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An exploration of wild & interesting places in Ireland and their western European/American flora and fauna…
Red-breasted Mergansers of Lough Allen +
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A Lough Allen special species:

Red-breasted Merganser

Mergus serrator The Red-Breasted Merganser is a common offshore bird around Ireland in Winter, occupying many of our estuaries, marine backwaters, open sea, but never straying far from shore. It breeds in somewhat varying numbers in western lakes with Lough Allen, Co. Leitrim, having a good population. Over the ten years we have studied them, numbers actively breeding have fluctuated but most years less than half the population breed successfully. These may be young birds not fully mature, unable to find a partner (though they can be active during the mating season), shortage of food supply, and changing weather or climate conditions. Early Summers in recent years have been cold up to June and Mergansers seems to hold off mating and laying until finer weather sets in!

This is typical of our first sighting of Mergansers as they move back into Lough Allen (20th April 2016). They are wild and excited

moving rapidly all around what is a rather large lake. Depending on weather, which can be very variable in April in recent years,

they will either concentrate on feeding or resting or they will prospect old sites and start displaying and courtship. It seems that

the birds are familiar with the terrain… they may have bred here or have been hatched out here in the previous year.

With a distant shot like this the sexes can best be determined by the bars on the wings with the two females (with 2 white wing

bars) being on the left.. Note, also, the male on the right has a conspicuous white collar which the other male does not?

Breeding Plumage changes:

After a short honeymoon phase in Lough Allen the Red-breasted Mergansers quickly resort to a breeding phase with all the changes and demands that that makes particularly on the female of the pair. The classical bottle green male Merganser is only briefly seen on Lough Allen; they quickly change (after arrival) to a rather ‘hen-pecked’ dull brown head and lose the striking green sheen often depicted in the books. Much of finest plumage of ducks is seen in the Autumn/Winter phase when the damage done to their finery by breeding has been moulted out and when the males (in particular) are keen to woo their mates. Typical breeding plumage in the male not only has a green head but the lovely speckled orange-red pattern on their breasts. Females do not change so much but have a very consistent bright fawn head, a redder bill and an overall very attractive grey flecked upper body. Despite an arduous breeding effort (incubating eggs almost constantly for 30 days), they do seem to stay ‘tidier’ than their partners. The pair shown below are unusually pristine for mid May Mergansers. (7th May 2015)

Lough Allen features:

Lough Allen in Co. Leitrim/Roscommon is one of Ireland’s major lakes, not as big as some of the lakes lower down the Shannon but the biggest open body of water in the north west counties of Ireland. It is wedge shaped, tapering towards the south. Bordered by steep mountains on nearly all sides, it also has many glacial features both in those mountains and in regards to a deep channel running down the middle of the lake which has the profile of an ice cut channel with its maximum depth of 42m in a small area near the north east of the lake. Lough Allen is mesotrophic and the water is soft due to the absence (mainly) of limestone shores. The shoreline bedrock is rarely exposed but is known to consist mainly of shales with some very narrow sandstone (and limestone) beds particularly on the north shore of the lake. These qualities are rather different from other Shannon and neighbouring lakes which are mainly hard water limestone lakes. This and the varying depths of the lake probably contribute to providing the feeding and breeding conditions ideal for the Mergansers. Alder carr being a supporting biological features…

Merganser habitats of

Lough Allen.

The habitats and flora and fauna of Lough Allen are much discussed in www.LoughAllenBasin.com but here we are looking at the lake’s landscape, water and environment from the viewpoint of… “Why is this locality so suitable as a habitat for Red-breasted Mergansers to successfully breed?”

The Habitats of Lough Allen.

The four pictures surrounding this text show examples of the conditions and the vegetation that seems to suit Mergansers. TOP LEFT: Headlands on either side of Kilgarriff Strand. The bay between these two promontories is fairly wide leading up to a small sandy beach. Both headlands have abundant alders. The near headland also has some Willows and a Black Poplar (another shore loving tree). The far headland has a dense and tall Alder woodland covering the first 50 - 100m of the shore. Behind that commercial conifer forestry has been planted, unfortunately, but this had no impact on the Mergansers. The beach at the head of the bay used to have a grass and sand based cluster of Alder but they are periodically removed to allow access to the shore. The near shore we know as a Merganser courting spot. The ducks don’t breed here but they seem to gather here in April - June to display and pair up. It may be a central location to known breeding areas up and down the shore and on large and small islands offshore. TOP RIGHT: Another area where Mergansers don’t breed! This is a shallow bay between farmland and and a rock shoal known as The Spit near Cormongan on the southern half of the lake. That has a large gull colony and also, in recent years, some breeding Common Terns. It has shallow water on the east side which almost dries out leaving it attached to the mainland and allowing cattle to reach The Spit, and deep water to its west. Merganser are often found here and resting on The Spit or feeding in the nearby shallows. (29th April 2014) BELOW RIGHT: Classic Merganser breeding habitat, tumbled rocks, remains of drowned drumlins with living Alder onshore and Alder stumps in the water. Mergansers prospect these sites a lot and it is one strong nesting preference. (25th May 2013) BELOW LEFT: A flooded river, The Yellow River, 30th April 2014. A quiet backwater in Winter but a busy place in Spring and Summer. Mergansers fly straight in from the open lake and pass over the boulders at the top, presumably attempting breeding. We have searched but it can be very hard to finds nests without much disturbance.  

Red-breasted Mergansers… 

A year on Lough Allen…

Mergansers are shy birds and their exact lifestyle in Ireland is not fully understood. For example, we often see returning groups of Mergansers coming back into Lough Allen in April with a very early bird one year on 25th March. Sometimes there seems an easy camaraderie between them and sometimes this familiarity is disrupted by one male trying to drive a younger male away. Then that younger male may have a female in tow. It looks very much as if the older couple (and there are some plumage differences to back this up) are a pair and have met in previous years. We often wonder are these hangers-on offspring from the previous year. Certainly by the time they arrive on Lough Allen the mature birds — and Mergansers aren’t mature until their second year — are well bonded. The mature birds can be recognised in Winter and Spring by a very clear white collar on the males. The male of an accompanying younger ‘couple’ will not have such a distinct collar. Also both younger birds can appear smaller though this may just be due to plumage or the young birds taking a reserved attitude. The numbers arriving in Lough Allen each Spring are often much higher than the number of pairs that breed. A population of up to 20 birds early in the season is common in Lough Allen but normally only 2 pairs will breed, sometimes 1, sometimes 3 pairs. Relationships are well established before the Mergansers arrive on their breeding grounds. Mergansers winter at sea and they are widely present around all Irish coasts with good populations in Sligo and Galway Bays — the nearest sea water to Lough Allen. Whether these are local birds that breed in Ireland or birds from more northern breeding areas, we do not know. The Merganser is a Holarctic species and breeds in northern latitudes throughout North America, Northern Europe and Asia.

The arrival.

Early arrivals can be seen flying fast around the area in late March but not appearing to settle. April is the main month for the breeding birds to settle in Lough Allen and start displaying and searching for territory and breeding. It is at this early stage that mature males (in particular) start to change their plumage. It is rare to see a classic bright green headed Merganser in Lough Allen and this is the only time they are obvious. One the other hand birds overwintering in Sligo Bay will universally have stunning green heads particularly when the sun shines. Bonding or re-bonding — it is not clear whether these birds mate for life — seems to occur at sea where it is much harder to observe birds. In Lough Allen, especially with the use of a boat, it is relatively easy to track movements of Mergansers; that is nigh impossible at sea with many islands and inlets and tidal shores where the scattered population can easily hide themselves. However this phenomenon of mating in one area (or country) and then breeding elsewhere is widely known in migratory ducks. For example Goldeneye are very active displaying and pursuing one another in Winter in local lakes such as Lough Meelagh and Lough Arrow in Roscommon, to a lesser extent in Lough Allen, and without doubt in many more Irish lakes before they return to Scandinavia in March to breed.
ABOVE:    A party of Mergansers in the sea in Sligo during the Wintering phase after moult and interacting socially. (27th October 2012) LEFT: This photograph shows a typical pattern of behaviour adopted by newly arriving Mergansers on their breeding grounds in Lough Allen. The ‘established pair’, in this case in the middle, seem mature and confident whereas the other two appear like gangling youths —full of excitement and mischief but not sure what to do! The central pair are holding themselves very upright, they seem to have longer bills and the male has that bright white collar. They tolerate the other birds which appear younger with the young female (RIGHT) appearing particularly submissive. The mature male will tolerate the other birds but chases them away if they approach his female. Whether this relationship is built over two or more years or whether this comfortable bond has been established at sea shortly before they migrated to Lough Allen, we simply do not know. (15th May 2014)
Part of another group of four, newly arrived on Lough Allen, with the two males both displaying snazzy white collars complete with little black curls running down the back of the neck! (23rd April 2013)

Settling down…

The struggling for position, the group encounters, and the final establishment of a breeding partnership proceeds very quickly. At the north end of Lough Allen the shoreline shown at the top of the page attracts Mergansers from all parts of the north end of the lake.* Particularly early in the morning and late in the evening in good Spring whether up to a dozen birds may be seen around here. Very much the centre of attention will often be a group of four as discussed above. In these situations a young male may often overstretch the mark and have to be driven away by the male from the older couple. These are wary birds and if pressed too much by eager watchers they will simply leap up and fly away! The only way to definitively establish the relationships would be to study a group of identifiable birds over a long period. This has not proved possible in Lough Allen even over ten years — there are simply too many places where birds can hide unobserved. * Lough Allen has two centres of population for Mergansers, one among the islands at the southern end of the lake but north of the distinctive Inishfail promontory, and the other at the upper end of the lake where again there are many islands. The central section  of the lake has no islands and it is rare to see Mergansers there in the early part of the year. We tend to assume that these populations are discrete but these birds are very fast fliers and they have often been seeing flying out of sight in one direction or another.

Alder Carr.

Carr is a term used to describe old stunted woodland associated with water edges. In Lough Allen all the shorelines have a fringe of Alder forest. Much of this still remains. It is often cut down for firewood, to provide access to the lake, or for grazing. However Alder is a very resilient species and quickly regenerates so there is always a large amount of Alder scrub growing along most shores of the lake and its many islands. Alder has some specific qualities that make it flourish around Lough Allen. It thrives in poor under-nourished  places due to its unique ability to fix atmospheric nitrogen through nodules on its roots. This turns a stony mineral soil into a more useful resource for other plants to grow in and this benefits certain specialised plants like the rare orchid Spiranthes romanzoffiana which struggles to survive here. Very variable water levels are a feature of the lake due to a large watershed from significant mountains on all sides gathering water from a wet climate and with only a very short run to entering Lough Allen. These sudden floods are a feature of recent Summers (seemingly linked to global warming) but have always been part of the life cycle in Lough Allen. The Alder Carr is tolerant of this flooding and hence it is the dominant tree on all shores. Alder trees seem to be very capable of withstanding deep immersion. They survive on rock shoals when all the rocks are flooded and no other life remains. If they do succumb to flooding the dead stumps will remain in deeper water as you approach an island or a shoreline from the water. These conditions suit breeding Mergansers very well and we think it is one of the reasons why Lough Allen has a significant breeding population of Mergansers
Mergansers near Corry Strand (13th May 2011) a very long shot but it shows the incumbent male protecting his partner and trying to drive off another male. Such contest rarely come to blows…
Feeding or looking for food is rarely seen but typically occurs early in the morning in Spring, and also in the evening of a hot day. If breeding conditions are poor the ducks will also lie up and become very sedentary. Similar behaviour is common in courtship but we believe the pair BELOW were hunting! (8am: 7th. May 2015

Plumage changes following mating:

Mergansers have a busy time in April in Lough Allen. They arrive in good numbers (perhaps 20 or more birds). There is a southern and a northern group. These consistently move around their zones in a flurry of excitement, displaying and defending, exploring territory, and starting to mate. It is not clear whether pairs stay together for one or more years or whether small groups that associate may be family parties with the parents in struggling with last years offspring reluctant to move on! What is often described as breeding plumage in Mergansers is really more like courtship clothes and is best seen outside breeding areas from November until April. Rapidly, on starting to breed, the males’ condition deteriorates. In the early days of incubation the male will be seen on station in the water off the breeding location, slightly irrelevant heroes with their fading plumage accenting their loss of status now that the eggs have been laid. They don’t seem to bring any fish to the females who are often seen flying urgently out of a nest site and then back into it — possibly quick feeding journeys? (More information is needed on this?) The two images below show stages in the moult change. As the female settles on her eggs the males start to moult and often disappear from Lough Allen by July. They will gather with other males and non-breeding females and this change of lifestyle seems to accelerate the subsequent moult and loss of courtship plumage. Male brown heads: Two stages in the moult of the male Mergansers. First male is tidy but green and chestnut colours have gone (29th May 2014). On right, this male is tattered with feathers missing around his face (28th June 2011).

Perfect Specimens!

The two photographs reproduced below show what we call our ‘perfect ‘ Allen Merganser males. The bright conditions also helped show up the bottle green sheen, the red eyes and the dappled chestnut breast. But this honeymoon phase is very fleeting… (8am. 7th May 2015)


The breeding cycle of Red-breasted Mergansers

on Lough Allen.

These observations are based on many years observation, on land and on water, of these passionate energetic ducks that make Lough Allen one of their most important breeding bases in the north west of Ireland.


Pairs can become very close and definitely act as a couple within a month of arriving on the lake. Unlike the photographs shown above it quickly changes from a scene where there may be two males attending one female to a close-knit pair staying around a possible breeding location and staying very close to one another. This may well be a period of bond formation before egg laying will commence.

The Lull.

Weather induced delay has been apparent in many recent years. Mergansers DO NOT WANT to breed in adverse conditions. They become lazy and sedentary in May and up to June if the weather remains cool as it as done more frequently in later years — perhaps this is a factor of global warming? There is an increasing pattern developing in Ireland where Summers are delayed, evidenced on land by a fodder shortage and very yellow fields and on water by cold conditions, ducks ready to breed but not willing to start. What triggers this behaviour in Mergansers is puzzling and it was not observed in the first few years of our observations (2002 - 2010). These are diving ducks and one would think that food availability would not be greatly deterred by a cold spell. Perhaps they are anxious for another food source to supplement their fish diet and this is absent if the Summer is delayed… Mayfly maybe? Certainly, around the islands there is often an abundance of young pike and other fish from early in the Spring.

Busy Females.

This lull can run into June but does eventually end and the females can be seen busily moving around the lake, with or without their male companions.  The 3 photographs show two females chilling out and then one male purposefully heading up Yellow River quite likely to a nesting site. In cold Mays the females will often be seen resting up or sun-bathing on isolated places around the islands — often alone and disinclined to move. This provides a good opportunity to study the strength, sturdiness and massive legs these ducks have — all features to aid fast flying and deep diving.
TOP: A settled pair (29th May 2014) BELOW: a duck with a purpose heading towards suitable nesting habitat
This looks like a female resting but NOT breeding. Perhaps after an early morning fishing trip? We often went out early but they were always quiet and resting by early morning! (7th July 2013)
On the bouldery shore of Round Island, Cormongan, this duck has been aroused by our boat coming by. Note the upright stance, the strong chest and powerful legs. These are powerful ducks. (29th May 2014)
A familiar pattern of behaviour, flying in from the open lake and entering a narrow channel at high speed. Only occasionally males. This is the Yellow River site shown at the top of the page and we suspected a breeding area! (6th June 2013)

May / June: Start of Breeding…

The presence and characteristic breeding behaviour of Red-breasted Mergansers in Lough Allen (where they have been most studied) can be described in several stages: 1. Arrival. They arrive in April (rarely late March). This arrival is fairly constant both in numbers and in time. It may be a trigger caused by changes at sea, weather, or hormonal effects. 2. Exploration. A short period of getting to know Lough Allen again. Remember these birds may have bred here, or been hatched here in previous years. Some are checking out their old haunts, some are prospecting for the very first time. (There may be subtle differences in the appearance of young and mature males and it seems that young Mergansers do not breed in their first year.) Flocks of Mergansers from both the southern and northern areas of the lake are seen to regularly fly between both patches. This is not often seen later in the season nor are Mergansers regularly seen in the ‘empty middle’ of the lake. There are no islands here and the shore lines are generally flatter and more exposed so they may well eschew this habitat. 3. Settlement. By this we mean a period when the birds tend to stay in one large area though they will still actively fly all around it. This can be a long period and is often unsettled, very much dependent on the weather in late May and June. There are favourite meeting places at both the north and southern areas and prior to mating all the birds in each area will tend to gather here, often in the late afternoon or evening. These flocks will be mixed flocks, will contain young and experienced ducks and early bonding will be indicated less by a couple but by 3 ducks (one female and two males) associating with other Mergansers on the fringes. 4. Breeding and delayed Breeding. This is a time (ideally by June) when breeding naturally commences. We have been studying these birds out on the lake sine 2010 and regrettably in recent years breeding has been strikingly delayed by cold weather in April, May and even June (2015). Compared with the initial five years the weather in later years has changed remarkably and this seems to have halted the Mergansers. Another consequence of this ‘climate change’ is seen when late Summer rains come early and heavy and the lake floods damaging another of part of Lough Allen’s very rare biodiversity — Spiranthes romanzoffiana or Irish Lady’s Tresses, an orchid — but this does not hinder the Mergansers as young will be hatched and on the lake  by then. When the weather eventually warms up the Mergansers have a frenetic period of activity (see photo BELOW), finding a ‘nest’, settling down, mating and laying eggs. The females are particularly active during this period often flying fast straight back to their nest where they are very constant mothers and reluctant to leave their up to 10 eggs. males are loyally in attendance for the early part of incubation! Busy female perhaps heading ‘home’ after a short feeding trip. (3rd June 2011)


We know five nesting sites on Lough Allen, three at the northern end of the lake and two in the southern area near Cormongan on the east shore. Two up north have been in river estuaries like Yellow River and one on Church Island (Inishmagrath). This latter site is unusual in that the nest was a considerable distance from the shore (50m.) and the female had to thrash her way from the nest through trees and vegetation to reach the water when disturbed. However she was rarely disturbed and incubated her eggs until they hatched. We assumed the ducklings then quickly departed the site and went onto the lake where they stay close to their mother and love to hide in waterside Alders or Willows guarded by their mother. RIGHT: These two pictures show the breeding habitat and the nest and eggs of a successful breeding pair on Church Island. This was in the past a burial site but its buildings and remains are in ruins now and it is a very peaceful site for most of the year. In Summer it is used as a base for Outdoor Pursuits with many canoes and young people arriving on good days. However the nest is on the quieter north side of the islands whereas the activities normally go on around the middle of the island and the landing area on the east side. The sitting Merganser does not seem disturbed by these activities. The nest was found by a Research Assistant working for LoughAllenBasin.com. We were simply walking along the shore exploring methodically for a suitable nesting site as a male ‘sentry’ was often visible off this side of the island. These male Mergansers watching out for their partners are a bit of a give away but you would need to be out on the lake regularly to notice their regular routine. The site was at the base of a ring of boulders marking the high water level zone. The Merganser’s nest would have been near the water’s edge if she had started nesting at Winter or Spring high water levels. It is probably more likely that this is a historical site that has been occupied for generations and the females swim in among the dense alder cover and then walk to the boulder and the cave underneath. Even though two of us were very close to the nest before the Merganser broke cover, we still had some difficulty in proving breeding — so well was the nest hidden, The lower picture shows the beautiful nest full of duck down in which 10 or more fresh eggs were settled. Our count is not exact as we were anxious, after proving nesting, to leave the site. These are rare breeding birds in Ireland and any disturbance may put them off nesting. We visited the site twice afterwards, once to see she was still sitting and once after the eggs should have hatched (30 days later) to see that they were gone. They were… with little apart from a few eggs fragments and a load of cold down remaining! The young birds were not seen in that area subsequently but two or three pairs did breed successfully that year and it is possible the female seen with young on the west shore of the lake could have been this family. Males abandon the females as the young hatch and are rarely seen associated with them. They need to prepare to moult and then they migrate, earlier than the females, back to their Winter range at sea, whether that be locally, in Ireland or further afield — we do not know. (9th July 2011)    Nests are well hidden and female will not stir until practically walked on. (Please don’t!)
Growing up and Departure:

Leaving the Nest.

The young are very shy and in the first fortnight, which these ducklings undoubtedly were, stay very close to the mother and all tend to shelter in the middle of the day in deep overhanging scrubland. Alder trees, because of their ability to survive in water, are a clear favourite. All young, until they are full grown, have been found along the west shore of Lough Allen. This is an area where we have little indication of breeding but where they go on leaving the nest and start to learn to fend for themselves. It may be like a ‘retreat’ or it may be that there is shelter from rough water provided by the Alder carr and the west coast being sheltered from turbulent westerly winds? The family shown below were keeping very quiet in among the roots and were only detected with binoculars: (4th. July 2012)

West shore

Lough Allen:

These three photographs show a well-groomed female away from her nest with her brood. She was in very fine condition and probably feeding well as her young started to fend for themselves. There may be good pickings in these shallow woody waters, invertebrates as well as small fish. The female flew out onto the open water as our boat approached and the young ‘ran on water’ to get to her, and then (RIGHT) happily united again as we withdrew with our photographs!
A mature family group near Cormongan (4th September 2014).

The mature Ducklings:


Young Mergansers grow very quickly and then can be seen either in family groups or as bunches of youngsters actively fishing, flying, and exploring their environment. The group shown on the Right, we think, is a family party with the mother 5th from right. It is not definite as this was quite a distant sighting and the birds were not waiting for us to approach. This would mean a brood of 10 ducklings which is within the normal range. The females are recognisable by their bright chestnut heads. The female leaves her brood shortly after this and the young remain on the lake for another month or so. We cannot be sure of date of departure as the birds become wilder and the weather rougher as Autumn progresses, but they are definitely present in the lake until early October. The largest flock seen was in 2016 when a party of 14 was seen off Fahy Point near the mouth of Yellow River (did they hatch there?). The size of the flock and the absence of an adult female would tend to make us believe that this was a merger of two broods hatching separately and coming together prior to departing the lake and migrating to the sea.


This is an intriguing but difficult species to study; we would not have been able to produce these photographs or even record numbers present and breeding success without our boat. Lough Allen is, however, probably, one of the most suitable lakes to observe this species both in terms of the numbers present and the great variety of suitable nesting areas. It is a large lake with restricted access to the shore and that shore is often covered with thickets or else rocky and uncomfortable to walk on. It seems that there are up to 20 birds returning to the lake every year, some breeders and others yet to mature. Breeding starts after 2 or 3 years and the accompanying non-breeders may be bachelors or relatives of the pair they are associating with. We are not sure if pairs remain together or if the Lough Allen group stay in maritime areas near to Lough Allen, e.g Sligo Bay. So much still to answer and we have less time to work on Lough Allen than ever. ALL COMMENTS AND OBSERVATIONS MUCH APPRECIATED. (Contact Us)


There are other lakes. Image on right is a Merganser from Lough Arrow photographed in Summer 2017. They are present here in probably small numbers. We now live near that lake but for personal reasons we have not had the time to investigate this and Lough Arrow’s other special species, the Common Scoter now reputedly no longer breeding successfully? However, there were still two distinct pairs (5 birds) exploring and scouting around suitable nesting areas on the shores and islands of that lake.

WildWest HOME

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This informations backs up observations made on Red-breasted Mergansers of Lough Allen over 10+ years… but in particular from 2010 to 2016. We have drawn on extensive Logs kept from 2012 to 2015. These Logs can be opened from either the Home Page or Site Map of www.LoughAllenBasin.com Please note that this site is not being updated as we no longer live on the shores of Lough Allen and don’t have the routine access to the lake as we enjoyed for many years. If you have any additional information or wish to make a query please contact us HERE at WildWest.ie. Many thanks! YEAR Date Details Location

Earliest Dates seen at Lough Allen:

2012 26/3/2012 1 female Drummans Island, NW Lough Allen 2013 18/3/2013 1 male Annagh Lake off NE corner of Lough Allen 2014 26/3/2014 3 males (1Brownhead*, 2 Greenheads*) Rossmore, Inlet on NE shore of Lough Allen

Latest Dates seen at Lough Allen:

2012 6/10/2012 9 young Mergansers Ross Beg Bay outside Rossmore inlet, NE Lough Allen 2013 8/10/2013 Female The Spit, Cormongan, SE Lough Allen 2014 8/9/2014 8 young Mergansers Inishfail, South Lough Allen

Latest dates seen at Sea:

2012 29/3/2012 8 Mergansers Ballisodare Bay, Sligo         “ 2 Mergansers Sligo Bay 2013 16/3/2013 7 Mergansers Sligo Bay Brownhead and Greenhead refer to the perceived colour of male Mergansers heads at the time of recording. This cannot always be discerned in poor light and both may just appear as ‘dark’ heads. Brownheads: Mature males will show a green head up to March/April and then will gradually moult into a dull brown for the Summer. Green returns after the Autumn moult. Immature males (up to 3rd Summer) are brown-headed. Greenheads: Mature males after the moult (August/September) until the start of the following breeding season.