Bulletin 28 - March 1986: Observations to Clarify the Status of the Reef Heron, Little Green Heron and Clamorous Reed Warbler on Abu Dhabi Island 1985



Observations to Clarify the Status of the Reef Heron, Little Green Heron and Clamorous Reed Warbler on Abu Dhabi Island 1985

by Mike Crumbie

Introduction

The status of birds falls into internationally-accepted categories, generally notated in reference books and lists by letters or numbers. The allocation of a status is governed by the collation of many factors -- for instance, where and when the bird was sighted, its plumage, its behaviour, etc. The status of a species is under constant review by various societies, that either confirm or regrade it in accordance with the latest information forwarded by field observers. The quality of the information plays a big part in the grading of a status or, as in the case of the Clamorous Reed Warbler in the list compiled by Mrs. F.E.Warr, the grading remains unclear through lack of information. It is thus hoped that this article will change the status of this species.

In Mrs.F.E.Warr's list, used to update information for "A Check List of the Birds of the Arabian Gulf States", the Reef Heron is shown as a resident breeder in the UAE. However, the records of the ENHG (Abu Dhabi) have only one entry for a Reef Heron nesting, in 1981 on an offshore island. Unfortunately, the eggs did not hatch as they were removed from the nest. It is possible that records of breeding Reef Herons exist in other Emirates.

To further the knowledge of the breeding birds in Arabia, an "Atlas of the Breeding Birds of Arabia" is being compiled. The co-ordination for this project, which it is estimated will take about ten years, is being done by Mr. M.C. Jennings. Already the ENHG has forwarded information to him on breeding birds in this area and will continue to do so. His classification of the breeding status is indicated by using numbers ascending according to the importance of the evidence supplied, with the exception of the allocation of the code XX instead of a number. This indicates 'occurrence in suitable habitat at any time, even outside the breeding season, giving a good indication of local breeding'. The breeding evidence code used by Mr.Jennings is based on the 17 point system developed by the European Ornithological Atlas Committee and used for several other atlas schemes. As yet Mr. Jennings has not allocated the Reef Heron the XX status on his list.

Mrs.F.E.Warr, on the other hand, using letters to indicate status of the Reef Heron, has allocated RB -- Resident Breeder. In her list the Little Green Heron is also allocated RB, but with a question mark against it, obviously indicating uncertainty of the full status. The comment is also made "none west of the Dubai area". Mr. Jennings' list does not indicate this as a resident breeder.

It is hoped that the observations recorded in these notes will add to or clarify the status of the birds mentioned. (1)

Examples of status coding by lists and publications
a. "A Check List of Birds of the Arabian Gulf States", by Mrs. F.E. Warr:
RB -- Resident Breeder
PM -- Passing Migrant
b. European Ornithological Atlas Committee:
Possibly breeding 01 -- species observed in breeding season in possible nest habitat
Probably breeding 05 -- display and courtship
Confirmed breeding 16 -- nest with young seen or heard
c. "The Birds of Britain and Europe with North Africa and the Middle East", by R. Fitter, H. Heinzel and J. Parslow:
R -- Resident
W -- Winter Visitor


As mentioned in Bulletin No.25, March 1985, a survey was to be carried out during the first half of 1985 to establish whether, as was suspected, the Reef Heron was indeed breeding in Abu Dhabi Island. Whilst there had previously been favourable indications no solid proof had been forthcoming. The overall results of the survey in fact proved more rewarding than expected, with a total of six breeding species (three of which were in one tree) being observed. Three of these -- Palm Dove, Graceful Warbler and Kentish Plover -- were expected and have been documented in Bulletins 20 (July 1983) and 24 (November 1984). However, notes pertaining to the survey on these three species and other observations follow at the end of this report.

Area of Observation
Area

The general area of the survey is shown on Fig.1, the scale of the map being 1/100,000 and each square is 1 km. by 1 km. Observations were concentrated on the south western area as this proved to be most productive; the areas to the east and south were visited on only two occasions, the northern fringe not at all.

To the north and east the area is surrounded by limited tracts of open water; to the south by a dredged channel which replaces a former tidal creek; and to the west by another tidal creek.



Tidal Effects

As would be expected with such a low-lying region, large areas are inundated at high tide and in some parts never fully dry out at low tide. When flowing the speed of the tides can reach up to about four knots in some of the deeper channels. Erosion of the banks of some of these channels as a result of tidal action can be observed. A possible increase in the rate of water flow, leading to widening and deepening of the natural channels and erosion of banks, can be at least partially attributed to the dredged channel to the south acting as a drain-off. The areas in the centre are of mud and sand on which the tidal flow has little effect with the exception of inundation at high tide.

Vegetation

The vegetation of the area falls into two main categories -- bushes (Arthrocnemum macrostachyum) and mangroves (Avicennia marina). The bushes cover a large area wherever conditions for growth are favourable. In some cases, where they grow on the edges of creeks that are subjected to erosion, they are being washed away. Where new growth of mangrove is appearing the ground is sometimes shared but in general, given the correct conditions, the mangrove advance would appear to be at the cost of the Arthrocnemum macrostachyum. Where mangroves have matured there is no common sharing of ground.

The mangroves cover a large area but are concentrated mainly towards the fringes, away from the central area. The trees, in various stages of growth, are found throughout the range in dense to scattered copses and isolated patches of single trees. Towards the east and north the trees are generally immature, closely-spaced, about 7 - 9 feet high, compared with the more mature trees in the south west which are sometimes in excess of 25 feet.

The bigger copses seem to originate from several large mature trees with stout limbs that spread over a large area. Evidence seemed to indicate that propagation was by new growth from pneumatophores as well as seeds dropped by trees and carried by the tide. In late September and early October 1985 there was evidence of fresh growth from fallen seeds.

Within the mature copses the general condition of the trees and foliage was poor in comparison to the trees found in the isolated patches. In the densely packed areas they were tall and spindly, the wood of the lower limbs was generally thin and brittle and the foliage sparse. What foliage there was was very dirty and salt-covered at these lower levels; that at higher levels was in better condition. The thinness and brittleness of these densely packed trees is in all probability a result of their forced growth to reach the sunlight that seldom filters below the upper canopy.

The floor of the copse is thickly covered with pneumatophores (possibly up to 50 per square foot) and these in turn are heavily encrusted, in the majority of cases, with barnacles. As would be expected in these conditions, any chance of a stealthy approach to observe birds, etc., is impossible. Photography is also very difficult due to poor lighting conditions.

In the non- or sparsely-vegetated areas coverings of dried algae are abundant in the form of a dried, dark coloured carpet or skin. When fully dried this covering cracks and curls, giving the appearance of dried mud. In its live state before deterioration the algae is in the form of long, slimy green tendrils of fine grass which flow with the tide and are easily snagged on any obstruction, hence accumulating to form the carpet layer.

Drainage

The drainage from these large copses appears to occur through several naturally developed run-off channels. While the mats of roots of the trees generally preclude any large-scale erosion of the subsurface some erosion does occur in these run-off channels. This generally takes the form of deepening the channel rather than wearing away the edges too much. During the run-off period at low tide and even during the initial rising tide the channel sources are marked by miniature waterfalls backed by swaying pneumatophores, choreographed by running water.

Conclusion

The whole area presents a miniature ecology in its own right, which at present is expanding. How long this expansion will be allowed to continue naturally, without impediment from the discarded necessities of man's twentieth-century existence (plastic Masafi bottles, etc.) remains to be seen.

Reef Heron (Egretta gularis)

Introduction

The Reef Heron, as already mentioned, is classed in the UAE as a resident breeder. The evidence to support this status, at least in the records of the ENHG, is its presence throughout the year in varying numbers and the finding of a nest on an offshore island in 1981.

The presence of the species throughout the year and, during the breeding season, in suitable breeding habitat, is a strong argument for classifying it as a resident breeder, but the ultimate proof of this status is to find nests, eggs and young.

As mentioned in a previous Bulletin, it was intended to search for breeding Reef Herons in 1985 to confirm their status within Abu Dhabi. It is known to be a summer breeder but the initial search was commenced in March to look for possible evidence of previous breeding. Some old nests, which were originally thought to be those of Reef Herons, were found early on. However, later evidence provided by the finding of active nests of Reef Herons indicated that the early finds were, in fact, of a different species, the main difference being in construction, size and positioning. No subsequent evidence of old Reef Heron nests was found.

General

Reef Herons can be seen all around the coast of Abu Dhabi Island but sightings indicate that the larger concentrations are in the tidal creeks and mud flats to the north of the island. In Abu Dhabi the birds have been observed in two morphs -- white and grey, with the latter predominant. Shades of grey range from pale to slate. Of the breeding pairs observed one pair consisted of a grey and white morph. The white morph is difficult to distinguish from the Little White Egret (Egretta garzetta), seen occasionally in Abu Dhabi. Possibly the only dissimilarity between the two is the darker beak of the Egret, which in some cases in Abu Dhabi is almost black.

Generally feeding in shallow waters, but occasionally belly-deep, the main diet from observations of the contents of two regurgitations would appear to be small fish. Sometimes feeding in company, but more often than not alone, several birds can at times be seen spaced widely along mud banks, etc.

Same publications indicate that the birds are not too wary of humans but this proved not to be the case in Abu Dhabi, as birds were not readily approachable.

The first indications that nesting activity might be taking place was on 22nd May when six birds were seen making approaches and and attempts to land in the tops of the trees of the main mangrove copse. Eight Night Herons (Nycticorax nycticorax) were disturbed from within the main copse by this activity, and further sightings were made of them on 29/5 and 30/5, leaving via the edge of the copse and not the canopy. On 2/6 two Night Herons were seen on the ground, one mature and the other possibly immature; this was the last sighting of them in the area for a while, although subsequent sightings were made at irregular intervals.

After the first sighting of the possibly breeding Reef Herons on 22/5 it was decided not to search in depth for a period of one week to prevent disturbance at a possibly critical time. However, a single empty nest was found in a lone tree with a broken eggshell beneath -- so far the most convincing proof of breeding attempts.

Nests

Distribution A total of eight nests were found throughout the area of the main survey, five of which were in the main copse. Of these two were in one tree, two a few yards away in separate trees and the fifth a few yards further out on the edge of the copse. Of the three outside the main copse two were in completely isolated trees (one in the company of a Clamorous Reed Warbler's and a Palm Dove's nest) and the third on the edge of a thicket. Reef Herons generally nest in colonies but are also known to do so in isolation, as evidenced by these observations. It was interesting to note that the three isolated nests were built on the leeward side of the trees away from the prevailing westerly to north westerly winds.

Construction Nests were built completely of twigs, between five and ten feet above the ground. The construction varied from being of a reasonably stout nature to one of extreme flimsiness, appearing hardly strong enough to support the weight of a heron. In some nests the twigs were very lightly placed enabling the eggs to be seen from below through the lattice-work. The overall appearance of the nests gives the impression of a haphazardly-constructed platform of twigs laid on branches -- as mentioned later, a possible factor in the loss of some of the eggs.

Approach Initially it was wondered how a bird with such a large wing span (86 -104 cms.) could get to the nests, which in some cases were in reasonably thickly-foliated parts of the trees. Subsequent observations showed that the birds generally landed higher in the trees and after a period of surveillance would drop or step from limb to limb down to the lower level of the nest. As would be expected from such a large bird, the bending and distortion of the lesser branches under the birds' weight was quite considerable. Large areas of foliage were heavily discoloured and polluted by the birds' droppings, this being exacerbated by roosting in the trees. Areas of foliage in trees away from the nests were also heavily discoloured by roosting birds.

Dimensions It was difficult to obtain exact dimensions of the nests due to their untidy construction. If, as in one case, the extreme dimensions were taken the general impression given would be incorrect, because a single twig extended the size to almost 30" across. The nests are usually round or oval in shape, measuring an average of between 15" and 22" across, the overall thickness being about 7" with a shallow depression in the centre, depending on the stoutness of the construction, of between 2 inches and 4 inches. It was difficult to see the sitting birds but in the one case observed, it was overhanging the edge of the nest.

Eggs These are oval, smooth, pale blue/green, with mean average measurements of 45 mm. x 34 mm. -- those measured in Abu Dhabi being about this mean. In two nests four eggs were laid; in three nests three eggs, and two nests had only one egg each. In the eighth nest no evidence of eggs was found. Of the overall total of nineteen eggs only five hatched, the rest being cracked, discarded or probably tipped accidentally out of the nest. One egg had been completely broken in the nest with remnants of the yolk found filtered through the twigs. There is a possibility that this could have happened in one other nest. As some nests were found already containing eggs the laying period was recorded in only three nests, with indications that eggs were laid at two-day intervals. The incubation period was observed in only one nest and would appear to be about 26 -28 days.

Young The indications were that the eggs hatched at approximately two-day intervals, this tending to give the first chick an almost insurmountable advantage of survival. In one instance the first hatched was seen bullying one of the smaller ones.

When first hatched the young are sparsely covered with a fine hairlike down, the skin is yellowish green and the eyes are closed. In the first few days they appear to sleep a lot between feeding.

Growth is fairly rapid and within a week the chick is covered with a grey hairlike down, 0.5 to 0.75 inches long, which appears most prominent on the head. The young are active within the nest standing, sitting and at times making a burring sound. In the second week it is noticeable that one chick begins to outgrow the other rapidly. Feathers on wings and back begin to form, albeit in spikes, but the head still has a downy covering. The flesh is still greenish yellow but the down has disappeared from the breast and throat area, leaving bald patches. The eyes on the larger chicks are well developed, showing indications of the classic yellow ring around the iris of the heron; the bill is dark coloured. The larger chick manages to totter to the edge of the nest followed by any remaining smaller chicks. Early in the third week the feathers are still in spikes, the legs are green and the grip of the feet is quite strong (as experienced when lifting one remaining chick back into the nest). The young are capable of walking along branches around the nest and can be heard making a squeaking noise. When disturbed the young regurgitate and defecate (let the unwary be warned). The contents of one chick's regurgitation were approximately 15 small fish ranging in size from 0.5 to 1.0 inches long. Further regurgitations, from an adult bird, were found to consist of 13 small fish from 1.0 to 2.0 inches long.

The rapid growth continues and in the fourth week the young are very active in the limbs of the tree. Feathers cover the main body and tops of the wings. During the fifth and sixth weeks the feathers turn dark grey and white feathers develop under the throat. The beak becomes paler and the slight down on the head stands upright like a crest. The ring around the iris appears white, The underbelly is pale and the bottom half of the legs are green, the top half grey with greenish rings.

The remaining observed young one finally left the shelter of the foliage and nest in the seventh week. During the ninth week this young one was wading in the proximity of the parent birds. The plumage was a pale, soft grey with a small crest developing on the head. The underbelly was pale, legs still grey/green but the feet now green. The flight movements at this stage still showed inexperience. Further observations showed the possibility of the young bird still in the company of its parents after the tenth week.

Breeding chronology

Days in breeding cycle are approximate but believed to be accurate within 2 -3 days. Allowance has been made for laying of four eggs, found only in one nest. Eventually one was cracked and discarded. Eggs are laid and hatched at approximately 48 hour intervals.



Conclusion

The evidence for the status of the Reef Heron as a resident breeder in Abu Dhabi Island is now conclusive. No evidence of previous breeding, in the form of old nests -- as in the case of the Clamorous Reed Warbler, Little Green Heron, Graceful Warbler, Palm Dove, etc. -- was forthcoming. However, the possibility of previous breeding must remain.

Given the attrition rate among the Reef Herons (five from nineteen eggs hatched but only two birds surviving from these five, one of which would not have survived had it not been replaced in the nest) the future of it as a breeding species is not assured in this area.

Various factors contributed to this rate of attrition. Certainly during the egg-laying stage the clumsiness of the parent birds must be of considerable importance. At least three eggs were found with cracks or indentations, indicative of having been pierced or cracked by the beak or feet, possibly during alighting onto the nest. The flimsiness of some nests and the shallowness of the depression would allow them to discard eggs by rolling, again probably caused by the birds alighting.

Once the young were hatched it became the natural law of survival of the fittest, this process aided by the approximately 48 hour interval between hatching, giving a huge advantage to the first chick. In one case a young bird died because it had fallen and become entangled in lower branches about two feet below the nest. Had this not happened the chances are that it would have survived, its growth rate having put it on a par with its companions.

The possibility of limited disturbance by humans cannot be ruled out but it is thought that this would be, at most, of a minor nature.

The fact that the area of suitable breeding habitat is increasing in size and maturity, and that abundant food sources are available, will hopefully lead to further breeding.




Clamorous Reed Warbler (Acrocephalus stentoreus)

Introduction

In Abu Dhabi the Clamorous Reed Warbler has not been recorded during the months of December and January, although it has been suspected of being resident throughout the year. There are no past records of it breeding although it was certainly thought to be a possibility. The finding of the first nest came by chance during the initial search for the Reef Heron in March. Unfortunately, confirmation of it being that of a Clamorous Reed Warbler had to wait, owing to a break in observations, until the middle of May. Thus observations over the early stages of the breeding period were not possible and later ones were not as detailed as would have been liked. However, the fact that nests were found and observed must count as a bonus.

General

The Clamorous Reed Warbler is one of the larger members of the warbler family. Its colouring for the upper part of the body is of shades of brown with the underparts being paler. In some birds the eye stripe is more pronounced. Owing to its secretive nature it is very difficult to study its behaviour at any great length and not one bird was ever witnessed actually sitting on a nest.

Occasionally a single bird could be seen around the base of a mangrove tree searching for insects. The birds are generally seen flying from bush to bush, very seldom over long distances and always below tree-top level.

Calls

During the breeding season by far the greatest indication of their presence is their calling. It is fairly melodious but, as the name would imply, clamorous in the extreme. It was very noticeable that towards the end of the breeding season (late July/August) the calls of the birds virtually ceased.

The calling seemed to fall into two categories. Firstly there were the loud, songlike calls, which could serve the purpose of either establishing territorial rights or as mating calls. Another suggestion is that by the sheer volume of noise they create an impression of larger numbers than actually exist, thereby warning off possible intruders.

Secondly, within the bushes calls of a shorter, less raucous nature could be heard, more as a caution or warning between parent and 'young, the latter usually responding with a subdued squeak or cheep. It was very difficult to pinpoint the source of the calls which, when one approached the apparent source, would cease and start again elsewhere.

Nests

Distribution Nests were found over a large area where accessibility at times proved a little difficult. All the nests -- and in excess of 30 were found -- were in mangrove trees, mainly in mature isolated thickets or single trees but a few were found in the main copse.

It was thought that the numbers in the main copse could have been restricted by the density of the trees, which are thin and tall with the foliage mainly at the higher levels. The few found here were, generally, higher from the ground - 10 feet on average - and more towards the outer perimeter. The nests found in isolated trees and thickets ranger from 5 - 7 feet above the ground. There were no noticeable differences in the methods of construction throughout the nesting range. Nests were dispersed and not in colonies. Three were found in one clump and evidence of an old nest was also apparent.



Construction Unfortunately, an occasion never arose whereby it was possible to observe the progress of construction of a nest. However, much information was gathered from measurements taken plus the disassembling of one abandoned nest. All were constructed between three vertical limbs of varying thickness, in two cases with two of the main uprights in one tree and the third in another in very close proximity. Only one nest was found supported by two uprights only and this had tilted in one direction through lack of equal support.

Initial inspection indicated a cup-shaped nest of grass and fibrous material, interspersed with a few feathers, odd narrow lengths of clear plastic and, in two cases, orange and blue nylon fishing line.

Closer inspection quickly dispelled any ideas of a simple nest. The fibrous material was deteriorated mangrove twigs, of which further examples were found in nests of other species, and samples were taken from the trees. The twig appears to deteriorate from one end; the core material under the bark (which is easily removed) becomes fibrous strands and it is these which are woven and laced into the construction.

In some cases the non-shredded end of these deteriorated twigs was still attached and where possible laced into the nest or just left protruding. One large sample of these twigs measured approximately 48 cm. long (17 inches) and 8 mm. at its thickest point -being about two and a half times the length of the average warbler.

Feathers contributed largely to the construction and are intricately woven with the other materials; in some cases the vertical and horizontal portions are tied with nylon line. Basically white, the feathers varied in length from a few mms. to 29.5 mms. (11.75 inches). In the nest which was examined in detail over 350 feathers were present. At the top of the nest it was thought that the materials were only tied or woven around the uprights but it became apparent that the final securing strands were glued as well. The adhesive, probably manufactured by the bird, tends to crystallise but still retains some adhesive quality.

Dimensions The following are the measurements taken from a sample of five nests. Dimensions are in inches to the nearest quarter.



Occupants Apart from the warblers themselves, other occupants were found breeding in the nests, namely flies (i.e. Diptera, of the sub-order Brachycera, family Otitidrae). The larva, hatching from their casters, live in decaying matter, of which the nests are an abundant source. This process was confirmed in the removed nests. Casters were also found in other, active, nests.

Eggs

The majority of nests contained three, but some had two, eggs. In nests where young only were present the maximum was three. There was a reluctance to remove eggs for purely measurement purposes, but of the few that were measured the length was approximately 20 -22 mm. The eggs have a blue/white background with dark brown/black splodges and lines.

Several nests were found with a single egg remaining, in two cases partially covered by a leaf. One nest was abandoned with three eggs. In one case an egg had been forsaken after two young had left the nest. This could possibly have happened in other cases of single eggs being found in nests later. One such was broken open and the contents showed no indication of young, just a heavily-bloodied yolk. No further activity on the part of the warblers took place with these apparently abandoned nests.

Young

The rate of attrition of young and eggs during the period from incubation until the young left the nest seemed to be very high. Of the six nests visited regularly only one showed indications (though not confirmed) of a complete brood of three leaving the nest.

When born the young are naked and basically orange-coloured, with eyes closed. After a few days they develop a dark down covering, their eyes are open and they make positive efforts, with beaks open and necks stretched, to reach for food when fingers are placed above the nest.

From the down stage the feather spikes develop quite rapidly, as does the growth rate. The general colouring is brown. Tail feathers appear very short and stick upright. It would appear that the time in the nest varies with the numbers of young present and in the case of a single young bird the growth is rapid. Only two young were seen out of the nest. The first one was unable to fly properly and was making its way by hopping and flapping from stem to stem of small mangrove shoots approximately 18 inches above the ground. Its overall colour was brown/fawn, its beak was broad and tended towards an orange colour towards the base. The ear holes were clearly visible, the tail was very short, brown and sticking upright. A close-by parent was giving warning calls to which the young responded with a very subdued cheep or squeak.

The other young one observed was in a tree isolated by water and mud from other trees and was the sole survivor of three. Its growth and development within a week of leaving the nest was staggering. When approached it made no attempt to flyaway, it just hopped from branch to branch. The feathers were pale brown/grey, legs were pinkish and the eyes black, large and young-looking with pale surrounds; the tail was short. The possibility that it was a visitor from another nest can be discounted as it could not fly properly, the tree was completely isolated and there were no other nests nearby.

Chronology
 


Owing to various circumstances the chronology tables are approximate and not as detailed as would have been like.

Conclusion

Although the period of observation was rewarding questions were posed for which no answers were readily available. As with the Reef Herons why the high rate of attrition of eggs and young? From where do the birds collect the large amounts of feathers and other materials used in the construction of nests?

It has been mentioned that in other areas second broods do take place but in Abu Dhabi this was not recorded. Of all the active nests visited on a fairly regular basis, once the young had left there was no indication of further egg-laying activity. However, eggs were still found in nests in July; whether these were late breeders or second layings in new nests is not possible to state at this time. One point that has not yet been fully clarified is that of its status in Abu Dhabi, since it has not been recorded in December and January. As the Clamorous Reed Warbler is known to winter in Oman the chance of it being a resident breeder in Abu Dhabi are probable. It is obviously a thriving breeder and, unless its habitat is destroyed by 'the march of progress' it should remain so.

NB -Since this article was written, the author has seen and heard the Clamorous Reed Warbler in Dec. & Jan. '85/86. It is now RB.




Little Green Heron (Butorides striatus)

Introduction

Detailed records of the Little Green Heron in Abu Dhabi are scarce and observations in other Emirates are inconclusive. Records in the ENHG (Abu Dhabi) show sightings in Dubai in November, December, January and in April, and for Fujeirah in January and April. In Bulletin 26 (July 1985) the article on the Little Green Heron suggested that it was a rare visitor to Abu Dhabi but in the light of subsequent observations made this year this would appear to be erroneous. As already mentioned Mrs. F.E. Warr questions its status as a resident breeder and Mr. M.C. Jennings does not grant it this status.

Possibly the lack of continual observations, the difficulty of access to its preferred breeding sites and its secretive nature have contributed to the uncertainty of status. However, it can now be confirmed that the Little Green Heron certainly breeds in Abu Dhabi, but whether it qualifies as resident can only be proved by further observations in the future.

Owing to its secretive nature and the late finding of breeding evidence the notes, of necessity, are unfortunately brief.

General

The Little Green Herons observed were in the area of the main mangroves, but they have been sighted occasionally in the vicinity of Muqta bridge and possibly, singly, to the south west of the island.

During flight the birds generally remain low over the water, with a fairly slow wing beat. Some were observed landing in the tops of isolated mangroves and on one or two occasions accompanied by a young bird which had great difficulty in imitating the correct landing procedures of the parent bird.

When searching for food on the banks of the creeks they adopt a head well forward, tilted to one side posture. Taking determined steps they make a stab at any unwary fish, but do not adopt the running-around-with-wing-spread tactics of the Reef Heron.

From observations it would appear that one of their favourite fishing positions is sitting on the lower limbs of bushes that are close to the water, thereby enabling tllem to make stabs at passing fish. These lower limbs also seem to be favoured as roosting positions on occasions when the water level is low.

Except when in the company of a young bird the Little Green Heron was generally seen feeding or flying alone, possibly up to 1 km. away from the nest. The call is similar to that of a Reef Heron but of a higher pitch and the young, when in the trees calling to parent birds, are of a raucous nature.

Nests

Distribution Two nests were found in the main mangrove copse in proximity to the Reef Herons. It is known that these birds do breed with other species sometimes, including the Reef Heron. No nests were found elsewhere in the area.

Construction The nests were built in trees approximately 5 feet above the ground. The reasonably tidy construction was of twigs, of a stouter nature and generally superior to that of the Reef Heron, conforming basically to an oval shape.

Dimensions Measurements to the extremes were approximately 10 inches by 19 inches (25 cm by 43 cm) with an overall depth of 6 inches - 7 inches (15 cm -18 cm) and a mean depth of the depression of approximately 2 inches (5 cm).

Eggs

Of the two nests found one contained four eggs and the other three young and one egg. Pale blue-green in colour and close-grained, the 4 eggs give more of a gloss appearance than the coarser-grained Reef Heron's eggs. The approximate measurements were 40 mm x 30 mm.

Young

Observations of the young were irregular and limited in continuity owing to their short time in the nest. However, some notes were made. In the nest found with four eggs three only hatched between 2nd and 6th June; the first two to hatch opened their eyes during this period, the eyes of the third remained closed. The two young with open eyes managed to raise their heads and open their beaks for food but were unable to maintain this position.

At the beginning of the first week the three young were down- and hair-covered, with yellow/green rings around the eyes. The beaks were yellowish-brown with a black tip at the end of the upper mandible. As they had probably just been fed they were sleepy and paid no attention to intruders.

By 15th June the young had gone; there were no indications of disturbances, etc.

On 3rd July another nest was found containing three young and one egg. From the appearance of the young it was deduced that they were a few days old. Their eyes were open, with green rings round them. The green colour was also apparent at the base of the bill. Their necks were stretched up with beaks open and their throats were trembling, possibly in expectation of food, as the parent bird had been disturbed from the vicinity.

By 9th July the young had left the nest, but an eggshell was found below, indicating that it had been, discarded very recently (otherwise the shell would have been carried away by the tide).

Subsequently in August approximately six Little Green Herons were seen, mature and young, in and around the main mangrove copse.

Conclusion

The finding of the nests, complete with eggs and young, proves that the Little Green Heron is breeding in Abu Dhabi and is probably a resident, though further sightings throughout the year are required.

As mentioned in the introduction to these notes other, older nests of very similar construction to the two discovered this year were also found in the same area. Although not definite proof they are an implication that the Little Green Heron could possibly have bred in Abu Dhabi in past years.

As young were seen, in some cases in the vicinity of the nests, at a later date it can only be assumed that the short time they spend in the nest is not detrimental to their progress, although how many survived to full maturity is impossible to say.




Additional Notes and Observations

Palm Dove (Streptopelia senegalensis)

Numerous nests were found containing eggs, young, a combination of both or simply empty. The nests in general were of the usual skimpy construction but'obviously strong enough to support the raising of broods.

In some cases Palm Doves had saved time and effort by occupying larger, more heavily constructed old nests of an unidentified species. These larger nests, in a few of the occupied cases, had been lined with the finer kind of twigs, more in keeping with the Palm Dove style of construction. In other nests there were combinations of twigs and droppings, presumably of a Palm Dove. In their nests the young doves appear more docile than the young of other observed species and can be approached easily.

Kentish Plover (Charadrius alexandrinus)

One Kentish Plover's nest containing two eggs was found on 29th May in an extremely precarious situation, just one metre from a track. In spite of the occasional passing vehicle one of the parent birds remained resolutely on the nest, only leaving when directly approached. How long the nest could remain intact was a matter of conjecture as one vehicle had already passed directly over it. (Suspicions that a nest was in the area were aroused in the usual way by one of the birds feigning distress and injury).

For the Kentish Plover the normal clutch of eggs is three, occasionally four. There have been suggestions that they might have two broods, which would be difficult to prove given the nature of their nesting habits. The nest, being just a shallow depression on the ground is, once abandoned, soon obliterated by driven sand.

On 11th June there was only one egg remaining in the nest and no sign of the parent birds. Early on the morning of 13th June the nest was revisited; the remaining egg had been cracked open at one end but still contained one perfectly formed young bird which had I apparently died in its attempts to break out.

Graceful Warbler (Prinia qracilus)

No effort was made to find Graceful Warbler nests this year but the birds were present in great numbers in their usual breeding habitat -- in the Arthrocnemum macrostachyum bushes.

Asian Honey Bees (Apis florea Fabricus)

Possibly the most unexpected find in the mangroves was that of numerous active colonies of the Asian Honey Bee. There was ample evidence of former activity in the shape of abandoned nests. In most cases these were in the classic shape of the Asian Honey Bee, namely round and thin. Diameter measurements varied from 5 inches to 18 inches plus, and averaged 2 inches to 3 inches thick. The majority were found in the denser parts of the woods at heights of 18 inches to 10 feet above the ground. The bees fed on the small, yellow flowers of the mangroves. It became apparent by mid-July that virtually all the known colonies had been removed or destroyed -- presumably by humans.

Crabs

As expected crabs in their hundreds were seen throughout the area. Small in size (approximately 1.5 inches - 2 inches across) they appeared in what could be three different species or sub-species as yet unidentified.

Colourings were distinctly different, the large majority being a dark purplish brown. This variety inhabited the whole area, mainly living in holes in the mud in the creek banks and further back in areas that became inundated at high tide. In the denser part of the mangrove copse this species was regularly seen to be climbing trees and some were seen in a few of the Palm Dove nests. Several of this variety were observed carrying small fish, roughly their own size, back to their holes. The fish being already dead it could not be ascertained whether they had been killed by the crabs or found stranded.

The other two varieties, of about the same size, were observed mainly in the small tributaries to the major tidal creek. Roughly similar but differing in colour from the previous crabs, one variety had a sky-blue covering on nearly all of its shell and claws, and the other a pink shade. This colouring sometimes becomes obliterated by silt from the muddy bottom of the tributaries, which possibly acts as camouflage.

Quite a few crabs get trapped at high tide in the thick growth of the scrub bushes and consequently die. The majority of them seem to be speckled with various shades of pink/orange. It is not known if this is another species or if the colouration is a result of bleaching and drying by the sun once they are trapped in the scrub.

Note

The survey was carried out over a period of a few months, in an area that, if it is to be visited in the less accessible regions, should not be treated casually. As a word of caution, it is not considered a suitable area in which to take young children and it would be prudent for adults to be accompanied.

Thanks are due to the following, who spent varying amounts of time during the survey getting bogged down or washed away -- Andy Harding, Bish Brown, Jilly Burrows and Ken Mackie. May their feet remain well and truly webbed.

Mrs. F.E. Warr and Mr. M.C. Jennings are both officers in the Ornithological Society of the Middle East. Return to top

 


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