares in the first (1993-96) breeding atlas survey, 0.8% in the first winter (2001-05) survey, 0.4% in the second breeding season (2016-19) and 0.8% in the second (2016-19) winter survey. These figures suggest a decline in range; however, there was no restriction on survey duration in the first breeding season survey and it is likely that some observers may have made a special effort to find more cryptic species such as Chinese Grassbird.

Chinese Grassbird is restricted to grassland from 200 to 900m, perhaps largely between 300 and 800m. So et al. (2012) showed that the preferred habitat appears to be long grass Miscanthus sp. with limited (less than 10%) woody vegetation, fern and herbs. Dwarf bamboo may also be an important habitat (KFBG 2009), but it was limited in extent at the sites surveyed by So et al. (2012).

OCCURRENCE

Chinese Grassbird was first recorded in HK on 20 June 1982 when a single bird was trapped on Tai Mo Shan (Melville and Chalmers 1984). Records there from at least 1957 that had previously been ascribed to Brown Prinia Prinia polychroa were undoubtedly this species (Melville and Chalmers 1984, Carey et al. 2001). Chinese Grassbird occurs at low densities even in its preferred habitat. Leader et al. (2010) suggested that it occurred at a density of 0.02 - 0.04 birds/ha, whilst So et al. (2012), using a more systematic survey methodology, arrived at a rather higher density of 0.13 birds/ha. Thus, based on the area of grassland above 200m, Leader et al. (2010) estimated a HK population of 50 – 100 pairs, whilst So et al. (2012) calculated that the population was a more robust 490 birds (which would equate to 245 pairs, about 2.5 times higher).

Both these calculations were based on the assumption that all grassland above 200m is potential breeding habitat; however, the lower limit of 200m was based on a record at Heung Yuen Wai on 14 May 2007, the low altitude of which was stated by Carey et al. (2011) to be noteworthy, and whilst So et al. (2012) did refer to an observation at about 200m at Lin Au, the lowest observation made during their systematic survey was at 384m, which is more in line with the body of records on HKBWS files. Assuming, therefore, that the true population probably lies somewhere between the lower and upper estimates discussed above, conservation of Chinese Grassbird in HK is a high priority.

As noted by So et al. (2012) most Chinese Grassbird habitat is within Country Parks where it is protected from development. However, it is not protected from ecological succession from grassland to shrubby grassland, a habitat that it does not use to a significant extent. As was noted by Leader et al. (2010) the area of grassland in HK is declining: from 25,752ha in 2003 to 21,572ha in 2004; the most recent estimate in AFCD (2022) is from 2008 when it had fallen further to 18,290ha. Hill fires in HK occur outside the breeding season and are probably not a major threat; indeed, it is likely they are beneficial in arresting succession (although they appear to occur less frequently as vegetative succession occurs and as public education takes effect). So et al. (2012) noted that whilst no Chinese Grassbirds were seen in March 2011 in a large area of grassland burnt at Robin’s Nest earlier that year, by June the same year the grass had regenerated, and grassbirds had reoccupied sites utilised in 2010.

Chinese Grassbird does make some altitudinal movements but is not clear if some higher altitude sites are vacated in midwinter or if birds are just more elusive then; there are no records from Tai Mo Shan between 28 December and 6 March, but there are early January records from both Lantau and Sunset Peaks. However, there are also winter records from lowland open country sites where Chinese Grassbird does not breed including Wu Kau Tang and Long Valley, whilst there were several midwinter records from Sha Lo Tung in the mid-2000s.

There is no evidence of movements in and out of HK, but as Chinese Grassbird is regularly seen at Robin’s Nest and has been recorded from about 900m at Wutongshan five kilometres away (Leader et al. 2010), it is not implausible that movements between these sites take place on occasion.

BREEDING

Breeding occurs from late April until mid-July; with a bird carrying food to a nest noted from 21 April and dependent juveniles seen until 13 July; two broods are raised. A nest found on 28 April contained three day-old chicks (Carey et al. 2001) Nests are in thick clumps of grass (So et al. 2012).

BEHAVIOUR, FORAGING & DIET

Rather cryptic and typically remains concealed in patches of long grass and dwarf bamboo.  Leader et al. (2010) suggested that song was infrequent and ‘invariably’ given from patches of tall grass or from within dense cover. It occasionally comes into the open and is seen perched on top of grasses or even rocks, perhaps especially when breeding, when it is often detected by its harsh, churring, alarm calls. Not social and only ever seen as single birds, pairs, or small family parties.

The only observations of the diet of Chinese Grassbird are incidental reports of birds carrying invertebrates, including a spider. Diet does not appear to have been studied elsewhere in its range (So et al. 2012); this, together with other aspects of its ecology would be a worthwhile subject of further research, especially in view of the importance of the HK population of this species.

RANGE & SYSTEMATICS

Chinese Grassbird has a tiny and fragmented global range. Small numbers occur in reedbed Phragmites sp. at Lake Inle, Myanmar and in grassland near Bakan, Cambodia, but there are no modern records from the remainder of the former southeast Asian range in Thailand and Vietnam (Eaton et al. 2014). In China there are no records from Hainan since 1899 and Leader et al. (2010) listed only single records from each of Guangxi and Guangdong, the latter from Wutongshan, Shenzhen only about 5 km from HK. However, it is reported to be not uncommon in suitable habitat in Guangxi (J. Martinez in litt.) and at Longgao Mountain near Xitouzhen in southwest Guangdong in 2020-21, the latter substantiated by photographs (eBird 2023).

IOC currently treats Chinese Grassbird as polytypic: G. s. striatus in southeast Asia and Hainan, and G. s. sinicus in southeast China. However, Leader et al. (2010) considered that there were only very minor morphological differences and recommended that they should be synonymised.   

CONSERVATION STATUS

IUCN: NEAR-THREATENED. Population estimated to be 2500 – 9999 individuals and decreasing (BirdLife International 2021).