Causeway Coast Ringing Group: Terns and Gulls

Since his early days as a ringer, Ken has been studying Gulls and Terns in Donegal, beginning in 1984. Over this period he has ringed over 10,000 birds, with a focus on Sandwich Terns, with 8377 ringed since 1986 (to 2015). Other important species were Black-headed Gull, Common Gull and Common Tern.
Much of the early study work was carried out on the islands of Mulroy Bay, Donegal but the invasive American Mink became a huge problem and devastated the colonies. The Mink not only ate as they went, but also killed every sitting bird they found (left uneaten) and cashed hundreds of eggs in burrows. The Mink are still prevalent in the area and it is no longer studied. Since then Inch Islet, at Inch Island Wild Fowl Reserve, has become the sole focus for study. The islet has breeding populations of Common & Sandwich Terns and also Black-headed Gulls - Common Gulls are thus no longer ringed.
As you can see from the totals below the Sandwich Terns have remained fairly constant, with the one blip in 2011, when high water flooded the whole islet. This year was also quite poor, with the bad weather in early summer, killing many chicks and lots of eggs were abandoned. The Common Terns are much more susceptible to changes in water levels, because they nest just above the water mark. Black-headed Gulls breed in big numbers on the island but there is limited focus on this species.

	Tern Species - Chicks Ringed			Gull Species - Chicks Ringed
	Arctic	Common	Sandwich	Black-headed	Common	Great Black-backed	Herring
1984		100		98	160
1985		31		50	145
1986			203	5	71
1987	10	14	133	16	136		3
1988		26	415		138
1989			342		131
1990			267		22
1991			144
1992			238
1993			294
1994			320
1995			197
1996			329
1997			131
1998		45	155	15
1999		86	324	95	3
2000		19	365		3
2001		24	335	49
2002		26	267		5
2003		23	272	5
2004			453		2	3
2005			317
2006			322
2007			343
2008			319
2009		11	291	10
2010		12	387	9
2011			94
2012		6	410	7		2
2013			251	26
2014		22	270	5
2015 2016 2017		31 32	189 357 139	22 161

Total	10	508	8873	573	816	5	3

Since the start of the project there have been 113 recoveries (more than 5km away) of the birds ringed. The Sandwich Terns, as expected, have weighed in with the majority, with 94 recoveries. The birds that are recovered experience a wide range of fates. For the lucky birds, they have had their rings read in the field, have been re-caught by ringers or caught unintentionally and released. Some are not so lucky with many being trapped and eaten, kept in cages, kept by children as pets, trapped for their rings to make jewellery, caught by dogs or simply found sick/dead.

The Sandwich Terns have been recovered in an impressive 23 countries (24 if we grant the Basque independence) although surprisingly none yet in Northern Ireland. I suspect some of the ringed birds I see in the Bann Estuary originate from Inch. Generally the main concentrations in West Africa are found near the main cities e.g. Dakar and this is down to the population size, increasing the chances of the birds being found/caught. Thumbs up to the people who found the birds in the Namib desert!
The biggest distance travelled was for a Sandwich Tern that reached Sardinia Bay, Port Elizabeth, Cape Province, South Africa at a straight line distance of 10,399 km. The bird was approaching 5 years old when it died, so it may have flown to South Africa and back to Ireland three/four times.
In terms of longevity there have been a few birds that have passed the 15 years old mark but the oldest two birds were both recovered in Spain at the ages of 20 years, 10 months and 5 days and 20 years, 4 months and 13 days. The majority of the birds recovered in the Europe are generally at least 3 years old, whereas many of the birds in West Africa are recovered in their first winter or second year.

Sandwich Tern Recoveries

Ireland	8	Guinea Bissau	2
Scotland	3	Guinea	1
Wales	1	Sierra Leone	7
England	5	Liberia	2
France	2	Ivory Coast	3
Belgium	1	Ghana	8
Netherlands	1	Gabon	1
Germany	1	Congo	6
Denmark	2	Angola	2
Spain	3	Namibia	2
Morocco	1	South Africa	8
Senegal	24
		Total	94

Sandwich Tern Recoveries - Europe & North Africa

Sandwich Tern Recoveries - West Africa

Sandwich Tern Recoveries - Southern Africa

With much fewer birds ringed, there are less recoveries for the other species. The Common Terns have managed a couple of recoveries in Ghana. In terms of longevity, the oldest Common Tern to date stands at 11 years, 3 months and 1 day. The oldest Black-headed Gull recorded = 12 years, 8 months and 6 days and Common Gull = 21 years, 6 months and 3 days.


Commn Tern Recoveries		B-headed Gull Recoveries		Common Gull Recoveries

Ireland	3	N Ireland	5	N Ireland	1
England	1	Ireland	7	Ireland	9
Ghana	2	Scotland	1	Scotland	1
		England	1
Total	6			Total	11
		Total	14