Week 12: Keas to King Parrots

Day 47: Kakapo - Strigops habroptilus

The lovable owl-parrot

If you don't know what a kakapo is yet, you need to get it in your life (see kakapo and Stephen Fry). This is a parrot with an interesting ecology, an endangered past and an adorable personality.

Kakopo is the Maori for night parrot and Strigops means owl-eyes; together these names sum up much of their ecology. The kakapo is endemic to New Zealand and, like the kiwi before it, has lost the power of flight in the absence of terrestrial enemies. Despite this, the kakapo's wings are not redundant but are used to parachute down through the branches up which it ably climbs with sturdy legs. Predators were not, however, absent altogether in the evolution of the kakapo. The existence of visually proficient aerial predators (such as the Haast's eagle or yore) pressurised the kakopos to stay low and hidden, employing cryptic green plumage and a freezing response to danger. At night, they could skulk in relative safety, using their huge eyes, whisker-like vibrissae and keen sense of smell to navigate and forage for plants, fruits and seeds.

As one might imagine, this suite of adaptations offers little protection against a relatively recent threat. Arriving in New Zealand around 700 years ago, the Maoris (formerly Polynesian) and their dogs hunted kakapos for food and feathers and had no problem picking the petrified parrots from the forest floor. Fast-forward 600 years and European settlers began to arrive, bringing with them their own mammalian entourage of cats, rats, stoats and ferrets which made a quick meal of the kakapos and their eggs. The ruthless efficiency of naturalists also played its part, each scientist or collector desperate for a kakapo in their cabinet of curios. Soon it was extinct on North Island and fast declining on South Island.

Into the 20th century, naturalists began to find and relocate kakapos to relative safety which tended to be islands or rugged glacial valleys. However it became apparent during the 1970's that only males were being identified until a small population was found on Stewart Island. A kakapo recovery programme set about relocating all kakapos to islands where predators could be removed and vegetation managed. Strangely, the sex ratio of relocated kakapos was skewed towards males (2:1) which was a concern for conservationists.

A typical conservation strategy may provide supplementary feeding for individuals to increase health and reproductive success. When applied to kakapos, however, the sex ratio became even more skewed in favour of males! In steps the Trivers-Willard hypothesis which states that a mother should manipulate the sex ratio of her offspring based on her condition. The idea is that her condition is correlated with her offspring's condition and condition matters more to males. Females are likely to breed regardless of their size and health however in males (i.e. the competitive sex) a big male may have many offspring whilst a small male has few to none. Thus a well fed female should have male offspring. This insight from evolutionary biology identified both the problem and the solution. The solution was to feed females up to their threshold for reproduction but not so far as to reach their male-biased threshold. The population is now (slowly) recovering and evolutionary theory saves the day!

Day 48: Major Mitchell's cockatoo - Lephochroa leadbeateri

A big fan

The cockatoos (superfamily Cacatuoidea) are one of the three superfamilies in the parrot order Psittaciformes, the others being Strigopoidea (kea, kaka and kakapo) and Psittacoidea (true parrots). All parrots possess a huge, sharp beak which is generally used for crushing fruit and nuts. They also have unusual, zygodactyl feet which means two toes face forward and two face backward. This adaptation makes parrots both impressive climbers and manipulators of food and even tools.

Major Mitchell's cockatoo is one of many cockatoo species in the Cacatuidae family which are confined to Australasia. The cockatoos are noted for their splendid crests: long, often colourful feathers which they fan out when aroused. The word cockatoo has Indonesian origins where it refers to cockatoos' vice like bills. These are kept sharp by the slow grinding of the mandibles. Cockatoos are able to tackle very tough nuts which no animal can deal wiith, pinning them against the roof of their beak whilst the lower mandible dismantles them.

Cockatoos are prevalent in the pet trade. Like many parrots they are colourful and intelligent and they can live for many years with a Major Mitchell's cockatoo called Cookie celebrating his 82nd birthday this year! This cockatoo is named after Major Thomas Mitchell, a 19th century explorer who remarked that 'few birds more enliven the monotonous hues of the Australian forest than this beautiful species whose pink-coloured wings and flowing crest might have embellished the air of a more voluptuous region'.

Day 49: Papuan lorikeet - Charmosyna papou

Red lorikeet, yellow lorikeet

The Papuan lorikeet is a stunning examples of the tribe of Australasian parrots known as lories and lorikeets (Loriini). The dichotomy between lories and lorikeets is not taxonomic but simply a grouping based on tail length with the latter having much longer, tapering tails (this distinction applies to parrots and parakeets too). Like most parrots, lories and lorikeets are also very colourful. The most well known is probably the rainbow lorikeet (Trichoglossus moluccanus), a raucous and conspicuous denizen if Australian suburbs. In my humble opinion, there is such a thing as an overly colourful bird so I chose the slightly more refined Papuan lorikeet.

Unusually amongst the parrots, the Loriini are specialised nectarivores. The genus Trichoglossus refers to their hairy ('tricho') tongue ('glossus') which is covered in tiny papillae that hold on to the nectar as the tongue is withdrawn into the mouth. The lorikeets are joined by the pint-sized fig-parrots and the budgerigar of pet fame in the parrot subfamily Loriinae.

Day 50: Eclectus parror - Eclectus roratus

Who wears the bright trousers?

Given the sexual dimorphism and dichromatism we have encountered so far on this journey it may not surprise you that male eclectus parrots look different from females. What is surprising, however, is both the extent of the dichromatism and the fact that it is the female that stands out most, in scarlet and blue, compared to the predominantly green males. This disparity has confused biologists for centuries who even originally recognised males and females as separate species.

The appearance of eclectus parrots reflects a unique and complex interplay of ecology, reproduction and evolution. The main constraint for eclectus parrots in the rainforests of Australasia is nesting availability. They require hollow tree cavities to nest which are hard to come by. Females invest much of their time competing for nest holes leading to 'social selection'. Social selection is a term used by some biologist to encompass the evolutionary change resulting from the pressures of social interactions including, but not limited to, classical sexual selection. It is well understood in evolutionary theory that males that compete with each other for females can avoid damage by honestly signalling their health and ability with colours and ornaments. Well the reasoning goes that there will be situations where conspecifics compete for commodities other than mates which result in the same pressure to appear impressive. Thus, competing female eclectus parrots evolved their colouration in competition for nest holes.

In this situation, the sex roles have not been reversed (as they were for jacanas and phalaropes); males still compete for females yet male eclectus parrots look so...green. Well that green is perfect camouflage for the male as it forages amongst the foliage, dodging the keen eyes of falcons and owls.  However, in the arena around the nest hole, the green plumage suddenly stands out and the males are able to compete in the traditional fashion. Similarly the females plumage is effective camouflage when she dives into the safety of her cavity. Moreover, unbeknownst to the keen-eyed predators, these parrots are even more eclectic in ultraviolet light, part of the spectrum which parrots but not peregrines can see in.

Limited nest holes have further implications for the eclectus parrot. When females can only breed in cavities the limiting factor becomes, not females, but holes and sometimes there aren't enough to go around. As a result, females cannot afford to leave their hard-won homes so they desperately need food provisioning. She will, therefore, mate with multiple males (polyandry) and the uncertainty of paternity causes the potential fathers to all help out. This isn't the best situation for a male when holes, and thus mating opportunities, are rare and the offspring they're feeding might not even be their own! To maximise their reproductive success, males occupy huge territories which include multiple nesting holes. This complicated and unique (amongst birds) mating system is known as polygynandry: the only way to succeed is to cheat!

Week 11: Sandgrouse to Fruit-doves

Day 43: Pin-tailed sandgrouse – Pterocles alchata

Pterocles Queen of the Desert

This is one of the most beautiful of the 16 species of sandgrouse which form their own order, the Pteroclidiformes. The name sandgrouse refers both to the generally dry habitat (and matching colour) of these birds as well as their superficial resemblance to grouse. Sandgrouse are roughly grouse like in shape and sexes are dimorphic with males bearing more ornate plumage. In the case of the pin-tailed sandgrouse the male is handsome in ochre and burnished gold with a blue eye-ring and a finely tapered tail.

One difference between sandgrouse and grouse, however, becomes obvious in flight. Sandgrouse have long, pointed wings which allow them to cover large distances at speed. This is necessary for life in the plains when water can be patchily distributed. This puts some constraint on parental provisioning, however sandgrouse have specially adapted belly feathers which enable parents to absorb water and carry it back to their chicks. Drinking at watering-holes must be brief as predators frequent such sites so sandgrouse maximise their chances by congregating in large numbers, usually only visiting at dawn or dusk.

The resemblance to grouse meant that sandgrouse were formerly considered members of the Galliformes. Now they are placed next to the pigeons although they might be more closely related to shorebirds.

Day 44: Crested pigeon – Ocyphaps lophotes

Respect the pigeon

Here we enter one of the largest non-passerine bird orders: the Columbiformes. This is the order of the pigeons and doves, two terms which mean little biologically but, generally, pigeons tend to be larger species whilst doves are smaller. Some people may have a derogatory opinion of pigeons but this is probably in part due to the most familiar species, the feral pigeon (Columba livia domestica) which derives from the cliff-living rock dove via domesticated populations. With over 300 species there is , however, more to the pigeons than the humble ‘flying-rat’!

The pigeons vary in size from the goose-sized crowned pigeons (Goura spp.) to the sparrow-sized New World ground-doves (Columbina). Although there is only one pigeon family (Columbidae) the pigeons and doves are split into around ten subfamilies including the typical pigeons (Columbinae) and the arboreal doves (Treroninae). Columbids are mostly granivorous however the latter subfamily specialise in fruit.

The crested pigeon is a small Australian pigeon of open habitats. It is notable for its erect crest which is surprisingly rare in the Columbidae given the importance of visual cues in courtship.

Day 45: Nicobar pigeon – Caloenas nicobaricai

You should meet his cousin

The Nicobar pigeon is a fantastic beast to behold. This large pigeon is covered in the most exquisite pointed, metallic feathers from bronze to blue. As well as the Nicobar islands the pigeon is found on small forested islands as far east as Palau. It is generally gregarious, roaming the forest floor in search of seeds and fruits. As well as their distinctive plumage the Nicobar pigeon has a notable vulturine look which gives an air of the prehistoric.

This brings me to its most important taxonomic relevance. The Nicobar pigeon is the closest living relative of the dodo. Everyone knows about the dodo, that charismatic species that met its demise at the hands of humans. The dodo was a large flightless bird that evolved in isolation from predators on the island of Mauritius. Like many flightless birds we have already come across, the dodo was at considerable risk when humans came to the island at the end of the 16th Century. Although hunting would have placed pressure on the birds the greater issue came from habitat destruction and nest predation by introduced pigs and macaques. With its loss, as well as the extinction of giant tortoises (Cylindraspis spp.), Mauritius lost both charismatic species and important ecosystem engineers, responsible for shaping the vegetation of the island. On nearby Rodrigues the swan-sized, flightless Rodrigues solitaire was another giant pigeon to become extinct because of man.

Day 46: Mariana fruit-dove – Ptilinopus roseicapilla

Jewel of the pigeons

The Mariana fruit-dove is a member of the largest genus of columbids comprising around 50 species distributed around the islands of Southeast Asia and Oceana. Fruit-doves generally occupy the same niche wherever they are, being arboreal frugivores. This raises an interesting question about what causes some groups to be so large. In some instances a clade will hit upon an adaptation which allows the group to specialise into many different niches facilitated by the new adaptation. Hummingbirds, for example, have capitalised on their hovering flight and long bills to diversify and this is generally seen as an adaptive radiation.

Examining the fruits-doves, however, reveals little niche diversification within the genus. One adaptation that precluded their diversity was the large gape which facilitates frugivory yet there is little further specialisation. Instead the clue is in thier short, rounded wings which are not evolved for strong, regular flight. When this is coupled with the distribution of fruit-doves over the islands of the Indo-Pacific it becomes apparent why there are so many species. After the origin of the genus (probably in Southeast Asia), sporadic events caused birds to hop islands and start populations in isolation. The lack of regular dispersal meant that gene flow was soon cut short and the populations diverged and speciated in allopatry. When this process is iterated across the Indo-Pacific, the species richness of Ptilinopuus becomes the result of a series of vicariant events.

It should be noted that fruit-doves are not identical despite ecological similarity. In fact they are the most colourful and aesthetically diverse group of pigeons, mostly green with patches of bright orange, purple or magenta. The greater similarity in appearance of some species to others tracks the evolutionary history of their divergence as they jumped from island to island. The Mariana fruit-dove is a typical Ptilinopus species endemic to the Northern Mariana Islands and Guam (both US territories). I chose this species because it looks cool. 

Week 10: Skimmers to Auks

Day 39: Black skimmer - Rynchops niger

Just skimming the surface

The black skimmer is one of three skimmer species in their own family: the Rynchopidae. Skimmers are yet another fantastic example of the avian beak as a highly adapted tool. In this instance, the lower mandible extends much further than the upper. The skimmer flies low over water and drags the lower mandible along the surface before hooking up an unsuspecting fish. Of the skimmers, the black skimmer is unique in being the only bird with slitted pupils. The cat-like vertical slits are thought to minimise the amount of light reaching the eye from staring so constantly at the water's surface at close proximity.

The skimmers are one of the firm member families of the charadriiform suborder Lari. I say firm as ,whilst taxonomists can agree on the inclusion of five families, others, such as the coursers (Glareolidae) and Egyptian plover (Pluvianidae), have debated inclusion. The remaining families in this order will be represented over the coming days but for the skuas: large, brown sea birds known for their kleptoparasitic bullying of other birds.

Day 40: Lesser black-backed gull - Larus fuscus

One ring to rule them all

As gulls go, the lesser black-backed gull does not stand out ecologically or aethetically (all though I think the smartness of gulls is under-appreciated). Larus is a genus of large, white-headed gulls in the gull family Laridae (other gull genera tend to have dark heads). The reason that the lesser black-backed gull is so interesting is because of its evolutionary relationship with the familiar seaside herring gull (Larus argentatus)

To us in Britain these two gulls are easy to tell apart with the lesser black-backed gull being darker with the bright yellow legs and the herring gull being pale-backed and pink-legged (the latter has also probably stolen your lunch). However they are part of a ring complex of species. As one moves east over Europe to Siberia the lesser black-backed gulls grow slightly paler becoming the Heuglin's gull (Larus heuglini). Continue through to far-east Siberia and Heuglin's gull is replaced by the grey-backed, pink-legged Vega gull (Larus vegae). Cross into North America and, paler still, we have the American herring gull (Larus smithsonianus). Finally, across the Pond and back in Britain the European herring gull is the dominant Larus species. 

Thus, when moving east, the differences between populations are slight and all species can hybridise with neighbours but by the time the circuit is complete the sympatric herring and lesser black-backed gulls are so different as to be obviously separate species. Ring species complexes like this are a nightmare for taxonomists. However they are a brilliant, if rare, demonstration of the fuzziness of evolution and how gradual changes can accrue almost imperceptibly over space and/or time.

Day 41: Inca tern - Larosterna inca

Movember

The Inca tern is a beautiful tern from the coasts of Peru and Chile. The bright-white moustache of the Inca tern gives it a unique look among the terns but otherwise its ecology is representative of the tern family Sternidae. The terns are able fliers with very long, tapered wings and tails. Flight is very important to the terns for two main reasons. Firstly, terns spend a great deal of the time on the wing, using their keen eyes to spot fish before plunging from a height to seize their prey in their sharp beaks. Secondly, many terns are migratory with the Arctic tern (Sterna paradisaea) travelling up to 91,000 km each year. Though I have not seen Inca terns in the wild they do form part of the unnatural bird community found in Living Coasts Zoo and Aquarium in Torquay, a fantastic attraction which gives close looks of many overlooked but fantastic coastal animals.

Day 42: Atlantic puffin - Fratercula arctica

Friar of the cliffs

Puffins! If you do not know what a puffin is then you live in a burrow (much like a puffin) and if you don't love puffins then you have a heart of stone. One of our most charismatic birds, the puffin is famous for its bright bill and pompous gait as it struts around the grassy knolls of rocky coastlines. The colourful beak that we know and love only looks like this during the breeding season when pairs return to land to breed. The bright colours are used to signal dominance whilst couples court by rattling their beaks together in 'billing' courtship displays. In winter the beak shrinks and becomes grey in colour as individuals live a largely solitary existence on the open ocean.

The word puffin derives from the Middle English 'poffin' which actually referred to the cured carcasses of Manx shearwaters (hence Puffinus puffinus) which were originally known as Manx puffins. The word later came to describe the puffins we know, perhaps because they nest in burrows as Manxies do. Otherwise they are very different, especially when it comes to locomotion. Whilst shearwaters can traverse huge distances with relative ease, puffins have very short wings which are well adapted for swimming but terrible for flight. Their swimming ability meant that puffins were thought to be part fish, part bird, a loop-hole which allowed Catholics to eat them on Fridays and during Lent!

The Atlantic puffin shares the genus with two other puffin species whose name Fratercula refers to their resemblance to little friars. The puffins are part of the auk family (Alcidae), a relatively small group of piscivorous sea birds. Cliffs in the UK can be populated with thousands of auks and other seabirds which form classist tower-blocks. Guillemots (Uria aalge) occupy the majority of the cliff face with the chunkier razorbills (Alca torda) cramming in above. The kittiwakes (Rissa tridactyla), small, gentile gulls, take the steepest part of the cliffs whilst shags (Phalacrocorax aristotilis) live nearest the waves. Above them all, the puffins share the cliff tops with tube-nosed fulmars (Fulmaris glacialis) and nocturnal Manxies. These seabird stacks show vertical niche stratification both on the cliffs and under the water where their diving abilities determine what prey different species can access. Of all the seabirds, auks have forsaken their flying ability in favour of increased diving ability with Uria guillemots reaching down to 100 m. Of these so-called 'northern penguins', one auk went so far as to lose flight altogether but this, as with many flightless birds, would be its downfall. The great auk (Pinguinus impennis) was hunted to extinction in the mid 19th century.

Week 9: Plovers to Pratincoles

Day 35: Wrybill – Anarhynchus frontalis

Right-beak politics

If you look closely at the photo of the wrybill below you may notice something awry. The wrybill is the only bird species whose beak bends sideways and always to the right! Asymmetry is relatively rare in animals. Most animals develop with bilateral symmetry with cues along an anterior-posterior axis determining body part placement. Additonal signals are needed to override this symmetry and of there must be an selection pressure favouring such abnormality. Obvious asymmetries in nature include the massive claws of fiddler crabs and the spiral shells of snails (there is even asymmetrical snake that eats asymmetrical snails!). Within the birds the crossbills are notable for the mandibles which cross over, enabling them to tweeze apart pine cones.

The wrybill is a New Zealand member of the Charadriidae, the family that includes lapwings and plovers and like many plovers it prefers stony coastal areas where it uses its dextral beak to probe under rocks. The wrybill rears its camouflaged eggs among the pebbles and uses deceptive behaviour to protect them, feigning distress to lure gullible predators away from its nest. This is a strategy seen in other species such as the killdeer (Charadrius vociferus) which holds one wing as if broken to entice predators.

Day 36: African jacana – Actophilornis africanus

These feet are made for walking

The most noticeable attribute of a jacana is its feet. The jacanas are eight species of ‘aberrant’ waders that have specialised to traverse leafy waterways. As with the coots, the jacanas use their huge feet to spread their weight allowing them to walk on precarious surfaces such as water hyacinths and water lilies whilst it picks invertebrates from the foliage. This ability to (almost) walk on water also gives them the name Jesus bird. The floating mats are their full-time home to the extent that the even build their nests on the vegetation, laying eggs camouflaged to resemble water weed.

Also like coots they have bright fontal-shields which are presumably used in sexual selection given their striking colouration. Jacanas are rather unusual in that the smaller males are responsible for incubating the eggs allowing the females of some species to be polyandrous. Reproductive ecology of this type is rare in the vertebrates. For the most part, females are the limiting sex because they invest more in their offspring and so males must compete for mating opportunities. In birds, some of the investment burden is shifted away from female internal development meaning males must play a larger role in parental care to ensure reproductive success. This predicts the large amount of monogamy and biparental care in the class.

Why a few shore birds including jacanas and phalaropes should shift to male care is relatively unknown. In fish, such as stickleback and seahorses, males care for the eggs fry essentially because the female has time to escape whilst the male fertilises so he is left with the task of their rearing. This is not obviously the case for jacanas so the reasoning is probably an idiosyncratic occurrence in their breeding biology which does not occur in other birds. One suggestion is that extremely high egg predation (due to being a floating buffet and all) means that females should spread their investment around rather than put all their eggs in one basket (couldn't resist). With eggs being more evenly distributed around males, females must now compete to put their eggs in the males' respective baskets (as it very much were).

Day 37: Long-billed curlew – Numenius americanus

Length matters

I was hoping that the long-billed curlew would hold some beak-related record. Unfortunately it has neither the longest beak (Australian pelican, Pelicanus conspicillatus) nor the longest beak to body ratio (sword-billed hummingbird, Ensifera ensifera). Having said this it is still a very impressive implement! Like the Eurasian curlew (Numenius arquatus) the long-billed curlew is able to use it beak to probe deep into the sediment of salt marshes and mudflats capturing bivalve molluscs and annelid worms.

Visiting these habitats in winter is (personally) one of the most brilliant wildlife spectacles because there are so many wader (and other) species milling around, doing what they do best. Curlews, with the rest of the snipe family (Scolapacidae), provide a much-cited example of niche differentiation. The sediment of the marshes and mudflats hold a bonanza of food, various invertebrates distributed through the sediment column. Different species have adapted to access different levels and thus different prey sources. We have seen that curlews can probe the deepest; next comes the godwits (Limosa spp) with their long, straight bills, then the Tringa sandpipers such as the redshank and greenshank. At the smaller end of the spectrum are the Calidris sandpipers ranging in size from knots to stints. Additionally there are more unusually specialised birds such as the avocet and waders occupying slightly different habitats such as the beach-loving sanderling (Calidris alba), the rock-braving purple sandpiper (Calidris maritima) and the pier-friendly turnstone (Arenaria interpes).

Day 38: Collared pratincole – Glareola pratincola

One pratincole does not make a summer

I once casually asked my friend to identify the birds on her top. She said they were swallow but I knew them to be pratincoles (yes, I am an insufferable know-it-all). Her mistake was an easy one to make because of the striking convergent evolution. Swallows (Hirundinidae) are aerial insectivores which use their slender and aerodynamic wings to snatch flying insects from the air. Well, it turns out that pratincoles do too! I did not know this for sure before looking into it and I began to second-guess myself when my friend and ornithological maestro questioned my statement of ecological convergence. Well it seems that, as I predicted,  the apparent similarities are not mere coincidence. Like swallows, pratincoles (Glareola) have long tapered wings and forked tails which enable them to manoeuvre through the air and grab insects with their short beaks and wide gapes. The collared pratincole is the only species to breed mainly in Europe so may be the most familiar. It is a bird of open country which gives it its name pratincole from the Latin pratum incola which means meadow resident.

The pratincoles share the family Glareolidae with the coursers (Cursorius & Rhinoptilus), shore birds much more at home running around then flying. This is the last family of ‘wader’ that we encounter before we move onto the charadriiform suborder Lari: the gulls, terns and auks.