Saving the Fig Parrot

Brisbane has some beautiful coastal wetlands.  In large cities like Brisbane, the coastal wetlands are usually the last native ecosystems present that would be similar to how they were when the early settlers arrived.  The bush and rainforest have been transformed by weeds and have become an alien vegetation that is dominated by a handful of adaptable and aggressive species such as noisy minors that exclude other birds and animals.  Brisbane was a biodiversity hot spot but much has been lost.  Mangroves forests and salt pans which were once the poorest habitats for fauna have now become one of the richest as they are relatively immune to degradation.  Mangroves and the small islands of terrestrial forest they contain may even be the last habitat of some species.

Perhaps the rarest and most endangered bird in South East Queensland is Coxen’s Fig Parrot (Cyclopsitta diophthalma coxeni).  There are an estimated 100 individuals left but no one really knows as they are a cryptic species.  The small green parrots feed quietly on native rainforest figs and being the size and shape of fig leaves, they are very hard to see so targeted searches for this species usually fail to find any.  To save the species, the QLD and NSW State Governments want to start a captive breeding program, but nobody can find an occupied nest.  Stock for breeding programs is normally taken from wild nests.  I suppose that this would make my discovery of some possible old nesting hollows in a mangrove tree a significant find.

Possible old fig parrot nest holes in a mangrove beside the board walk at Nudgee Beach

A lizard in a stag beetle hole in the same tree.  The stag beetles may make pilot holes for the parrots.

Fig parrots make their own hollows.  Over about a month, they chew their way into a rotting branch.  Some hollows are about 60 cm deep which I discovered by finding fallen nest branches which split open when they landed.  If you find a fallen nest or any nest, be sure to report it to the national parks service.

Fig parrot in Cairns starting to tunnel - 17 July 2014.

Stopping for a look around.

30 August, been sleeping in the hole for while now, but when there is a noise, the parrot comes to the entrance for a look (flash photo taken just after dark).

Female fig parrot begging for food from its mate.

Male fig parrot about to feed the female.

There is a species recovery plan for this species but it does not appear to address the nesting requirements for this species.  My knowledge of the subject comes from observing another subspecies of fig parrot, the red browed fig parrot (Cyclopsitta diophthalma macleayana) which is still common in Far North Queensland.  Fig parrots need rotting branches between 10 and 25 cm in diameter where the sapwood softens without the branch falling.   Live timber is too hard and in many cases would have unpleasant sap.  In nesting branches, often the sapwood rots away completely and the dead branch becomes an empty tube of bark when the parrot scrapes out the contents.  The favoured species are fig trees (F. drupacea) but I have seen nests in beach almonds (Terminalia arenicola).  I even have a nest near my house in a rainforest tree with one of the hardest scientific name I know of (Blepharocareya involucrigera).  Many of the nesting trees are in parks.  Twenty years ago, I would only see fig parrots flying in small groups high in the sky.  In only a few years, the fig parrots have moved into town.  I suspect many/most urban nests are lost to tree loppers who are called in to remove sick trees and dead branches.   If we can find places where trees can be allowed to old and decrepit, then every park fig in Brisbane City could one day be visited by this species.  Figs branches tend to rot until they become as light as foam before falling and if dead branches of suitable diameter were cut off a bit more than half a metre from living timber, the safety hazard from falling branches would be very small.  In fact many of the local nests around Cairns are in the stubs of branches that were trimmed by the city council.   Any branch with a gnawed hole or a gnawed test pit should be off-limits to tree trimmers.  The birds tend to chew out test pits until they find timber that just right.

Although I did find nest hollows in the mangroves, I do not believe that in general mangroves are suitable habitat.  Mangroves have high populations of rats which predate crabs and which would prey on parrot chicks as well.

Red browed fig parrot feeding on Ficus racemosa on an isolated tree on a sand ridge in the mangroves.

I suspect that another serious oversight of the recovery plan is that it does not address the food supply of the fig parrots.  Fig parrots eat green figs and not ripe figs. The northern fig parrots feed very heavily on Ficus racemosa and to a lesser extent on F. drupacea, both of which are native to Brisbane but which are rarely planted.  These figs are deciduous and drop very heavy crops of fruit a number of times a year so are not ideal park trees.   Planting these species around the margins of parks, particularly on the edges of the mangroves creeks and other places where people don’t typically venture might be a way of boosting food resources.  Fig parrots are highly mobile and isolated trees make up most of their food supply.  Another undocumented food is Melaleuca viridiflora flower buds.

Fig parrots feed for days to weeks on a single tree until fruiting stops and they return as soon as fruiting begins again, so isolated urban trees are likely to be extremely important to this species.  The species recovery plans should include the establishment a network of isolated trees which can fee the birds year round.  All the photos above were planted trees.  I planted them.

The 1.5 km long km board walk at Nudgee Beach is just across from Brisbane Airport - something to do before you catch a plane. 

Further Reading:
Coxens fig parrot Species Recovery Plan

Hovering Stilt Mangroves

There is an old question of whether stilt mangroves need to have a trunk running down to the ground or can survive held up by stilts alone.  On a recent trip up the Blind Barron, near Cairns, Australia, I found my answer.  The mangroves in this strange place appear to be walking over the mud until they fall like lemmings into the creek.  Some living mangroves are even defying gravity and are hovering over the water, supported entirely by no more than a few skinny stilts. 

Rhizophora (stilt) mangroves hovering over the creek

Going up the creek was like being in a tunnel with a fallen roof.  Stilt roots reached out over the creek from both side for almost 2 metres.  It was a case of going in on a very low tide to get under the overhanging stilt roots.  It is a creepy place and was famous for having a large crocodile.

Close to entrance of Blind Barron

The creek tapers quickly and becomes impassable by boat as the fallen trees block the way through. Normally creeks maintain their width with erosion on one site and regrowth of mangrove on the other.  I have never seen encroachment from both sides at once and this probably relates to the origin of this creek.

As far as boats will go

How did Mangroves Evolve?

When I Google mangrove evolution all I find are a few pithy generic statements and no real information.  I think that if all the mangroves we currently have were to disappear, other plants would race to fill the ecological vacuum.  Next time you are in the mangroves, look for non-mangrove trees that are dipping their toes in saltwater.  It is surprising how many there are and how many species can actually survive in the edges of mangroves swamps, where they are surrounded on all sides by mangroves and are growing in mud.  The question is why are these species not completing the transition?  That is a very big question so lets investigate a small part of it, how mangrove stilt roots may have developed.

The one scientific paper on mangrove evolution that I could get for free (most are locked up behind science journal paywalls) was about the biogeography of mangrove evolution and it said that almost all the mangroves present today evolved in the Tethys Sea which was sort of where Arabia and India are today.  The earliest species were Acrostichum, the mangrove fern and Nypa, the mangrove palm.  These species like lower salinities so that is a clue.  The main mangrove species (Avicennia and Rhizophora) were around 50-70 million years ago so forests just like those lining the worlds tropical oceans today would have seen dinosaurs.  Perhaps the Tethys Sea was like the sea between Australia and the island of New Guinea is today.  The information from the paper tells me what evolved and where but does not tell me how the plants evolved.  If I knew how mangroves evolved, then perhaps I would be able to understand the barrier that is preventing more mangroves from evolving.

Recently I have been seeing stilt roots on some species of mangrove that normally do not have them.  These mangroves usually have pneumatophores which are breathing roots that protrude from the mud.  If the trees have a choice of stilt roots or pneumatophores, why do they choose pneumatophores?  Fortunately it is possible to collect evidence on conditions that favour stilt root development.

In a swale, which is a shallow valley between sand ridges, I found several white mangroves (Avicennia marina var. eucalyptifolia) with stilt roots instead of the usually pencil roots.  This is very strange as Avicennia is the champion producer of pneumatophores. The stilt roots are not as well developed as those of stilt mangroves (Rhizophora) but are clearly stilt roots none-the-less.  

Avicennia tree with stilt roots instead of pencil roots (pneumatophores)

The swale traps a pool of freshwater in the wet season and saltwater in the dry season.  I happened across the swale on one of the few days when it was completely dry.  During the wet season, the swale appears to be a window lake, which means that the freshwater table is above ground level.  Several large paperbarks live or lived among the mangroves.  However as sea level rises by a few millimetres each year and the drainage line to the sea expands due to tidal and storm water flows, the ingress of seawater is increasing and the paperbarks are declining. 

Mangroves growing around a paperbark tree (Melaleuca leucadendra) 

Two days later a full moon brought in one of the highest tides of the year and flooded the swale and covered the entire stilt root system of the Avicennia trees.  It seems that in the centre of the swale the water is just too deep for pneumatophores.  Avicennia on the margins of the swale grow thickets of pneumatophores.  

Mangrove swale with standing water at full depth

Stilt roots and a few pneumatophores when pool is full

Avicennia can also grow adventitious roots (roots growing from the trunk above ground level) in more exposed situations, such as river mouths, where regular tides are experienced. In these areas, however the adventitious roots rarely become stilt roots.

Adventitious roots on tree a creek mouth

Another mangrove species that can also form stilts instead of pneumatophores is the black mangrove (Lumnitizera racemosa).  Normally, black mangroves have very few pneumatophores unless they are in areas with freshwater seepage, then they grow strange root loops.   In one special place, near Pormpuraaw in the Gulf of Carpentaria, I found a forest where black mangroves have stilt roots instead.  The Gulf has only one high tide per day, whereas the east coast of Australia has two high tides each day.  There is much less tidal exchange of water and the headwaters of rivers probably remain brackish longer than their east coast equivalents.  Upstream of the tidal creek is a vast flat swampy plain that slowly drains into the mangroves for several months a year, creating freshwater tides for part of the year. It is these special conditions which create this strange forest.

Lumnitzera mangroves in headwaters of a creek which has strong seasonal freshwater flows

Lumnitzera on stilts with super long Avicennia pneumatophores

Brackish water swamps with still pools of water do not foster stilt roots, in these places pneumatophore development goes crazy.  In a back swamp close to the black mangroves is a brackish water swamp with pools of water surrounded by mangroves and reeds.  The mangrove pneumatophores are exceptionally long and dense.

Avicennia around a brackish pool with Baumea reeds

The Avicennia pneumatophores are as dense as the reeds

So my concluding conjecture is that stilts seem develop more in areas with seasonal freshwater flooding or tides.  In fact this is just the type of place that the forest mangrove grows.  The forest mangrove (Carallia brachiata) is the only non-mangrove member of the stilt mangrove family in Australia. Carallia has a propensity to grow masses of adventitious roots even when it is in rainforest on wet foot hills, so perhaps the stilt mangrove families propensity for this type of root structure combined with an opportunity is what lead to stilt mangroves.  

Life in a Beach

Each area of coastline is different.  It is not a case of the same species be present is slightly different numbers, each place seems to be the product of different ecological rules.  Sandy beaches are normally somewhere where animals are very scarce, perhaps only a few ghost crabs are present.  However the beach at Archer Point, close to Cooktown, is literally crawling with life.

Amphipod burrows near high tide line

An amphipod

I have never seen a beach covered with burrows all the way from the low tide mark to the high tide mark before.  I even had to dig up the ground to find out who was in the burrows.  Amphipods jumped out of the first handful of sand so must be just below the surface.

Amphipods are basically a small (1 cm long) prawn-like animal that walks on land.  They have very big eyes and are nocturnal.  When chased, they can jump like crazy to avoid being caught.

Since seeing the amphipods at Archer Point, I have kept my eyes open and have scanned several beaches which seem similar in terms of protection and sand properties.  Finding amphipods on these other beaches is a struggle.  Normally, there are a few amphipods under washed up leaf litter and seaweed.  It is unusual to find large numbers on a beach that is almost clear of plant debris.  I suspect that there is freshwater seepage concealed within the beach which some how helps the amphipods.

Recently 4WD vehicles were allowed back on many Queensland beaches.  Scientific research had shown that vehicles driving on the beach crush many of the animals that live in the sand and hurt the ecology of the beach. My position on this matter is that each place has to be assessed individually.  It is nice to be able to pull up right beside the sea and relax and I would not like to see every beach fenced off.  Many beaches are reworked so much by wind and waves that few living animals are present and driving on these beaches does little damage.  However it is repulsive to find tyre tracks all over remote beaches where people should be able to enjoy freedom from such things.  In this case, there is no reason to drive on the beach at Archer Point as the beach is only 300 m long and has an unusual ecology featuring vast number of amphipods which would suffer due to vehicles on the beach.

There is no point in driving onto this beach as it is so short, yet lots of people do it

Amphipod holes beside tyre tracks

Grassy Salt Pans of Cairns

Almost exactly 100 miles/160 km down the coast from the succulent covered salt pan near Cooktown is one of the few remaining salt pans near Cairns. Despite being so close that a lazy crocodile could drift from one to another in less than a week, the botany of these two salt pans is very different. At Cooktown, it was all succulents, near Cairns it is usually nearly all grass. In Google Earth the photo pattern of each vegetation type is remarkably similar. Surprises like this remind me that neither I nor anyone else I know of can fully understand why things grow where the do. Until we can understand why what grows where, environmental management is just educated guess work.  I think students and rangers could do mini science projects to find out why some places that should be similar are entirely different.  Professional scientists don't answer these questions as they need to maintain their fame and are not interested in easy research.

Saltwater couch grassland/salt marsh at Yorkeys Knob

Most of the original salt pans and samphire flats around Cairns have been lots to development so I have to be careful about deciding that Cooktowns salt pans are different to those found near Cairns. Many salt pans within Cairns City were reclaimed. Cairns Airport is on what once was a salt pan and the major agricultural folly of East Trinity also included saltpans. Fortunatelly, we have a couple of good examples left and I think the remaining examples are similar to the ones lost. It is also unlikely that any halophytic (salt tolerant) species would be lost from the entire region. Salt pan plants are great colonists and show up even in salty ruts around the edges of sugarcane fields. For these reasons, I suspect that the succulent flats like those near Cooktown never occurred on salt pans near Cairns.

The natural park lands are quite pleasant provided you wear long clothes and don't dally around after sunset

Cooktown is in the Cape York Peninsula Bioregion and Cairns is in the Wet Tropics Bioregion. Bioregions are like countries for flora and fauna so this suggests that the salt pan vegetation could be different. Queensland has 13 bioregions. The bioregion boundaries were originally drawn by smart people with marker pens on paper maps. They were not something that came from a sophisticated analysis. Yet it is strange that even intertidal communities seem to have a sudden transition at the bioregion boundary. It is strange because most mangrove plants and animal species (fish, crabs, molluscs) occur from here to Africa and on almost every coastline in between. Given that most species are so widespread, why to comparable salt pans that are so close by natures standards have such different vegetation? I can only guess. Climate and geology and tidal inundation cycles are all quite similar. The founder effect may be at play. The founder effect is natures version of losers/keepers. The founder effect is when the first plant species to find a new island or in this case salt pan multiplies and occupies all the space making it very hard for new species to establish.  In very flat places, I have noticed that even a few centimetres in altitude makes a big difference to how long an area is flooded in inland areas or how many tides per month are experienced in coastal areas and I would start my investigations here. Succulents (Halosarcia sp.) do grow on slightly lower ground around the margins of the grassy swards in Cairns but are low and straggly.

Saltwater couch (Sporobolus virginicus) is the grass that covers the salt pan. We also have a second species of saltwater couch (Paspalum vaginatum) which often grows with the first species and looks very similar. The leaves of the first species are spirally arranged on the stems and the on the second only grow on opposite sides (called distichous).

Sporobolus virginicus has little tufts of leaves from underground runners.

Crabs and mud lobsters thrive in the saltwater couch and the ground is so full of hummock and hollows that I stumble through the grass rather than walking through it.  I wonder how the productivity of this marine grassland compares with mangrove ecosystems.  

Mud lobster mound peppered with crab holes

Shed exoskeletons were hanging in the grass

Ant plants also like the margins of salt pans and I suspect this is related to mists but I don't really know.  

Myrmecodia beccarii - the spiny ant plant

Miniature Forests of the Salt

The salt pans and samphire flats of South East Queensland receive a lot of attention.  Yet the salt pans of Cape York Peninsula have a strange flora that is barely described on the internet or even in scientific reference sites such as the Atlas of Living Australia.  On a saltpan that is within  bike riding distance of Cooktown I found a veritable rainforest of succulents.  Within this miniature forest, the canopy was almost closed, the understorey was dark and humid and a thriving crab population.

Batis argillicola mini tree

Being on a salt pan is to experience open space.  If you value open space and enjoy the visual intensity of colour and detail, being on a salt pan is like freedom to breath.  In this particular salt pan, it is also about being a giant that needs to tread carefully through a forest that reaches as high as our knees.

Should I even call this a salt pan?

Batis (Batis argillicola) is the main plant although approximately six succulents were present in total. Grass which is ususally present was not to be seen. Batis is quite large for a succulent and stands about half a metre tall.  The leaves are bright green and of similar shape and size to grains of rice and the seed pods are like green peas.  I am not sure how old the Batis are and I don't know if any one does but their stout trunk suggest they are old.  As there are no good photos on the net, here are a few more (yes it is true, stacks of stuff is still not on the net).

Batis argillicola is big enough to compete with young mangroves

Leaves and flowers of Batis argillicola - the flower are tiny and only stamens are clearly visible

In the salty margins are some red and pink Halosarcia succulents, which come from the salt bush family.  The red is a protective pigment (a carotene) that allows plants to avoid damage caused by intense sun.  It is a sunscreen and a way of dissipating excess energy.  In such a dry landscape, plants cannot open their stomates to get CO2, so the energy captured by the photosynthetic pigments cannot be used and would generate free radicals that would corrode the plants cells if it the energy was not passed to pigments which reradiates the energy.  The pigments also have a sunscreen effect by blocking some of the incoming energy.  Back in the days of the ozone hole, it was predicted that many plants would go orange or red as they increase pigment levels to protect themselves as UV light also creates free radicals.  Breeding programs were established to put protective pigment genes into crops as many crops are badly damaged by intense UV.  The succulents on the salt pans also experience high UV from the sky and reflected UV from the salty surface.

Red succulents dominate very salty areas

Thinking of fauna, the crabs were in hiding and all I could find were mud whelks.  It seems that mud whelks thrive in a narrow band of ground around the margins of the saltpan.  Here shallow pools exposed to the sun provide better grazing than the surrounding mangrove forest.  However on this flat terrain, a mud whelk can easily move in the wrong direction and by after as little a five metres, it can find itself lost in the miniature forest with fatal consequences.

Hundreds of mud whelks clustered seeking shade under an isolated mangrove

There is a sad fate for those that crawl a few metres in the wrong direction

A Clean New Land

It is a surreal experience to go to a place that you know well and to find that it is entirely different.  Ellie Point has never been attractive.  It is a stark, shadeless place with an incredible sandfly population and appears to be the final resting place of any rubbish that the good folks of nearby Cairns throw into the sea.  It it a place that I wished could be better and maybe I have gotten my wish.  I found my self standing on clean new land where only three years ago, I was motoring my boat.

A new beach facing the City of Cairns

Ellie Point with a new beach - it would be more than 400 m long and would extend 100 m into the sea

In my life time, the coast line has only ever seemed to retreat, but now I am beginning to see this trend reversed.  The long period of beach erosion was caused in part by human appetite for sand.  For many years, sand was dredged from the nearby Barron River as it was transported toward the sea.  More than 20 000 tonnes per year were taken.  As a result, the Cairns northern beaches were starved of sand supply and began to erode.  Seawalls are still being built to protect houses from disappearing into the sea where the beaches have been all but lost.  Even as I write, I can hear machinery crunching on massive rocks to build a new seawall for Machans Beach on the northern side of the Barron River.  Sand was also mined from the sand flats at Ellie Point.  This was unfortunate as it delayed the development of sand flats around the recently moved Barron River mouth.  The new mouth emptied into deeper water and sand was carried by the flow of the river into deeper water where waves could not bring it back to the beach.  For these reasons sand extraction from rivers was banned (~1990) and sand mining at Ellie Point ceased.  Sand mining is now only allowed in so called in-active sand deposits which are old beach ridges or alluvial deposits which are located mainly under sugarcane fields.

View from the new beach back to the previous shoreline across a shallow sandy basin

Geology maps tell me that the oldest beach ridges are about 5 km inland and that they are about 5000 years old.  This suggests that the coastline should be prograding at an average rate of about 1 m per year.  In recent years, the beach at Yorkeys Knob has been prograding even faster as it receives sand from both the Barron River and Richters Creek.  Only this year have there been clear suggestions that beaches are again growing within the delta.  Shallow waters over sandflats now extend out hundreds of metres from the beach and waves can been seen refracting around the higher sandbars, resulting in sand being moved toward the beach.  However within the delta, prevailing winds and waves can also strip sand from one area and deposit it in another so prograding beaches are often matched with nearby areas of coastal erosion.

Just to the north the coastline is regressing and trees are falling into the sea.

There is another reason why sand is not mined at Ellie Point.  It contains acid sulfate materials.  Behind the new beach is a backwater that has filled with mangrove detritus.  When this material is buried, the organic matter feeds bacteria which combine sulfates from seawater with iron from seawater or from the mangrove detritus to create iron sulfide.  On exposure to air, the sulfides oxidise and become sulfuric acid which can eat concrete and steel and burn living organisms.  Whilst the process of acid sulfate soil formation is well known, as far as I can tell, it has never been visually documented.  Hopefully, I can fill this gap.  Another post describes the acid and hydrogen sulfide being produced by organic matter that was buried in the old Barron River mouth 40 years ago.

In the basin behind the new beach is a vast deposit of mangrove detritus

Where it has been buried by sand, black rivulets issue from the ground