Subject: Po Toi Seawatch Autumn 2021 [Print This Page] Author: badesc Time: 13/09/2021 11:32 Subject: Po Toi Seawatch Autumn 2021
9 to 11 September
Here we are with the first survey of the autumn, i.e. September, October and November. There have been few seawatching surveys in the past during autumn and winter (much more during April and May) and I even don’t know of anybody ever doing seawatching a whole day long with a telescope at Nam Kok Tsui. So there is a lot of new data that we can gather.
The reason to go from 9 to 11 was the prediction of this weather system, which looked like a dream for a seawatcher:
This were the predictions for Friday 10th at 10 AM. Left is Severe Tropical Storm Conson and right is Super Typhoon Chanthu.
9 September was the first day of this survey, and I started soon after arriving with the ferry, as usual. I watched from 11h45 to 17h45. The weather was fine, with east to northeast winds, force 2 to 3. The afternoon saw the passage of mostly terns. It is likely that at least the same number passed during the early morning. Alas many were very far out.
Interesting is to note that I did not see a single tern from the ferry from Aberdeen to Po Toi. This strongly indicates that the ferry trip provides no indication for what to see at Nam Kok Tsui, as the migration route of birds is far away from the ferry route.
1 adult-type large white headed gull; very far also, but appeared to have a rather light mantle, lighter than Heuglin’s Gull
866 terns spec.
80 Common Terns
32 Greater Crested Terns
20 White-winged Terns, 1 group
1 Little Tern
So Friday 10 September was the day that looked fantastic from the predictions, with winds up to force 6. It would be “mainly cloudy with occasional squally showers and thunderstorms”. Okay for me, as I’ve seen shearwaters in that kind of weather in Hong Kong, so bring it on.
Alas, the reality was quite a bit different. Apart from some scattered clouds in the morning but not a drop of rain, it turned-out to be hot and sunny for most of the day. Winds coming from the east and northeast, but only force 3 to 4. During noon, shortly force 5.
I had to make a construction with my umbrella against the sun, not against showers and thunderstorms.
Not a single tubenose was seen, but tern movement was massive. As soon as I put my scope at the sea, I witnessed these birds flying west. I think I counted over a 100 in the first 10 minutes and soon after up to 300 in just 15 minutes. My voice recorder proved to be very valuable, as I was able to count and record without taking my eye from the sea.
The peak of tern movement was between 06h00 and 09h30, but they kept on coming for most of the day.
I’ve probably missed some terns, as it happened frequently that when I zoomed-in to 70x from 30x to try to identify the distant birds, I discovered that there were even more terns passing further out that were invisible with 30x magnification.
11 September was again a pretty good day, but it appeared that the largest number of terns had moved through. The majority on this day occurred between 06h00 and 08h00, with very few afterwards. It was cloudy in the morning with one distant thunderstorm, but soon turned really very hot and sunny. Winds coming from the west now, force 2 to 3.
Seawatchers need FOPP – focus, optimism, patience and perseverance. Even though it turned really hot and there was not much movement, another good species flew-by at 10h37 and FOPP was rewarded. But I must admit that the weather and the observation that most terns passed-through at that point, eventually made me quit earlier than planned.
1 Swinhoe’s Storm Petrel, flying to northeast at 10h37
47 white egrets spec.
46 Little Egrets
14 Eastern Cattle Egrets
2 Heuglin’s Gulls
1,207 terns spec.
100 Greater Crested Terns, 96 flying west, 4 to northeast
37 Common Terns
22 Aleutian Terns
7 White winged Terns, 1 group
1 Gull-billed Tern
1 Bridled Tern
Once more a very worthwhile and most enjoyable survey. I can only repeat that this place is awesome.
A total of exactly 5,600 terns were counted on one full and two half days (only!).
For Greater Crested Terns, we set a new record high count for Hong Kong with 165 individuals seen. The previous record was 105 last April, but only with counts during early morning and late afternoon, not during the whole day.
This species is one of the best examples of how the status of a bird can be different from reality. The status in Hong Kong up to now is “Common spring passage migrant through coastal waters with occasional summer and autumn records.”. What is really occasional in summer and autumn is not the occurrence of this species, but birders looking for them. Of course, the status of a bird can only be determined with what’s been seen and reported, but this illustrates that too few observation days can lead to an inaccurate status. Greater Crested Tern is common in spring, not uncommon in summer and it looks like to be common in autumn as well. But let’s first get some more observation days for the autumn.
Something similar can be said about terns in general. Record counts of Common Tern and Aleutian Tern have been reported during typhoons in spring (mainly typhoon Leo on 2 May 1999, from Cape D’Aguilar). But our survey here produced 5,600 terns without any typhoon near Hong Kong. The two storms mentioned above were actually quite far away and not even a storm signal 1 was issued in Hong Kong during the survey. Yet thousands of terns passed-through. Although weather conditions might have an effect, we don’t necessarily need a typhoon. More likely there was just a normal, regular passage at the right time in autumn.
It’s indeed a pity that so many terns flew very far out, and more so that I was unable to identify the majority. Firstly, when more Common Terns than Aleutian Terns (or vice versa) were counted, that doesn’t mean there were really more Common than Aleutian, just that the birds that flew close enough for a positive ID happened to be Common. But I did feel that Common were the majority, but can’t be really sure.
Secondly, on Saturday 11th and for a limited time, some terns suddenly flew a lot closer than on the previous days. Two fishing boats relatively nearby, with their nets in the water, seem to attract the terns.
It’s interesting to note that this caused the migration route to be different – after the boats were gone, terns flew far off again. It could be a useful fact when doing boat trips for observing birds: any kind of fish-based chum will most probably (at least) attract many terns, even more likely during migration time.
I’m looking forward to future autumn surveys and am expecting an increase in species of a broader variety of families of birds, like herons, egrets, gulls, ducks, grebes, waders, etc., but also swifts, swallows, passerines and raptors. I will miss most of the ones that fly high, as I will continue to focus on seawatching.
I wrote in a previous post, about spring (http://www.hkbws.org.hk/BBS/view ... amp;page=1#pid86924), that I believed Swinhoe’s Storm Petrels are too close to never appear in Hong Kong and should pass through like once a year or every two years. (I had and have the same thoughts on Bulwer’s Petrel, but here the jury is still out!). But it now looks like that I was very wrong. Not only does the end of May not seem to be the best time, but that could be early autumn instead. And the species does not seem to pass through “once a year or every two years”, but likely every year and in very small numbers, not just one individual.
It is well known that Swinhoe’s Storm Petrels pass through the Singapore Straight in September (e.g. https://singaporebirdgroup.wordp ... raits-of-singapore/). That’s roughly 2,600 km southwest of Hong Kong. Based on the below screenshots from eBird Singapore, the peak is in the third week of September.
It makes sense to expect the species passes-by Hong Kong in late August/early September. This is just a provisional estimate, of course. But there is now some data to support this.
Not only have we done seawatching surveys from Nam Kok Tsui, Carrie Ma has organised three boat trips in Hong Kong Southern Waters this autumn (these are usually done only in spring). And Chris Campion and Michael & Elizabeth Leven have done seawatching with a telescope from Genting cruise ships, known as ‘cruises to nowhere’, so basically relatively close to Hong Kong. All efforts were made in the last two weeks of August and the first two weeks of September (so far), and everybody (!) has seen at least one Swinhoe’s Storm Petrel. Let’s sum them up below:
Included is an older record from this century, of a very likely Swinhoe’s in 2000; I’ve included my possible Swinhoe’s on 26 August; the one on 29 August was found by Jemi Holmes and seen by more than 20 people.
During the previous century, other dark-rumped or (possible) Swinhoe’s Storm Petrels have been seen in Hong Kong, but more in autumn than in spring, measured by number of individuals. No Swinhoe’s Storm Petrels have been accepted by the RC so far.
On a map, the coordinates of the birds since 2000 are marked by the blue pointers:
It seems logical that most of the presumably hundreds of Swinhoe’s move over sea in a south-westerly direction between the Taiwan Straight and the Singapore Straight and thus are too far away from Hong Kong. But we’re seeing evidence that some of these birds move a lot closer and even fly through Hong Kong Waters. Note that of the above observations, some birds flew west or southwest, while some flew to the northeast. And also, that they have been seen on days with no strong easterly winds.
So, let’s hope all these sightings will increase awareness and make more people looking for Swinhoe’s Storm Petrel during what could be the right time of the year for this species. When more efforts will be made, maybe more will be seen, and it could become obvious that they are at least a rare passage migrant in (early?) autumn. Whether we’ll see more this year as the autumn progresses, remains to be seen, so I am by no means drawing definite conclusions here. Just bringing it up.
A final thought on confusing species (hence there’s often talk of ‘dark-rumped storm petrel’). For Hong Kong that would be Tristram’s and Matsudaira’s Storm Petrel. I remember the time when together with Swinhoe’s, the ID of these species was considered extremely difficult or they even could not be separated in the field. Anno 2021 a lot more information is available and these are actually three pretty different species.
The most unlikely to ever occur in Hong Kong is Tristram’s Storm Petrel. It breeds only off Japan and on Hawaiian Islands and does not migrate outside an area between the breeding grounds. However, it has been recorded off Taiwan (https://cwbftaiwan.wixsite.com/cwbf/important-links), but not in Singapore. It’s the largest storm petrel, with a deep-forked tail and prominent upperwing bar, and has a different jizz and flight behaviour than Swinhoe’s.
Although it has never been recorded in Taiwan, nor is it on the Singapore list (https://singaporebirdgroup.wordp ... klist-2021-edition/), Matsudaira’s Storm Petrel breeds off Japan (Volcano Islands) and is a long-distance migrant that moves through parts of South-East Asia to the East coast of Africa. It is a large storm petrel as well, very dark-coloured (appearing blackish), has prominent white primary shafts, with deep-forked tail, different jizz and flight behaviour than Swinhoe’s.
But Swinhoe’s should by far be the most-likely storm petrel of the three to occur in Hong Kong. All the odds are in its favour. Actually, we all approach all-dark shearwaters in a way, that the first and obvious choice (certainly in April-June) is Short-tailed Shearwater. So almost all are reported as such. We then look for deviant features that could perhaps indicate a Sooty Shearwater (no records in HK as far as I know). But we’re not saying: it’s an all-dark shearwater that looks very much like a Short-tailed and all odds are in favour of this species, but we cannot 100% exclude Sooty, so it’s an all-dark shearwater spec. Maybe Swinhoe’s and Matsudaira’s can be approached in a very similar way.
The reason to go on these dates was not because the weather looked good for seabirds, but actually precisely because it did not particularly look good. Winds were predicted to come from the west or the south, with only force 2 to 3. Unlikely to make a number of seabirds occur in the Lema Channel. So with no expectations we went to see what’s out there.
It turned-out interesting, and even before I was at Nam Kok Tsui. I noted almost 170 egrets and herons on the move from the ferry from Aberdeen, some 40 Barn Swallows, 50 or so terns spec. and 5 Greater Crested Terns. Three points to put forward:
1. I was on the lower deck, but on the upper deck Peter Ho and others saw a distant dark shearwater. As I did not see it, I cannot comment on it, apart from noticing that it is very interesting to still see a shearwater in what we consider to be unfavourable wind conditions for them to move through Hong Kong Waters.
2. What I did notice was that some terns flew very far away from the ferry, but a decent number flew close and, most importantly, came from the waters between Beaufort Island and Hong Kong Island, and also from between Beaufort Island and Po Toi. So did one group of c150 white egrets. Needless to say, is that I miss all these birds from where I am on Po Toi. So what passes-by on some days can be even more numerous than what I see/report.
3. What I did see on the ferry was a good indication for what I was about to see on Po Toi (except for shearwaters). This was the opposite of the survey from 9 to 11 September when I saw basically nothing from the ferry, but many terns from Po Toi.
16 September was the first day of the survey and I hurried to the seawatch point like never before, arriving 15 minutes earlier than usual. I was on duty from 11h30 until 17h30. It was mostly cloudy with limited visibility and with one distant thunderstorm (that hit Hong Kong elsewhere). Winds came from variable directions, from the west to the southeast, with force 2 to 3.
As soon as I looked through my scope, terns appeared moving west, and just like on the ferry, a good number of egrets and herons was on the move as well.
Egrets and herons:
174 white egrets spec.
30 Little Egrets
19 Chinese Pond Herons
7 Great Egrets
2 Grey Herons
With seemingly quite a lot of birds – mostly terns – on the move, I was looking forward to the next, full day, 17 September. I watched and counted from 06h00 until 17h30. It was cloudy in the morning, but turned hot and sunny afterwards, with limited visibility. Winds blew from variable directions, from southwest turning to east, force 2-3.
18 September was already the last day, which is then usually a half day (morning to noon only). I watched from 06h00 until 11h00, but there were almost no birds after 8 o’clock. It was cloudy and rainy in the morning, afterwards hot and sunny with limited visibility. Eastern winds, force 2-3 (maybe up to 4).
Similar remarks as on the first September survey can be made, certainly with regard to terns. This time a total of 4,455 were counted. Sometimes they almost only occur in the morning, but the two Thursdays (9 and 16 September) saw good passage in the afternoon. Who knows how many came through in the morning, when I wasn’t yet there… Plus how many flew to the north of Po Toi, which I did not see…
It is difficult to ignore the fact that some tens of thousands of terns pass-through Hong Kong Waters in autumn. Autumn could be even better than spring. And I like to stress again, the complete absence of any storms during this survey as well.
Another point to make is indeed the total absence of seabirds (okay, you could perhaps call Red-necked Phalaropes seabirds), apart from the dark shearwater seen by others. No tubenoses, no boobies, no jaegers for me. Perhaps we could carefully make the point that we need the extra help of strong winds (perhaps at least force 5 from the east to the south) for a number of seabirds to appear in the Lema Channel during autumn. Yet, the 11 jaegers and 1 Swinhoe’s Storm Petrel of the previous survey did occur in much less than such ‘perfect’ winds. So you never can exclude anything. And that’s also the best attitude: anything can turn-up at any second, no matter which weather.
As we wanted 3 surveys in September, these 3 days were chosen; two half days and one full day. The weather was totally different from the previous survey, so that in itself was interesting. The prediction was for easterly winds, averaging force 5. It is usually associated with the chance for seabirds off Po Toi.
23 September started on the ferry with zero birds. The day on Po Toi was with sunny periods, but mostly cloudy and with a few short showers. Winds were blowing from the east, with force 4 to 5, maybe up to 6 at some point. I watched from 11h45 until 17h00. When I put my scope towards the south, to catch birds flying to the west as well as to the northeast, it was like on the ferry: zero birds. No migrants. No terns. Nothing, and this for quite a while. But one of the first birds was a Red-footed Booby, which saved the day.
1 Red-footed Booby, flying northeast at 13h11
24 September saw very similar weather, but after a cloudy morning it turned mostly sunny. Winds were the same. There was a some improvement, of course also because we started at 06h00, and watched until 16h30. The afternoon was very very quiet and it was ticking away the moments that make up a dull day, fritter and waste the hours in an offhand way…
25 September was the last day. After a short cloudy morning, it turned way too sunny. This is a disturbing issue, because when watching to the south, the light is very bad, certainly on a bright sunny day as this. I started at 06h00 but stopped at 12h00. Migration died down very early, but the morning was again better than the previous day.
Lastly, one interesting ‘white’ tern was seen, but a bit too far out. After having seen more than 10,000 terns in September, this one stood out immediately (so not like the ones seen before). A very elegant bird and an elegant flyer, dark trailing edge to outer primaries of underwing though primaries did not appear clearly translucent. Tail appeared rather short, missing long streamers, or they were not visible. Greyish hint on underparts, but pale (i.e. white) cheeks. The only species that came to mind was Arctic Tern. Most noticeable was that the bird was in complete summer plumage, with full black cap. No photos were taken.
I’m not making any claims here, but it’s just a good reminder that Arctic Tern perhaps could actually turn-up in Hong Kong. The issue of its rarity along East Asian coasts was recently discussed by Limparungpatthanakij et. al. (2021)*. It is “an extremely widespread and numerous Holarctic breeder”, breeding alongside the in Hong Kong common migrant Aleutian Tern. So, it could occur here, although the forementioned article assigns its rarity along coastal waters because it’s a pelagic bird, on migraton. But in Europe that is not entirely the case, so we’d better be on the lookout. By the way, also for Chinese Crested Tern, as this is even more likely to occur in Hong Kong. First step is to pay attention to terns, with these species in mind, and the chance of finding one is greatly increased. That’s the main point here.
* Limparungpatthanakij, W., Ekkul, J., Aderik, K., Angkaew, R., Sutibut, S., Round, P.D. (2021) Terns in the Thai Gulf—a potentially important over-summering area for Aleutian Tern Onychoprion aleuticus and documentation of Thailand’s first Arctic Tern Sterna paradisaea. BirdingASIA 35: 92-96.
[ Last edited by badesc at 27/09/2021 20:25 ] Author: badesc Time: 27/09/2021 20:41
Let’s wrap-up September. There were 9 observation days during this month, three full days and six half days. There were no typhoons in Hong Kong this year in September. It felt hotter than in summer.
What without a doubt stood out this month was the number of terns that we counted: 10,143 in total. We’ll never know the real total for the whole month. But if you add mornings of the half days and the afternoons of the other half days to the full days, we were counting on only 20% of the available days in this month. I don’t say you should multiply the actual counts by 5 to get an estimated number for the whole month, but it’s clear that thousands upon thousands of terns pass-through. And note that the tern migration starts to take-off by the end of August.
Some other interesting statistics/species for September:
October would be a very interesting month, as very few seawatching surveys have ever been done on Po Toi. There were also two storms in the first half of October, Tropical Storm Lionrock closely followed by Typhoon Kompasu. Both storms triggered a signal 8 and in theory you want to be on Po Toi for seawatching, then.
Alas, it turned out less favorably. To make a long story short, there simply was no ferry in between the two storms. My original plan to go for the first one had to be cancelled, because I was not sure if I could get back and the prospect of having to stay 10 days on Po Toi during two typhoons was not really ideal. I then tried to go before the second storm, but, indeed, no ferry.
So that’s why I had no choice to let these opportunities go. October typhoons or storms are rare in Hong Kong, although it seems they might get more regular in the future.
Before we go to our own sightings, let’s summarize what others did see during the storms.
* On 9 October a storm petrel was found on Shek O beach. The video clips that were shown indicated a Swinhoe’s Storm Petrel, but the rump was not visible so Leach’s could not be excluded.
* Graham Talbot and others did manage to get to Cape D'Aguilar on the day typhoon Kompasu passed-by, on 13 October. Graham’s results were fantastic:
Between 11h30 and 17h00, with most birds flying northeast.
5 Streaked Shearwaters
1 Bulwer’s Petrel; heading to Shek O bay
7 dark-rumped storm petrels, almost certainly Swinhoe’s
1 Swinhoe’s Storm Petrel
1-2 juvenile Sooty Tern(s), feeding; the same or another one seen 40 minutes later
10 terns spec.
3 Whiskered Terns
So, two storms in October (!) brought 9 storm petrels and 1 Bulwer’s Petrel to Hong Kong waters. And nobody was even at what is widely considered as the very best seawatching point: Nam Kok Tsui on Po Toi. We do have to keep in mind that there were no similar storms in September, so it doesn’t mean that October by definition is the best month or better than September.
Okay, let’s now move to our own sightings, starting with seawatching from Po Toi on 16 October. I watched from 11h45 to 17h15. The weather was bright and sunny, with force 5 winds coming from the north to northeast.
So I was present at 06h15 and seawatched until 17h15. It was mainly cloudy, with some sunny periods. Winds were still coming from the north to northeast but had increased to force 6. The sea off Po Toi was rough and the waves were high.
1 tubenose spec., to northeast at 06h50; too far and seen briefly, but likely Bulwer’s Petrel
2 Bulwer’s Petrel, to west, 1 at 13h14 and 1 at 15h05
66 duck spec.
Egrets and Herons:
4 white egrets spec.
1 Grey Heron
18 October turned out to be a good day for ducks, but all groups were too far to identify. Quite a few terns passed through as well. I was again present at one of the seawatch-points, from 06h15 to 16h45. The morning was mostly cloudy, while it turned mostly sunny in the afternoon. Winds were blowing from the northeast, starting with force 5 and later with force 4.
I choose the southwest watch point again, as seen on this photo.
And 19 October was already our last, half day for seawatching. This time from 06h30 to 14h00. It was sunny with winds still blowing from the northeast, starting at maybe force 5 but mainly force 4. It was relatively quiet.
33 ducks spec.
2 Northern Pintails, males
Egrets and herons:
2 white egrets spec.
35 Eastern Cattle Egrets
14 Chinese Pond Herons
12 Great Egrets
7 Black-crowned Night Herons
2 Little Egrets
1-2 Gulls spec.
2 terns spec.
5 Common Terns
5 Barn Swallows
1 Eurasian Hobby was present, hunting for dragonflies. Also, 1 Common Moorhen was seen at the very small pool at the watch point. This is a very rare occurrence in autumn on Po Toi and probably even the first autumn record ever. Here the checklist: https://ebird.org/checklist/S96457058
Most remarkable sightings were of course those of the two Bulwer’s Petrels that flew to the west. They interrupted their journey from time to time to feed. The sightings will be submitted to the Records Committee in due course.
Also, the 6 Black-headed Gulls on 18 October is the first autumn record for Po Toi. There is only one other record of this species off Po Toi: 2 birds on 22 February 2013. I saw another group of 11 on 19 October that were most probably also Black-headed Gulls, but they were much too far to be certain and this sighting has not been included in the above listing. But we’ll certainly keep an eye on these in the coming surveys.
Greater Crested Terns were still coming trough and all our sightings were new late dates, the previous late date was 3 October. So, the new one is now 18 October.