Red-breasted Merganser    

Mergus serrator
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The Red-breasted Merganser is another of Lough Allen’s iconic species. It is not a rare bird globally and it does breed elsewhere in Ireland. It is also a common sea duck around all coasts of Ireland in the Winter.

However it is found as a marginal breeder in Lough Allen. Further east and south it does not occur and is also not found in many other lakes which would be in its north-westerly range. There is something about Lough Allen that suits it.

The Merganser is a fish feeder and breeds on tree covered shores. Lough Allen’s water quality has started to decline and if this affects the small fish this diving Duck needs to breed and survive... then we could lose this species.

Go to... 2012 Update ... a Good Breeding Year.

An on-going Study into one of the rare Species in Lough Allen’s Natural Biodiversity.

BIODIVERSITY = "the totality of genes, species, and ecosystems of a region" WIKI
SPECIES = “a group of organisms capable of interbreeding and producing fertile offspring.”

“If we lose this Species...

...we lose part of our Natural Heritage!”




Introduction & World Distribution.


These images from Lough Allen show some of the character of these birds. They are very wild, love isolated places, and will move very rapidly around a large area of water. In a habitat like Lough Allen they are hard to view from the shoreline but we will attempt in this report to indicate where they are best seen.

2011 was a difficult year for this species, numbers were down, breeding attempts were abandoned, and we know of only one successful breeding pair.

The Photographs on this page are mainly taken from a rocking boat and at a very long range. So apologies for any lack of quality. We wish mainly to record their presence on Lough Allen, whether they are increasing or declining and, as much as we can possibly find out about their biology and conservation.

We hope, in future years, to see this bird thrive and we may be able to produce better and better images... with the minimum of disturbance to these elusive breeders.


Lough Allen’s breeding Mergansers

At the start of the breeding season many Duck species (including Mergansers) consort in groups of three.

A breeding pair on Lough Allen, the slightly tatty male on the right!


Male Merganser found sleeping in the middle of Lough Allen. We approached quite close before the bird wakened and headed off!

Ideally the Red-breasted Merganser drake has a shiny green head during the breeding season. This is the way the males are always depicted in the Bird Books!

However the stresses of courtship and mating and looking for a nesting site often leaves them a bit tattered. They are still a stunningly attractive duck and we are very lucky to have a breeding population of them in our area. The males have a striking marbled grey flank and tail but also a spotted reddish breast. The bill and feet are bright red at this time of the year. This species also has a crest which can be very visible or may be tucked down.

The biggest single characteristic for recognising a male Merganser, even at some distance, is the broad white bar on the middle of the wing contrasting with the dark grey primaries. All males have this and it runs right through the wing from front to back. Many males will have a dark chocolate brown head, instead of green. These may be last year’s non-breeding males or they may be males that have lost their full breeding plumage.

A Female Merganser near one of the many prospected nesting habitats around east and north Lough Allen...

The female Merganser is, also, a very attractive bird with a simpler, more refined, taste in plumage. Red bill and feet are still maintained but the head is a smooth less variable tan colour. This merges gradually with an even pale grey plumage for the rest of the body.

These ducks may appear small when seen on the water but they are deep bodied with a powerful chest and feet set well back — both features designed for fish feeding and diving. Mergansers dive deeply for fish in both marine habitats (in Winter) and in their freshwater breeding areas. Later photos show a female basking on the shore of one of the breeding islands and the bird looks quite big there.

The female also has a white bar on a grey wing but the bar is not nearly so obvious and does not go through the whole wing. If you see three Mergansers flying around in May or June they will probably be a female and two males and, very likely, at least one of those males will be an immature brown-head!

Worldwide Distribution.

The Red-breasted Merganser is a holarctic species. This means that it occurs in a band around the northern part of the northern hemisphere including northern Europe, northern Asia, northern North America, southern Greenland and adjoining islands including Iceland, Japan, etc. It occurs over a wide band but its presence in Ireland is very much at the southern end of its range. It occurs inland thoughout this area during the breeding season but migrates to the coast after nesting. It is not common in England but present in Scotland. Outside of the breeding season this species is a sea bird, distributed more widely along coastlines and open ocean of northern nesting zones but also much further south into tropical waters. It’s a widespread sea bird found all around Ireland during the Winter. Like other species significantly present in Lough Allen, this is a species that we must consider as marginal and subject to changes such as global warming as well as other possible disimprovements to the habitat in which it breeds.

The green sections of the Map,below, show where the bird is present year round; elsewhere it is either a Summer or a Winter visitor.

Historical occurrence in Ireland.
(Literature search.)

In 1900, the Red-breasted Merganser was recorded as breeding in 14 counties in Ireland, namely Kerry, Tipperary, Westmeath, Meath, Longford, Galway, Roscommon, Mayo, Sligo, Leitrim, Donegal, Fermanagh, Tyrone and Down. ( Ussher and Warren, 1900)

Ussher and Warren state that... “this bird...has an extensive and increasing breeding range in Ireland, from Kerry to Donegal and Down. It nests both on marine inlets, and on the islands of the larger lakes of the interior, where it is very common in summer, and may be accounted one of our most numerous resident ducks”

For County Leitrim, they list breeding locations for Mergansers as Lough Allen and Lough Melvin. Lakes in adjoining counties where they also bred include Lough Key and Lough Gara in Co. Roscommon, Lough Arrow and Lough Gill in Co. Sligo and the Erne lakes in Co. Fermanagh.

According to Ussher and Warren, eggs have been found as early as May, but June is the regular breeding month for Mergansers. They give a good description of nest sites.

 “A favourite site is in the zone of rank herbage, flags, nettles or meadow-sweet, intervening between the stony shore of an island and the scrub: but it is sometimes a depression among rough gravel, with scarcely any nesting-material, and is often among tangle and bushes, under masses of coarse ivy, or in a nook or crevice under the rocks or the roots of a tree, but never to my knowledge in a burrow. A well-marked but very tortuous path or run is made by the bird to its nesting-place, which is a snug hollow overshadowed by sedge or other plants, and the eggs are surrounded with the parents grey down.”

They also state that in winter, the Mergansers are to be found all around the coast, quoting Sir R. Payne-Gallawey as seeing several hundreds swimming together in Queenstown (Cobh) Harbour in the severe winter of 1878/9. Thompson 1851 (Natural History of Ireland) Vol.111, (as quoted in Ussher and Warren) reports that...”On Dublin Bay, this is the first of the ducks to appear in the autumn and the last to leave in spring, being sometimes seen before the end of August and so late as the middle of May.”

Lake to Sea migration.

Lough Allen is unique as an inland lake, some considerable distance from the sea, having a good population of breeding Mergansers. To many birdwatchers in both Ireland and Britain, these are common birds of estuaries and both sheltered and exposed marine waters. They are quite at home, in winter time, in the wild Atlantic or the Irish Sea. It is safe to assume that for many ornithologists Lough Allen’s breeding Mergansers have slipped their minds.

The nearest sea to Lough Allen would be Sligo Bay and there are two distinct migration routes. Either from the north end of the lake via Belhavel Lough to Lough Gill, or from the southern end of Lough Allen to Lough Key/Lough Arrow and then up to Ballysadare Bay in Sligo.

Mergansers are widespread in small flocks around Sligo throughout the Winter. In the Graphic, below, we have tried to synchronise known movements of Mergansers around Lough Allen and in Sligo Bay. Are the birds found there the Lough Allen birds?

At present we have no information about this local migration but it would be very interesting to prove where our local breeding birds are coming from. It seems that local movement may well be the pattern for our Mergansers, according to studies done elsewhere. This could be proved by catching and ringing specimens, by observing flight or migration along the routes suggested at the beginning or end of the season, or by close monitoring of numbers and groups at both locations at the same time. (We are much obliged to people in Sligo who have sent us information about movements of Mergansers in their area.) Undoubtedly, over the years, someone will provide an answer to this puzzle! Dates and locations of regional Merganser populations are plotted below (Pending completion):

This TimeLine is a very preliminary effort to relate Mergansers on the sea to Mergansers at Lough Allen. As you can see they spend a relatively short time in Lough Allen, longer if they are successful in breeding. After that there is a period of over a month when they are not visible, nor have they appeared at their sea locations. Possibly the adults have flown and the immature young are still in Lough Allen but keeping very discreet as they may be flightless? The data used for this outline is very scanty but, hopefully, in years to come we will be able to build up a more accurate picture. The main thing is... to keep Mergansers breeding here! Birds found in the seas around Ireland may come from several sources:

Locally bred birds returning to the Sea

Birds from other parts of Ireland

Migrants from northern latitudes wintering here.




Movement around Lough Allen.

In this section we have recorded patterns of movement around the Lake during a breeding season. This is a device aimed at identifying breeding areas for this species and, eventually, an assessment of the population size and whether it is declining or increasing over the years.

Merganser distribution and movement within Lough Allen during the breeding season.


Data from 2010

Occurrence around Lough Allen

This large Map has been copied from our last year’s report (2010) on this species. It is an exact copy of the map from that report. That year was the best year we have seen for Mergansers though we failed to prove any breeding (which was successfully recorded this year.) But breeding sites, feeding areas, pairings and territories were identified and these are probably the same from year to year.

2011 was a disappointing year with fewer Mergansers in the lake, evident abandoning of breeding areas, significant pollution through much of the Summer, and very cold weather during the early part of the breeding season. This latter factor was probably the main reason for many ducks to be seen not to be breeding for most of the Summer. When breeding they are very secretive; this year they were frequently seen flying around or resting onshore after feeding either in pairs, individuals or groups of three.

The one pair that successfully hatched their eggs did so late in the year and presumably had not started laying until the start of June, which actually may be quite the norm for this species. (See details below.)

This map is shown here as it is useful in depicting how active these ducks are, their use of sheltered lagoons and islands (for breeding) and deeper water areas for fishing. Mergansers need both — tree-lined shores for nesting and nearby deep water for fishing. (Mergansers are consummate fishers and dive deep and swim strongly underwater.)

For people not familiar with this species, it also shows you where to look. But, remember, they will only be common from April to August. The rest of the year they are found in the sea, as discussed above.

Historical Status in Lough Allen.

In 1954, Kennedy et al stated that the “breeding range of the species has extended and its numbers have increased since the beginning of the century.” He mentions that since Ussher's publication in 1900, breeding has become established in Cork (1920), Wexford (1929) Antrim and Armagh, as well as all the counties recorded for breeding Mergansers in 1900. However, he does not mention the status of Mergansers in Co Leitrim.

Kennedy et al concur with Ussher in that they state that the bird usually does not lay eggs until early in June, but add that pairs may be seen as early as the first week in March, and young broods, still unable to fly, may frequently be seen in the third week of September. One female, incubating eggs, was seen in Strangford Lough as late as10th. August.

The recent records for Lough Allen are less clear...


According to the BTO and their Breeding Bird surveys, good numbers of Mergansers were seen at Lough Allen during the 1968-1972 survey period. Some of these were 'confirmed breeding'. In the next survey, from 1988 to 1991, Mergansers were seen at Lough Allen, and breeding was confirmed, but there was a overall loss in breeding numbers.

The BTO estimates that the numbers of Mergansers in Ireland between 1970 and 1990 decreased by about 32%. This number is based on the number of survey areas (10km square) where they were present, and breeding.

There is an estimate of a minimum of 700 breeding pairs of Mergansers in Ireland in the 1988-1991 period and a wintering population of 3,390 for the same period. (Cabot)



Two Images of Mergansers in Flight.

Here are Images of a female and a male Merganser on their busy movements around Lough Allen.

What beautiful birds they are and they are the fastest Ducks in the air. A very skilled species with superb flying and diving skills.

Presumably these are adaptions that enable them exist on a permanent fish diet in different habitats?


The female (Top) clearly shows the diagnostic feature of a large white wing bar which does not include the leading edge of the wing. Many ducks have white bars on their wings but, even at a distance the white bars on Mergansers (of both sexes) are very prominent and a good way of identifying brids in flight.


The lower picture is of a male showing his wing bar reaching all the way across the wing. There are many other differences in appearance but the size of the wing bar is the best way of sexing these birds at a distance and in poor visibility. Both breeding males (green head) and non-breeding males show the same wing pattern.




Breeding and Behaviour

A breeding pair prospecting on the west of Long Island, near Cormongan

Breeding Pairs

In Lough Allen the Merganser breeding population is distributed at the north and south east ends of the lake — basically where most of the small wooded islands are to be found. Mergansers will nest on wooded lake shores but around Lough Allen they seem to much prefer the offshore islands. This is probably because the islands are uninhabited and there is normally no human (or cattle) disturbance.

As soon as they arrive in Lough Allen, Mergansers spend their time between fishing in the open water and exploring suitable nesting sites around islands and isolated bays.

Both territorial and courtship behaviour are commonly seen, though hard to photograph. As work develops and the Mergansers are better understood, it will be possible to present further photos of their display and aggression. Some sketches are reproduced here from last year’s work.

These are based on observations of individuals too far away to obtain good images. The male raises his head and may ‘stand up’ in the water; the female lowers herself into the water in a submissive manner.


Merganser Year Planner.

But they may not stick strictly to it!

January - April

At Sea off the coast of Ireland.

End of March and early April

Move inland or to coastal marine nesting sites. Arrive in Lough Allen


Prospecting for Nesting Sites, fishing and courtship.


Nests occupied and eggs laid. Exact timing seems very dependent on weather conditions, warmth and amount of rainfall. Females incubating and tending young. Male moved away to go through flightless moult.


Adults with young seen on Lough Allen... in a good year.


Adults leave the lake. If young have fledged they may be left to fend for themselves until they can fly.

October onwards.

All Mergansers in marine coastal waters. Whether these are near to their Summer breeding location or further south, remains to be determined



The two Mergansers shown below were a courting pair exploring around Fossil Strand at Corry Point on the north shore of the Lake. As usual, they were accompanied by another male hanger-on. This often leads to a situation where the male (of the pair) is displaying to the female by trying to look imposing, at the same time as trying to drive off the competition with a display of aggression.

This male is being agressive to another male — unfortunately out of the picture. The wide open bill, flapping of wings and the thrashing of the water are all designed to get the unwanted visitor to move on!


Mating in Red-breasted Mergansers is very rare to see in Lough Allen, because of the numerous quiet inlets where the pairs may go, but it is often associated with a visit to the shore in an area that may seem suitable for nesting. Early in the morning the birds will feed often right out in the middle of the lake. They are then hard to see from the shore.

In the Summer feeding will be carried on for an hour or two and then the birds rest. Typically, after this, pairs will head for the shore and display and territorial activity will take place. Often the birds feign indifference and swim up and down slowly off shore. When they identify a location that interests them, they will rapidly head ashore and courtship and mating may occur. At this time other Mergansers are actively chased away.




As birds start to lay eggs the female will stay close to the nesting area even if she feels it wiser to move away from any disturbance. After such disturbance finishes they are very quick to get back onto the nest.

This female, off Cormongan, looks like she is just taking a break from nesting duties — though we weren’t able to prove that this year in this location.


Other Comments on Breeding Mergansers.

As with their distribution, so too very little information is available in the literature about the breeding habits of Mergansers in Ireland. They are a native species that, for some reason, has been largely overlooked? The following comments have been culled from the international literature on this species

Breeding Decline & Sensitivity to Pollution.

In an interesting aside we discovered describing the Red-breasted Merganser population in the Great Lakes, USA, the author refers to problems with contaminants causing loss of Mergansers. One risk listed was organochlorines and this is regarded as no longer an important factor. We assume that applies to Lough Allen too. However, as the quote below highlights, the species is subject to decline following increasing levels of contamination in its breeding waters.

We are seeing a decline in breeding numbers in Lough Allen. We are also seeing an increase in contamination. Perhaps these birds provide a handy monitor for effluent levels in Lough Allen. If we can control blooms, persistent (detergent based) foam, and shore deposits — then maybe our Merganser populations can recover to 1950 levels?

James Ludwig (1991) suggested that due to this species’ sensitivity to environmental contaminants, it would make a good ecosystem monitor. If this is indeed the case, the precipitous decline in Red-breasted Merganser numbers may indicate an ominous specter threatening the health of our northern Great Lakes.”

Ludwig, J.P. 1991. Red-breasted Merganser (Mergus serrator). Pages 152-153 in R. Brewer, G.A. McPeek, and R.J. Adams, Jr. The Atlas of Breeding Birds of Michigan. Michigan State University Press. East Lansing, Michigan, USA.




Male Mergansers will concentrate on fishing and they can be seen a long way away from the nest. However, they are fast fliers and can get from the centre of the lake to any of their probable nesting areas in Lough Allen, within a matter of minutes!




Breeding Site.

Nesting Location.

A lot of the literature seems to suggest that Red-breasted Mergansers nest among rocks and trees practically in the water. Their related species, the Goosander, nests in trees and out of the reach of water!

This would be of considerable concern in Lough Allen as the water levels can fluctuate widely. In recent years there has been a pattern of sudden heavy Summer rains during which the water level may rise over a metre in a matter of days.

Indeed old Merganser nests have been found on exposed rocks very close to normal Summer levels. Needless to say, these nests appear to have been unsuccessful. Maybe Lough Allen’s Mergansers have already adapted to a changing environment?

The nest site shown on the right is approximately 2.6 metres vertically above normal Summer water level. This year the eggs were laid in this nest at a time when the water was far removed from the site. Also, if we were to have disastrous flooding in the middle of the Summer, this nest would have been safe. It’s almost as if the Mergansers knew this?

Or is that to attribute too much intelligence/instinct to mere birds? However, this nest was not close to the water during this years (2011) breeding season. Maybe this was a pair that had nested here before in a wetter Spring and they knew naturally to come back to a safe elevated site!

What’s special about Lough Allen?

Lough Allen is well known for its Alder Carr — linear tracts of Alder woodland along many shores of the Lake. This is a result of it being surrounded by shale and sandstone mountains with large areas of glacial till or boulder clay covering both its basin and the surrounding lands. It is a nutrient poor landscape in which Alder, as a Nitrogen fixing tree, thrives. It can tolerate a lack of minerals, it fixes Nitrogen through nodules on its roots, and it can thrive with its roots largely immersed in water.

All Merganser nesting areas we know of around Lough Allen are associated with Alder carr. This is probably the main reason that brings Mergansers here. There are numerous niches and hidey-holes formed between the stems of Alder, fallen boughs, and large boulders left from the Ice Age — pure heaven for Mergansers.


Mergansers are ‘sawbills’ with long serrated bills designed for the capture and retention of fish. It is thought that they also feed on invertebrates. They are also adapted with their deep chests and strong legs for diving deep after their prey. A lot of ducks do not dive; they either feed on the surface or up end to feed off weeds on the bottom of shallow water. Mergansers are actual hunters that will chase their prey and would be entirely flesh eaters. Because of its glacial past Lough Allen has many deep channels in between areas of shallow shoreline water. The deepest location we have measured goes down to 40 metres and this is very close to Church Island where this nest site was found. has extensively surveyed the contours of the floor of the Lake and some prliminary information can be seen from a cross-section published HERE.

Adults are estimated to eat 200-250g. of fish (20-25% of body weight), requiring 15-20 average sized fish, caught in 250-300 dives requiring 4-5 hours of foraging. (Cabot)

A Merganser nest starts off as a soft scrape in soil or sand. This one was totally invisible under a fallen log resting on a boulder from the hill at the centre of Church Island. It was c. 2.6 metres above normal Summer water level (i.e. a water level of 1.8 m at Drumshanbo water gauge).

This meant that the nest was c. 50 m away from the shore line through a jumble of rocks, trees and fallen branches. The birds could not swim into this nest, neither could they easily fly from it! Instead when we accidently came upon this site the Merganser ran under the rock and most of the way down the shore before flying out over the lake.

This nest with eggs was discovered on the 1st. of July and observed on 3 seperate occasions during that month. They were incubated throughout and the female was keen to return to the nest each time we visited. The nest was found empty in early August and a subsequent report of a Merganser with 4 ducklings was obtained from the area south of Drummans Island on the 20th and near Spencer Harbour on the 23rd.

Unique food species.

Lough Allen also contains some unusual food species, a corygonid fish called the Pollan and a recently found shrimp, Mysis relicta. Apart from the usual coarse fish population and some salmonids, these could contribute to the Mergansers’ diet.

This year some samples of excreted fish bones were collected from a Merganser roost on an exposed shoal near Corry point. However, Cormorants were also using this roost and it is possible these bones came from them or even otters — though none have been seen in the area.

Fish comprise the major component of the Merganser's diet. When in fresh water, they feed on salmon and trout, roach, pike and eels, but have also been recorded eating crustaceans and molluscs. They feed on cod, hake and plaice while in coastal areas, but are also thought to feed on sticklebacks and gobies. (David Cabot. New Naturlist Series,  ‘Irish Wildfowl’)




What a cosy nest! No nest material in terms of vegetation or sticks, just a few feathers and loads of down, presumably plucked from the breast of the incubating female. The colour is typical of the lower feathers of a female Merganser.

From this photograph, it can be seen that this Merganser was incubating at least seven eggs. We just took this quick photograph and then left the site. It was not thought wise to delay near the nest as the Duck was in the vicinity and swam ashore and went up to the nest soon after we left the area. It is possible that there was more than 7 eggs here as Mergansers lay large clutches

Minding their young!

After the clutch of eggs had hatched on Church Island a female Merganser was reported in the middle of the Lake with a group of 4 ducklings. In view of the paucity of breeding records from Lough Allen this year, it is probable that this was the same bird looking after her young. The females, apparantly, also take responsibility for this and stay with their young for the first month. After this the young birds are still flightless but well able to fend for themselves and eventually find their way to the sea.

Unfortunately, Mergansers with young have become a very rare sight on Lough Allen in recent years. In the early 2000’s it was a frequent occurrence to see a family party at the southern end of the lake either near Cormongan or on the western shore of the lake. The report we have above is the only record we have for young Mergansers on Lough Allen either this year or last year.

Are they declining? If so... why?


A non-breeding female?

Breeding and Weather....

The Summer of 2011 was a season in which many water birds failed to breed in Lough Allen.

This could be put down to 3 factors:


1. Unseasonable weather.

2. Pollution/disturbance

3. Global change in breeding.


Apart from Mergansers, Lapwing and Curlew, Lesser Black-backed Gulls and Common Sandpipers also seem to have been affected by (probably) the weather.


The fine specimen shown above was obvious by being idle at a time of year when she should have been busy. Why was she not incubating or minding young? Instead she had a habit of lying up and sun bathing (when there was sun) on a particular place on Round Island west of Cormongan.

The suspected reason is... the weather! May was a windy damp month and birds seemed to be chilled incubating. (e.g. Sandpipers) There were also many fewer Mergansers in Lough Allen in 2011 than in 2010. Last year, though we lack the proof, we suspect that breeding was much more successful than this year.

The Mergansers that were present in 2011 spent longer prospecting possible nesting sites and then seemed to resort to pointless moving from island to island in pairs or as individuals. Eventually they were seen, like the pair on the right, peacefully cruising around their nesting sites at a time when they would normally have eggs.

NOTE: The male shown here has an unusual pattern on his head.This could be just going from breeding plumage into moult or it could be an injury or some feather removed in a dispute with a rival. Several of our photos show the same pattern. It could well be the same bird or it could be a normal part of the moult cycle.

Though the weather was quite dry in April and early May, it became damp and misty later. Water level remaind low but several species abandoned their nests (Common Sandpipers) or totally gave up any attempt to breed in established colonies (Lesser Black-backed Gulls)





Winter Plumage and Moulting.

This pair roosted, or rested, on a shoal off Corry point towards the end of the Summer. It is presumed that they had either not tried to nest, or had failed to do so. Mergansers can stay on to rear ducklings quite late into the Summer but this pair were seen regularly together at the same time as another female was hatching a clutch of eggs on the nearby Church Island. The two birds on the left are well into Winter plumage with the male looking like a darker female but still retaining the full white wing bar.

Breeding (or non-breeding) seems to affect moult. The breeding female seems to retain a bright tan head which goes duller as the season moves on. Also, males will leave the nesting site after the eggs are laid and move some distance away to undergo moult. This is called eclipse and Merganser males become flightless for a while during this process.

Moulting and wintering

The recovery of 16 of 196 adults ringed in Britain and Ireland shows that they undertake, in general, only local movements from their breeding grounds to nearby coastal areas to moult and to winter. Males desert the females after the start of incubation and get together with immatures and non-breeding birds at coastal locations during June and July to moult. In Ireland, relatively large numbers congregate at Dundrum Bay in Co. Down, the mouth of the Erne, and off the north Dublin coast. (Crowe 2005)

It is thought that wintering numbers of Mergansers remain relatively constant between September and March, and that most wintering birds come from the local breeding population.(Hutchinson 1989) Since 1998/99, Donegal, Ballisodare and Drumcliff Bay, as well as Sligo Harbour, are considered no longer to be important sites for concentrations of wintering Mergansers. The mean peak counts for these locations now range from 25 to 38 birds (Winter Wetlands Survey.)

2012 Account and Pictures

This year was a confusing one at Lough Allen. The Pollution that has been developing for tha past 4 years, and which we first reported and studied last year, has come to a head in 2012. It was everywehere! Also the weather and water levels were both bad for most of the year. However, the Mergansers have done alright — at least by the standards we have come to expect recently. Two broods have weened and 9 strong young seem recently (7/10/2012) to have successfully migrated away from their birthplace. How this species survives when on many days and in many places it is surrounded by detergent type pollution? However, this is a diving species and the contamination may tend to be on the surface. But it cannot be a healthy situation for a protected species and if insects and fish become affected — as may already be happening — then this top level feeder will also die out. Let’s try and curtail this ridiculous contamination, please!


One of first Pairs we saw scouting around Lough Allen in 2012




These 2 birds were flying out of Rossmore as we entered it by boat. This is an inlet of Lough Allen popular with Mergansers in the early Spring, as is the Druminalass inlet slightly further east.

We have seen Mergansers coming from bushes on the east shore of Rossmore and taking flight but have never seen any other signs of breeding here. It is probably not secluded enough or doesn’t have sufficent shrubby overgrowth for them to go ashore undetected.



By the time Red-breasted Mergansers arrive in Lough Allen the males are already starting to lose their green head gloss. It is unusual to see a male with a very green head. It is often blackish with underlying dark brown feathers and they often look a bit dishevelled. The easiest way to sex Mergamsers is to look for the white wing patches, much larger in the male and almost reaching the front edge of the wing.

Mating and Courtship:

Mergansers bring a lovely sense of excitement and adventure to Lough Allen in early May. They spend a lot of time both fishing and courting, fishing out in the middle of the lake in the early morning. later in the day they can be seen flying in from the main body of the lake to sheltered islands and inlets — presumably prospecting for suitable places to nest and claiming territory from their rivals.


An unusual shot of many Mergansers together.



Social Life:

The Mergansers of Lough Allen have complex social lives. They are alternatively gregarious and solitary. The males contest one another for a mate during the first month on the Lake. But when a nest is started the females are very much on their own and the males may leave a brood before it hatches. Females in turn will leave their broods at the end of Summer once they are able to fish and fly.


Apologies for the slightly iffy quality of the photo above, but it is a classic example of territorial behaviour and there is a nice contested symmetry between to 2 pairs. The male on the right is threatening the other male and the 2 females are keeping in the background. The male on the left may be younger as it has no sign of the green head. It may have been a last years chick coming back to Lough Allen to breed?

Meeting Places:

Mergansers can be seen around the south end of the lake and particularly the north end in the Spring; often found in pairs or, commonly, a pair with another male disputing ownership!

The photograph above, however, was taken just at Deadman’s Point south of Kilgarriff. This seems to be a ‘local dance hall’ where groups of courting couples get together to show how well they are doing!


New Pair starting off in life?

These were 2 of the birds involved in the social gathering above. Unfortunately the male is looking away but you can see clearly from this shot that his head is dark brown, not green. Also, their closeness and harmony would seem to suggest they are an item?

We often wonder about these brown-headed males. Later in the Summer they can look very dishevelled and possibly damaged from territorial disputes or courtship. But this male looks like it never had a green head. i.e. it was a young bird (like the ones shown below from this years broods) that went to sea and then came back to breed. They, certainly, seem to have no trouble attracting a mate but often seem to be the object of threat or attack from older looking males. Maybe they haven’t taken the message to quit the family shelter!

We have searched the literature but there is surprisingly little informnation on the breeding habits of Mergansers available. Perhaps a closer look at some of our wintereing birds in the sea of Sligo and Donegal may show up more of these brown head males and whether they stay brown for the first winter or do take on the typical green cap?




An Interesting Story revealed!

One day in high Summer we were exploring the shoreline south of Spencer Harbour looking for Mergansers. We spotted this pair and were quite interested in them. Young were out on the lake at this stage and it was unusual to see a male and female together. They seemed to be non-breeders who had stayed together when the duties of nesting and incubation had not caused them to separate. Males tend to leave the females at this time. They don’t seem to take any role in incubating the young or providing for the female?

At this time of the year it is unusual to see any males on the lake as they, apparently, migrate early. Also, this male seems to be unusually unkempt. You’d wonder what she’d see in him? This pair were skulking under thick Alder cover coming right down to the water. Lake level was high at the time and there was loads of protection in among the Alder roots and brances for the Ducks. Ideal breeding ground?

But there was a more compelling reason for their presence...




Just as I was taking the photograph above I heard an excited yelp from my dear wife behind. She had seen this lovely group of mother and 7 young Mergansers emerging from the Alders where the other Mergansers had also been. We had heard from Joachim and Saskia of Lecarrow Farm that a brood of young ducklings had been seen at their place a few days earlier. We were about 2 km south of that point but assumed that these birds were the same group as had been reported to us.

The nesting location was never determined. It could well have been the little overgrown stream at Lecarrow, or the place where we found them. It was not, however, the successful nest on Church Island in 2011, as this was not occupied this year.

This is the first photograph we have been able to get of a proud mum and her happy brood of these rare and elusive ducks. What a valuable and a charming part of our heritage they make. We know of no lakes south and east of Lough Allen to have breeding Mergansers and few to the west either.

Note that this female is on her own — typical behaviour as described in the books. They are dutiful mothers until the young are fit to fend for themselves.




Happy Families!

What a delightful sight to come upon somewhat unexpectedly. The mother was swimming strongly as our boat approached but the little ducklings were simply running on the water as fast as their little feet would carry them! Needless to say, we only followed then briefly and they quickly regrouped under the bushes.

We believe this family and the older pair were associated — even related — and the older birds may have been undertaking a grandparenting role? With the population the size we have in Lough Allen it is entirely feasible that they were grandparents to this little brood. Whether such relationships can help the mother care for her brood is not known!



Mother and young ducklings keeping very still
in among the bushes.

We see you


These little Merganser chicks are the cutest little things!



Female and her 7 ducklings heading away peacefully/








A truly classic Lough Allen picture...



One last Chapter:

We are happy to report that that was not the end of the story. About a fortnight later we came upon this group with 5 young off Long Island near Cormongan. The size of the brood was different but that could be easily explained. However, thankfully, when we got home we received an eMail from Joachim saying that he had recently seen the Lecarrow family again at almost exactly the same time as we were taking this photograph. These young birds were not flying at this stage.

So 2 female Mergansers successfully reared their broods in a very difficult Summer at Lough Allen. This is the first time we know of that this has been established. Of course, long ago, things may have been much different.... but there is no record of that. Just like there is no record of those outstandingly rare Lough Allen Orchids (Spiranthes romanzoffiana) before 2000?

To bring things right up to date, a party of 9 young Mergansers were seen off Ross Beg on the 6th of October 2012. They were now flying very strongly over long distances and there seemed to be no adult with them. We assume this group was made up of the 2 broods that hatched in Lough Allen this Summer.

We attempted to photograph this party but were unsuccessful and despite 2 further days searching, north and south, they have not been seen again. This probably concludes this update on Lough Allen’s Mergansers for 2012.







Conservation Requirement and Potential

It is clear both from our recent work, and other reports, that Mergansers — a species on the increase worldwide — need protection in Lough Allen and the general area of North West Ireland. The decline in numbers in Lough Allen, as indicated by the Bird Surveys cited above, is shocking. We accept that surveying Mergansers from the shore is a difficult task but our intensive surveys over 2 years does confirm a very low success rate in breeding.

We would attribute some of this failure to poor weather (especially this year) but there seems to be other factors at play, some natural and some man-made. The natural factors may be controllable in some ways but may be outside our control also. As regards Man’s influence on the environment, we do feel that we need to be very careful with enrichment and pollution on the Lake. There is considerable EVIDENCE that these problems are increasing rapidly and the visible impact of pollution (not to mention its toxic effects) may be deleterious to the Merganser.

A previous concern about wildly fluctuating water levels may not be as justified as we had thought in regard to this species — but it certainly is a factor in regard to that extremely rare orchid, Irish Lady’s Tresses, also significant for Lough Allen. The ability of Mergansers to adapt and nest further up the shore does mean that they can weather this possible impact of climate change!

This is a very brief outline of the problem. We hope to come back here and address the solutions at a later date? Any suggestions as to how to implement conservation measures for Mergansers at Lough Allen would be very much appreciated. (CONTACT us.)










Bird Web on Mergansers. Audobon Society, USA

Brief Introduction and Sound file for Red-Breasted Mergansers in North Amerioca.

Studies both species of Sawbill in British rivers with some interesting notes on male Merganser movement and moult.

Abundance, distribution and habitat use of breeding Goosanders Mergus merganser and Red-breasted Mergansers Mergus serrator on British rivers (R.D. Gregory, S.P. Carter & S.R. Baillie)

This is just a Bibliography of 105 articles; it does not provide links to their content!

Bibliography of Red-breasted Merganser - Mergus serrator

Study fron The Auk on Merganser behaviour in Alaska

Migratory Patterns and Population Structure among Breeding and Wintering Red-breasted Mergansers (Mergus serrator) and Common Mergansers (M. merganser). John M. Pearce,1,2,5 Kevin G. McCracken,2 Thomas K. Christensen,3 and Yuri N. Zhuravlev4


IUCN Red List of Threatened Species

Merganser: Range, Distribution, Breeding status and Conservation Issues. BirdLife International 2009. Mergus serrator. In: IUCN 2011. IUCN Red List of Threatened Species. Version 2011.2. <>. Downloaded on 04 December 2011.

Best Wishes from all at
With many thanks for your help during the year.


5th December 2011

[MORE STUDIES to come!]

If you have any interesting records of animals or plants from the Lough Allen basin, we will be very pleased to reproduce them here.