16 to 20 May
May is one of the best months for seawatching on Po Toi. So we planned another survey, in the third week of the month. We were there last year during the same time, so it would additionally be interesting to compare both years.
That May is a good month, was immediately illustrated by an excellent start of the survey on
16 May, even when we watched just for half a day (and missing the busy morning hours). We counted migrants from 11h40 until 18h10. It was quite a dull, cloudy day, with some drizzle or light rain. Visibility was only about 3 km around noon, but we had clear views in the afternoon. Winds were blowing from the southeast, with force 2, slightly increasing to 3.
Seabirds:
147 Red-necked Phalaropes
3 Parasitic Jaegers
1 Bulwer’s Petrel
1 shearwater spec.
2 Streaked Shearwaters
38 Short-tailed Shearwaters
Egrets and herons:
13 egrets spec.
Ducks:
1 duck spec.
Gulls:
1 Slaty-backed Gull
Terns:
110 terns spec.
40 Bridled Terns
13 Aleutian Terns
14 Little Terns
7 Gull-billed Terns
402 White-winged Terns
6 Whiskered Terns
1 Black-naped Tern
162 Common Tern
40 Greater Crested Terns
Swift(lets), swallows and martins:
6 Barn Swallows
Checklist on eBird:
https://ebird.org/checklist/S139063785
Count on Trektellen:
https://trektellen.nl/count/view/3323/20230516
17 May wasn’t a bad day either, and we could watch from 05h50 until 17h45. The weather was mostly cloudy, but with sunny periods in the afternoon. There was basically no wind when we started, but a southeasterly wind gradually increased to force 3 by noon and decreased to 2 in the afternoon.
Seabirds:
117 Red-necked Phalaropes
3 Parasitic Jaegers
2 jaegers spec.
1 Bulwer’s Petrel
2 Streaked Shearwaters
38 Short-tailed Shearwaters
Egrets and herons:
17 egrets spec.
Gulls:
1 Black-tailed Gull
Terns:
80 terns spec.
29 Bridled Terns
14 Aleutian Terns
21 Little Terns
1 Gull-billed Tern
102 White-winged Terns
1 Whiskered Tern
9 Roseate Terns
10 Black-naped Terns
222 Common Terns
85 Greater Crested Terns
Swift(lets), swallows and martins:
1 swift spec.
1 Barn Swallow
Passerines:
1 Eastern Yellow Wagtail
Checklist on eBird:
https://ebird.org/checklist/S139065198
Count on Trektellen:
https://trektellen.nl/count/view/3323/20230518
You could say we had seen the best days of the survey and the party was over on
18 May. Nevertheless, we seawatched from 05h45 until 16h45. Again, mostly cloudy, but with lengthy attempts for sunshine. Visibility was limited to less than 3 km throughout the day. Winds had turned to the southwest, with force 1, increasing to 2 in the afternoon.
Seabirds:
37 Red-necked Phalaropes
1 Streaked Shearwater
3 Short-tailed Shearwater
1 Brown Booby
Egrets and herons:
9 egrets spec.
10 Little Egrets
Terns:
12 terns spec.
12 Bridled Terns
1 Sooty/Bridled Tern
1 Little Tern
25 White-winged Terns
8 Roseate Terns
41 Common Terns
9 Greater Crested Terns
Swift(lets), swallows and martins:
2 Barn Swallows
Checklist on eBird:
https://ebird.org/checklist/S139064328
Count on Trektellen:
https://trektellen.nl/count/view/3323/20230517
And
19 May saw even less migrants. We started at 05h50, but finished at 13h30, after witnessing an empty sea during the last hours of the seawatch. Still some cloudy periods, but now mostly sunny, with limited visibility, between 2 and 4 km. Hardly any wind: force 1 from the southeast.
Seabirds:
8 Red-necked Phalaropes
1 Short-tailed Shearwater
Terns:
2 Little Terns
5 Gull-billed Terns
1 Black-naped Tern
2 Common Terns
5 Greater Crested Terns
Swift(lets), swallows and martins:
1 House Swift
Checklist on eBird:
https://ebird.org/checklist/S139065485
Count on Trektellen:
https://trektellen.nl/count/view/3323/20230519
And there was no change for the better on
20 May, our last day. We started early again, at 05h50, but finished at 10h20. Sunnier now with only some scattered clouds. Still not much wind, with force 1 to 2 from the southeast.
Seabirds:
2 Short-tailed Shearwaters
Terns:
5 terns spec.
20 Bridled Terns
6 Aleutian Terns
4 Little Terns
2 Gull-billed Terns
10 White-winged Terns
4 Roseate Terns
36 Common Terns
8 Greater Crested Terns
Swift(lets), swallows and martins:
4 Pacific Swifts
1 Barn Swallow
Checklist on eBird:
https://ebird.org/checklist/S139065975
Count on Trektellen:
https://trektellen.nl/count/view/3323/20230520
Remarks
Well, that was a pretty good survey, as the month of May lived up to its reputation. Quite a few remarks to make.
Starting with record counts of Short-tailed Shearwaters on both 16th and 17th. We could only start seawatching on 16th from 11h40 and one of the first birds that appeared almost as soon as we started watching, was this species. A total of 38 was counted during this half day, a new high count for Hong Kong. The previous high count was 18 on 7 May 2022. Coincidently, we counted exactly 38 Short-tailed Shearwaters on the next day (17th) as well, but during a full day (11 hours and 55 minutes). Interesting, we counted half of that number – 19 – before 12pm and half after 12pm. I don’t claim we should double the count on 16th to 76, but with a very high degree of certainty can we say that a lot more than 38 passed Po Toi that day, probably between 50 and 80.
The sighting of more Bulwer’s Petrels, singles on 16th and 17th, is further confirmation that this is a scarce passage migrant and visitor to Hong Kong waters. May might be the best month to see them, and you don’t need a typhoon or even strong onshore winds.
Why have they not been seen from boat trips, you might wonder? Note that boat trips generally arrive off Po Toi around 8h15 and leave at around 13h00, depending on the routes they take. Below is a list of the times we’ve seen Bulwer’s Petrels while seawatching from Po Toi, plus one we saw from a boat (though not part of the organized seabird trips):
07h25
07h54
08h15
13h14
13h22
14h22
15h05
15h39
Indeed, we’ve never seen one between 08h15 and 13h14 either, exactly when the boats are in the area. Maybe we don’t have enough data to draw conclusion, but at least this seems interesting.
The Slaty-backed Gull on 16th is a new late date for Hong Kong, the previous late date being 22 April (source: Annotated Checklist of Hong Kong Birds July 2022). Although the bird clearly had the big and bulky appearance typical for this species, it was only after checking some more literature at home that I was sure of its identification: Third-winter/4th calendar year. Large and very bulky gull, heavy-bellied. Wings and back dark-grey; darker grey saddle, some brown tinge on the wings and clear sign of wing moult. Head whitish. Tail still with quite full dark markings.
Also on 16th, we counted 402 White-winged Terns. This is the highest count since we started our surveys in 2021, but the highest count ever on Po Toi was 490 on 5 May 2006.
On 18th, a very likely adult Sooty Tern flew by (see full comments on eBird or Trektellen). Most Sooty Terns in Hong Kong are juveniles. Although there are a few sightings of adults, both the Bird Reports and the Annotated Checklist mention “only juveniles”. Anyway, we should be more alert to adults, even on days with calm weather.