Tag Archive | Arctic Skua

Seawatching Ngor – September 2019

I count myself extremely lucky to live just a few minutes away from what must surely be one of the best seawatch sites in the world. What other capital can compete with Dakar on that front? It does make it hard not to go out there every day, especially at this time of the year when so many migrants can be seen from this privileged spot. And I’m fortunate to have a very flexible work schedule that allows me to spend an hour or so counting seabirds before heading to the office! I’m obviously spending too much time at the Calao at the moment… but then again it’s always better being out birding in the field than sitting behind a desk (especially when The Field is a comfortable terrace, sat under a sun umbrella with a cup of decent coffee).

Anyway, time for the September numbers:

  • 25 days
  • 38 hours
  • 20,109 birds belonging to 36 species counted (total so far: 27,303 birds!)

This is a much better coverage than in previous years, and as a result the number of birds counted is higher for most species; Lesser Crested Tern is the main exception due to a later than usual passage, which only started properly at the very end of the month, picking up rapidly during the first few days of October (Sterne voyageuse).

As usual, here some of the highlights: good numbers of Manx Shearwater (also two possible Balearics… unfortunately too distant and poorly seen), and several Macaronesian Shearwaters including at least one that seemed right for Boyd’s (Puffins des Anglais et de Macaronésie). Sooty Shearwater passage was clearly more intense, or at least more visible, than last year, probably because of more favourable winds (Puffin fuligineux).

Numerous terns were counted of course, with the four most common species – Common & Arctic, Sandwich, Black Terns – accounting for nearly 90% of the twenty thousand birds counted this month (Sternes pierregarin et arctique, caugeks, Guifette noire). Roseates continued to pass through almost daily, up to 12 BPH (that’s birds per hour!), and so did Little Tern: with 304 birds in September, far more were seen than in previous years (and the passage continues: on 5.10 a total of 31 birds were seen in one hour, including a flock of 22) (Sternes de Dougall et naine). A Bridled Tern on the 4th is so far the only one of the season (Sterne bridée).

sandwichtern_ngor_20160925_img_5344_edited

Sandwich Tern / Sterne caugek, Ngor, Oct. 2016

 

September is also peak month for Sandwich Tern (Sterne caugek), which passes through daily in double or even triple digits (that’s BPH). The peak at the end of the month is clearly visible on this chart combining 2017 and 2018 data:

SandwichTern-Ngor_2017-18_chart

Hourly average number of Sandwich Terns per decad, 2017 & 2018

 

Now for some slightly more advanced data viz’ fun: I tried to find a clever way of visualising the intensity of bird migration at Ngor alongside wind speed and wind direction. The chart below shows average “BPH” per day as histograms (primary axis: number of birds) and wind speed as the dotted line (secondary axis: knots), while the colour represents the wind direction: dark green for WNW to N winds, pale green for SW to W winds, and orange for SSW to ENE. One would expect the highest number of birds during the favourable winds, i.e. higher wind speed from a WNW to N direction, and less so on days with little wind and/or with winds coming from the “wrong” side. That does seem to be the case on most days, but not always… though in general it’s fair to say that days with stronger NW winds usually see the highest number of birds, and also a higher diversity of species. Shearwaters, skuas, Sabine’s Gulls and most terns are largely influenced by these conditions, which can rapidly change from day to day or even within the same day. A good site to check out wind forecasts is Windguru.

BPH-Wind_Chart_September2019.JPG

Disclaimer: nothing scientific here, just fooling around with Excel!

 

Arctic Skuas continued to pass through on a daily basis, and Long-tailed Skuas were seen on 13 dates, mainly at the start and at the end of the month, with a max. of 61 birds in 2h15′ on the 4th (Labbes arctique et à longue queue). The four Catharacta skuas were seen in the last week of the month but as usual could not be identified down to species level (Great or South Polar Skua, Grand Labbe/Labbe de McCormick).

A usual, waders were fairly well represented this month: Whimbrel and Oystercatcher remain the most frequent migrants and thanks to the regular rains this autumn there has been a good diversity of waders in general, including my first Grey Plovers here and regular sightings of migrating Turnstones (Courlis corlieu, Huîtrier pie, Pluvier argenté, Tournepierre). Red Phalaropes were seen on five occasions in relatively modest numbers (Phalarope à bec large).

Oystercatcher_Ngor_20170930_IMG_4931

Oystercatcher / Huîtrier pie, Ngor, Oct. 2017

 

Table with September totals for 2019, 2018 and 2017:

Species

2019

2018

2017

Cory’s/Scopoli’s Shearwater 2 0 0
Sooty Shearwater 271 87 393
Balearic Shearwater 0 0 1
Manx Shearwater 98 6 60
Boyd’s/Barolo Shearwater 9 16 1
Shearwater sp. 51 22 34
Storm-Petrel sp. 1 0 0
Northern Gannet 0 1 1
Brown Booby 0 4 3
Oystercatcher 51 20 16
Whimbrel 211 75 78
Eurasian Curlew 0 0 2
Bar-tailed Godwit 4 1 8
Grey Plover 2 0 0
Common Ringed Plover 0 2 0
Turnstone 33 2 0
Dunlin 0 0 40
Sanderling 12 0 25
Little Stint 1 0 0
Common Sandpiper 1 0 0
Greenshank 1 0 0
Common Redshank 3 1 1
Grey (Red) Phalarope 163 133 1
Audouin’s Gull 21 1 3
Lesser Black-backed Gull 1 15 1
Kelp Gull 1 0 0
Large gull sp. 1 5 0
Slender-billed Gull 6 1 1
Grey-headed Gull 0 1 2
Sabine’s Gull 95 43 123
Arctic/Common Tern 11,161 4,100 4,500
Roseate Tern 144 89 35
Little Tern 304 57 76
Sandwich Tern 2,425 2,080 1,928
Lesser Crested Tern 61 147 95
African Royal Tern 295 305 219
Caspian Tern 10 13 19
Black Tern 3,870 2,187 2,342
Sooty Tern 0 1 0
Bridled Tern 1 0 0
Great/South Polar Skua 4 1 2
Pomarine Skua 13 5 35
Arctic Skua 400 172 142
Long-tailed Skua 215 265 59
Skua sp. 167 64 226
Total birds 20,109 9,922 10,472
Number of days 25 17 15
Number of hours 38h35′ 24h50′ 20h30′

 

In addition to the seabirds, as usual a few other species were noted on active migration: a Purple Heron on 10.9 and more surprisingly two Squacco Herons the next day coming from out at sea. Common Swifts were spotted on at least three occasions (max. 66 on 11.09, migrating low over the ocean), while a Hoopoe was seen on 8.9 and a Sand Martin on 12.9 (Heron pourpré, Crabier, Martinet noir, Huppe fasciée, Hirondelle de rivage). What appeared to be a juv. Barbary Falcon was seen several times from 4 – 12 Sept., with a Peregrine also here on 9th (Faucons de Barbarie et Pèlerin). This provided for some action as both birds were regularly seen hunting pigeons and other birds; on the 6th it was a juv. Common Cuckoo (or at least I assumed it to be this species and not African Cuckoo) which was seen coming on land from Ngor island or islet, chased by the Barbary Falcon only to disappear into the Calao gardens and never to be found again… (Coucou gris).

PurpleHeron_Ngor_20170924_IMG_4800

Migrating Purple Heron / Héron pourpré en migration, Ngor, Sept. 2017

 

That’s all for now – let’s see what October brings (Pomarine Skuas! Sooty Shearwaters! Sabine’s Gulls!). Conditions are expected to be good in the next few days.

The August report can be found in this post.