Tuesday, 22 November 2016

Coral Cay Island Birds – Great Barrier Reef – Part 5 Other bird species.


The background to our recent visit to Lady Musgrave Island on the Great Barrier Reef (GBR) was given in Coral Cay Island Birds – Great Barrier Reef – Part 1 Background.

While at Lady Musgrave Island and lagoon we recorded a total of 18 bird species. The Part 2 - 4 posts covered 8 of these species and this post covers the remaining 10 species.

Lady Musgrave Island lies about 60kms offshore from the Town of Seventeen Seventy with no islands in between, so it was not surprising that no land birds were recorded there. Although National Park information signs on the island indicted Silvereyes may be present – we did not hear or see any Silvereyes. No doubt vagrant land birds turn up on offshore islands such as Lady Musgrave Island from time to time however they do not become established as permanent residents.

Three species of migrant shorebirds were seen.

Wandering Tattler (Tringa incana)

Due to the difficulties of separating the Wandering and Grey-tailed Tattlers I may be wrong with my ID of the bird in the following two photos (both photos are of the same bird on different days in different locations and light). I came to my ID based on checking the field guides, the overall dark grey appearance, the bird was alone on rock platforms of a coral cay island plus the Warden on Lady Musgrave said she had seen the bird and also thought it was a Wanderer (she has had a lot of experience with both Tattler species and told me that the Wanderer has become quite common along the Queensland coast in recent years). 

Please click on photos to enlarge.

My first encounter with the Tattler.

Second encounter in different location and light.

Ruddy Turnstone (Arenaria interpres)

Each time I visited Lady Musgrave Island I came across Ruddy Turnstones in various locations around the shoreline, both resting and actively feeding on coral platforms at other times. I think there were six altogether.

It is always a delight to find Turnstones.
 
Bar-tailed Godwit (Limosa lapponica)

I found a Bar-tailed Godwit on two occasions – it is possible that there were two birds on the island though one bird is more likely to be the case.

Lone Bar-tailed Godwit feeding among coral rubble on Lady Musgrave Island.

Eastern Reef Egret (Egretta sacra)

Reef Egrets are common along the tropical East coast of Australia and on the Great Barrier Reef islands. About 12, including both white (light morph) and dark grey birds, were present on Lady Musgrave Island. The white birds outnumbered the dark by about 3 to 1. They rested in trees on Lady Musgrave Island during high tides and became active at low tide feeding on the reef around both the island and on the fringing reef around the lagoon.

A white and dark morph Reef Egret resting together in a casuarina.

White morph Eastern Reef Egret.

White morph Reef Egret in flight.

Dark morph Reef Egret

Bird from the photo above in flight.

I saw one Reef Egret looking for food in the Pisonia Forest.

In addition to insects and spiders, eggs and in time, chicks falling from Black Noddy nests would provide food opportunities for the Egrets.

Buff-banded Rail (Gallirallus philippensis)

Dozens of Buff-banded Rails foraged on the Pisonia jungle floor – no doubt the supply of nutrients via Black Noddy droppings supported many insects and other life forms living in and on the forest floor which the Rails were exploiting. In addition, they would take any eggs and chicks that fall from the thousands of Black Noddies nesting above.

Two Buff-banded Rails foraging on the floor of the Pisonia forest on Lady Musgrave Island.

Both species of Oystercatchers were on Lady Musgrave Island.

Australian Pied Oystercatcher (Haematopus longirostris)

One of two Pied Oystercatchers I found on Lady Musgrave Island.
  
Sooty Oystercatcher (Haematopus fuliginosus)

One of two Sooty Oystercatchers I found on Lady Musgrave Island. This one is trying to open a small mollusc prized from the reef.
 
Coral cay islands due to their isolation from mainland Australia have been relatively free of predators and so many sea birds have evolved to use the islands to breed. Certainly humans until recently were no threat to the islands. Mainland avian predators such as many of the raptor and owl species did not visit the islands and terrestrial animals such as dogs, cats and large reptiles, including the monitors (goannas) and snakes, did not reach the islands.

However, we did see a number of predatory bird species at Lady Musgrave Island, including about thirty Silver Gulls. In small numbers gulls can provide a clean-up role and provide an important part of the ecological balance around a large colonial nesting event such as the Black Noddy event on Lady Musgrave Island. However, with the Silver Gull population increasing in Australia as a result of our waste food and rubbish, they can and have had a serious negative impact on some nesting birds (note the experience of bird surveyors with Brown Boobies nesting on Fairfax Island mentioned in the Part 4 post).

Silver Gull (Chroicacephalus novaehollandiae)

Silver Gull looking to pick up Black Noddy eggs under the Pisonia trees.

Silver Gulls have become so common around humans that we tend to overlook their beauty.

Another sea bird that could be regarded as a predator or indirect predator on coral cay island nesting birds, are Frigatebirds. There are three species of Frigatebird found in Australian tropical waters - the Great, Lesser and Christmas Island Frigatebirds.

Lesser Frigatebird (Fregata ariel)

One afternoon I observed five Lesser Frigatebirds lazily riding the updraft of a sea breeze above Lady Musgrave Island. At times the birds hung in the sky almost motionless, certainly at no time did I see them flap their long slender wings.

Lesser Frigatebird above Lady Musgrave Island.

Frigatebirds have poorly developed oil glands, so unlike many other sea bird species their feathers do not allow them to enter the water in pursuit of food or to rest on the sea surface. If they did enter the water their feathers would become waterlogged and they would be unable to fly – they would eventually drown.

Frigatebirds snatch food from the sea surface. Flying fish and squid, young birds and carrion are listed as their main foods. Part of their food supply is obtained by forcing other seabirds to drop or even disgorge their food. Frigatebirds are supreme aerialists and often harass other seabird species in order to force them to give up food. Hence Frigatebirds have been called pirates. The technical term for this behaviour is kleptoparasitisim. To the extent that the unfortunate birds are only deprived of some food and not their life, the Frigatebird is not strictly a predator. The Brown Boobies nesting on nearby Fairfax Island possibly provided opportunities for the Frigatebirds to obtain some easy meals as the Boobies returned to their young with food.

Unfortunately I was not able to capture all five Frigatebirds in the frame at once.
 
White-bellied Sea-Eagle (Haliaeetus leucogaster)

A White-bellied Sea-Eagle was the only raptor species I saw at Lady Musgrave Island. No doubt Eastern Osprey and possibly Brahminy Kites also visit Great Barrier Reef islands such as Lady Musgrave from time to time.

White-bellied Sea-Eagle.
 
This was the last post in the Coral Cay Island Birds series.


End note:

We were very privileged to be able to visit the Bunker Group on the Southern GBR and Lady Musgrave Island. Coral cay islands are special places. A small number of seabird species have adapted to living and breeding on these unique islands.

Rising sea levels and temperatures and sea water acidification due to CO2 and other greenhouse gas emissions will impact Lady Musgrave Island and the birdlife that depends on it over the course of this century. Even a moderate sea level rise could/will destroy the perched freshwater table on Lady Musgrave Island which in turn will kill the Pisonia trees that are so important for breeding birds such as the Black Noddy. More widely the destruction of coral and the disruption of marine micro-organisms such as plankton will alter the food chain and the coral reef ecosystem.

It is hard to contemplate this wonderful World Heritage area, that has taken thousands of years to evolve, being put at risk of destruction during this century by the Earth’s human population, especially considering we humans have brought about this state of affairs in less than a century of industrialisation and exponential growth!

Tuesday, 15 November 2016

Coral Cay Island Birds – Great Barrier Reef – Part 4 Boobies and Shearwaters


The background to our recent visit to Lady Musgrave Island on the Great Barrier Reef (GBR) was given in Coral Cay Island Birds – Great Barrier Reef – Part 1 Background.

This post covers Brown Boobies and Wedge-tailed Shearwaters, both tropical water birds and both breeding when we visited Lady Musgrave Island.

Click on photos to enlarge.

Brown Booby (Sula leucogaster)

Brown Boobies are closely related to and are very similar to Gannets – perhaps a tropical version of the Australian Gannet (Morus serrator) so often encountered along the Victorian coast.

Less pelagic than Red-footed and Masked Bobbies, the Brown Booby can be found in shallow tropical coastal waters, harbours and estuaries.

Brown Boobies are relatively sedentary in Australian waters though immature birds may disperse more widely. They turn up in Victorian coastal waters now and again when their vagrant presence causes great excitement among twitchers.

The Brown Booby relies heavily on flying fish and squid for its food. Like the Gannets it can plunge dive from great heights to capture food.

Brown Booby – the streamlined body and sharp bill - which extends to and protects the forward facing eyes - are adaptions that enable spectacular dives into the sea at great speed.
 
I was lucky to capture a photo of a flying fish from the deck of Alchemy 1.

We saw individual flying fish and small schools burst from the sea and fly (glide?) a surprising distance before dropping back beneath the surface again.

Brown Boobies breed on offshore islands including in the Bunker Group. The breeding season is almost continuous with peaks in spring and autumn. They were breeding on Fairfax Island just north of Lady Musgrave when we were there so we saw many flying over Lady Musgrave lagoon as birds flew out and returned from fishing expeditions.

We planned a visit to Fairfax Island however some checking showed it was closed to the public for “scientific reasons”. I suspect this is at least in part to protect nesting sea birds. The Warden on Lady Musgrave Island told me her husband had recently joined some National Parks staff to conduct a survey of birds on Fairfax Island however they had to abandon their survey when the nesting Brown Boobies left their nests and Silver Gulls moved in to attack eggs and small chicks.

Brown Booby chicks can survive near-starvation for lengthy periods and then make up lost ground. Their ability to resist starvation is needed because tropical seas are less productive than colder waters closer to polar regions. This at first seems counter intuitive as one would expect warm tropical seas to be more productive than cold seas. The underlying reason is due to warm water containing less oxygen compared with cold water. In tropical seas the water column can stratify with warm low-oxygen water on top and cold below. The stratification in turn stops nutrients from cycling into the surface waters which then cannot support as much phytoplankton nor higher level sea life including fish supported by phytoplankton. As a consequence, tropical seas do not always support large numbers of sea birds.
For breeding sea birds, the energy to not only support themselves but also raise young can be a very delicate balance and breeding may fail if sufficient food resources are not available or diminish to below a workable level as the appetite of their chicks grows.

So Brown Booby photo opportunities were limited to chance when the odd birds happened to fly close by Alchemy 1 anchored in Lady Musgrave Lagoon and when I happened to see them coming, have the camera ready and the light was right. After some persistence I managed to get a few acceptable images.

Booby wings are similar to other large sea birds – they have evolved to minimise effort by maximising the use of wind to stay aloft and roam the ocean.



This Brown Booby was almost adjacent to the yacht when it noticed me on the deck and in alarm did a rapid about-turn.

As we left Lady Musgrave lagoon early one morning a pair of Brown Boobies rested on one of the navigation markers beside the entrance to the narrow channel through the reef. Their strong green-yellow legs and large webbed feet are obvious in the photo. The large webbed feet help propel them under water, sustaining the momentum of the dive for pursuit of prey.

A pair of Brown Boobies on a navigation marker in Lady Musgrave Lagoon.

So where did the name Booby come from? It certainly sounds derogatory? For an answer here is what Fraser and Gray have to say in their excellent book “Australian Bird Names – A Complete Guide”:

“Booby was used in the sense of a “foolish fellow”, presumably for the poor beast’s trusting habits which allowed them to be easily slaughtered by sailors. The word itself appears in English from the very beginning of the 17th century, apparently from the Spanish bobo, a fool.”


Wedge-tailed Shearwater (Puffinus pacifica (Christidis & Boles 2008 Ardenna pacificus))

The Wedge-tailed Shearwater is a pelagic seabird that inhabits the tropical waters of the Indian and Pacific Oceans. The Australian East Coast birds breed on islands and cays in the Coral Sea and along the Great Barrier Reef and on offshore island as far south as Montagu Island on the NSW south coast. They rarely come south of the NSW-Victoria border so, apart from some rare vagrants, are not seen in Victorian waters.

In Victoria we have the similar but much more numerous Short-tailed Shearwater (Ardenna tenuirostris) which breeds on islands in Bass Strait and feeds in cold Southern Ocean waters to fuel its breeding effort.

Wedge-tailed Shearwaters were breeding on Lady Musgrave Island when we were there. Given the adult birds only visit the breeding colony after dark how did we know they were breeding?

A number of observations made it clear they were breeding on Lady Musgrave Island.

First, we knew the island was used for breeding by this species. A well-marked walking track through the Pisonia forest and good signage helps keep human visitors away from the Shearwater nest holes that are very vulnerable to collapse as they are dug in soft sand.

Second, it was the right time of year for birds to be incubating their one egg in the underground nests.

Thirdly, while looking at their nest holes in the Pisonia forest I could hear the distinctive mournful call of the odd incubating adult coming from underground.

Fourthly, just after sunset and before it was completely dark I could see from our yacht anchored across the lagoon from Lady Musgrave Island the silhouettes of hundreds of Shearwaters flying against the orange glow in the western sky at the NE corner of the island as they milled about for it to become dark enough to go into their nests.

In addition, the Warden on Lady Musgrave Island told me it was a very noisy event each night as the Wedge-tails came in to land and then scurry across the jungle floor to their nest holes.

Wedge-tailed Shearwater nest holes at base of a Pisonia tree.
 
During the day we only saw the odd bird as it passed over the lagoon on its way to deeper waters beyond the reef looking for food. The majority of birds left well before dawn and headed out to sea to hunt for the day. As we sailed/motored on our trip south we sighted, well out to sea from the mainland, the odd Wedge-tailed Shearwater - only single birds for they are not particularly gregarious and generally forage alone or are seen in small parties of four or five birds - though they do flock in large numbers at fish or other food concentrations to gather food.

Capturing photos of a Wedge-tailed Shearwater from a moving boat at sea as the odd bird happened to fly by close enough and with the sun in the right position, proved to be impossible for sharp images. At Lady Musgrave it was not until day three and four when a strong early morning easterly wind blew that some Wedge-tails flew across the lagoon and some by our yacht. I spent an hour or two standing with my camera ready on the forward deck to capture a few, just acceptable, photos of the Wedge-tailed Shearwater.

A distant shot of two Wedge-tailed Shearwaters flying over Musgrave Reef lagoon. The bird at top left shows the typical wing position with wrists held well forward and the long pointed wedge-tail.
 
The Wedge-tailed Shearwater’s flight follows a similar pattern to an albatross as it rises and falls using the wind to maximum advantage without the need to flap its wings. At the low point of the pattern they almost touch the water and often disappear behind waves.




Post No. 5, the last post in this series, will cover the other/remaining bird species we saw at Lady Musgrave Island.

Sunday, 13 November 2016

Coral Cay Island Birds – Great Barrier Reef – Part 3 Terns


The background to our recent visit to Lady Musgrave Island on the Great Barrier Reef (GBR) was given in Coral Cay Island Birds – Great Barrier Reef – Part 1 Background.

We saw 6 species of terns on Lady Musgrave Island. The Black Noddy was covered in the Part 2 post. The other 5 tern species present on the island were Crested, Lesser Crested, Roseate, Black-naped and Bridled.

The Crested Tern is the most widespread and common tern to be found in Australian coastal waters. All of the other tern species we saw on Lady Musgrave Island are relatively uncommon and are more or less tropical species confined to tropical waters and therefore rarely found in southern Australia, particular along the coastline of my home State Victoria.

Bridled Tern (Onychoprion anaethetus)

Bridled Terns are similar to Sooty Terns and have a similar range in Australia. There were at least 20 pairs of Bridled Terns observed on Lady Musgrave Island in the early stage of breeding. Most birds were seen in pairs with many at nesting sites and courtship displays were also seen.

A pair of Bridled Terns resting together near a prospective nest site on Lady Musgrave Island. The distinctive white eyebrow is probably the feature that most obviously distinguishes this species from the Sooty Tern.

Pair of Bridled Terns courting. They rotated about one another with much graceful bowing and their wings held slightly away from the body. Holes under the tree stump behind contained three nesting pairs of Bridled Terns.

The Bridled Terns were nesting along the sandy beach not far above high tide level in a number of situations including under beach washed tree trunks and low dense shrubs and in long grass. This tropical tern breeds every six to seven months.

Bridled Tern above Tournefortia argentea (tree heliotrope) bush.

Same bird as above a second or two later.

Black-naped Tern (Sterna sumatrana)

This small elegant tern is exclusively tropical and marine, resting and breeding on coral reef cays and feeding mainly on small fish taken in adjoining tropical seas.

There were possibly 50 to 60 Black-naped Terns on Lady Musgrave Island when we were there. They did not show any signs of breeding however many gathered together at the top of the beach and at times fights broke out among some birds – perhaps this was a preliminary stage to forming pairs ahead of breeding which mainly takes place between October and December. One bird was seen carrying a small fish – fish flights and offerings to females are a part of courting for many tern species.

A small gathering of Black-naped Terns on coral rubble at the top of the beach on Lady Musgrave Island.
The pink blush visible on the birds in the above photo is mentioned in only the Pizzey and Knight field guide. While subtle it was quite obvious so it is somewhat surprising none of the other three popular Australian birding field guides mention this feature.

Periods of relative peace were punctuated by fierce squabbles among some birds.

The black napes show clearly on both the attacker and the attacked in this shot.

There was plenty of space for resting birds – this altercation most likely relates to competition for a mate and not roosting space on the beach?

In flight, the Black-naped Terns appeared a brilliant white against the intense blue tropical sky.




Roseate Tern (Sterna dougallii)

Roseate Terns are another tropical waters tern rarely seen down south. Only one pair was seen on Lady Musgrave Island. One of the Wardens on the island said more were expected to arrive shortly to breed there. I encountered the pair on a number of occasions, usually resting close to the shoreline among Crested Terns. They were very wary so I could only get a couple of long shots of them.

Based on the full black cap and red and black bill this pair in the photo below are in breeding plumage/condition. Non breeding birds have all black bills and a white forehead. The bird on the right has a silver band on its left leg.



Lesser Crested Terns (Thalasseus bengalensis)

Once again this is another tropical waters tern not found down south. The Lesser Crested Tern looks very similar to the much more common Crested Tern however it is easily identified by its noticeably smaller size and orange bill – the Crested Tern’s bill is yellow.

Only one pair were found on Lady Musgrave Island. They associated closely with the larger and closely related Crested Terns. The Lesser Crested could easily be overlooked among a large flock of Crested Terns so it is always a good idea to check carefully through a large flock of terns to see what other species might be lurking within their ranks.

One of two Lesser Crested Terns found on Lady Musgrave Island. Note the white flecks on the forehead – this bird is probably moulting to breeding condition, that is to a fully black cap.

While the Lesser Crested Tern on the left in this photo is a little fuzzy it does provide a good size comparison with the similar but much larger Crested Tern and also the bill colour difference shows well.

Crested Tern (Thalasseus bergii)

There were 200 to 300 Crested Terns on Lady Musgrave Island with most adults in breeding plumage. There were also a few juveniles and non-breeding adults. Some rested on the sand spit at the NE end of Lady Musgrave Island and others on a couple of defunct structures in the lagoon used in the past for tourists to view the underwater world of the lagoon without the need to enter the water.

A small section of a Crested Tern flock on the sand spit at Lady Musgrave Island. The two smaller terns in the foreground are White-naped Terns.

The black shaggy feathers at the back of the head on display here are not really a true crest. The dark bird is a Black Noddy.

For anyone wanting to see a range of tropical tern species in one place, a visit to a coral cay island on the Great Barrier Reef is a must.

Post No.4 will cover Wedge-tailed Shearwaters that were breeding on Lady Musgrave Island and Brown Boobies which were breeding on nearby Fairfax Island.

Thursday, 10 November 2016

Coral Cay Island Birds – Great Barrier Reef – Part 2 Black Noddies


The background to our recent visit to Lady Musgrave Island on the Great Barrier Reef (GBR) was given in the previous post.

There were thousands of Black Noddies breeding on Lady Musgrave Island.  However long before reaching there we crossed paths with Black Noddies out at sea as they moved about hunting for food.

Noddies are terns. Three species are found in Australian waters, the Black Noddy (Anous minutus), Common Noddy (Anous stolidus) and the much less common Lesser Noddy (Anous tenuirostris) which appears to be restricted to the Indian Ocean with some birds found off the Western Australian coast.

Click on images to enlarge.

Black Noddy perched in a Pisonia tree on Lady Musgrave Island.
 
Black Noddies take small fish, plankton and jellyfish from the surface of the sea and while we passed many birds flying alone out at sea, the feeding events we saw involved small to large flocks of birds (I am not implying here that individual birds do not forage alone).

Part of a Black Noddy flock feeding at sea. There are over 100 birds in this image which has captured about half the flock.
 
At times the feeding seemed frenzied and in places it looked like a chaotic melee.

Black Noddies are sedentary and do not migrate after breeding. Their breeding is “aseasonal” (without season, that is no rigid breeding schedule) with an increased likelihood of breeding events in spring and autumn. They are colonial breeders and may have one or to broods per year. They build substantial nests of leaves and seaweed, cemented together with faeces, in trees and small shrubs and occasionally they nest on the ground. Only one egg is laid per brood. Both sexes share incubation and the care of young.

Given there is no rigid breeding schedule, we were very fortunate to visit Lady Musgrave Island when a large Black Noddy breeding event was underway. Thousands of nests were either finished with birds sitting on eggs or still under construction as we saw many birds gathering leaves and seaweed. Most of the nests were located in the Pisonia trees however Pandanus Palms and Tournefortia trees (see previous post) were also being used. There were dozens of nests in each tree.

Black Noddy on a nest of leaves and other material, held together with faeces.

The price of nesting colonially and using faeces to cement nest materials is a good amount whitewash on feathers at times. I guess the next trip to sea to feed will wash off the mess!

This piece of seaweed proved to be far too large and heavy to be lifted and carried to the nest.

A piece of grass floating near the shoreline was of great interest to a number of Noddies still gathering nest material.

I watched many attempts to pick up the grass, often with two or more birds competing.

This bird managed to lift the grass a short distance above the water but eventually had to drop it as it was far too heavy.

I found small groups of Noddies, between 5 and 20 birds at times, on the beach sand picking up and swallowing grit. At first I speculated that this was used to somehow help digestion, however given the grit was calcareous (pulverised coral and shells) perhaps it was to aid egg shell production, in which case they would have been female birds! Small groups of Noddies also gathered on the beach to sun themselves, often with an outstretched wing, this may have been a way of removing parasites?

Noddy on the beach picking up shell grit.

Photographing the Noddies in flight at sea from a moving boat proved to be a great challenge partly because they are small fast moving birds but also because their dark soft sooty plumage makes autofocus difficult even under static conditions. In addition, on the beach the tropical light was very harsh. Also the birds have predominantly near black/dark brown plumage with a maximum contrast silver/white cap which makes exposure difficult. Either the body is well exposed - in which case the white cap is overexposed, or in the reverse case  - the cap looks good but the body is rendered completely black. However, I eventually managed to capture some acceptably exposed and in focus images of Black Noddies in flight.

Black Noddy in flight.

Bird with another leaf to add to the nest.
 
Each tail feather ends with a point.

I think I may have become a little obsessed with the challenge of capturing Black Noddy photos?

It is hard to estimate how many breeding Black Noddy pairs were on Lady Musgrave Island but the number was easily in the thousands. It was relatively quiet while we were there with birds finishing nests or sitting on eggs. Once the young hatch I imagine the Pisonia jungle would be a very busy, noisy and smelly place.

Regarding the genus names for Noddies, both scientific and common, Anous and Noddy respectively, Fraser and Gray, “Australian Bird Names” provide the following explanations:

Anous ”stupid bird”, from Greek anous, foolish (having no nous, in fact).
Noddy  “is and old English word meaning simpleton. It is presumed that insult was directed at the bird for being trusting of marauding sailors in its breeding colonies.”

Clearly Noddies evolved to breed colonially on remote offshore islands free from human and other mainland predators. In addition, the birds are pelagic, spending their lives at sea and rarely visiting mainland beaches so they did not come into contact with people over the thousands of years of their evolution. It was not until relatively recently that these birds encountered European sailors in their breeding colonies. Today the names do appear to be insulting for a beautiful trusting bird that has simply evolved that way. The names are certainly an historic reflection of the minds and world view that existed in the early days of European exploration and colonialism.

We found the Black Noddies just as trusting today – they tolerate very close approach to their nests which is a very special experience – thousands of years of evolution does not change in a few short years.

In the next post (Part 3) I will cover other Tern species found on Lady Musgrave Island.