Thursday 4 February 2016

Irish Bird Ringing Data - Tree, Grass and Sylvia Warblers

Sylvia Warblers

A total of eight Sylvia warbler species have been recorded in Ireland with three of these being regular breeding birds.  Of the eight species recorded, all but one have been ringed - Sardinian Warbler, which has been recorded on three occasions, all from Cork. The main breeders are Blackcap, Garden Warbler and Whitethroat, although Lesser Whitethroat have made intermittent attempts.  
Barred Warbler and Subalpine Warbler are near annual vagrants.  The final bird is the Dartford Warbler which is a rare vagrant with two birds ringed in Ireland.  The first bird was trapped at Tacumshin, Wexford in September 1989, with the second bird also coming from Wexford in October 1995, at Hook Head. 


The Blackcap is the most common of the breeding Sylvia warblers and probably has the most complex migration habits.  At one time, in the not so distant past, the Blackcap was a very uncommon bird in Ireland and particular breeding birds were actually twitched!  Nowadays they are found in almost all wooded areas and scrub with the exception of the dense coniferous plantations. 
A total of 5831 Blackcaps have been ringed in Ireland since 1975, with 2205 in the north and 3453 in the south since 1977.  There is a general trend of increasing numbers, with the most productive years in 2013-2014 with 294 and 295 respectively and the least productive in 1978 with 44 birds.  The rise of the Blackcap is quite remarkable and is in contrast to its fellow breeding Sylvia Warblers.
A mere 46 Blackcaps were ringed at Copeland Bird Observatory in it's first 20 years of operation from 1954.  At Cape Clear there were 13 birds ringed between 1959-68, rising to 157 between 2000-09, a rise of over 870%. 

It is thought that the majority of our breeding Blackcaps head to the Iberian Peninsula and North Africa to spend the winter.  The ringing recoveries would support this theory with birds recovered in Morocco, Portugal and Spain.  Many of these birds will pass up through Iberia and migrate along the west coast of France before hitting the British Isles.  The recoveries show many of these birds to pass through the south of England before making the leap to Ireland.  None of these movements from England are direct movements and are recovered in subsequent years, so it makes interpretation a little more difficult. 
The other main movement of Blackcaps are the birds that migrate into Ireland for the winter.  These birds are believed to come from central Europe and the recoveries back up this theory.  One such bird ringed in Northern Ireland in January was subsequently recovered in its breeding grounds in the  Black Forest in southern Germany.  There are also further recoveries of birds that passed through Belgium, England and The Netherlands which spent the winter in Ireland.  Two birds appear to have switched their wintering location in different years between SW England and Ireland.  The number of wintering Blackcaps appears to be increasing in Ireland and it is thought that the plentiful supply of food in gardens and the shorter migration is helping to increase survival rates.  The fact that these birds aren't hunted for the plate in northern Europe is bound to help!  It is thought that upwards of 1.8 million Blackcaps are killed by humans around the Mediterranean each year. 

We also receive birds coming from the north, shown by the two recoveries from Norway and North Ronaldsay, which are quite interesting.  Both birds were recovered in late December, one of which was recorded at garden feeders in Donegal.  It is still possible that these birds moved further south in Europe to spend the winter but it is quite possible they were here for the winter.  They potentially could have been Scandinavian birds but also, quite possibly, could have been central European birds which overshot their migration, taking a little detour north before heading west. 
The greatest distant covered was the bird to Morocco at over 2500 km, which probably made a similar journey five times, before it met its end with a lead shot.  The oldest recovered bird was at least eight years old in Portugal when it too, was shot. 

Blackcaps coming into Ireland
Blackcaps departing Ireland

Garden Warbler

The Garden Warbler is a very scarce breeder in Ireland these days with the last strongholds around the lakes of Cavan and Fermanagh.  They were formerly much more widespread but the numbers have reduced considerably.  The species is no doubt under recorded because of the similarity of its song to the Blackcap and the dense foliage in which it inhabits. 
The graph below, although with a number of peaks and troughs, shows a gradual trend of decline.  The majority of these birds are trapped at coastal migration sites for example, there were 21 ringed at Cape Clear BO in 1986 and probably over 90% of N Irish records have been trapped at Copeland BO.
A total of 460 Garden Warblers have been trapped in Ireland since 1975.  The most productive year was 1988 with 40 ringed across Ireland and the least productive years were 2012-14 with 1,0 and 1 trapped.  There were at least 105 ringed before 1975, 43 of these from Copeland BO and 36 from Cape Clear.   

There are only two recoveries of Garden Warbler in Ireland, one in and one out.  The bird originally ringed in Ireland was a bird trapped at Copeland BO in September 1974 on its southern migration to sub-Saharan Africa.  The bird was killed by catapult on its return journey north the following May, near Agadir, Morocco.  The second control was a first year bird ringed at Herent, Belgium on the 27th of August 1988 and controlled 19 days later at Great Saltee.

Garden Warbler (green in/red out) and Lesser Whitethroat (blue) recoveries

Lesser Whitethroat

In Ireland three races of Lesser Whitethroat have been recorded with the British nominate race curruca, the Central Asian race halimodedri and the Siberian race blythi.  The British nominate race is of course the most common, breeding across England, Wales and southern Scotland. Over the past few decades there has been a 33% range expansion of Lesser Whitethroat across England & Wales and has led to an increased occurrence of the species in Ireland including a series of intermittent breeding attempts along the Irish east coast.     

The graph below would seem to suggest a reduction of numbers being caught from year to year but it does remain fairly consistent from the mid 90's.  A total of 91 have been ringed throughout Ireland since 1976, 8 of those from Northern Ireland.  There were eight years when no Lesser Whitethroat were ringed in this period and the best year was 12 records in 1982.  There were at least 6 ringed before this period but certainly appeared to be much less regular. 

The graph above is flawed and the bars should sit above the dates from 1977

The single recovery (on the same map as Garden Warbler) involved a bird ringed in Devon in the autumn of 1979 which was controlled at Great Saltee the following May on route to its unknown breeding grounds. 
Siberian Lesser Whitethroat and some unassigned Eastern races (either halimodedri or blythi) have been trapped in Ireland and show examples of reverse migration.


The Whitethroat in Ireland is much less common than it once was and although still widely distributed, in key habitats.  The species was very abundant pre 1968 but a population collapse across western Europe (up to 75% in places) in 1969, followed by another collapse in the mid 80's saw the numbers drop away in Ireland and they have never recovered. 
A total of 1931 Whitethroats have been ringed in Ireland since 1975 - 1329 in the south, and 525 in the north since 1977.  The must productive year in this period was 2001 with 132 captures and the least productive year was 2005 with only 7 birds!
There is a record somewhere of a huge fall of Whitethroat at Copeland BO where the ringers fast ran out of the correct ring size and had to release a large number of birds un-ringed.  It may coincide with falls at Great Saltee of over 500 birds on May 12th 1960 or perhaps May 8th 1963 when over 400 were recorded.  201 were ringed at Saltee BO between1960-1963 with 92 of those in 1960 and 731 were ringed at Copeland Bird Observatory between 1954-1976 highlighting how much more common the species were c50 years ago. 

From the map it is clear to see a main passage route into Ireland with four of the recoveries coming from a relatively small area of East Sussex and Kent.  Great Saltee and Copeland BOs are important passage points with each having two birds recovered, including a foreign recovery each.  The Great Saltee was ringed in spring migration in 1987 which was recovered the following spring on its way north through Morocco near Ben Ahmed - a minimum distance of 2177km.  Copeland BO had a Whitethroat recovered in south west Portugal when it was at least eight years old - unfortunately the bird was shot, similar to the Portuguese Blackcap.      

Whitethroat Recoveries (green in, red out)

Barred Warbler & Subalpine Warbler

Barred Warblers are recorded annually in Ireland with an average of perhaps 5/6 birds each autumn.  There are years with upwards of a dozen records with a general bias towards the south coast, Cork in particular - Tory Island in Donegal is a notable spot for the species in the far north. 
In the period between 1975 and 2014 there were 9 Barred Warblers ringed in Ireland.  Six in the South and three in the North (all CBO).  There is no obvious pattern in the graph below with fairly random occurrences.  There were at least 7 Barred Warblers ringed before this period. 

Subalpine Warblers occur less often in Ireland than Barred Warbler with generally one record a year - 2008 was a record year with 7 birds recorded.  Almost twice as many Subalpine Warbler have been ringed than Barred Warbler, with 17 records between 1975-2014.  In Ireland the occurrence of the species is almost four times as common in the spring than it is in autumn.  That and their feeding habitats may be the reason more are caught.  The species are fairly confined to the south coast with only five records in other areas (3 NI, 1 Mayo, 1 Kerry).  The autumn birds are centred on the south-west with 10 of the 12 autumn records from Cork.  The Spring records are focused on the south-east with Great Saltee and Wexford being the focal point.
Before 1975 there was at least 1 Subalpine Warbler ringed in Ireland. 
The majority of the records are thought to refer to Western Subalpine Warblers, although often not distinguished from the Eastern race. 

Grass Warblers (Locustella)

Three species of Locustella warblers have been recorded in Ireland with Pallas's Grasshopper Warbler, Grasshopper Warbler and Savi's Warbler.
There are only two records of Pallas's Grasshopper Warbler in Ireland with the first at Rockabill, Dublin on the 28th of September 1908. The second record was a bird trapped at Cape Clear Bird Observatory on the 08th of October 1990.
Savi's Warbler have been sighted on more occasions with c9 records but none have been ringed.   

Grasshopper Warbler

The Grasshopper Warbler is one of those species which is seldom seen but often heard.  They are widespread in Ireland but rarely in any great densities.   
The catch graph for Grasshopper Warbler is very staggered, particularly for the South.  A total of 717 have been ringed across Ireland since 1975, with 505 from the South and 204 from the North since 1977.  The most productive year was 2006 with 39 birds and the least productive was the year previous with 4 trapped.  Surprisingly there have only been 8 ringed at Cape Clear BO since 1959 when it can boast 5 Red-eyed Vireo!  Copeland BO has been a little more prolific and notched up 77 ringed between 1954 to 1973 which includes 44 ringed in 1970, 36 of which were caught in a big fall on the 2nd of May.


 The recoveries of Grasshopper Warbler are rather limited but this is to be expected for the rather low numbers that are caught.  There appears to be an obvious preference for the birds passing through the south of England (as with many southern migrants) before they head to and  depart Ireland.  The three locations on the south coast of England (including Icklesham and Pett Level) are well known stop over sites for the likes of Reed & Sedge Warblers in late summer/early autumn before heading south and look to be of similar value to Grasshopper Warblers.  The two sites on the south coast of Ireland are of similar wetland habitats with large areas of reedbed and again appear to be staging sites (due to ringing date) before migrating south. 
It is interesting to note the inefficient movement of the bird (blue line) controlled in Fermanagh in June 1969 which had passed through Copeland BO a few months before.  It may have a better route cross country - perhaps following the Blackwater from Lough Neagh to join the Erne system?      

Grasshopper Warbler Recoveries (Green in, red Out, blue inter-Ireland)

Tree Warblers (Iduna & Hippolais)

Three species of Iduna warbler have recorded in Ireland with Booted Warbler, Sykes Warbler and Eastern Olivaceous Warbler
The Olivaceous warblers are a bit of a minefield and all records have been reviewed by the Irish Rare Birds Committee. As such, a few older records have been disregarded and I believe we have been left with three confirmed records of Eastern Olivaceous Warbler in Ireland. Of these three, two concern birds that were ringed with birds in 1999 and 1977.       
Sykes warbler has not been ringed and has just two records which were both October birds in west Cork in 1990 and 2013. 
Booted Warbler has been recorded on five occasions with all records appearing between the 26th of August and 27th of September. The first four records occurred between 2003 and 2006 and the fifth came in 2013 and was the first to be ringed in Ireland

Two species of Hippolais Warbler have been ringed in Ireland,
Icterine Warbler and Melodious Warbler.

Icterine Warbler & Melodious Warbler

These closely related vagrants are pretty much annual in Ireland and as with most rare vagrants, the south coast is the place to find them.  Of the two species, Melodious Warbler is more common with greater records, particularly in recent years.  More Melodious Warblers were also been ringed between 1975-2014 with 26 records, compared to the Icterine Warblers 19.  Of these only a single Melodious Warbler was ringed in Northern Ireland with the rest of the birds in the south.  1983 was a good year with 5 Melodious and 2 Icterine, while 1977  produced 3 Melodious and 4 Icterine.  The birds have really tailed off in the last 17 years with only three of both species combined.
Before this period there were at least 9 Icterine Warbler and 18 Melodious Warbler ringed in the Republic of Ireland including 9 Melodious from Great Saltee BO in 1962.  Northern Ireland has notched up a further 2 Melodious and 1 Icterine, all from Copeland BO between 1954-1974.        


  1. Excellent blog post - a really interesting read

  2. Thanks. There are previous posts on Irish bird ringing data covering Owls, Thrushes etc. and more to follow in the coming months covering the rest of the passerines, near passerines and raptors.