Showing posts with label arctic skua. Show all posts
Showing posts with label arctic skua. Show all posts

Saturday, 20 July 2019

Shetland Waders & Seabirds

On Sunday Two Barred Crossbills still arrived in Shetland with further birds at Veensgarth, Yell, Hillwell, Bressay and Stromfirth around 17 in total with 25+ Common Crossbill.

It was interesting to read that a dead Arctic Tern was recovered a few weeks ago near Aberdeen and it was found that it was 32 years old, beating the previous record by two years. It was estimated that it may have covered at least 1.5 Million miles in its lifetime.


I ventured south and arrived in a very foggy Sumburgh. At the tern colony young terns could be seen, six in total with adults feeding them. Several first year birds flew around the pool and adults brought in some Sandeels.






Lots of Oystercatcher still fed in the paddocks and a small party fed and drank from the loch. What was unusual was one taking green weed out of the loch, not once but five times and this was draped over its beak.












A small flock of Dunlin arrived, one bearing rings. This bird was ringed at  Ynyslas Nature reserve near Aberystwyth, Wales in 12 August 2017






Several Ringed Plover including young also mixed in.


Not a lot on the beach excepts around 50 Common Gull.



At a voe in the South mainland I came across two otters, good to see in this area as two adults had been killed by cars two years ago so it looks like they have recolonised. There are plenty to go round with an estimated 1500 animals, the highest density in Europe

They both fed in the middle of the voe having a lot of success then the split up with one coming up to preen and eventually going to sleep.

Up at Sumburgh Head there was a lot of Puffins, People and Gt Skuas. The smell and sound is nothing like it was 25 years ago but still a great place to visit.



The Guillemot young, jumplings are at a stage they are ready to jump off the cliffs and onto the sea to be quickly followed by the adults and then they swim out into the north sea for a life that is full of hazards.





Never seen so many Skuas around the head, at least 25 with a few Arctic Skuas all looking for prey.



I did see one lift a young bird from a nest, possibly a herring gull. News of an Otter at the lighthouse is now become a regular feature, unfortunately its taking young Puffins.






Saturday, 1 September 2018

Shetland Skuas

The population of Arctic Skuas has declined by 81% according to the latest report by the British Ecological Society.




The National Seabird 2000  census recorded 2,136 Arctic and 9634 Gt Skuas with 90% of the population in Orkney and Shetland


Full report https://besjournals.onlinelibrary.wiley.com/doi/10.1111/1365-2656.12890

Locations of Arctic skua colonies used in analyses of population trend (n = 33 sites) and annual productivity (underlined, n = 20 sites). Dotted line = southernmost extent of Arctic skua breeding range during Seabird 2000. Overall percentage change in Apparently Occupied Territories (AOTs) between the first and last year surveyed (1992 and 2008–2015) is given for each site (see Supporting Information Table S1 for further details). Symbol sizes are scaled to AOT counts in 1992 (four categories: 0–12, 16–26, 30–66, 101–159). Symbol shape denotes colony type, classified by cliff‐nesting seabird host abundance within 5 km of colony during the Seabird 2000 census: squares = type 1 colonies (>10,000 pairs), circles = type 2 colonies (1,000–10,000 pairs), triangles = type 3 colonies (<1,000 pairs)



Arctic Skuas declined at all the study colonies from 1061 ATO 's (1992) to just 200 in (2015), indicating the largest declines took place in the north with the largest productivity in Handa in NW Scotland.


Attacks on Kittiwakes which had only come down onto a loch to bathe  






Arctic Skua nest next to colonies of seabirds either Arctic Terns, or cliff dwelling birds that usually feed on Sandeels - Puffin, Kittiwake, Guillemot and Razorbill. These skuas rely on stealing food from these birds, this is called Kleptopasrasitism


An Arctic Tern attacks an Arctic Skua

Gt Skuas increased at most sites except Foula where a 24% decline occurred. Its odd that the greatest declines in Arctic Skuas occurred where Gt Skua population were small. Food availability and density of Gt Skua were associated with breeding success of Arctic Skua

Gt Skuas are larger and more powerful that Arctic Skuas , they rely on harassing large birds such as gannet for a free meal

Gt Skua seen off by a Fulmar

The world's Gt Skua population is around 16,000 with 57% being in Scotland (Bird life International 2018) especially in Shetland and Orkney. Around 9,634 ATO (Apparently Occupied Territories) can be found in the UK (2004)


They are very aggressive towards humans and animals that stray onto their breeding grounds, making a head on attack and sometime hitting the intruder with their feet.



Gt Skua population in Shetland has fluctuated with numbers up and down at various throughout the isle. Gannet numbers are increasing so you would think that there would be more fish brought back to young gannets and therefore more opportunities for GT Skuas . Noss for instance has around 25000 Gannets double that of 1970

On Foula in 2015 a lot of cannibalistic predation of well grown chicks was again high, although a census count of 1,846 AOT was 11% higher than 2007

In Shetland, 4 colonies at Hermaness, Noss, Mousa and Fair Isle had 1,747 ATO's in 2013, an increase of 27% since  2007. But on Foula a decrease of 28% occurred between 2000 & 2007 (2,293 down to 1,657 ATO's)


In Orkney, a complete census revealed a 23% decrease between 2000 - 2010 (1,710 ATO's)

Discards from fishing boats used to be an important part of the Gt Skuas diet in Shetland but with the reduction of discards they have now started to either concentrate on attacking Gannet for fish, eating birds such as Puffin or resorting to cannibalism .

Having just taken part in the 2018 Seabird census I am very interested in seeing the current figures