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Subject: Po Toi Seawatch Spring 2021 [Print This Page]
Author: badesc    Time: 26/07/2021 13:56     Subject: Po Toi Seawatch Spring 2021

Introduction

After a young and enthusiastic American birder, Samuel Baxter-Bray, invited me to join him for birding on Po Toi in spring, I have returned several times since. My main focus has been and will continue to be seawatching, from Nam Kok Tsui, the southernmost tip of the island.

I use both 10x bins and a 20x-60x telescope.

I report the seawatch surveys that I have conducted here. These are mostly irregular visits to the island, so no lengthy stays. These are an addition to the pioneering work Geoff Welch has done over many years (2006-2012 and posted on this forum), on a much more regular base and including landbirds.
Author: badesc    Time: 26/07/2021 14:00

Last Week of April

I started, then with Sam, on 27, 28 and 29 April.

From the ferry Aberdeen – Po Toi I encountered 2 Greater Crested Terns on the 27th (full checklist on eBird: https://ebird.org/checklist/S86702044).

The very first seawatch session took place on that day from 16h15 to 18h00. The weather was cloudy with limited visibility (unable to see the Dangan islands across the Lema Channel). A through of low pressure brought unsettled weather to South China coastal waters. Wind east to southeast, force 4 to 5.
All birds flew to the northeast, unless otherwise mentioned.

Of most interest were:
1 Short-tailed Shearwater
4 Greater Crested Terns
20 White-winged Terns

(https://ebird.org/checklist/S86632092).

The next day, 28 April, was very good – at least for me, as a starter on seawatching off Po Toi. Weather was cloudy with limited visibility again (unable to see the Dangan islands). A through of low pressure brought unsettled weather to South China coastal waters. Wind east to southeast, force 4 to 5. Seawatching in the morning from 06h00 to 09h30 and in the afternoon from 15h30 to 18h30. Good passage of mainly terns. Birds were more far out in the afternoon and most terns unidentifiable.

Seabirds:
10 Short-tailed Shearwaters, 6 during the morning session, 4 during the afternoon sessions. All singles, except two together in the afternoon.
5 Parasitic Jaegers, 2 during the morning session, 3 (2+1) during the afternoon session. All birds adult-type and pale morph.

Waders:
150 Black-tailed Godwits, one group in the morning session.
8 Curlew Sandpipers, one group in the morning session.
63 Red-necked Phalarope, 22 during the morning session, 41 during the afternoon session.
1 Oriental Pratincole, during the morning session.

Terns:
5 Bridled Terns, only during the morning session.
4 Aleutian Terns, only during the morning session. Probably more, but too far to ID with certainty.
30 Little Terns, 26 during the morning session, 4 during the afternoon session.
7 Gull-billed Terns, one group during the morning session.
18 White-winged Terns, 8 during the morning session, 10 during the afternoon session.
3 Whiskered Terns, only during the morning session.
22 Black-naped Terns, only during the morning session.
13 Common Terns, 2 during the morning session, 11 during the afternoon session. Probably more, but too far to ID with certainty.
61 Greater Crested Terns, 14 during the morning session, 47 during the afternoon session. A good number.
335 unidentified terns

Also 3 Grey-faced Buzzard in one group coming from the south.

The checklist is here: https://ebird.org/checklist/S86701394.

The following day, 29 April, was the opposite. We now had clear views (able to see the Dangan islands very well), with some rain and dry periods. A northeasterly airstream was affecting the South China coastal waters. Winds north to northeast 4-5. Basically no movement of (sea)birds. I seawatched from 06h00 to 07:10 only.

Waders:
75 Red-necked Stints, one group.
Some Red-necked Phalaropes, but probably some birds staying around, as there were flying in different directions and frequently landed on the sea.

Terns:
Only 2 local Black-naped Terns and 1 unidentified tern.
That’s all for April. May will be next.

[ Last edited by badesc at 7/08/2021 07:56 ]
Author: badesc    Time: 26/07/2021 14:18

May

In May, I did two surveys: from 9 to 15 and from 25 to 27.
Author: badesc    Time: 26/07/2021 15:15

9 to 15 May

9 May was the first afternoon and there was not much migration going on.

Most noteworthy were only a few terns, Bridled, White-winged and Black Naped: https://ebird.org/checklist/S88361037.

10 May was a lot better. I watched from 05h30 until 10h00 and from 15h30 until 18h30. These are generally the peak hours for migration, although I changed my strategy later. It was dry with clear views and winds blowing from the south, force 3 to 4.

Seabirds:
3 Short-tailed Shearwaters
1 Parasitic Jaeger

Waders:
1 Grey Plover
5 Red-necked Phalaropes

Terns:
211 Bridled Terns, but likely some double counts from local birds
9 Aleutian Terns
9 Little Terns
68 White-winged Terns
24 Whiskered Terns
2 Roseate Terns, local birds
5 Black-naped Terns, local birds
15 Common Terns
4 Greater Crested Terns

That’s 9 species of terns, which is not bad. All birds flew to the northeast, except for some local ones. Here is the checklist: https://ebird.org/checklist/S88361522.

10 May was a similarly good and enjoyable day, with very similar weather conditions. Hours ‘on duty’ were also similar, from 05h30 until 10h30 and from 15h30 until 18h00.

Seabirds:
1 Parasitic Jaeger
3 Short-tailed Shearwaters

Waders:
13 Red-necked Phalaropes

Terns:
220 Bridled Terns (likely double counts from local birds)
4 Aleutian Terns
5 Little Terns
3 Gull-billed Terns
60 White-winged Terns
18 Roseate Terns, migrants this time
23 Black-naped Terns
11 Common Terns
6 Greater Crested Terns

Again, 9 species of terns.

Furthermore, 3 Eastern Cattle Egrets and 2 Black Drongo’s were seen on migration. Here is the checklist: https://ebird.org/checklist/S88438936.

12 May was a rather quiet day, although the same weather conditions persisted. I watched from 05h30 until only 09h00, because of a lack of migrants, and again from 15h45 until 18h00.

Seabirds:
2 Short-tailed Shearwaters, during the morning hours.

Terns:
328 Bridled Terns (double counts likely)
2 Gull-billed Terns
53 White-winged Terns
7 Black-naped Terns, local birds
11 Common Terns
10 Greater Crested Terns

Here’s the checklist: https://ebird.org/checklist/S88441171.

13 May was again a better day. I watched drom 05h45 until 09h30 and from 15h30 until 18h00. Weather was still same: dry, clear views, winds from the south, force 3 to 4.

Seabirds:
5 Parasitic Jaegers
2 Short-tailed Shearwaters, on in the morning and one in the afternoon

Waders:
9 Red-necked Phalaropes

Terns:
281 Bridled Terns (double counts likely)
77 White-winged Terns
4 Whiskered Terns
3 Roseate Terns
7 Black-naped Terns
23 Common Terns
8 Greater Crested Terns

Here’s the checklist: https://ebird.org/checklist/S88441712.

14 May was especially good for White-winged Terns. Weather was still the same. Watched from 05h45 until 10h00 and from 15h45 until 18h00.

Seabirds:
3 Short-tailed Shearwaters, 2 in the morning, one in the afternoon

Waders:
4 Red-necked Phalaropes

Terns:
198 Bridled Terns (likely double counts)
3 Little Terns
176 White-winged Terns, with the largest flock 130 individuals
11 Roseate Terns
11 Black-naped Terns
1 Common Tern
5 Greater Crested Terns

Also 1 Great Egret and 1 Eastern Cattle Egret on the move. Here’s the checklist: https://ebird.org/checklist/S88442519.



15 May was the last day of this survey and I watch only a half day, from 05h45 until 09h30. I left too early, as a Red-footed Booby was seen by Ivan from a boat nearby.

Seabirds:
3 Short-tailed Shearwaters

Waders:
16 Red-necked Phalaropes

Terns:
Bridled Terns, probably mostly local birds, so stopped counting
1 Little Terns
1 Gull-billed Terns
30 White-winged Terns
6 Roseate Terns
6 Black-naped Terns
5 Common Terns

Here’s the checklist: https://ebird.org/checklist/S88443104.

During this survey, a total of 12 sessions were done on seven days, every morning and every late afternoon, for a total of 39 hours and 45 minutes. More hours might have produced slightly better results, and that would certainly be the case with more observers. A lone observer always misses birds; a minute without attention and a seabird or a group of terns might pass-by unrecorded.
Total for migrant seabirds and terns (so no Bridled Terns and some numbers of some other terns):

16 Short-tailed Shearwaters; quite a few very close to the seawatch point; seen every morning and on some afternoons; status might maybe be more like “scarce but regular spring passage migrant”, instead of “uncommon spring passage migrant”, but these are thoughts for later.
7 Parasitic Jaeger; all adults light phase, some chasing terns along the way

47 Red-n Phalaropes

26 Black-naped Terns
13 Aleutian Terns
18 Little Terns
29 Greater Crested Terns
6 Gull-billed Terns
66 Common Terns
27 Roseate Terns
466 White-winged Terns
28 Whiskered Terns

10 tern species in total

Even in the absence of any rarity or large numbers of seabirds, this survey was very enjoyable to me, every day. Could really be much better on days with appropriate weather.

[ Last edited by badesc at 7/08/2021 07:58 ]

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Author: orientalstork    Time: 26/07/2021 21:58

I head that you saw quite a few brown boobies and big amounts of streaked shearwaters. Since those records were only from po toi, it might be possible that more are passing through HK, unnoticed. Is it possible that their numbers are increasing in HK?
Author: badesc    Time: 27/07/2021 07:56

Quote:
Original posted by orientalstork at 26/07/2021 21:58
I head that you saw quite a few brown boobies and big amounts of streaked shearwaters. Since those records were only from po toi, it might be possible that more are passing through HK, unnoticed. Is i ...
Yes, I think you’re right that a lot passes through HK unnoticed. Numbers will increase if the amount of seawatching increases. I know of no reason why the numbers, seen or unseen, are increasing. It’s just that we notice more if we are on the lookout more.
Author: wcaptain    Time: 28/07/2021 09:42

Author: badesc    Time: 28/07/2021 20:16

25 to 27 May

This was a shorter survey again, on 3 days; 2 afternoons, 2 mornings.

25 May was only a half day birding, but as I said earlier, I changed my strategy and now birded a longer period in the afternoon, from 14h00 until 18h30. Weather was clear and dry with force 2 to 3 winds from the south.

Seabirds:
1 Short-tailed Shearwater

Gulls:
1 Heuglin’s Gull, a 2nd calendar year bird, a very late and unexpected sighting

Terns:
Bridled Terns, probably all or mostly locals
14 White-winged Terns
Roseate Terns, locals
Black-naped Terns, locals
7 Common Terns

Here’s the checklist: https://ebird.org/checklist/S89179526.

26 May saw similar weather, but the wind force increased to 3 to 4. On this day also, I birded longer than I did during previous surveys: from 06h00 until 11h00 and again from 14h00 until 18h00.

Seabirds:
3 Short-tailed Shearwaters, during the morning
1 Lesser Frigatebird, immature
1 Parasitic Jaeger, this time a dark morph individual

Terns:
Bridled Terns
Black-naped Terns
13 Roseate Terns, only 3 considered to be migrants
3 Common Terns

And also 1 Pacific Swift. Here's the checklist: https://ebird.org/checklist/S89179662.

27 May was a half day for me, as I left in the afternoon. Weather was same as yesterday, with winds from south to southwest. I watched from 06h00 until 11h00.

Seabirds:
1 Swinhoe’s Storm Petrel. Storm petrel with dark rump, light carpal bar, forked tail, brownish plumage. A 12-page Unusual Record Form has been submitted to the Records Committee. Very interesting was that the bird came from the northeast at 08h56, flew into Hong Kong Southern Waters and then returned at 09h51 to the northeast. On the way in, it flew in a slow and relaxed manner, as if it was looking for food. On the way out it flew faster and more decisive. See further comments below.
1 Short-tailed Shearwater

Here’s the checklist: https://ebird.org/checklist/S89179772.

It was to be expected that there would be much less migration on the 3-day survey, but there was a chance to see something more unusual or even rare. This was indeed the case, with an immature Lesser Frigatebird and a Swinhoe’s Storm-Petrel. Geoff Welch and I have talked about Swinhoe’s Storm-Petrel and I was deliberately looking for it. I’ve shared my thoughts with some people that I believe that Swinhoe’s Storm Petrel and Bulwer’s Petrel should pass through HK waters from time to time (like once a year or every two years), they are too close to never appear here. But I was still surprised to see a Swinhoe’s on my very first end-of-May survey.







I’d like to come back on the behaviour of the bird. It did by no means appeared as a migrant, in which case it would have just flown straight to the northeast, like all other migrant tubenoses typically do. But the bird came from the northeast, flew around in a non-straight way into Hong Kong waters and returned to the northeast about one hour later.

The below links offer various studies on storm petrels and what distances they travel while looking for food during their breeding season, in particular the incubating period. Some species have been reported to travel over a 1,000 km!

https://www.int-res.com/abstracts/meps/v668/p121-132/
https://www.birdguides.com/artic ... -uks-storm-petrels/
https://twitter.com/SeabirdEcology/status/1419808574180634629
https://onlinelibrary.wiley.com/doi/abs/10.1111/jav.00361

As Swinhoes’ Storm Petrel have been reported to breed around Nan’ao Island, which is a mere 330 km from HK, a foraging bird coming to here is a serious possibility. Even birds that would breed further than that could easily make their way to HK and back, which would not be that abnormal for a storm petrel.

This could (more research is required) mean that they indeed visit HK more often than known. Of course, the incubating time should be around the end of May to support this theory of the observation on 27 May.

One seen as a migrant could then pass-by around half May or so, but most probably there should be strong south or south-easterly winds. That winds were not strong at all on 27 May, further indicates a non-migrating bird and thus much more likely a ‘nearby’ breeder. And by the way, are we sure there are no colonies on any more nearby small islands in China?

Note that Geoff also reported a Swinhoe’s off Po Toi at the end of May (30 May 2012, see http://www.hkbws.org.hk/BBS/viewthread.php?tid=16569), and this bird also flew in the ‘wrong’ direction.

Back to the 3-day survey. Of further interest were – again – daily Short-tailed Shearwaters. If extrapolating all my observations in May (16+5) and adding those of April (11), one could argue that at least 50 to possibly 100 Short-tailed Shearwaters pass through HK waters in spring. Or was this an exceptionally good spring? We’ll see again next year.

One very late (*) and dark morph Parasitic Jaeger was noteworthy as well.

We also saw a batch of migrating terns, with very small numbers of Common, Roseate, White-winged and Greater Crested.

(*) Future surveys have proven this was not a late record at all…

[ Last edited by badesc at 7/08/2021 07:58 ]

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