Ian’s Bird of the Moment – Christmas Island Birds

Ian’s Bird of the Incident he’s called it this time in his newsletter. By Ian Montgomery
Well, I’ve finally emerged from various Christmas Island induced rabbit holes and we can have our virtual trip to look at some of the special birds of this remote island. There aren’t any feral rabbits on Christmas Island, so Red Crab burrows might be a better metaphor.
Christmas Island is both remote and very old, making it an interesting place in terms of both biogeography and avian evolution. It is about 350km/220 miles south of the western tip of Java and 1,550km/960 miles northwest of Exmouth in Western Australia. There are no nearby islands – the Cocos Keeling Islands are 980km/610 miles to its west. It first appeared about 60 million years ago as a 5,000m/ high volcanic seamount which then underwent several geological uplifts over the following 10 million years giving it a layered structure with cliffs, both coastal and farther inland, formed by coastal erosion. Coral reefs deposited limestone over the basalt core.
christmas_island_map.jpg
60 million years ago was shortly, geologically speaking, after the extinction event, thought to be a global collision with a large object, about 66 million years ago that marked the end of the Cretaceous period. This caused the extinction of many plants and animals, notably the dinosaurs, and resulted in rapid adaptive radiation of many surviving groups, particularly birds and mammals. At the time Australia was still attached to Antarctica and the other tectonic plates of the former Gondwana were still drifting to their current locations and resulting land masses: South America, Africa, Madagascar and India.
The island has an area of 135 sq km/52 sq mi and the coast is an almost continuous cliff with few bays or beaches, as shown in the photo of the east coast. Although known to European sailors from the 17th century, the cliffs made landing, exploration and settlement difficult and it remained uninhabited and consequently undisturbed until the late 19th Century. The largest bay is Flyingfish Cove near the north of the island where the Settlement is located. The photo below shows a typical stretch of coast looking south from Margaret’s Knoll on the eastern side of the island.
margarets_knoll-ps.jpg
You’ll probably know from previous posts that I’m particularly interested in the evolution and ecology of birds, and by extension their taxonomy and biogeography. Isolated islands both provide fascinating insights into and pose intriguing questions about both evolution and biogeography and I’m going to look at the species on Christmas Island from these angles. We’ll start with the taxonomically most unusual, Abbott’s Booby, which belongs to a monotypic endemic genus, then look at other interesting seabirds and finish with land birds.
abbotts_booby_40307_pp.jpg
Three of the seven global species of Booby breed on Christmas Island: Abbott’s, Brown and Red-footed. Both the Brown and Red-footed are widespread, found throughout tropical waters around the world and members of the genus Sula which comprises all the species of Booby except Abbott’s.  Abbott’s, however, breeds only on Christmas Island and is the only member of the genus Papasula. It was originally included in Sula but structural differences between it and both Gannets and other Boobies led Olson and Warheit 1988 to move it to a new more primitive genus of its own. Subsequent DNA studies have confirmed this and Papasula is thought to have branched off the early Gannet-Booby lineage about 22 million years ago.
abbotts_boby_39566_pp.jpg
We can’t, however, conclude that it evolved in isolation on Christmas Island. The species was first described from a specimen collected by the American naturalist William Louis Abbott in 1892 on an island near Madagascar in the western Indian Ocean, either Assumption Island or the nearby Glorioso Island. Fossil evidence indicates that it was quite widespread in the Indian and Pacific Oceans and there are eyewitness reports of it breeding in the Mascarene Islands near Mauritius (as described in Wikipedia). So its endemic status on Christmas Island is a result of its extinction elsewhere. On Christmas Island the population, currently estimated at about 2,000 pairs, has declined owing to habitat clearance and the species is classified as endangered.
red_footed_booby_40375_pp.jpg
Here, by way of comparison, is the white morph of the Red-footed Booby. There is also a widespread brown morph of this species but all, or almost all of the ones on Christmas Island are of the white morph. You can see photos of the brown or dark morph here: Birdway Red-footed Booby.
Frigatebirds are very well represented on Christmas Island. Three of the five global species nest on the island: Lesser, Great and the endemic Christmas (Island) Frigatebird. The other two species are the Magnificent (Birdway: Magnificent Frigatebird) of Atlantic and eastern Pacific Oceans and the Ascension, endemic to Ascension Island in the Atlantic. The Lesser (Birdway: Lesser Frigatebird) has colonised Christmas Island in small numbers relatively recently while the Great (Birdway: Great Frigatebird) is an endemic subspecies (listeri) with a population of about 3,300 pairs.. The Christmas Frigatebird is globally the rarest with a population of about 1,200 pairs. The population has declined since human settlement and the species is now classified as critically endangered, both because of its small, declining population and the fact that its breeding range is limited to a single location.
Unlike Abbott’s Booby, it’s probably fairly safe to assume that it evolved on the island and differs from the other species of Frigatebird mainly in the patterning of the plumage. The male has a diagnostic white belly, while the female has a white breast and belly extending further down the belly than in other species.
chris_is_frigatebird_40587_pp.jpg
Frigatebirds feed both by snatching prey such as squid and flying fish from on or near the surface of the water and by harrying Boobies, Tropicbirds and Terns until they drop their food. In the photo above, this female has just regurgitated a no doubt tasty mixture for its chick including a flying fish, the “wings” of which you can see sticking out on both sides of the chick’s mouth.
While we’re on the subject of tropical seabirds, Christmas Island has two of the three global species of Tropicbirds: the White-tailed and Red-tailed Tropicbird. Most of the local White-tailed Tropicbird population has black and apricot rather than the typical black and white plumage and has been ascribed to a separate subspecies fulvus. It is known locally as the Golden Bosunbird. However, 7% of the local population has the normal black and white plumage and apricot coloured birds occur in small numbers elsewhere, so it may be better to consider the differences just as colour morphs.
whitetail_tropicbird_39817_pp.jpg
For me, the Golden Bosunbird was the most beautiful bird on the island and I spent hours watching them in flight from this lookout near the settlement overlooking Tai Jin House, below, the former resident of the governor in more colonial times.
tai_jin_house-ps.jpg
The Red-tailed Tropicbird, or locally Silver Bosunbird, is quite beautiful too. In pristine condition, the birds have long red tail streamers, but these frequently get broken off when the birds are nesting. They do a spectacular fluttering display flight travelling downwards and often slightly backwards near the cliffs where they nest.
redtailed_tropicbird_40016_pp.jpg
Both of these Tropicbirds are quite widespread. The White-tailed occurs in tropical parts of the Indian, Pacific and Atlantic Oceans while the Red-tailed ranges from the western Indian Ocean to the central Pacific.
Special birds on Christmas Island are not restricted to sea birds: it has some unusual land birds as well. Here is the splendid and abundant Christmas Island Imperial Pigeon.
xmas_is_imp_pigeon_40723_pp.jpg
The dorsal plumage is this lustrous green which reminds me of Connemara marble. The breast is plum-coloured, the vent rufous and the eyes are a spectacular golden. It’s endemic to the island and its closest relative is the Pink-headed Imperial Pigeon (D. rosacea), widespread in the Indonesian islands of the Java Sea.
xmas_is_imp_pigeon_40171_pp.jpg
A much more elusive member of this family is endemic race natalis of the Common or Asian Emerald Dove. This used to be treated as the same species as the Emerald Dove that occurs in Australia but the latter has been split into two species: the Common or Asian and the Pacific. As a result, Christmas Island is the only place in Australia where the Common or Asian species occurs.
common_emerald_dove_40178_pp.jpg
Also elusive is the only resident owl, the endemic Christmas Island Boobook. With a length of 26-29cm/10-11.4in, it is generally smaller than the rather variable Australian Bookbook of the mainland: 27-36cm/10.6-13.8in. We went out one night near the golf course with David James, one of the leaders of the first Christmas Island Bird Week, who was armed with a recording of the call. The recording was of poor quality but to our delight and surprise we got a response and a family of three appeared at close quarters. The species is regarded as vulnerable with a population of maybe 500 pairs and there are concerns that the introduction of yellow crazy ants is affecting the availability of the invertebrate prey that is its main source of food.
christmas_boobook_39728_pp.jpg
Christmas Island also has an endemic diurnal predator, the Christmas Island Goshawk. Its taxonomy has proved a challenge for various taxonomists and it has generally been treated as a race of the Brown Goshawk (Accipiter fasciatus). In fact there are significant differences in structure, appearance and behaviour, so there is probably justification for treating it as a separate species. It is the rarest of the endemic birds with a population of probably less than 250 individuals. Unlike the Brown Goshawk, the birds are relatively tame and approachable.
variable_goshawk_39610_pp.jpg
Christmas Island has only two endemic Passerines, the endemic race of the Island Thrush that was the subject of the last Irregular Bird and the Christmas Island White-eye. White-eyes are famous for finding their way to and settling on remote islands so there are nearly one hundred species ranging from Africa through the warmer parts of Asia to Australasia and the islands of the Pacific. This one is posing on a coral tree near Tai Jin House.
xmas_is_white_eye_39318_pp.jpg
So, there you are. Plenty of rabbit or red crab burrows to be explored by budding taxonomists and biogeographers. Talking about Red Crabs, itt wasn’t the right time of the year for the Red Crab spawning event and I don’t remember seeing any as they keep out of sight at other times of the year. We did encounter some Robber or Coconut Crabs, however. This species  is the largest terrestrial arthropod, weighing up to 4kg/8.8lbs and measuring up to 1m/39in in span from leg tip to leg tip. Their range comprises islands of the Indian Ocean and parts of the Pacific.
robber_crab_39595_pp.jpg
Greetings and stay safe,
Ian

Lee’s Addition:

“Thus the heavens and the earth were completed, and all their hosts. By the seventh day God completed His work which He had done, and He rested on the seventh day from all His work which He had done.” (Genesis 2:1-2 NASB)

Very interesting how these birds have developed and interbred over the centuries. With isolation, much interbreeding within the species has helped influence these varieties within the families and orders.

See More of Ian’s posts at:

Ian’s Bird of the Week

Who Paints the Leaves?

Lee’s Two Word Tuesday – 5/30/17

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Red-tailed Tropicbird (Phaethon rubricauda) feeding a chick ©WikiC

FEED ME

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“Remove far from me vanity and lies: give me neither poverty nor riches; feed me with food convenient for me:” (Proverbs 30:8 KJV)

Red-tailed Tropicbird (Phaethon rubricauda) feeding a chick ©WikiC

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More Daily Devotionals

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Sunday Inspiration – Flamingos and Tropicbirds

American Flamingo Beak at Gatorland by Lee

American Flamingo Beak at Gatorland by Lee

“But now is made manifest, and by the scriptures of the prophets, according to the commandment of the everlasting God, made known to all nations for the obedience of faith:” (Romans 16:26 KJV)

As we continue through the taxonomic order of birds, we have come to two Orders that are small. The Phoenicopteriformes Order is made up of one family, the Flamingos. Our other Order is the Phaethontiformes, which has the Tropicbird family. There are only six birds in the first family and three in the other.

White-tailed Tropicbird (Phaethon lepturus) by Ian

White-tailed Tropicbird (Phaethon lepturus) by Ian

So, let’s go find out what the Lord Created these birds to appear like, and find out a little about them.

Flamingos are a type of wading bird in the genus Phoenicopterus (from Greek φοινικόπτερος meaning “purple wing”), the only genus in the family Phoenicopteridae. There are four flamingo species in the Americas and two species in the Old World.

Chilean Flamingo (Phoenicopterus chilensis) ©Wiki

Flamingos often stand on one leg, the other tucked beneath the body. The reason for this behavior is not fully understood. Recent research indicates that standing on one leg may allow the birds to conserve more body heat, given that they spend a significant amount of time wading in cold water. However, the behaviour also takes place in warm water. As well as standing in the water, flamingos may stamp their webbed feet in the mud to stir up food from the bottom. (Wikipedia with editing)

Red-tailed Tropicbird (Phaethon rubricauda) by Ian

Red-tailed Tropicbird (Phaethon rubricauda) by Ian

Tropicbirds are a family, Phaethontidae, of tropical pelagic seabirds now classified in their own order Phaethontiformes. Their relationship to other living birds is unclear, and they appear to have no close relatives. There are three species in one genus, Phaethon. They have predominantly white plumage with elongated tail feathers and small feeble legs and feet.

Tropicbirds plumage is predominantly white, with elongated central tail feathers. The three species have different combinations of black markings on the face, back, and wings. Their bills are large, powerful and slightly decurved. Their heads are large and their necks are short and thick. They have totipalmate feet (that is, all four toes are connected by a web). The legs of a tropicbird are located far back on their body, making walking impossible so that they can only move on land by pushing themselves forward with their feet. (Wikipedia with editing)

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“Hast thou not known? hast thou not heard, that the everlasting God, the LORD, the Creator of the ends of the earth, fainteth not, neither is weary? there is no searching of his understanding.” (Isaiah 40:28 KJV)

“You Are the Everlasting God” ~ 3 Plus 1 Quartet – Faith Baptist

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PHOENICOPTERIFORMES – Flamingos

Phoenicopteridae – Flamingos

PHAETHONTIFORMES – Tropicbirds

Phaethontidae – Tropicbirds

 

Ian’s Bird of the Week – Red-billed Tropicbird

Red-billed Tropicbird (Phaethon aethereus) by Ian Montgomery

Red-billed Tropicbird (Phaethon aethereus) by Ian Montgomery

Ian’s Bird of the Week – Red-billed Tropicbird ~ by Ian Montgomery

Newsletter – 6/6/11

Last November a Red-billed Tropicbird was recorded on Lord Howe Island (http://aussiebirding.wildiaries.com/species/23736). This is the first Australian record and it is a long way from its closest breeding colonies in the Galapagos. I photographed this species in 2005 at another Ecuadorean site, Isla de la Plata (‘Silver Island’) so I thought I’d share it with you as Tropicbirds are among my favourite birds. Lord Howe Island, incidentally, has breeding Red-tailed Tropicbirds (http://www.birdway.com.au/phaethontidae/red_tailed_tropicbird/index.htm). Isla de la Plata is often called the poor man’s Galapagos as it’s a mere 40km from the Ecuadorean coast as can be visited on a day trip for about $40 and has some of the Galapagos specialties such as the Blue-footed Booby (http://www.birdway.com.au/sulidae/blue_footed_booby/index.htm).

Red-billed Tropicbird by Ian Montgomery

Red-billed Tropicbird (Phaethon aethereus) by Ian Montgomery

The Red-billed Tropicbird is easily distinguished from the closely related Red-tailed by its white tail streamers and black barring on the back and wings (first photo). It is the largest of the three species with a body length of about 50cm/20in, tail streamers of at least another 50cm/20in and a wingspan of about 1metre/40in. The two tail streamer feathers are longer in the male and used in aerial display and may also be used as a rudder in flight. They are fragile, often broken (second photo) and are replaced continually.

The courtship display of the Red-billed Tropicbird starts with a number of birds flying around near the colony which is usually on a rocky cliff. A pair of birds may then separate from the flock and start synchronised aerobatics, as in the third photo. This time I’ve embedded the photos in the body of the email; if this causes any problems, eg with older email programs that don’t support HTML, just let me know ian@birdway.com.au and I’ll revert to attaching them.
Red-billed Tropicbird (Phaethon aethereus) by Ian Montgomery

Red-billed Tropicbird by Ian Montgomery

This display may lead to a choice of nest site (from the air). Tropicbirds have webbed feet and weak legs and can move only with difficulty on land, so the choice of inaccessible cliff sites is supposed to offer protection from terrestrial predators and allow easy take off.

They feed by diving for prey, often flying fish and squid, as do gannets and boobies and, like them, have air sacs in the head and neck to absorb the impact of hitting the water. The tropical waters in which they feed have low prey densities so they travel far and when not breeding lead a pelagic existence. They aren’t closely related to gannet and boobies; DNA studies suggest that they have no close relatives and Christidis and Boles (2008) place the three members of the Tropicbird family, the Phaethontidae, in their own order, the Phaethontiformes. The third and smallest species is the White-tailed Tropicbird, best known in Australia as the apricot-coloured morph found on Christmas Island and known locally as the Golden Bosunbird (http://www.birdway.com.au/phaethontidae/white_tailed_tropicbird/index.htm).
I’ve had an encouraging response to last week’s request for photos of Australian birds that I can’t supply, with about 60 species of the wanted list being offered. There are still 200 to go, so have a look at the update wanted list to see if you can help.
On the website, I recently changed my policy of not including captive birds under any circumstances and have added photos of a Malleefowl (http://www.birdway.com.au/megapodiidae/malleefowl/index.htm) and Little Penguins (http://www.birdway.com.au/spheniscidae/little_penguin/index.htm)  in tolerably natural-looking sets.
Best wishes,
Ian

Ian Montgomery, Birdway Pty Ltd,
454 Forestry Road, Bluewater, Qld 4818
Phone: 0411 602 737 +61-411 602 737
Preferred Email: ian@birdway.com.au
Website: http://birdway.com.au

Lee’s Addition:

Ian made some interesting observations about the Tropicbirds:

  • Have webbed feet
  • Have weak legs
  • Can move only with difficulty on land
  • The choice of inaccessible cliff sites is supposed to offer protection from terrestrial predators and allow easy take off.
  • When diving for prey air sacs in the head and neck absorb the impact of hitting the water.

Looks like these features add up to a neatly created design to provide for and protect the tropicbirds.

Then God said, “Let the waters abound with an abundance of living creatures, and let birds fly above the earth across the face of the firmament of the heavens. (Gen 1:20)

The Tropicbirds are in the Phaethontidae – Tropicbirds Family. There are only three species in the family and they are the only family in the Phaethontiformes Order.

More of Ian’s Birds of the Week – Click Here

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