Subject: Po Toi Seawatch Summer 2021 [Print This Page] Author: badesc Time: 28/07/2021 20:51 Subject: Po Toi Seawatch Summer 2021
8 to 10 June
I did only two surveys in June, early in the month and at the end of the month.
8 June was my first day of the first period, 3 days; 2 mornings and 2 afternoons. I started somewhat earlier again in the afternoon, from 13h30 to 18h00. No special weather: clear views and sunny, winds from the east to the southeast, force 3 to 4.
9 June was already a lot better. The weather was similar, but there were some thunderstorms this time. Again, I stretched the observation times, which paid off. I birded from 06h00 until 12h00 and from 14h00 to 18h00.
6 Short-tailed Shearwaters
1 Brown Booby, an adult
So, that concluded this week’s short seawatch survey. I expected even less migrants than on the previous survey (25-27 May), but there was nonetheless still some passage.
This 3-day survey is summarized as follows:
9 Short-tailed Shearwaters (a pretty good number, but perhaps that’s just normal)
3 Whiskered Terns
18 White-winged Terns
20 Greater Crested Terns (not bad either, but maybe this is normal, too)
1 Common Terns
15 Roseate Terns (assuming all birds that headed straight to NE and not turning back were migrants. Local birds usually fly slower, more buoyant, regularly feed, and often call)
2 Gull-billed Terns
And of course, birds that did not appear to be migrating were the adult Brown Booby that flew to the north/northwest, in the direction of Stanley, and the immature Lesser Frigatebird, which circled high above the Lema Channel/Southern HK Waters, on the eastern winds (so going west).
Together with the survey in late May, my main takeaway is this. Mornings were way better than afternoons. Seawatching was done on four mornings. Every morning produced a rare or scarce bird: Lesser Frigatebird on 26/05, Swinhoe’s Storm Petrel on 27/05, Brown Booby on 09/06 and Lesser Frigatebird on 10/06 (you could argue that this might be the same individual from May, but still). That is a hit ratio of 100% for a morning with a rare or scarce bird. So, have I been really lucky? Or am I very skilled? No, I don’t think that is the case.
Of course, we need to do much more surveys, over a number of years (!), but I do believe that the presumed typhoon-driven and rare seabird species might actually be not that rare and not necessarily exclusively typhoon-driven. There wasn’t any typhoon near or far during the surveys. Not even strong winds. Not even misty weather. Mostly just ‘normal’ weather with light to moderate winds, lots of sun, and occasionally a thunderstorm or rain.
The point is that surveys in June and during the summer have been largely absent. It’s like nobody would go to Mai Po; quite a few (e.g. wader or gull) species would be very rare in any given year elsewhere in HK, then. So, more surveys are in the pipeline and let’s find out what’s there during the summer months and not draw definite conclusions, yet. But I do think we have a darn good spot for seabirds at Po Toi, and for migration of terns, gulls and many other birds.
24 June was the first, half day of this 3-day survey. I watched for seabirds and migrants at the usual spot at Nam Kok Tsui from 12h45 until 18h00. There was a trough of low pressure in the South China Sea and I experienced rain until 16h00. Winds blew from the south to southwest, force 3 to 4.
1 Streaked Shearwater, at 12h57
5 Gull-billed Terns
4 Roseate Terns, locals
1 Greater Crested Terns, flying to the southwest
On my way to the village I also encountered a Black-winged Kite.
25 June was a full day, but I took a lunch break and watched from 06h00 until 12h00 and from 14h15 until 18h00. Weather was similar, but the south to southwest winds increased briefly to force 5. It was mostly cloudy and rainy.
1 or 2 Parasitic Jaeger(s), 1 pale morph 3rd cy to northeast at 11h50 and the same or another one feeding and then northeast at 16h20. Most probably just two individuals, but at the time I thought summer records would be highly unusual.
An (or still the same) immature Lesser Frigatebird was seen over Mat Chau around 13h00.
So that concludes this week’s seawatch survey, two mornings, two afternoons. As could be expected, the number of birds declined further, as the migration peak is almost completely over. But still there were some migrating terns and a few seabirds. E.g. 10 Greater Crested Terns in total. Also recorded the first migrating tern (Greater Crested) to fly southwest instead of northeast.
Note that weather conditions were not exactly supportive to bring in seabirds: again, there were no strong winds (expect briefly force 5 on Friday, which is not ‘strong’), cyclones or typhoons or anything. We really looking forward when windy conditions will be around.
There was no obvious peak of birds in the morning hours. Streaked Shearwater at 12h57, Parasitic Jaeger(s) at 11h50 and 16h20, terns evenly spread in time over the day.
Also, what was not seen is of notice, namely Short-tailed Shearwater. Seems they indeed migrate through HK up to the first half of June (probably a bit later than generally thought) (*). It was the most regular oceanic bird to be seen. From now on, any dark shearwater will be very interesting.
Very surprising were actually some good landbirds: Black-winged Kite, Watercock, Himalayan Swiftlet, a decent number of Pacific Swifts and a Red Turtle Dove. I don’t make much effort looking for landbirds, they just popped-up along the path to the village, so not bad.
Surveys in July, an even more interesting month because of lack of data, are in the pipeline.
(*) Later surveys will reveal that this statement was incorrect.
[ Last edited by badesc at 7/08/2021 07:54 ] Author: badesc Time: 28/07/2021 22:14
1 to 3 July
1 July was the first day of another 3-day survey and I headed to the watchpoint almost straightaway, so birded from 11h45 to 17h00. Winds force 4 to 5 from the southwest on an otherwise dry day.
1 Greater Crested Tern, the one and only migrating bird to be seen today
So that concludes this week’s seawatch survey, one afternoon, one morning and for the first time one whole day. The latter was to check whether we’d be missing something, but that was not the case, at least not on that day. 95% of migrants flew-by between 06h00 and 10h30. So, after that it was more like being in an airport waiting 6+ hours for your connecting flight, but then without something to read and no coffee. Afternoons were extremely quiet this time, but you don’t know that in advance. So, contrary to the previous survey (with rain), the morning hours peak was back.
Of course, there was little migration. But there still was some. However, first survey for me this year without any tubenoses. They were greatly missed. Again, Greater Crested Terns (total 12), Common Terns (total 3) and (what appeared to be migrating) Roseate Terns (total 9) kept on coming through.
Even though there have been “occasional records” in this season (cfr https://www.birdinghongkong.com/ ... ong-birds-2021.html, but this list is regularly updated), Greater Crested Tern does actually not seem to be that much of an occasional summer visitor to HK. The summer is not yet half way, but over 40 individuals have been recorded in 2021, and on most observation days. It could of course well be that later in July and August they really become occasional.
We also have a new last date for Parasitic Jaeger; it was historically 19 June. Interesting to see if more will follow as the summer progresses, as they are recorded all year round in e.g. Spain and Florida according to eBird, so maybe some might linger in the South China Sea in summer as well.
[ Last edited by badesc at 7/08/2021 07:54 ] Author: wcaptain Time: 29/07/2021 00:14
Superb. A painstaking survey, in particular the harsh conditions of summer weather in hk
It does fill the info gap of seabirds in early and mid summer. Our previous records were largely based on routine tern surveys n sea watching during typhoon invasion. No such systematic sea watching has been carried out as far as i can remember
Keep up ur good work.
Thx a lot for ur sharing Author: badesc Time: 29/07/2021 20:32
6 to 8 July
After the previous survey, I returned to Po Toi rather soon, because of this:
A low-pressure system that created south-easterly winds and was also moving northwest.
On 6 July, after I arrived with the ferry, I again went to the watch point almost straightaway and was present there from 11h45 until 17h00. The weather turned out to be diverse: from sunny to very large and heavy showers with squalls. From barely force 3 to what felt at least force 6. No birding possible during this relatively short period (c15 minutes). The winds were blowing from the southeast, and there were high waves at times.
7 July was a whole day of seawatching, from 06h00 until 18h00. The weather was mostly sunny and dry, with only a few showers. The winds were strong off Po Toi, force 6. The tropical depression was reaching Hainan Island today.
4 Parasitic Jaegers, 1 single at Hong Kong waters and one group of 3 immature flying northeast at 15h45
1 Brown Booby at 13h15
8 July was already the last day and I again stretched the observation time to the maximum, from 06h00 until 14h15. The effects of the depression diminished and the south-easterly winds blew with force 3 to 4 only. Even though I stayed longer, there were no more migrants seen after 10h30.
4 Parasitic Jaegers, 1 + 3 to northeast
1 Short-tailed Shearwater, to northeast at 10h24
So that concluded this week’s seawatch survey, one long afternoon, one whole day and one long morning. Total watching hours were 25 hours and 30 minutes.
First, tubenoses were back. I had to let the first one go, due to the distance and unfavourable light. Short-tailed came closest and that was probably what it was. Also because a very certain Short-tailed was recorded two days later. I checked clearly, this was no Sooty or any other dark shearwater. Classic Short-tailed. So they’re still coming through. This new late date is more than one month later than the previous late date prior to 2021. All observations this year indicate higher numbers than thought, over a longer period of time than thought.
Second, Parasitic Jaegers were also still there. A total of 8 on two days was remarkable, but maybe/likely this is just normal and some do over-summer in the South China Sea.
And third, Greater Crested Terns continued to pass through, with a total of 6, on two days.
I picked the next survey for 18 to 20 July, not knowing/realizing that another storm was approaching Hong Kong.
An innocent-looking low-pressure system eventually turned into typhoon Cempaka, with signal n° 3 issued by the Observatory. Yet, the first two days yielded virtually nothing, but what came after was fantastic…
On 18 July I headed to the watchpoint soon and birded from 10h15 until 17h30. Winds were already blowing from the east with force 5 and it was mainly rainy with a few dry periods.
1 Roseate Tern
1 immature Sooty Tern or noddy spec. at 13h34. All dark tern-like, but under-wing and vent not seen clearly. No primary moult. Disappeared too soon between the waves.
19 July was even quitter and was one of the quietest days I encountered this year. Usually there’s more to be seen, but today only the local terns, a Little Egret and a few Barn Swallows. I started at 06h30 but gave up at 12h30, also because there were so many showers and squalls, with south-easterly winds force 5 to 6. On this day, signal 3 was issued at 16h10 and the next day was predicted to be rather stormy.
20 July was a very good day but I failed to make it an epic day.
I started at 6am at the temple, expecting a storm. The sea was relatively calm and after 45 minutes I decided to go to the usual spot at Nam Kok Tsui, but was halted by heavy showers and strong squalls while on my way. So I wasted 2 precious hours. Weather was mostly rainly with showers and squalls. Winds blew from the east to southeast, force 4 to 6. Signal 3 was lifted at 13h20.
The winds looked like this:
9 Streaked Shearwater, to northeast and to southwest (so a double count can perhaps not be excluded - but I likely missed some as well)
3 Short-tailed Shearwater, to southwest
1 possible Wedge-tailed Shearwater
1 very likely Bulwer's Petrel
1 Red-necked Phalarope
About the possible Wedge-tailed Shearwater. It was seen during a shower, flying southwest and picked up a bit late. All-dark shearwater, but appeared stronger, larger than Short-tailed, and Streaked crossed my mind for a second as it was flying slow, with strong wingbeats. But certainly all-dark. Looked like to have a long tail.
About the very likely Bulwer’s Petrel. Too far to be sure. All-dark. Not flying in a particular direction, but rather flying around in more or less S-shaped patterns. Disappeared between the (not that high) waves regularly. No wingbeats seen. Flight vertically also in shallow S-shape, but never rising really high. Behaviour completely different in many ways from Short-tailed Shearwater, and it fits Bulwer's. But some useful characters like paler diagonal on upper wing and long tail not seen. Appeared slim, though, with narrow, pointed wings and wings held forward at carpal joint.
Too bad for not been able to identify the best birds, but if I would submit the sightings to the RC and describe what I've seen, they would probably not be accepted, and rightly so. Conditions were pretty challenging today, as well (to say the least). It was raining for hours on end, just too much of it.
But Bulwer's and Wedge-tailed are birds that we've been anticipating. There's still room this year for a next time, maybe.
21 July was again a pretty good day. Although I only birded from 06h45 until 14h45; it died down completely after 11am. There was some light rain at first, but it became dry afterwards. East to southeast winds, force 4 to 5.
22 July was my last day. I started at 06h15 and finished at 12h15. It was a fantastic day. Weather was just hot and sunny, southeast winds force 2. Nothing special.
149 Streaked Shearwaters, apart from the first single one (to northeast), all flew in groups to southwest. Two largest groups 31 individuals, 2 other large groups 24 and 21. First one at 07h00, last group (11) at 10h23. A new high count for Hong Kong.
1 Brown Booby
1 Parasitic Jaeger, pale morph adult or 4th calendar year
4 Little Terns
2 Common Terns
6 Greater Crested Terns, 3 pairs to northeast; one seen at close range and this was clearly a second summer bird.
And so that concluded this week’s seawatch survey, five days, two mornings and three whole or shorter days. This most probably also concluded surveys for July. We’ll be back in August.
This was more than a fantastic survey to me, but the toughest one as well. Just a real pity that I had to let go 3 possible vagrants, but it does illustrate the great potential of the Lema Channel during the summer.
Also very happy to confirm that Parasitic Jaegers remain here in summer, or at least they do during surveys in June and July. August remains to be seen. And Greater Crested Terns kept on coming through as well.
Interesting was that this was the first survey done by me before, during and after a storm signal 3 was in force. It was issued from Monday 19th 16h10 until Tuesday 20th 13h20. Not drawing any conclusions, but we can observe that the 2 days prior to signal 3, Sunday and Monday, were off-days with zero seabirds, except for the possible Sooty Tern/noddy spec. The day of signal 3, Tuesday, was (probably) THE day for rare seabirds (possible Bulwer’s and Wedge-tailed) and shearwaters. While the two days after signal 3, Wednesday and Thursday were still good to excellent days for shearwaters, but before 11h00.
Wrapping-up July below. There were only 10 observation days during this month, some half days.
165 Streaked Shearwaters (record high count of 149 on 22nd, no records in July pre-2021)
7 Short-tailed Shearwaters (no records in July pre-2021)
2 Brown Boobies (with one in June, 3 have been recorded this year, a record year)
59 Red-necked Phalaropes
10 Parasitic Jaegers (no records in July pre-2021)
21 Greater Crested Terns (presumed to be occasional in summer; including June, the total count is 51)
Plus the possible Bulwer’s Petrel, Wedge-tailed Shearwater and Sooty Tern/noddy spec.
July is supposed to be a calm month, maybe even a dead month for birding in HK. It is alive and kicking off Po Toi, for sure, although certainly not every day. It may be weather-related to some extent. Author: orientalstork Time: 30/07/2021 21:44
Maybe petrels were way commoner in Hk than we thought. Congratulations! Author: John Holmes Time: 5/08/2021 12:04 Subject: Summer Po Toi seabirding..
Really interesting set of records so far, Bart, and I’m looking forward to your August accounts, too ! Author: badesc Time: 6/08/2021 16:06
3 to 5 August
August started with this relatively small weather system:
It was tropical storm Lupit that moved northeasterly and passed Hong Kong during this survey.
So 3 August was the first day of another short survey and thus the first for August. The weather was okay: rain and showers, but also long dry periods. Visibility was limited, as seen from this photo, normally you’d see the Dangan islands:
Winds blew from the southeast, force 5. I watched from 11h45 until 17h45. At 16h25 the Hong Kong Observatory issued storm signal 3: it gave me good hope that the next day would see strong southerly to easterly winds, but the signal was withdrawn at 04h20 in the morning of 4 August. But let’s first look at the 3rd, which was not a bad day to start the month.
1 immature Lesser Frigatebird, circling above Southern Hong Kong Waters, south of Lamma Island at 12h45
1 Red-footed Booby, to north at 14h15
2 Red-necked Phalaropes, to northeast
2 Whimbrels, to northeast
1 Common Sandpiper present
3 Greater Crested Terns, to west
2 Caspian Terns, to west
3 Himalayan Swiftlets, to northeast.
On 4 August the wind was a lot less and coming from northerly directions. The storm had passed overnight, alas. The weather was mostly dry, a bit of rain but heavy showers at the end of the day. Northerly winds, force 2 (mostly) to 4/5.
There was good passage of terns throughout the day, indicating the autumn migration has started.
3 Streaked Shearwaters, 1 group flying west at 07h52
Bridled Terns; some in mixed groups with other species to west, so I’ll start counting them next time
29 Greater Crested Terns, flying west, amongst them at least 7 juveniles
26 Common Terns, flying west (1 flying to northeast)
2 Roseate Terns, flying west
1 Black-naped Tern
24 tern spec, flying west
3 Little Egrets, flying west
1 Grey Wagtail, flying over
6 Himalayan Swiftlets feeding for 2 hours near the rocks from 07h48, with 1 House and 1 Pacific Swift; c8 Himalayan Swiftlets at 11h50, so total count at least 8.
5 August was an even better day for terns, but not any seabird was seen. I was present from 06h15 until 13h00. The weather was cloudy, dry, with a few rainy periods. Winds were blowing from the northwest (indeed not ideal for seabirds), force 4 to 5.
Quite a few left unidentified
1 Grey Plover
This short survey, three days with one afternoon, one morning and one full day, again produced very enjoyable birding with tubenoses, a rarity (the booby) and good passage of terns. I can once again only conclude that the Lema Channel and Southern Hong Kong Waters are a terrific birding area; every single survey since the end of April this year produced good birds/numbers. There certainly have been (a few very) quiet (half) days but the survey of always (at least) three days turned out to be great.
Interesting was the somewhat sudden start of the autumn migration of terns. During the previous survey (18-22 July) migrant species like Common Tern and Greater Crested Tern were still moving mostly to the northeast, but now almost all of them were flying west.
Additionally, some remarks on the direction of migrants. In spring and in June/July the ones that are heading to northern breeding or wintering (e.g. Short-tailed Shearwaters) grounds fly east-northeast to northeast and they are coming from west-northwest to west. The autumn migrants actually fly west, not really southwest. In both cases, birds seem to bent their route around Nam Kok Tsui. I have actually not been able to see migrants and seabirds flying along a southwest-northeast-axis, illustrated with the red line on the illustration below. It’s more a west-east-axis, the green line, which also does not seem to be straight.
It’s puzzling to me that birds coming from the north-northeast to east-northeast don’t fly straight to the southwest, but turn around Po Toi to head westwards. But of course, birds that are flying very near the Lema islands can not be seen from Po Toi, as the distance is at least 11 km.
In spring, it seems that all migrants and seabirds likely fly to the north almost up the Pearl River, then probably make a turn to the east, flying between the cluster of Chinese islands southwest to Lantau Island, and then approaching Po Toi from between Shijao and Lamma Island, while turning northeast but chose to round Po Toi and not fly between Beaufort Island and Hong Kong Island (and pass Cape D’Aquilar). So their route is not straight, but likely with quite some bends and curves.
Also interesting is that 3 of the 4 boobies I’ve seen flew along the same north-south-axis.
Two Brown Boobies (one flying south, the other flying north) and one Red-footed Booby flew in the same area, roughly 1 to 3 kilometers off Nam Kok Tsui, along that axis. It’s like we have a booby lane there ;-).
Note that there are three main watchpoints, consisting of different rock ‘platforms’ of different heights: one facing (roughly) southeast to northwest (the western watchpoint), one facing southwest to northeast (the eastern watchpoint) and one facing northwest to east (the southwestern watchpoint). Where to sit depends on the wind force (safety first!), direction and the height of the waves and where birds are mainly coming from. Species like most boobies and all Lesser Frigatebirds were seen from the western watchpoint and might not have been visible from the other watchpoint. So I certainly regularly miss birds.
In spring there has proven to be a peak of migration between 6 and 8 or 9 o’clock in the morning. It was similar in this few early autumn migration days during the above survey, but migrants did continue to pass after this peak period. Noticeably on 4 August, there also was a peak in tern movement in the late afternoon hours. So basically, I think the best strategy is to spend all day at Nam Kok Tsui, as migration just continues from early morning to late afternoon/early evening. Note that boobies also have appeared outside the peak periods, at 10h08, 10h39, 13h15 and 14h15.
16 and 17 August
NB.: there was an error with the checklists from eBird, because the “.” to end the sentence was included in the weblink. It has been removed everywhere.
Although the weather & wind conditions were probably not very favorable for true seabirds (absence of fresh to strong easterly winds), I still wanted to do a short survey in the middle of the month. Seabirds were indeed completely absent, but the survey turned out to be pretty good for migrating terns.
On 16 August the weather was cloudy, dry, with also some sunshine. Winds from the east with force 2 in the morning and from the south-west force 3 in the afternoon. A fairly flattish sea.
I started in the morning at 6 o’clock and instantly there was a stream of terns flying west. A total of 1,015 were counted when I finished at 18h15.There was clearly a peak between 06h00 and 08h00. Then sporadic passage until around noon, when the terns flew-by on a more regular basis, and then also a peak again in the late afternoon.
With low or no waves, I tend to sit at a lower elevation. Here facing the east Dangan Islands.
327 Bridled Terns (only counted the ones that flew to the west), with quite a few juveniles now
310 terns spec.
219 Common Terns
81 Roseate Terns
71 Greater Crested Terns
4 Aleutian Terns
3 Black-naped Terns
17 August was even hotter and sunnier than the day before, with almost clear blue skies. Winds were still blowing from the south-west, with force 2 to 3.
Tern movement was better than yesterday, as I stopped counting at 13h15 to catch the ferry in time. A total of 893 terns were counted up to then.
So this was a very short survey, one whole day and one long morning, with a total of 19 hours and 30 minutes of observation time.
The tern movement clearly stood out and I guess that’s just a normal event off Po Toi, actually. Still, 1,908 individuals is a nice count to make, certainly in the absence of seabirds. Many flew very far out, hence the large number of tern spec.
How do I count? Since recently, I use a voice recorder and that allows me to record every count while keeping my eye on the eyepiece of my scope. It’s an improvement compared to writing down the numbers in a paper notebook.
The last survey of the summer (June, July and August).
The afternoon of 26 August was mostly sunny, but winds came from a good direction, east to southeast, with force 3 to 4. The survey took a slow start, without any seabirds. All migrants flew to the west.
1 Black-winged Stilt
3 Eurasian Curlews
4 Common Redshanks
27 August was a pretty dreadful day, weather-wise. The weather forecast two days earlier was “Sunny intervals and a few showers. Isolated thunderstorms later.”. The actual weather on 27th was one thunderstorm after another, with very heavy rain and strong squalls. A few photos of it below.
28 August was the best day, with lots of terns on the move. I counted 728 in only 5 and a half hours, so there might have been another 1,000 or so for the whole day. The morning saw mostly sunny weather and no rain (thunderstorms after the survey).
8 white egrets spec.
4 jaegers spec.
1 1st CY Black-tailed Gull
348 tern spec.
300 Common Tern
33 Greater Crested Tern, of which 3 flying northeast
27 Bridled Terns
16 Aleutian Terns
1 Black-naped Tern
So that concludes this 3-day survey, one full day and two half days.
Terns were the main migrants again. I do feel they are more comfortable migrating during calmer weather, with not much or no rain. Thunderstorms seems to hold them back. But approaching thunderstorms do push the few ones that are still flying, towards Po Toi.
Also, it seems that birds are more far out when migrating west than when migrating northeast in spring, but that finding will have to be confirmed in subsequent autumn surveys.
Of further interest was the very first bird on 26th, during a short sprinkle. It was an all-dark, apparently blackish rather smallish bird flying low over the waves on very smooth, somewhat tern-like wingbeats and not in a perfectly straight line to the west. My first thought was a (Swinhoe’s) storm petrel, but it was far out and I was struggling with my umbrella and alas lost it too soon.
A too bad of an observation to report, actually (although no other species come to mind), but I mention it here, because a certain Swinhoe’s Storm Petrel was seen by many and photographed on a pelagic trip just a few days later, on 29 August (see John Holmes' blog https://johnjemi.blogspot.com/20 ... ong-kong-ticks.html). I was lucky to see it from the boat as well and it flew about 3 kilometers off Nam Kok Tsui. So, from there, it probably would have looked pretty much like the bird on the 26th. But at least it points to some Swinhoe’s that migrate through Hong Kong waters at the end of August. Furthermore, an all-dark storm petrel – and most likely Swinhoe’s as well – was seen on 30 August 2000 on a pelagic off the coast of east Lamma Island (actually also along the presumed flyway of seabirds described in an earlier post above; I will come back to that in a later post).
As hundreds of Swinhoe’s pass through the Singapore Straight in September, it is not that much of a surprise that some also move through Hong Kong waters by the end of August and perhaps also during early September. However, easterly winds might increase this possibility, or might even be a necessity to see them here. So this time might actually be better to find them in Hong Kong than during the end of May.
I reckon there is a chance that more attention will be paid for autumn seawatching and pelagic trips and as a result more Swinhoe’s might be encountered. Who knows that the status as a rare vagrant will be removed in a couple of years and changed to a rare but annual autumn migrant?
Let’s wrap-up August. There were only 8 observation days during this month, including some half days.
Terns seems to be the main migrants throughout the month and most of them were Common Terns, 884 were seen on the three surveys. (Most tern spec. were probably Common Terns as well.) But also Greater Crested Terns passed-by in good numbers, totaling 255. Interesting is what seems to be the peak for Roseate Terns around the middle of the month, with a total of 95 on two survey-days. By the end of the month, they were absent (at least I haven’t seen any).
For seabirds, it was a calmer month, with 1 Lesser Frigatebird, 1 Red-footed Booby, 3 Streaked Shearwaters, and 1 Parasitic and 5 jaegers spec. at the end of the month. There were no typhoons encountered during August 2021.
Summarizing the summer of 2021 will be for a later post. Author: badesc Time: 7/09/2021 10:15
Summary of summer 2021
This is an overview of all seabirds, terns and gulls seen during the summer (i.e. June, July and August) of 2021. Below are the totals for the whole season. Colours indicate wind direction and force.
There were 25 survey-days in the summer, but many of them only half days. 2 surveys in June, 3 in July and 3 in August. It is consistent with the goal to do 2 to 3 surveys per month.
Only one close-by tropical storm was encountered (typhoon Cempaka), with the storm signal raised to 3 by The Observatory while surveys where performed. Concerning wind direction and force, I can’t really find ‘golden rules’ or anything that guarantees the passage of a certain species of seabird.
For example, Streaked Shearwaters have been seen – although in very different numbers – during the following wind conditions (number of individuals in parentheses):
South to southwest, force 3 to 4 (1)
East to southeast, force 1 to 2 (149)
East to southeast, force 3 to 6 (9)
East to southeast, force 4 to 5 (7)
North to northeast, force 2 to 5 (3)
So on days with light winds, strong winds, coming from the north to coming from the south.
But overall, the period around the tropical storm (20-22 July) saw a noticeable peak in the numbers of Streaked Shearwaters, Short-tailed Shearwaters and Red-necked Phalaropes. During these days, the very likely Bulwer’s Petrel and possible Wedge-tailed Shearwater passed-by as well, making such weather patterns worthwhile for seawatching, and for bringing seabirds closer to shore. The latter is of course well known in Hong Kong.
What seems to be obvious, is that terns prefer calmer, and especially dry weather to migrate. Shearwaters don’t care the rain, they’ll fly right into a thunderstorm.
Some totals of birds migrating off Po Toi this summer that are interesting:
As stated before, the summer is a pretty decent period for (sea)birds off Po Toi. We probably don’t have enough data to conclude exactly which trends there are, but seabirds appeared throughout the summer, as did terns in small numbers during June and July. From early August onwards, terns started moving west and their numbers clearly increased towards the end of the month. By the way, a total of 3,293 terns were counted during the summer, making them by far the most numerous family here (Bridled Terns were only counted from 16 August onwards and only the ones that flew west and were likely migrants).
Looking forward for the usual 2 to 3 surveys a month in the autumn…