Notes on the Black-headed Gull Larus ridibundus at the Broome Sewage Ponds 

On Saturday 19th October 1991, a local birder Brian Kane rang the Broome Bird Observatory to report a dark headed gull at the Broome sewage ponds, maybe a Laughing Gull in full breeding plumage.  The following are the notes of the observations that I made leading up to the confirmation by the observatory wardens that the gull was in fact a Black-headed Gull, and the first known sighting in Australia.

The Sequence of Events

Brian had first seen the bird at about 8am. He made a note of many of the details, and then called someone in Melbourne who suggested that it could be a Laughing Gull.  Brian then rang the observatory.

Bruce Ferry (the assistant warden) arranged to meet Brian at 3pm, and I was invited along.  The bird was there and we observed it from distances ranging from 50m to 20m for a period of 40 minutes before it was disturbed and left the area.  The conclusion was that it may be a Laughing Gull (based on the limited information in Simpson & Day), but that there were a number of details that did not seem to fit, such as the head colour and wing markings.  Bruce took a number of photos.

The bird was seen by local birders on the Sunday.  Meanwhile, Bruce located a British book by Vere Benson which opened the possibility of the bird being a Black-headed Gull, but the information was extremely limited.

Bruce and I returned at 10:30am on the Monday.  The bird was still there and we stayed for two hours observing from within 15m at times, although I was distracted for about 30 minutes looking at Yellow Wagtails, etc.  Bruce took more photos.  I spent most of the time updating the notes I made on Saturday, and looking for the features mentioned by Vere Benson such as no windows in the primaries.  We now knew that it wasn't a Laughing Gull, and the chances of it being a Black-headed Gull were improving.

The BBO wardens Kira and Stuart Jackson found the Japanese field guide donated by a member of the Japanese delegation of the JAMBA conference held in Broome a week earlier.  The Black-headed Gull was shown as a non-breeding migrant to Japan (and further south) from central Asia.  The details that we knew matched, but there were also important details that we had not noted, and we did not know if there were any other gulls that might be possible.

On Tuesday, Stuart phoned RAOU headquarters in Melbourne and asked for details of any relevant gulls to be faxed.

On Wednesday, Mavis Russell (a volunteer at the BBO) and I returned to the sewage ponds at 4:15pm.  The gull was not there and had not returned when we left at 5:30pm.  However, it was low tide and very little else was there either.  We met a local who had seen the bird at about 7am that morning.  After some problems, the fax of a paper by Grant in British Birds arrived in the late afternoon but could not be collected.

On Thursday, Stuart visited the sewage ponds at about 7:30am and then picked up the fax.  The bird had returned, and he confirmed the details and took some photos.  Kira, Bruce and I had been on a tour, but we visited the sewage ponds at 11:15am and observed the gull for 40 minutes.  Bruce took more photos.  We confirmed the white wedge and leading edge on the top of the wing, and the dark patch under the primaries.  The fax confirmed what we now knew - that the bird was a Black-headed Gull.

The Behaviour of the Gull

The most noticeable aspect was that the bird never stayed still.  On the water, it continually swam back and forth feeding.  On the bank, it preened.

On the Saturday, the bird was initially swimming with a few Silver Gulls, but it spent most of its time preening itself amongst a loose flock of Silver Gulls on the bank between two ponds.  It flew back to the pond when we approached closer than 20m, and it eventually left the area altogether.

On Monday, the Black-headed Gull spent most of its time swimming and feeding.  We disturbed it several times by approaching too close.  Most times it landed on the bank with the Silver Gulls, or back on the pond.  Once it flew less than 100m to a shallower pond, and then back again when it was disturbed there.

On Thursday, the gull spent all of its time swimming and feeding.  Even if it flew when we approached too close, it landed back on the pond.

The gull swam with its head held high, frequently dipping its bill presumably to catch small prey near or just below the surface of the water.  There were no noticeable mannerisms that indicated if the gull was successful or not.  The gull swam laps near one side of the pond of no particular preferred length (about 1m to 20m were observed) and reversed direction at no particular place or for any discernible reason.  The laps were shorter when we were closer.  The gull made none or several dips on each lap.

The Japanese field guide describes the habitat of the Black-headed Gull as inland waters or coastal.  This gull seems to have a definite preference for the sewage ponds, this pond in particular, and even the same side of this pond.  There are about 10 ponds at the sewage works, five others which appear to be identical.  However, the Silver Gulls seem to prefer this pond and one other, although most spend their time loafing on the bank.  There are many other places around Broome where Silver Gulls congregate in numbers such as the main town oval, Cable Beach, the Pearl Coast Zoo and near the Crab Creek mangroves.

If you looked for them, there were many small circular ripples on the surface of the water indicating the presence of small insects or other prey.  There might possibly have been more near the bank of the pond that the gull prefers, but I made no rigorous comparison.  I did not check the other ponds either.  The wind did not appear to be a factor as it blew from different directions on the Saturday and Monday.

The preening of its wings and body was mostly with its bill, although on one occasion it scratched its head with its right foot.  We mostly saw it preening on the Saturday when we were more concerned about the details of identification rather than its behaviour.

With caution, the bird could be approached comparatively closely (between 10m and 15m), especially when it was on the water.  It did not appear to be disturbed when several Pacific Black Ducks and Grey Teal took off close by during our initial approach. It also ignored a flock of 40 Black Kites, even when some kites passed overhead fairly closely (within 10m).

It was difficult to approach the gull within 20m when it was on the bank, but I suspect that this was largely because the Silver Gulls would take off en masse.  If you approached very cautiously the Silver Gulls took off in ones and twos.  There were 40 to 100 Silver Gulls on the bank compared to about 10 at most on the water.

The Silver Gulls seldom came within 1 metre of the Black-headed Gull when it was swimming.  On the Thursday as we initially approached, a Silver Gull came within half a metre (or vice versa) near a corner of the pond. Both gulls called and the Black-headed Gull appeared to peck in the direction of the Silver Gull.  After about 10 or 15 seconds the Silver Gull moved away.  The Black-headed Gull appeared to be dominant.

On the bank there appeared to be no interaction between the gulls, even though on the Saturday two Silver Gulls were standing within half a metre of the Black-headed Gull allowing us a very good comparison of size and colour.

The Details of the Gull

Size.  When the bird was on the bank, it was approximately the same size as the Silver Gulls that were very close to it, or very slightly smaller if there was any difference.  However, when it was swimming it appeared slightly but noticeably larger than the Silver Gulls, but this may have been because of its more upright posture.

Head.  The head was a dark chocolate brown colour mostly, although the forehead and down to the bill was lighter.  The line of the edge of the hood was distinct.  From the rear it was level with the eyes.  From the side, the line was slightly more vertical than diagonal.  From the front, the line could be clearly seen below the throat.  Also from behind when it was swimming, the neck appeared much thinner than the head, probably because of its upright posture.

Eye ring.  The bird had a pale yellow or cream coloured eye ring, although the front half (or part of it) was often not apparent.  The eye was dark.

Bill.  The bill was a very deep red colour, and was similar in shape and size to the Silver Gulls.  There was no significant difference in the colour of the tip of the bill.

Legs.  The legs were also a very deep red colour, very similar to the darkest leg colour of the Silver Gulls.  They were a similar length to the Silver Gulls.  The legs did not quite extend to the end of the tail in flight.

Wings in flight.  There was a thin black band on the trailing edge of the outer primaries with nothing between.  There was a bright white wedge on the leading edge of the primaries joining (but not as wide as) the black band.  The white continued along the leading edge of the full wing.  The remainder of the top of the wing was silver grey.  There was a dark patch and smudges underneath the primaries.  The remainder of the underneath was whitish.

Wings when not in flight.  The wings were slightly but noticeably greyer than the Silver Gulls.  There was no hint anywhere of any brown.  The primaries had black tips without any windows, unlike the Silver Gulls.  The wings crossed in a deep V when the bird was swimming.  I can't remember if the left or the right wing was usually above the other.  The bottom of the wing was sometimes partly tucked into the body feathers when the bird was on the bank.

Body.  The back of the head, the front and the belly were a clean white.  From memory the colour of the back in flight was silver grey, but it might have been white.

Tail.  The tail was a clean white above and below in flight.  It was very slightly rounded and was occasionally fanned wider.  The underneath of the tail appeared discoloured when the bird was swimming, but this was due to the reflection of the colour of the water.

Call.  The call was very similar to a Silver Gull, although it could be distinguished when both called together.  It probably had a slightly higher tone.  It called once while it was preening, a couple of times as it took off, and a few times when the Silver Gulls were too close when it was swimming.

Gape.  The inside of the mouth was a bright red when it opened its bill to call.

The Identification of the Gull

The identification was hampered by a lack of information for what turned out to be a very easy bird to identify.  The observatory would very much appreciate the (tax deductible) donation of reference books for the identification of international gulls, seabirds, waders, ducks, etc such as the Black-headed Gull, Garganey, Ruff (Reeve), Little Ringed Plover and Pacific Swallow.  Field guides are a help, but they don't describe the many age variations that are possible, or details such as migration.

Before the fax arrived to confirm the identification, we had ruled out several species with dark hoods that we knew of because of details such as size (Little Gull), colour (Franklin's Gull), tail (Sabine's Gull), windows in the primaries (Saunder's Gull), and wing patterns (Laughing Gull) or a combination of many inconsistencies.

The Black-headed Gull fitted almost all the details that we had for it except for some slight inconsistencies.  These included a pale yellow eye ring rather than the whitish colour described.  The legs as illustrated were much redder and brighter than the darker legs that we observed.  The fact that the Black-headed Gull is a migrant at this time of year was a factor in its favour.

The fax of the paper by Grant made the identification very simple.  It is described as easily separable from all gulls except the others in this group (Slender-billed, Bonaparte's, Grey-headed and Black-headed Gulls), the best point being the white along the leading edge of the outer wing in flight.  The brown hood of summer adults is diagnostic among the west Palaearctic gulls.

The detailed descriptions in Grant's paper identify the gull as being in its adult or second (northern hemisphere) summer plumage which it has from March to October.  This makes it highly likely that the gull will moult into its non breeding winter plumage within the next few weeks.

Its breeding distribution is shown extending from central and southern Europe (including the UK) through to central continental Asia but not including Japan.

In the non breeding season its normal range is shown extending southwards to include parts of Africa, India, the Malay Peninsula, Sumatra (but not Java, Borneo or the Philippines) and Japan.  It is described as the commonest gull throughout most of its range, so it is somewhat surprising that it has not been sighted in Australia before.

If the gull stays until March, it will be interesting to see if it returns to the northern hemisphere or stays on longer like the Laughing Gulls in Cairns.

Broome and Migratory Birds

Broome is one of the most important sites in the world for migratory birds.  In particular, October is near the end of the arrival of hundreds of thousands of migratory waders from the northern hemisphere representing over 30 species including Asian Dowitchers, Redshanks and Broad-billed Sandpipers.  October is also the beginning of the arrival of other species such as Dollarbirds, Yellow Wagtails and Barn Swallows.

The sewage ponds in particular have been the site of uncommon sightings in the past at this time of year such as Wood Sandpipers, Long-toed Stints, Gallinago spp Snipe, Little Ringed Plovers, Garganey and a Ruff (or Reeve).

It is therefore not surprising that a vagrant from Asia or Europe should be found in Broome, especially at this time of the year.

Please note that the gate to the sewage ponds is kept chained and locked by the local water authority.  You should get permission from them before visiting.  However, the wardens of the Broome Bird Observatory have been given a key and have permission to take groups to the sewage ponds.  They also have permission to visit many places on the Roebuck Plains cattle station which is otherwise off limits.

The best plan is therefore to stay at the observatory (PO Box 1313, Broome 6725 - 08 9193 5600).  They arrange a variety of tours to the best bird locations around Broome.  In three stays there I have seen over 180 species (from the 250 seen in the area) including over 150 during my last stay.  Many species I have never seen elsewhere such as Common Redshank, Asian Dowitcher, Long-toed Stint, Mangrove Golden Whistler, White-breasted Whistler, Dusky Gerygone, Baillon's Crake, Yellow Wagtail, Orange Chat, Little Curlew, Oriental Plover, Little Button-quail, White-fronted Honeyeater, Grey Falcon and now the Black-headed Gull.  Other highlights have been a Gallinago spp Snipe, Lesser Frigatebird, Mangrove Gerygone, Red-headed Honeyeater, Striated Heron, Pectoral Sandpiper, Pacific Golden Plover, Brown Booby, Beach Stone-curlew, Olive-backed Oriole, White-throated Gerygone, Crimson Chat, Grey-headed Honeyeater, Pheasant Coucal and Spotted Harrier.

References

Simpson,N & Day,K (1988), Field Guide to the Birds of Australia, Viking O'Neil, Australia

Wild Bird Society of Japan (1990), A Field Guide to the Birds of Japan, Kodansha, Japan

Vere Benson, S (1975), The Observer's Book of Birds, Frederick Warne, UK

Brit. Birds 72 : pp142-182 (1979), Grant, PJ, Field Identification of West Palaearctic Gulls

Copyright Frank O'Connor 1997-2002 Visits Last Modified 31st January 2002