Po Toi Seawatch Year 2021

Po Toi Seawatch Year 2021


This is a review of the year 2021 in which regular seawatching surveys were done from Nam Kok Tsui on Po Toi Island.

The surveys started in March, by Sam. We did two sessions together at the end of April, and I continued on my own from there until the end of the year.

Some important points to start with. Firstly, some records still need to pass the Hong Kong Records Committee. And secondly, the list which follows below is a review, but the ‘official’ records will later be published in the Hong Kong Bird Report 2021. Of course, they should be the same, but one should refer to the Bird Report. The review on this site is kind of provisory.

Although there have been several new findings, there is still much work to be done to get a more complete picture of migrants off Po Toi. A ton of pioneering work has been done mainly by Geoff Welch from 2006 until (the spring of) 2013, although the focus was then not exclusively on seawatching, but on landbirding as well (with extraordinary sightings). In 2021, I focused almost entirely on seawatching, and from July onwards also spending all available time doing just that on almost all survey-days.

So, please keep in mind that this review is just about 2021 and that we started from the end of March, so data of the two first months and most of March is lacking. The list below is of seabirds and coastal migrants, mostly species for which Po Toi is a specifically good spot in Hong Kong. Also note that it is based on a few surveys per month, so the gaps on the graphs (from – are mostly because we weren’t there. Hence this overview does not intent to draw a full picture, just some snapshots that we try to connect.


Let’s look at some general items first.

• We seawatched for a total of 492 hours and 25 minutes.
• We watched the most hours in July, followed by September and August.
• Record non-stop hours seawatching were 12 hours and 15 minutes on 16 August and 12 hours on 7 July. We also watched for 10 to 11 hours non-stop on several other days.
• The most birdy month by far was September, with 11,101 migrant birds counted. August is next, but with ‘only’ 3,236 birds counted. June was the quietest month, with just 115 birds counted.
• As we did not do any full-time surveys in spring, southbound migration numbers (birds flying past Po Toi to the west) were much higher than northbound ones (birds flying past Po Toi to the northeast). Southbound: 18,766, northbound: 3,458. But it might also be that autumn is just busier than spring, especially for terns.
• We counted a total of 22,224 migrating birds*. Not bad, but note that nobody was seawatching during most of the time in 2021 and that I was mostly alone when I did seawatch and must have missed some birds. I leave it up to your imagination how many birds pass Po Toi every year, but I’d say: a lot!
• We identified 69 migrating species during the year. A 70th species, Common Swift on 22 December, is still under consideration and has been submitted to the Records Committee.

* This is based on Trektellen, but “gull/tern spec.” cannot be reported on the site. It involves 130 individuals, which does bring the total count of all migrating birds to 22,354. Indeed all migrant birds, so besides the below list also raptors, passerines, swifts, swallows, etc.

Here is the chart from Trektellen with all the numbers:

For reports on every survey, please consult these posts:

Spring - ... &extra=page%3D1
Summer - ... &extra=page%3D1
Autumn - ... &extra=page%3D1
Winter - ... &extra=page%3D1


You don’t hear me complaining, for sure, but I just believe that we did not encounter any true rare vagrant seabirds off Po Toi in 2021. No rare shearwater, no storm petrel that wasn’t Swinhoe’s, no Pterodroma petrel, no tropicbird, no rare frigatebird, no noddy, no rare tern.

I did submit eight Unusual Record Forms (URF) of seabirds to the Hong Kong Records Committee, but all involved more than one individual of the following species: Bulwer’s Petrel (2 individuals), Swinhoe’s Storm Petrel (2 individuals), Brown Booby (3 individuals) and Red-footed Booby (2 individuals). Brown Booby has recently been removed from the rarities list, no longer requiring observers to submit a URF.


I will not go in much detail on the complex and comprehensive subject of weather, but just shed some light on the most obvious elements. After all, when it comes to seawatching, everybody keeps an eye on the weather and wind direction.

I used both the websites and apps from the Hong Kong Bird Observatory ( and Windy ( for predictions and actual weather conditions, while Ventusky has been particularly useful to dive into the history of wind and weather patterns (

Winds and typhoons

To start with typhoons, we encountered only one typhoon, Cempaka, when it was relatively close to Hong Kong on 20 July (see: ... amp;page=1#pid86932). That day produced more than a dozen tubenoses: 9 Streaked Shearwaters, 3 Short-tailed Shearwaters, 1 possible Wedge-tailed Shearwater and 1 very likely Bulwer's Petrel (and by the way, almost nothing else).

But the main point I want to draw attention to, is that good species or good numbers of birds were seen on days with no typhoons at all. That is actually excellent news: we don’t necessarily need a typhoon to see Swinhoe’ Storm Petrels, Bulwer’s Petrels, boobies, thousands of terns or record numbers of Streaked Shearwaters. Typhoons can produce excellent birds as well, of course, and maybe more and better ones than during other types of weather. And it is possible that after the typhoon has already passed, interesting stuff can still be seen. So, I don’t downplay the positive effect that a typhoon can have, but just want to emphasize that you can see great stuff without one as well.

I’m hesitant to express any strong opinion on wind direction and birds off Po Toi. I’ve watched with strong onshore winds (southeasterly force 5 to 6) and seen nothing. I’ve watched with offshore winds (northeasterly or westerly), strong or light, and seen Bulwer’s Petrel and Swinhoe’s Storm Petrel.

The message is similar as with typhoons. Yes, strong onshore winds can bring in more seabirds, but one shouldn’t be reluctant to go out seawatching on po Toi in any other wind condition. As Geoff often says: “With seabirds, you never know for sure”. I couldn’t say it any better. The best approach is to take the weather as it is, although I must admit that strong onshore winds or foggy circumstances do look more attractive.

Cold fronts

I did a few ‘tests’ with cold fronts, but don’t believe any clear and meaningful conclusion can be drawn from it. Maybe our data are not yet sufficient enough and we might perhaps get a clearer picture in the future. It’s a complex matter as well, and might not only be about temperatures dropping, but the weather system that comes with it.

Map area

This is the map of the area:

Po Toi is circled in black and the blue ‘line’ is the flyway of most migrating seabirds and coastal migrants; northbound from west to northeast and southbound from northeast to west. Raptors and passerines seem to have a very different flyway. In spring they come from the south, but in autumn as well. In the latter case, they have most probably chosen a route over the sea (from Taiwan?) and then make a northwestwardly bend to continue their southbound migration over land. Hence, on Po Toi we see them coming from the sea.

The Lema Channel, also called the Dangan Passage, is the waterway to the south of Hong Kong. And to the south of the Lema Channel is a part of the Wanshan Archipelago, more specifically the Dangan Islands. The closest island of the archipelago is Dangan Island, about 11,3 km. off Po Toi.

Apart from that, there is one red lightboat in the area.

The fixed location of this lightboat, which is clearly visible from Po Toi, is 22°07′36″.3N,114°13′32″.2E. This information is based on the Notices of Mariners published by The Maritime Safety Administration of the People′s Republic of China and kindly provided by the Hydrographic Office of the Marine Department of Hong Kong.

In other words, the lightboat is positioned about 4.4 km to the southwest of Hong Kong, in Chinese territorial waters. I haven’t seen any bird flying behind that lightboat. This is most likely due to heat haze or distant fog, but even on clear days I was unable to see birds behind it. In theory, one should be able to see larger birds, like shearwaters or large gulls and terns, flying at that distance. Then the obvious questions come to mind: what else passes through the Lema Channel, further out, that we are unable to see? Or do most migrants follow the blue line as depicted on our map? Why don’t we see any migrants flying southwest or coming from that direction? Are there higher numbers of birds migrating closer to the Dangan Islands? And what about seabirds on the other (south)side of the Dangan Islands? Indeed, many questions remain unanswered (at least to my knowledge).


A few words on how I seawatched at Nam Kok Tsui.

I go to any of these watchpoints on the peninsula, depending on the season and the direction and strength of the wind. We’ve now found five suitable points on the rocks. Plus, an option for the lighthouse area in case of a strong typhoon.

Looking from the southwest, these are the 5 points and the 6th, being the lighthouse, in the back.

Looking from the southeast, these are the 5 points on the rocks.

Let’s go into more detail.

Watchpoint 1
This is the most westerly positioned point, excellent in spring, but not ideal in autumn. As there is a high rock formation to the east of this point, the entrance of the Lema Channel, to the southeast of Nam Kok Tsui, is not visible. It is well shielded from south to easterly winds, up to force 6. But strong(er) winds, certainly from the south, could splash seawater on the rocks, though. So, it’s not ideal in all circumstances.

Watchpoint 2
Perfect if winds are blowing from any northerly direction. This is the southernmost watchpoint with a very good – if not to say: the best – panoramic view and it is relatively high positioned, so suitable when there are high waves. You can view the northeast and also most of Hong Kong southern waters. Alas, not shielded from onshore winds, coming from the southeast. Northeast winds are okay.

Watchpoint 3
This is the watchpoint that Geoff used. Well-located and easy to reach, but on days with ferries, you won’t be alone there nowadays. So, personally, I choose another watchpoint, where I can sit quietly on my own (of course, I wouldn’t mind the presence of other seabirders!).

Watchpoint 4
Down from watchpoint 3, this is the most ‘private’ of all the watchpoints. Hardly anybody will come down here, for the simple reason that it requires a short but steep and a bit risky climb to reach it. I’ve been sitting there for several surveys, but have changed this difficult-to-get-to-point for watchpoint 5, which is a lot safer to reach and is at the same height. Both points 4 and 5 are ideal for observing southbound migration. In spring, I would choose points 1 or 2.

Watchpoint 5
Is very easy to reach and positioned more to the northeast than the other ones. Like watchpoint 4, it also has plenty of space and plateaus of slightly different heights. Not shielded from onshore (south-easterly) winds, though. But in (late) autumn, I’ve not experienced any onshore winds here, but mostly north-easterly winds. And then this watch point is fine.

Watchpoint 6
The lighthouse. I’ve never watched from there but it might be the only point that’ll be suitable in case of a strong typhoon (force 7 and higher), as the rocks will then be partly flooded and being splashed with seawater. The lighthouse has a few disadvantages, namely that it is very high up and there is at least 60 meters of land on the southeast side and even 330 meters to the southwest side, making it far from ideally positioned. And it remains to be seen how well you’d be shielded from typhoon winds up there.

To conclude: I use watch point 1 in spring/summer and during strong southerly or south-easterly winds. I use watchpoint 2 at any season if winds are not strong onshore. And I use point 5 in autumn and winter.

I mainly use a telescope (30x-70x), which I usually put at a fixed point. But it can be rewarding to scan the area from time to time. I sometimes scan with binoculars (12x). As a lone observer, I’m sure I miss birds that fly somewhere else than were I’m watching and I also miss birds that fly very close (below my scope view) or high (above my scope view).

My strategy is to spend as much time as available at the watchpoint and don’t limit seawatching to only the morning hours. So, full-time seawatching. It’s simple: sit on your ass, watch and wait for it. Yes, the early morning hours were usually the best, but I’ve seen both continuing migration or the appearance of rare/scarce (sea)birds during the rest of the day. I’m of the opinion that it is definitely worth to spend the whole time seawatching, as it greatly increases your chances of seeing more birds.

I record all my observations on a voice recorder. On busy days, this has the advantage of not having to interrupt the seawatch to write down the counts. A description of a bird can also be made in real-time by speaking and watching.

[ Last edited by badesc at 28/01/2022 15:53 ]


List of observed seabirds and coastal migrants

duck spec.

Unidentified ducks appeared from mid-September, but October had the highest total count (544), with a maximum of 398 individuals on 18th. It’s a surprise to me that we didn’t see more ducks in November and that the peak was in mid-October. The distance to these fast-moving birds, bad lighting and/or heat haze were the reasons why I could not identify them to species level, certainly not female-type birds. A total of 708 were counted during the year.

Northern Shoveler Spatula clypeata

Although this was a new species for Po Toi, a total of 25 Northern Shovelers were counted, indicating they are not a rarity here.

Eurasian Wigeon Mareca Penelope

One record: a male going west on 9 November. First record for Po Toi, but they shouldn’t be that rare.

Northern Pintail Anas acuta

Seen on 19 October, 21 November and 4 December, each time two individuals. First records for Po Toi.

Eurasian Teal Anas crecca

Only 5 Eurasian Teals were identifiable with certainty, on 24 September.

Garganey Spatula querquedula

Only 1 male identifiable, on 18 September. Many more have most probably passed-by, but were too far to identify with certainty. It is believed that most teals off Po Toi should be Garganey. Teals were among the first ducks to appear in autumn.

Tufted Duck Aythya fuligula

4 on 4 December. A first record for Po Toi, but there are most probably more regular as well.

Red-Breasted Merganser Mergus serrator

2 female-type birds on 21 November and 1 female-type on 22 November. They flew to the north/northwest, which is not the standard direction for migration ducks in autumn, which fly west. The mergansers also flew rather close and appeared as if they could be staying in the area, but some checking of bays did not yield anything.

Great Crested Grebe Podiceps cristatus

One record of a group of 3 on 22 December. Only the second record for Po Toi and the first alive; the previous record was of a dead bird in 2009. They should migrate off Po Toi, so most probably our record is not exceptional.

Black-winged Stilt Himantopus himantopus

One record of a single bird on 26 August.

Northern Lapwing Vanellus vanellus

One record of a single bird on 22 November. Second record for Po Toi, the previous one was 2 individuals on 3 December 2017.

Grey Plover Pluvialis squatarola

Single migrants seen on 5 and 17 August and 23 September.

Eurasian Whimbrel Numenius phaeopus

A total of 53 were counted, with an obvious peak in August.

Eurasian Curlew Numenius arquata

3 on 26 August and 1 on 22 December.

Black-tailed Godwit Limosa limosa

One record of a group of c150 on 28 April.

Red-necked Stint Calidris ruficollis

One record of a group of c75 on 29 April.

Red-necked Phalarope Phalaropus lobatus

Seen in most months, except in June and from October onwards. Highest count 125 on 29 March.

Common Redshank Tringa tetanus

One record of 4 on 26 August.

Common Greenshank Tringa nebularia

One record of 1 on 18 September.

Oriental Pratincole Glareola maldivarum

Only seen in April: 4 on 16 and 1 on 28.

gull spec. Larus spec.

Involves large gulls: large-white headed gulls and also possible Pallas’s Gull. 103 individuals counted, with 89 in December (but double counts cannot be excluded). Obviously, a winter species, with a nice graph of increasing numbers. Still higher number should occur in late winter/early spring (February/March).

Black-headed Gull Chroicocephalus ridibundus

One of the surprises from seawatching in autumn and winter. 1,508 were counted in total, of a species that was thought to be rather rare in Hong Kong southern waters and off Po Toi, with very few records of a few individuals in the past. First appeared on 18 October this year (6 individuals) and our highest count was 371 on 3 December.

Black-tailed Gull Larus crassirostris

One of the earliest gulls in autumn, with the first record on 28 August. Besides that, quite regular in small numbers, with two high counts of 10 on 21 and 22 December. A total of 39 have been counted in 2021, but of course we lack data from the first months of the year.

Vega (Mongolian) Gull Larus vegae mongolicus

Three records: 2 on 20 November, 2 on 21 December and 1 on 22 December.

Lesser Black-backed Gull (Heuglin's Gull) Larus fuscus heuglini

Although most of the unidentified large gulls were probably Heuglin’s, perhaps we could have excepted more than the total of 23. Highest count was 13 on 22 December.

tern spec.

The numbers of – alas mostly unidentifiable – terns we counted have been called unprecedented and this indeed looks as another very nice discovery. It indicates that, on a regular basis and without the impact of typhoons, the highest numbers appear in autumn, not in spring. And there is an obvious peak in September, when we counted a record high of 2,969 individuals on 10 September. 1,900 on 17, 1,490 on 16 and 1,207 on 11 September were nice counts as well. The total count for the year is 11,183, of which 9,232 in September.

The challenge in the future is obviously to get to identify more of them, although I believe these were mostly either Common Terns or Aleutian Terns.

Gull-billed Tern Gelochelidon nilotica

Appeared both in spring, early and late summer and early autumn, with September being the peak month. A total of 52 individuals were counted, of which more than half (28) in September. Highest count was 21 on 16 September.

Caspian Tern Hydroprogne caspia

Another species that appeared in previously unknown high numbers in autumn. 2 on 3 August is an odd record. But November was the peak for this species, of which we counted a total of 263 individuals this year. The highest count was 72 on 7 November.

Greater Crested Tern Thalasseus bergii

This species appeared to have had an exceptional year, but more likely is that the surveys revealed its true status. I also refer to the Birds Reports of 2013 and 2017 and it’s amazing how our understanding of the appearance of Greater Crested Terns in Hong Kong has evolved, as it certainly also did in 2021. Interesting to look at the below graph of 2021 and to compare this with the one on page 120 of the Bird Report 2013 ( ... eport_protected.pdf).

At first, we counted a record high of 105 on 16 April. But the numbers were even higher in autumn, noticeably in September, when a new record high of 165 birds on 10 September was counted. On four days during the year, more than 100 individuals were counted. It also turned out to be one of the most regular migrant terns throughout the summer, when it was seen on most survey days.

The total number for the year is 1,108; I don’t think any previous year comes even close to that number, while it is yet a fraction of the real number that passes Po Toi.

The latest record was 6 on 18 October.

Little Tern Sternula albifrons

Appeared more common in spring than in autumn, with a high count of 30 on 28 April. A total of 70 Little Terns was counted in 2021.

Aleutian Tern Onychoprion aleuticus

Perhaps not that much surprises here. Appeared in much higher numbers in late summer/early autumn than in spring. Only 142 birds were counted, but probably much more, that were left unidentifiable, passed through. The highest count was 33 on 10 September.

Bridled Tern Onychoprion anaethetus

A bit of a tricky species to count, as it is also a local breeder and these birds might fly along the same route, to feed out at sea, as migrants do. So counting locals for migrants cannot be excluded. The graph below nevertheless shows our attempt to only count what we believed to be migrants. And then we see two peaks, in May and in August. A total of 1,800 individuals was counted, with highest counts of 328 on 12 May and 327 on 16 August. The last Bridled Tern of the year flew by on 25 September.

Black-naped Tern Sterna sumatrana

Also a local breeder, of which the graph only shows counts of birds of which we believed were migrants. Obviously a peak in spring, with the highest counts of 23 on 28 April and 11 May. The last one appeared on 28 August.

Common Tern Sterna hirundo

Obviously more numerous in late summer/early autumn than in spring. We counted a total of 1,176 individuals, with the highest count 300 on 28 August. Of interest were two late records: singles on 23 November and 2 December, the latter being a new late date for Hong Kong and the first winter record.

Whiskered Tern Chlidonias hybrida

This was not a common tern species off Po Toi, with only 88 birds counted, on very few survey days. The highest count was 48 on 10 May.

White-winged Tern Chlidonias leucopterus

Clearly mainly a spring migrant, with a peak in May. The highest count was also in this month, with 176 on 14 May. Very few in autumn, with the latest record 5 on 18 October.

[ Last edited by badesc at 8/06/2022 16:29 ]


gull/tern spec.

This involves distant birds, or observations that were disturbed due to severe heat haze or bad lighting, of either a gull (primarily Black-headed) or a tern species.

We counted 130 such birds, between 29 October and 9 November, with a peak of 46 on 7 November.

Jaeger spec. Stercorarius spec.

Only recorded in autumn, when most jaegers apparently flew much further out than in spring. All of the 18 individuals were most probably either Long-tailed or Parasitic Jaegers.

Pomarine Jaeger Stercorarius pomarinus

One record: 2 adult-type and pale morph birds on 22 November. Autumn Pomarine Jaegers usually appear during a typhoon, which was not the case for our observation. It is also a new latest date for Hong Kong.

Parasitic Jaeger Stercorarius parasiticus

Our counts in April and May were within the status of the species in Hong Kong, but apparently it can occur throughout the summer months as well. The previous late date was 8 July, while it was encountered also during our surveys in August, September and October. A total of 26 birds were seen, with high counts of 5 on 28 April and 13 May. The latest one appeared on 28 October.

Long-tailed Jaeger Stercorarius longicaudus

Only one record of a single juvenile on 24 September. A bit of a disappointment.

Swinhoe's Storm Petrel Oceanodroma monorhis

Apart from a probable one on 26 August, two records: singles on 27 May and on 11 September.

If my count is correct, a total of 17 birds that were dark-rumped storm petrels (most probably Swinhoe’s) or Swinhoe’s Storm Petrels have been seen by birders in Hong Kong waters and nearby in the South China Sea this year, indicating that 2021 was an exceptional year for Swinhoe’s or – and much more likely – it is a scarce passage migrant in the area, for which August to October are probably the best months to see it.

shearwater spec. Ardenna spec.

Only two shearwaters had to be left unidentified: 1 on 6 July (probably Short-tailed) and 1 on 20 July (probably Wedge-tailed).

Streaked Shearwater Calonectris leucomelas

Seen in spring, summer and autumn. It was quite a year for this species, with about 322 birds counted.

There was first a record count of 129 on 16 April and then again one of 149 on 22 July, two days after the passage of typhoon Cempaka. Interestingly, we also observed 8 individuals on 7 November and 10 to 20 on 23 November, being a new late date for Hong Kong. These were also the first records in November for the territory.

Short-tailed Shearwater Ardenna tenuirostris

Short-tailed Shearwaters were seen much more regularly, with a total of 48 individuals. The highest count was 10 on 28 April. The last ones were 3 birds on 21 July, a new latest date for Hong Kong.

Bulwer's Petrel Bulweria bulwerii

Two singles were seen on the same day, 17 October, several days after the passage of typhoon Kompasu (meaning there was no typhoon on 17 October, but force 6 winds were encountered). There was also a possible one earlier that day and a very likely one on 20 July during typhoon Cempaka.

A single Bulwer’s Petrel was seen off Cape D’Aguilar on 13 October during typhoon Kompasu. So, with 3 certain ones and 2 possible/very likely ones, we could have gotten up to 5 Bulwer’s this year. Maybe October might be a good month to look out for this species in Hong Kong.

Lesser Frigatebird Fregata ariel

Three records: singles on 26 May, 10 June and 3 August. We noticed, it was actually more drifting in a direction, while circling at relatively high altitude, and not going straight in a certain direction like a migrant. It could have been the same, long-staying individual that roosted at Cheung Chau. We also saw this species around Mat Chau, the small island next to Po Toi, on 26 June (1).

Red-footed Booby Sula sula

Two records: singles on 3 August and 23 September.

Brown Booby Sula leucogaster

Three records: singles on 9 June, 7 July and 22 July.

cormorant spec. Phalacrocorax spec.

1 on 9 November.

egret spec. Egretta/Bubulcus spec.

The families here are both Egretta and Bubulcus. 871 unidentifiable egrets passed Po Toi, mainly in September.

heron spec. Ardea spec.

2 unidentified herons, either Grey or Purple, were seen on 30 October.

Black-crowned Night Heron Nycticorax nycticorax

One record: 7 on 19 October.

Chinese Pond Heron Ardeola bacchus

Mainly seen in September and October, with a high count of 19 on 16 September.

Eastern Cattle Egret Bubulcus coromandus

Here the peak occurred in October, with the highest count being 39 birds on the 18th of that month.

Grey Heron Ardea cinerea

Seen from time to time from September onwards, with the highest count 9 on 23 November.

Great Egret Ardea alba

Mainly seen in autumn, from mid-September to mid-November. Highest count 12 on 19 October.

Little Egret Egretta garzetta

A more regular appearance off Po Toi, including in July and August. But peak in September, with 46 as the highest count on 11 September. Of the egrets that were identifiable, this species is the most common one and 151 were counted during the year.


I want to thank Sam Baxter-Bray for getting me into seawatching on Po Toi in the first place.

Thanks to Geoff Welch for his tremendous help, encouragement and support on numerous levels, including with this review.

Several people kindly helped or provided support or information in various ways: Geoff Carey, Chris Champion, David Diskin, Mike Kilburn, Michael and Elizabeth Leven, Richard Lewthwaite, Ben Lisse, Morten Lisse, Carrie Ma, Yann Muzika, Graham Talbot, Gerard Troost, Mike Turnbull and Martin Williams. Apologies to whom I might unintendedly forgot to mention.

[ Last edited by badesc at 2/01/2022 19:34 ]


HI Bart,

A nice report. Will u submit this report to the Hong Kong Bird Report?




Po Toi Seawatch

Hi Bart,

Very interesting tables and results, clearly presented.

Now - same as a lot of other birders - I’m really looking forward to your 2022 reports !

Happy New Year



Hi Captain,

Thanks. We're not done yet with seawatch surveys and I hope to be able to first fill some gaps in 2022.

Hi John,

Thanks. I'm looking forward to 2022 myself, especially January to April. But please, have low expectations.

Happy New Year.