Gannets and Boobies; formidable fishers

Gannets and boobies form a Family of 10 distinctive large seabirds, now known to be most closely related to the cormorants and darters. They are strikingly handsome birds, and dramatic to watch, as they hurtle headlong into the water from high above it (mostly from between 10 and 30 metres up, but in the case of Masked Boobies this may be as much as 100 metres). They close their wings as they hit it (at speeds of up to 100kph, according to Bryan Nelson's classic The Gannet) and continue to chase the fish or squid beneath it. This chase can take them as far as 25 metres beneath the surface; fish are usually swallowed before they resurface. This latter strategy is useful for avoiding the thieves - frigatebirds, gulls, skuas - which are lurking above with intent to steal the rewards of their skill and labour.

Blue-footed Boobies Sula nebouxii fishing, Puerto Vilamil, Isla Isabela, Galápagos, above and below.
You can see the streamlined shape they adopt just before hitting the water.
This was a spectacular sight, right in the harbour.

'Gannet' is based on the same Old English word root as 'gander', which at that stage simply meant a goose, with no implication of gender; for reasons uncertain it came to be applied to the Northern Gannet, which in northern Scotland is still referred to as 'Solway Goose'. The general usage of the word didn't occur until the 19th century. 'Booby' was used in the sense of a 'foolish fellow' - presumably for sitting trustingly in colonies in the face of marauding sailors. We really are shameless! The gannet genus Morus means the same thing, from the same Greek word which gave rise to 'moron'. If I were a gannet (or booby) I'd be suing...

It was long believed that they were closely related to pelicans, but that is no longer the case; pelicans are closer to herons and ibis. The gannets and boobies share the Order Sulidae with frigatebirds, as well as cormorants and darters. (From Sulidae comes the world sulid, referring to a member of the family; I will use it here, not to be smart but because it's easier than saying 'gannets and boobies' each time!) One characteristic that they share with pelicans, which contributed to the misunderstanding, is having all four toes connected by webbing for better swimming power. It seems however that they and the pelicans evolved this adaptation independently.

Blue-footed Booby feet (as if you couldn't have guessed!), Puerto Ayora, Galápagos.
The hind toe has been dragged around to the side to enable the more extensive area of webbing.
In ducks and gulls, for instance, only the front three toes are joined.

The plunging lifestyle inevitably requires other adaptations too.

Nazca Booby pair Sula granti, Española, Galápagos.
The eyes are set right alongside the bill, enabling binocular vision, which is most unusual in birds.
They seem to choose the prey from high up and adjust their dive as come down to follow it, which of course
requires very accurate depth perception. Moreover in a vigorous headlong dive, external nostrils would
be a serious hazard, so they have been dispensed with them; instead they open inside the bill.

A less obvious adaptation is in the breast, which is cushioned to protect internal organs by a remarkably developed set of air-sacs (bronchial extensions which spread throughout the body of a bird to enable their unique respiratory system), like bubble wrap. Their neck muscles are unusually strong, they have membranes to protect the eyes, and a layer of spongy bone at the base of the bill to absorb the impact.

The sulid bill has small serrations to assist in handling fish; on the other hand it lacks the hooked tip of many other large fishing birds.

Red-footed Booby Sula sula, Genovesa, Galápagos.
You can see the serrations here if you click on the photo to enlarge it.

Within the family many (but not all) authorities recognise three genera. The oldest seems to be the Abbott's Booby Papasula abbotti of Christmas Island and surrounding oceans, which apparently split from the ancestors of the other species some 22 million years ago. The ancestral gannets and other boobies parted company 17 million years ago. Despite this the differences between the two groups are not particularly striking. The six Sula boobies are essentially tropical and subtropical, while the larger three Morus gannets are mostly birds of temperate seas. The boobies are generally darker (though as with the Nazca Boobies above there are exceptions). Gannets are white (except for wings and tail) with yellowish heads.

Australasian Gannet Morus serrator, south coast New South Wales.
These long narrow pointed wings are typical of the family.

Here are a couple more examples of these very elegant wings.

Masked Booby Sula dactylatra, Muttonbird Point, Lord Howe Island.

Nazca Boobies, Galápagos.

Peruvian Boobies Sula variegata, Islas Balasteros, Peru.

A further difference lies in the sex size ratios; female boobies are notably bigger than their males, but this is not the case with gannets.

Most sulids are completely white beneath, presumably to provide camouflage from predators coming from beneath them in the ocean. However there are two exceptions; the Brown Booby Sula leucogaster, found throughout most of the world's tropical oceans, and some Red-footed Boobies... This strange latter statement is based on the fact that Red-footed Boobies come in two basic morphs, a brown (shown above) and a white - plus variations on those themes!

Brown Booby, Lady Elliot Island, Queensland.
Even here the belly is white.

All sulids nest in colonies, though this is presumably mostly due to necessity - suitable island sites are not easy to find. The size of the colony and the breeding area will also determine how densely packed the colony is.

Nazca Booby colony at sunset, San Cristóbal, Galápagos.

Masked Booby colony, Lord Howe Island.

Cape Gannet colony Morus capensis, Lambert Bay, South Africa.
This is an extraordinary experience; the huge colony comes right up to a viewing hide.

All these species nest on the ground - in most situations there is no choice, and the gannets in particular are large birds. The nest is no more than a scrape on the ground.

Nazca Booby nest scrape.

This nesting Masked Booby on Lord Howe Island seems to have prepared even a scrape among the grasses.

 However Red-footed Boobies, the smallest sulids, nest in shrubs and trees.

Red-footed Booby colony, Genovesa, Galápagos.
Most Galápagos Red-foots are brown morphs...

... but not all! This is a white morph Red-footed Booby, with an egg.

At first sight, this looks like the brooding strategy of most birds, but sulids lack brood pouches (featherless areas of the belly which have blood vessels close to the surface for warming eggs and chicks) - perhaps they would cause too much heat loss in the water. This parent - they both take turns at brooding - is covering the egg with its feet under the body. These feet have many blood vessels, which warm the egg. On the other hand the bird is basically standing on the egg, so it must have a particularly thick shell!

Nazca Booby and egg, Genovesa.

Most sulids lay only one egg, though Blue-footed and Peruvian Boobies breeding in the great anchoveta grounds of the Humboldt Current lay two or three and aim to raise them all. In other cases, where two eggs are laid (ie Brown and Masked Boobies) the second is simply insurance against loss of the first, and the second chick always dies.

The two eggs of this Nazca Booby on Genovesa represent a most unusual situation for this species,
but they would certainly not have resulted in two fledged chicks.

For the first few days of the chick's life it is brooded on the warming feet, beneath the parents' bodies.

Nazca Booby with young chick on feet, Genovesa.

Here are some more chicks at increasing ages; ages cited are of course approximate. Except where specified, all photos were taken at different colonies on Genovesa.

Nazca Booby with one week old chick, just growing down feathers.

Nazca Booby and 2-3 week old chick.

Red-footed Booby chicks, 2-3 weeks.

Nazca Booby feeding 3-4 week old chick, growing but still quite helpless.

Blue-footed Booby and 3-4 week old chick, North Seymour, Galápagos.

By now the parents may start to leave the chick on its own, as it is now able to adequately manage its body temperature, while both parents forage. However fledging in most species takes around 15 weeks - and this is after some six weeks of egg incubation!

Red-footed Booby chick losing the last of its baby down.

Red-footed Booby chick, now fledged, practising flapping its wings in preparation for
its first flight lesson.

But even after fledging the youngster will depend on its parents for food for another few weeks; it presumably takes this long to learn the complexities of the plunge-diving feeding system.

This relaxed approach to breeding means less stress on the parents, a strategy which is made possible by their longevity, which may be 20 or more years. They may not start breeding until six years old.

Displays, both for reinforcing pair bonds, and for defending territories in crowded colonies, are highly ritualised. Famously, Blue-footed Boobies flaunt their feet, presenting them overtly when landing, and performing slow dances featuring the feet, lifted for inspection. As in most animal blue bits, the effect is a trick, utilising bubbles in cells stacked in precise ways to reflect blue light; more on that here. However Blue-footed Boobies' feet aren't just blue - they cunningly brighten them up by incorporating yellow carotenoids to form the most sought-after shades, which are bright aquamarine. (Mind you, when I started to look up this colour on line I found many shades all called aquamarine, so I'm no wiser as to which is the optimal Blue-footed Booby foot.) Birds with feet artificially dulled by experimenters lost their attraction to their mates. And there was a real correlation between foot colour and fitness. Here are a couple of very different shades I've seen in Blue-footed feet.

Puerto Ayora, Galápagos.

Pucusana, Peru.

And that is probably enough for today, though I've greatly enjoyed preparing this tribute to the wonderful sulids; I hope you've enjoyed it too. Here are just a couple more images...

Peruvian Boobies, Islas Balasteros.

Masked Booby preening, Lord Howe Island.

NEXT POSTING THURSDAY 17 MAY.

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Palms; old and successful. Part 2

This posting forms the conclusion of last week's post on palms; today I'm simply going to introduce some species from both Australia and elsewhere.

Alexandra Palms Archontophoenix alexandrae forming a swamp forest in Centennial Lakes, Cairns.
This is their normal habitat in the east Queensland tropics.

Climbing Palms Calamus sp., Atherton Tablelands, north Queensland.
The stems can be up to 200 metres long; they form no crown, but have leaves crowded along
the end part of the stem.

A climbing palm with the delicious name of Vicious Hairy Mary Calamus radicalis, north Queensland.
In addition to the spines on stems and leaf edges, it has savage spiny 'whips' of tendrils up to four metres
long that assist in climbing and will tangle horribly in clothes or skin.

Kentia Palm Howea forsteriana, Lord Howe Island.
This lovely palm is endemic to the tiny Pacific island, but has now spread around
the world as a cultivated plant. It was also the subject of one of my first ever blog postings,
nearly five years ago. There's a lot more information about it there.

Queensland Fan Palm Licuala ramsayi, Daintree NP, north Queensland.
Restricted to streamsides and boggy areas of lowland rainforest of far north Queensland.

Livistona is a genus of some 30 species scattered across southern Asia - Australia, and in north-east Africa.

Cabbage Palm Livistona australis in wet gully, Kioloa, south coast New South Wales.
The 'cabbage' refers to the growing tip which was cut out by settlers for food - this of course killed the tree
Less lethally the leaf fibres were woven into 'cabbage-tree' hats.

Sand Palms Livistona humilis in tropical woodland, Kakadu NP;
the species is endemic to the Top End of the Northern Territory.

Livistona benthami growing by Cooinda Lagoon, Kakadu NP, Northern Territory.
This is its typical habitat, here and in north Queensland and New Guinea.

Red Cabbage Palms Livistona mariae, Palm Valley, Central Australia.
This species lives in isolation along just two kilometres of creek, surrounded
by desert where it could not survive. More on it here.

Mataranka Palms Livistona rigida, Boodjamulla NP, north-west Queensland.
It has a disjunct distribution here and around Mataranka in the northern Territory.

Livistona victoriae, Gregory River NP, western Top End, above and below.
Only recently recognised as a species, described in 1988, and found only in the
Kimberley district of the Northern Territory and Western Australia.

Chilean Wine Palm Jubaea chilensis, La Campana NP, central Chile.
This species (shot here looking into the sun, of necessity!) is found only in a small
area north of Santiago. The wine is fermented from the sap.

While we're on that theme, this is an iLala palm Hyphaene coriacea in woodland east of Masindi, Uganda.
In South Africa I was told that iLala is from a Zulu word meaning 'lie down', for the
supposed effect of the wine brewed from it.
(Naturally it will have different names in other parts of its extensive range.)

Still in Africa, this is a Raffia Palm, Raphia sp., Bwindi Impenetrable National Park, western Uganda.
This has the longest leaves of any plant in the world - they can be over 20 metres long and three metres wide!

Mauritia carana, Tambopata Reserve, southern Peruvian Amazonia.
These big leaves are in high demand for roof thatching, for their longevity - they may not
need replacing for a decade.

The same species, I am almost sure, from Waqanki Lodge on the lower eastern slopes of the Andes
in northern Peru. This lovely lodge is on the outskirts of the busy town of Moyobamba, some of
which can just be seen in the top left of the photo.

Also in Tambopata, the distinctive prop stems of Walking Palms, Socratea sp.
Despite the attractiveness of the story that they allow the palm to perambulate to more desirable sites
by means of shedding roots on one side and growing more on the other, it has no basis in the real world.
I don't really blame guides who are loth to abandon such a good yarn however!
On the other hand nobody seems to have demonstrated a convincing alternative explanation for the structures either.
The genus was indeed named for the philosopher by German botanist Gustav Karsten, for no evident
reason other than his assumed admiration for Socrates.

I hope that this relatively brief foray into the world of palms has been of interest or enjoyment - or preferably both! They certainly deserve our admiration and attention.

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Palms; old and successful. Part 1.

Here is another in my irregular series on favourite trees (you can find the most recent one here, and work back from there). I've travelled a bit in some of the warmer parts of the world and I've found that palms can pop up just about anywhere in such places. The family arose by around 80-85 million years ago, apparently in Laurasia (the northern counterpart of Gondwana, comprising what is now Eurasia and North America) from where they spread south.

Kentia Palms Howea forsteriana Old Settlement Beach, Lord Howe Island.
By the sea in coastal forest.

Red Cabbage Palms Livistona mariae, Palm Valley, Central Australia.
In desert ranges.

Palms are flowering plants but despite their woodiness and fact that most of them are trees, they are monocots, like grasses, orchids and lilies. Their trunks differ from those of dicot trees (ie pretty much any other tree you could think of) in not having annual growth rings - unlike dicots, monocots don't produce secondary growth, ie thickening of the trunk with age by laying down new layers of cells annually from the cambial layer. (Quick revision. A 'normal' tree trunk comprises bundles of tubular vessels; the inner ones, the xylem, carry water and some nutrient up from roots to foliage - the innermost xylem tubes are dead and provide the trunk's support. The outer ones, the phloem, carry products of photosynthesis, notably sugars, down from the leaves. The cambial layer lies between them and produces annually new xylem on the inner surface and new phloem outside it.) A palm trunk is basically at full diameter below the ground, and grows only upwards.

In palms the vessels are in bundles encased in fibrous sheaths, scattered through the fibrous woody material. Towards the surface of the trunk the wood is surprisingly hard and dense, becoming softer toward the core. The effect is somewhat like that of a fibre-reinforced fishing rod, very flexible and capable of withstanding storm winds. 

This Coconut Palm on the beach at Cooktown, north Queensland, has survived the full brunt
of more than one tropical cyclone, due to its flexible trunk.

The leaves, generally at the tips of the single unbranched trunk (the exception being in climbing vine palms which may have leaves along the stem), are in one of two distinct forms.

Pinnate leaves on Alexandra Palms Archontophoenix alexandrae, Cattama Wetlands, near Cairns.
Such 'divided' leaves comprise many leaflets growing along the central leaf stem.

Palmate leaves on Queensland Fan Palm Licuala ramsayi, Daintree NP, north Queensland.
These are also compound, but the leaflets all grow from the tip of the leaf stem.

Individual flowers are fairly small and inconspicuous, but they grow in often mighty inflorescences, sprouting from within or just below the foliage.

Inflorescences of Sand Palm Livistona humilis; Litchfield NP above, and Kakadu NP below.

Some palms are wind-pollinated, but the attractiveness of Sand Palm flowers to butterflies is obvious!

Fruit may be berries (comprising a fleshy ovary with seeds embedded in the flesh) or drupes (where the fleshy ovary wall encloses a woody capsule containing seeds).

Alexandra Palms have huge bunches of berries, beloved of birds such as this
Metallic Starling Aplonis metallica, Centennial Lakes, Cairns.

Coconuts Cocos nucifer, Sabah, Malaysia.
These are drupes (the outer fleshy layer soon dries out) and are superbly adapted to long-distance
ocean dispersal, by which they have spread throughout the Pacific.

Coconuts are not the only palm of major economic significance to humans. Date Palms Phoenix dactylifera have been cultivated in the Middle East for at least 7,500 years for their fruit. Sago Palms Metroxylon sagu have long been harvested in south-east Asia for their starchy pith, which is a carbohydrate supply for the production of the palm's massive fruit crop, produced after some 15 years. The harvesters can't afford to let the sago be used for the purpose for which it evolved so the tree is cut down as soon at it flowers, and the trunk cut open to extract up to 300kg of sago! (I grew up with sago pudding, and would be very happy to leave it to the palm, but that's just me...)

Sago Palms, Klias River, Sabah. I think these are wild plants.

Oil Palms Elaeis guineensis, originally from West Africa, have now been spread far and infamously across the tropics, beginning when the Dutch took it to Java in the 1840s. Vast tracts of rainforest are daily being cleared for palm planting in Indonesia, Malaysia, South America and Africa.

Oil Palms west of Sepilok, Sabah.
No wildlife corridors or refuge forest blocks here.

Oil Palms crowding to the Mana River, which marks the boundary of Korup NP in western Cameroon.

 Palms feature widely in botanic gardens.

Darwin Botanic Gardens.

Emerald Botanic Gardens, central Queensland, which makes a special feature of its palm collection.

And of course humans (and Metallic Starlings) are not the only animals to appreciate palms as food or habitat. In Cape York Peninsula and New Guinea the huge Palm Cockatoo Probosciger aterrimus is in part associated with palm swamps, but there may also be a confusion here with unrelated Pandanus spp. too, the seeds of which it certainly also eats.

Palm Tanagers Tanagra palmarum (here in northern Peru) are certainly associated with palms (an observation
reinforced in both its scientific and Spanish names) but not exclusively.
They are found throughout the northern half of lowland South America.

The Palm-nut Vulture Gypohierax angolensis (here in Entebbe Botanic Gardens, Uganda)
is most atypical in eating mostly palm fruit, especially of Oil Palms.

And of course palms are excellent places just to hang around in!

Utilising the palms at Blanquillo clay lick, southern Peru, either while waiting to descend to the clay
(Red and Green Macaws Ara chloropterus, above),
or waiting for unwary prey (Zone-tailed Hawk Buteo albonotatus, below).

 

Brown-throated Sloth Bradypus variegatus in palm (you might need to click on the picture,
it was a long way off!), Yasuní National Park, Ecuador.

I had intended to conclude here with a walk-through of a series of palm species from different parts of the world, but that would make this just too long, so I'll wrap it up next time. I hope you'll be back for it.

Moon through palm fronds, Darwin.

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