Week 17: Bee-eaters to Honeyguides

Day 67: Rainbow bee-eater – Merops ornatus

No sting in the tail

Bee-eaters are a charismatic group of birds in the family Meropidae. They are conspicuous birds, known for their bright and varied palette of plumage colouration. They are also conspicuous in their behaviour, frequenting prominent perches such as telephone wires from which they can spy prey up to 50 m away. They are capable of catching all manner of insects on the wing but, as the names suggests, bees can form a large part of their diet. Large and/or venomous prey is taken back to the perch where it is neutralised with bashing and scraping. Aerial insects abound so foraging opportunities are plentiful. Bee-eaters are limited more by nesting opportunities, requiring dry substrates in which to build their burrows. They have a largely tropical and subtropical distribution across the Old World with many species migrating annually.

The rainbow bee-eater is a typical bee-eater species. It is, however, the only species I have seen (despite multiple trips to the Med where European bee-eaters can be found). Rainbow bee-eaters were a common sight for me in the open areas of the Daintree Rainforest in Queensland. They are by no means confined to this habitat, perching anywhere where flying insects are in abundance including parks and gardens. I was observing them during the winter/dry months after they have spent the summer breeding in Southern Australia. They are a fun bird to watch and their bubbly calls are a delight.

The Meropidae, along with the three kingfisher families, are members of the order Coraciiformes. Coraciiforms lack a unifying name despite being generally colourful, small-to-medium-sized predators. The order includes the acrobatic, Old World rollers (Coraciidae), the stockier, Malagasy ground-rollers (Brachypteraciidae), the Neotropical, long-tailed motmots (Momotidae) and the tiny Caribbean todies (Todidae). Formerly a member of this order, the cuckoo roller (Leptosomus discolour) is an obscure bird from Madagascar and the Comoro islands now placed in its own order: Leptosomiformes.

Day 68: Southern ground hornbill – Bucorvus leadbeateri

Luscious lashes

This looker is the largest species of hornbill. Hornbills are notable for their large, curved bills which resemble cows’ horns (buceros in Greek). Their bills, supported by their uniquely-fused first two vertebrae, serve a variety of purposes including nest construction, fighting and preening but their most obvious use if for crushing food such as fruit and small animals. Many species have a hollow casque atop the bill which can be used to resonate calls or to joust with competitors (in the helmted hornbill, Rhinoplax vigil). Whilst their plumage is usually dark, the bills and naked facial skin of hornbills is often brightly coloured with yellows and reds that reflect the carotenoids of their diet. Once again, this is classically honest signalling of health for mate choice. 

Hornbills are largely arboreal, found in habitats from savannah to rainforest across Africa, southern Asia and Melanesia. The Southern hornbill and its sister species (the Abyssinian ground hornbill, B. abyssinicus) are a bit of an exception amongst the hornbills, being far more terrestrial than their relatives. In fact they might forsake the trees altogether were in not for the tree cavities in which they need to nest. The two ground hornbills can be found striding across the plains of sub-Saharan Africa in search of small vertebrates and large invertebrates. To cope with the dusty habitats in which they forage, the ground hornbills have very long lashes and bare skin around the face and throat. In the Southern ground hornbill, this skin is bright red.

Ground hornbills are some of the most (if not the most) long-lived birds with life expectancies around 30 years and with individuals living up to 70 years in captivity. They are also obligate cooperative breeders. Individuals must spend half-a-dozen years assisting at the nests of older birds (parents) before becoming breeders themselves. Cooperative breeding always necessitates explanation. Usually in birds it is a bet-hedging strategy; if it is too risky to start your own family (i.e. low chance of success) better to stay at home and help rear your younger siblings. Perhaps the risk in starting a new family for hornbills is either not gaining a suitable territory (or nest site) or not being able to bear the costs of rearing large chicks without help.

Ground hornbills share the family Bucorvidae with the Bycanistes genus of hornbills. The rest of the hornbills, from the small, African Tockus species to the large, casqued Buceros species, are found in the family Bucerotidae. Hornbills traditionally had the order Bucerotiformes to themselves but recently they have been joined by hoopoes (Upupidae) and wood-hoopoes (Phoeniculidae). Hoopoes (Upupa epops) are a fantastic bird with broad, barred wings and a salmon pink head and crest. Their name is an onomatopoeic rendering of their call (an oop-oop-oop) as is their generic name Upupa whilst the specific epithet epops was the name of a hoopoe in the Ancient Greek play The Birds by Aristophanes.

Day 69: Emerald toucanet – Aulacorhynchus prasinus

Big-billed birds

Whilst bearing a passing resemblance to hornbills (although not the species pictured above), the toucans, toucanets and aracaris are quite unrelated with their own family, Ramphastidae, in the order Piciformes.  Their resemblance (especially the large, flashy bills) reflects the convergent evolution of toucans into a similar niche of arboreal faunivory but in the forests of the Neotropics. Although sometimes making up more than half the length of the bird, the toucan’s beak is surprisingly light, being filled with spongy keratin. Serrations on their billss allow toucans to crush fruit whilst the length allows them to lazily reach many fruit without having to move. As with hornbills, toucan beak are huge advertising boards of colour.  

The emerald toucanet is (as the name suggests) one of the smaller toucan species. Though their bills are not as brightly coloured as some of the larger toucans and aracaris, the plumage of the green toucanets (Aulacorhynchus spp.) is vivid, the bright green sometimes embellished with red or blue. The emerald toucanet was my first wild toucan, seen feeding in the cloud forest canopy of Honduras. This was closely followed by the ornate collared aracari (Pteroglossus torquatus) and the spectacular keel-billed toucan (Ramphastos sulfuratus).

Day 70: Greater honeyguide – Indicator indicator

Show me the honey!

As mentioned above, toucans are members of the Piciformes. This is the last order of birds on our list so the end is very much in sight!  I do not have space to detail the bee-eater-like jacamars (Galbulidae) and the related puffbirds (Bucconidae) nor the four, chunky barbet families. However I will, of course, discuss at length the largest piciform family: the woodpeckers (Picidae). But first, honeyguides.

Honeyguides (Indicatoridae) look a bit out of place in the Piciformes, an order of well-built birds with large heads and beaks. In fact the honeyguides look like passerines, the humongous order of perching birds which would come next in the sequence however you should note the woodpecker-like zygodactylic feet. Although they are relatively dull birds, honeyguides are unusual in their regular consumption of wax which is taken mainly from bee hives. The greater honeyguide, feeds on the eggs, larvae, pupae and wax of bees nests and this has lead to a surprising relationship with man. As suggested by both the common name and the Latin Indicator, honeyguides lead humans (African bushmen) to honey.

Honey-guiding is a classic of example of a mutualism where individuals help each other for mutual benefit (symbiosis is a word often used instead of mutualism but symbiosis actually refers to organisms that inextricably depend on others where this relationship is not necessarily mutualistic. Conversely mutualists need not be obligate mutualists, but merely cooperative from time to time). It is relatively easy to explain this mutualism as a form of ‘partner choice’ where both parties must cooperate in order to receive the reward. Honeyguides lead hunters to bees’ nests with loud, distinct calls. After the humans have smashed open the nests and taken the honey, the birds can eat their fill. If the humans were to cheat the system, leaving nothing for the honeyguides, the selection pressure for the birds to guide would disappear followed by the behaviour itself. Likewise, the birds save a lot of time guiding the humans rather than waiting for them to find the bees themselves. Thus cooperation is needed on both sides for a successful relationship.  

Honey-guiding has only been demonstrated in this Indicator species despite the whole family sharing the name. One thing all members do share is brood parasitism, as seen in the cuckoos.

Week 16: Woodnymphs to Kingfishers

Day 63: Marvellous spatuletail – Loddigesia mirabilis

What’s in a name?

That which we call a marvellous spatuletail, by any other name, would NOT smell as sweet. Although ‘hummingbird’ itself is an interesting name, with so many hummingbird species of such fantastic diversity, naturalists have given them a variety of interesting and colourful names which encapsulate their beauty. Although more descriptive names might be more useful for hummingbirds, I think the suite of monikers adorning these birds really add to their beauty and mystique.

Some hummingbirds’ names refer to their prominent features including the streamertails (Trochilus), firecrowns (Sephanoides), coronets (Boissoneaua), pufflegs (Haplophaedia), plumeleteers (Chalybura), trainbearers (Lesbia), metaltails (Metallura) and visorbearers (Augastes). Some species appeal to groups of people such as the cowled jacobins (Florisuga), the enticing coquettes (Lophornis) and the native caribs (Eulampis) and incas (Coeligena spp).

Colour is often referenced in hummingbird names from the drab hermits (Phaethorninae) to the brightly-coloured brilliants (Heliodoxa). Many names reflect the jewel-like appearance of hummingbirds such as the topazes (Topaza), emeralds (multiple genera), sapphires (Hylocharis), moutaingems (Lampornis) and sungems (Heliactin). Other groups have a more cosmological feel including the sunbeams (Aglaeactis), hillstars (Oreotrochilus spp.), starfrontlets (Coeligena), comets (multiple genera), starthroats (Heliomaster) and woodstars (multiple genera). Finally, some species appeal to the mythical creatures they resemble such as the woodnymphs (Thalurania), sunangels (Heliangelus), sylphs (Aglaiocercus) and fairies (Heliothryx).

One of the most impressive to look at and glorifyingly named, the marvellous spatuletail is a stunning hummer coated in green and bronze with a dazzling turquoise gorget. The defining feature of this Peruvian endemic is the pair of long, indigo, racquet-like tail feathers which extend from a tail unique for only having four feathers. As with many hummingbirds, it is the males who bear the brightest colours and most extreme ornamentation. He waves his spatulas in a frenetic courtship display in the hope of wooing a mate.

Day 64: Bee hummingbird – Mellisuga helenae

Life in miniature

The bee hummingbird is the smallest bird in the world. If you saw this creature flitting round the gardens of its native Cuba you could be forgiven for thinking it a bee or moth on first inspection. It weighs just 1.6-2 g. A male and female perched together on your hand would weigh as little as a penny! Normally its wings beat around 80 times a second but the courtship flight of a male raises that rate to 200 per second! It is the bird with the fewest feathers and the highest body temperature and its heart beats up to 1,200 times a minute. Meeting its dietary needs means consuming half its weight in food and eight times it weight in water every day. In most hummingbirds, nests are small cups fused to twigs and, unsurprisingly, the bee hummingbird’s is especially tiny, being just 2.5 cm in diameter and made from plant matter, lichen and cobwebs. The smallest bird on the smallest nest must be and endearing sight!

Day 65: Gartered trogon – Trogon caligatus

Toe to toe

The gartered trogon is one of 39 trogon species in the order Trogoniformes. They are colourful, arboreal birds which feed on insects and fruit in generally tropical forests around the world. Trogons are cavity nesters, using their strong bills to gnaw at rotting wood. This has given them the name trogon which means ‘nibbling’ in Greek. Gartered trogons, as well as the related violaceous trogon (T. violaceus), can also nest in wasp, ant or termite nests.

Let’s use this opportunity to talk feet. The archetypal bird foot is anisodactylic with digit 1 pointing backwards and digits 2 to 4 facing forwards. This is more than adequate for the many terrestrial and aquatic orders we have come across so far. However, on the road to passerines it various groups have tried a multitude of digital arrangements.  Trogons are, uniquely, heterodactylic meaning that both digits 1 and 2 face backwards. This arrangement is tailored for an arboreal life, allowing trogons to grip branches firmly. 

This is similar to the zygodactyly of the parrots, cuckoos and woodpeckers however, in their case, it is digits 1 and 4 which face backwards. Owls and ospreys are able to adopt this arrangement when needed, for example when catching prey, but they can also revert back to more typical anisodactyly. In mousbirds and some swifts, both digits 1 and 4 can be rotated to either face forwards or backwards. The swifts use this ability to have all four toes face forward to hook onto rough surfaces. Last but not least, the kingfishers and allies (Coraciiformes) have partially fused second and third digits. Since birds have two limbs devoted to flight, the feet have become increasingly important for interaction with the environment and thus they have been adapted to meet many needs. 

Day 66: Laughing kookaburra – Dacelo novaeguineae

Merry merry king of the bush is he

The laughing kookaburra is one of Australia’s most famous birds, known for its loud, cackling call. Whilst staying in Cairns, a pair of kookaburras (or just kookas) would frequent the garden, sitting together and raising their heads in howls of laughter. They would then plop to the ground where they bounced around in search of food. They eat a lot, mainly taking large insects, reptiles and small mammals and birds. One thing they don’t eat is fish, despite being the largest species of kingfisher.

The laughing kookaburra is one of five kookaburras which also include the demonic blue-winged kookaburra (D. leachii) and the impressive shovel-billed kookaburra (Clytoceyx rex). Kookaburras are part of the Halcyonidae, collectively known as the tree kingfishers. None are fish specialists, preferring to watch and wait from selected vantage points. There are two other families in the kingfisher suborder Alcedines. Our own Eurasian kingfisher (Alcedo atthis) is a member of the river kingfisher family Alcedinidae. These are a group of small, bright kingfishers with short tails and long, thin beaks. By contrast, the water kingfishers of the Cerylidae are larger and chunkier with longer tails and more dour plumage. They are also the only kingfishers found in the New World. Both of the families are expert fishers, plunging head first into the water from well-placed perches.

When allocating Latin names to the kingfishers, naturalists made some interesting decisions. The genus of river kingfishers Alcedo was a reasonable enough starting point. It is the Latinised version of Halcyon which refers to the Greek myth of Alcyone. Alcyone and her husband Ceyx referred to themselves as Hera and Zeus. This sacrilege invited the wrath of Zeus himself who smote Ceyx, aboard his ship, with a lightning bolt. When Alcyone was informed of his demise (via the dream god Morpheus), she threw herself into the sea. Out of pity, the gods transformed the couple into kingfishers. Every year, Alcyone would lay her eggs in a nest on the beach whilst her father, Aeolus, protected her efforts by calming the waters of the sea for a week either side of the winter solstice. This is the probable etymology of the phrase ‘Halcyon days.’

So far so good, we have bird named for a mythical kingfisher. Next, Alcyone’s husband Ceyx gets its own genus, the dwarf kingfishers (Ceyx). I suppose that’s fair as Ceyx was also transformed. We also have the long-tailed paradise kingfishers in the genus Halcyon which is simply the Greek from of Alcedo. This is a touch lazy, although Greek and Latin tautology does exist a lot in binomial names (e.g. Corvus corax means crow-crow in Latin then Greek). Follwing this, naming just got silly. The Dacelo kookaburras we started with are actually just an anagram of Alcedo as is the banded kingfisher genus Lacedo. Finally the belted kingfisher Megaceryle alcyon once again references Alcyone. With a wealth of binomial Latin names in existence, biologists have demonstrated their imagination abundantly but they were having an off day with the kingfishers.

Week 15: Nightjars to Emeralds

Day 59: Standard-winged nightjar – Macrodipteryx longipennnis

Flying the flag for nightjars

I struggled to find a decent photo of this splendid nightjar and that fact alone is indicative of nightjar ecology. Like the owls and frogmouths before them, nightjars are crepuscular or nocturnal. However they generally live in dry, open country and nest on the ground so observations are generally made of shapes flying through the twilight or spotlights picking up flashes of white.

Nightjars are able fliers and hawk insects from the air, using their facial bristles to aid in capture and protect the large eyes from flailing insect wings. Measuring nightjar beaks was intriguing as there was little beak protruding from the skull yet the gape was as wide as the head, presumably allowing nightjars to effectively become flying mouths. Their aerial insectivory lends some American species the name 'nighthawk' whilst the name ‘nightjar’ was originally ascribed to the European nightjar (Caprimulgus europaeus) where it referred both to their nocturnal activity and their remarkable ‘churring’ song which reverberates around British heathland. The genus Caprimulgus harks back to an old myth that nightjars suckled from goats (capra=goat, mulgere=to milk).

Although generally cryptic in colouration, male nightjars are often distinguishable from females by patches of white on the throat, wings or tail. These are used in courtship displays; the white reflecting whatever light might be left in the sky. This African species is notably one of a few nightjars that have modified their feathers in unusual ways to aid in courtship. The remarkable ‘standards’ of this species are actually modified primaries which can be erected during courtship. 

Day 60: Edible-nest swiftlet – ­Aerodramus fuciphagus

Enjoy the bird, not the nest

To look at, this swift is a typical member of the swift family Apodidae. Swifts are characterised by their extremely long, scythe-like wings which make them supreme fliers. They are able to reach tremendous speeds with the white-throated needletail holding the record for the fastest bird in flapping flight: an eye-watering 112 km/hr (or more?!). You may have seen our own swifts (Apus apus) hurtling round the spires and towers of our towns and cities where they come to breed in the summer. Like the closely related nightjars, swifts are aerial insectivores however they hunt during the day. They spend the vast majority of their time on the wing, eating, drinking, mating and sleeping in mid-flight! In fact, the genus Apus (from which the names of the family and order are derived) means ‘without feet’, referring to early misconceptions about swifts.

When swifts do come to land it is to breed. For us, in the UK, we are used to seeing the convergently evolved (Passeriformes: Hirundinidae) swallows (Hirundo rustica) and house martins (Delichon urbica) building their nests under eaves and beams where they bind together mud with their saliva. Swifts engage in similar practices but using vegetation over mud. In the Aerodramus swiftlets, saliva actually forms the majority of the nesting material and in two species, the edible-nest swiftlet and the black-nest swiftlet (Aerodramus maximus), saliva is the sole component.

These two species nest in huge caves dotted around the islands of Southeast Asia. There, they form large colonies, covering the walls with glistening nests. Aerodramus swiftlets navigate around the colonies using echolocation, an ability that evolved just twice in the birds (the other incidence being the caprimulgiform oilbird, Steatornis caripensis).

Such large congregations of birds make them easy pickings, not least for humans. In China, the nests of edible-nest and black-nest swiftlets have becoame a delicacy. Served in the infamous bird's-nest soup, swiftlet nests are believed to bring health benefits and an increase in libido. This has resulted in the harvesting of some colonies to near extirpation. In Hong Kong, the centre of swiftlet-nest trade, demand is high and nests can fetch up to $10,000 per kilo. The creation of artificial nesting sites has allowed a regular supply of nests, shifting attention away from the natural sites. As with ivory and tiger claws, it is important that China, and the rest of the world, comes to value our wildlife living rather than dead. 

61: Antillean crested hummingbird - Orthorhyncus cristatus

The first of many

I have a hazy memory of the first time I ever saw a hummingbird. In the year 2000, my sister and I were walking through hotel gardens on the south coast of Grenada in the Lesser Antilles of the Caribbean. There, a tiny bird reared up in front of use before promptly wizzing off in the opposite direction. The bird in question was an Antillean crested hummingbird, one of over 340 hummingbird species in the second largest bird family Trochilidae. There is plenty to say about hummingbirds but luckily I will have a few days to explore them.

Humming birds are generally placed in the same order as the swifts (Apodiformes). Why this might be is an interesting question as hummingbirds are very un-swift-like but both groups share similar wing morphologies. However whereas the swifts use their wings to zoom through the skies, the hummingbirds have their own specially adapted flight. Hummingbirds are expert fliers, able to hover and fly forwards, backwards, up, down and sideways. Using a technique similar to insects, hummingbirds flex their wings in quick beats generating lift on the upward stroke in addition to the downward stroke by inverting the curvature of the wing. With typically between 50 and 80 wing beats per second, the hummingbirds are able to generate sufficient lift to facilitate their astounding aerobatics.

To support their flight, hummingbirds need additional adaptations. They have light, hollow bones with fusion in the vertebrae to remove unnecessary muscles and ligaments. The feet are also tiny to reduce weight and drag. By contrast the sternum and pectoral muscles are enlarged for increased wing power and strong finger bones stabilise the wing. Perhaps the most important requirement for hummingbirds is the highest metabolism of any non-insect animals. Their hearts beat up to 20 times per second and they can breathe 250 times per minute.

Such high energy expenditure requires near-constant feeding and hummingbirds have made use of the most energy-rich and readily-available food supply: nectar. They must visit hundreds of flowers a day in order to drink more than their weight in nectar. Their metabolism ensures sugar makes it to the muscles as soon as possible but this means hummingbirds are never far from dying, so constant is their energy need. Overnight, hummingbirds must shut down, entering torpor where there metabolism decreases and their body temperature halves. This sleep-like state allows them to get through the night until the first drink of the morning. Being a hummingbird sounds knackering! 

Day 62: Violet Sabrewing - Campylopterus hemileucurus

The purple flash

Violet sabrewings are one of a few hummingbird species that I encountered on my trip to Honduras in 2011, my first Noetropical experience since Grenada. The sabrewing is a stunning bird and the name aptly describes both the striking purple colouration and the unusual wing morphology. I had assumed that 'sabrewing' referred to the overall shape of the wing however closer inspection reveals the broad, flattened central rachis of the first two primary feathers which resemble curved swords. We speculated as to the function of these structures and, being only on the males, the most likely explanation seemed to be for noise generation (by rattling) during competitive displays. Sabrewings are polygynous birds, holding leks where they attract and court multiple females.

Another intriguing difference between males and females is the difference in bill morphology. Despite being smaller, the female has a longer and more curved beak. Again, the explanation for this was not obvious but could be a difference in foraging behaviour between males and females. This is highly unusual in the bird world as most members of the same species tend to have similar diets. It could be the case that males and females specialise on different flowers so as not to compete with each other. Alternatively, (and perhaps more likely), if longer, curvier bills are indicative of greater flower specialisation, perhaps females must specialise more in order to access richer nectar sources for their young. As hummingbirds also eat invertebrates, the same arguments apply for insectivory i.e. males hawking for aerial insects whilst females glean them from foliage.

I have already alluded to the close association of hummingbirds and flowers and what a fascinating relationship it is. Hummingbirds, much like bees or butterflies, are in search of the nutritious nectar provided by flowers. Plants are not altruistically offering a free meal but instead aim to be pollinated with pollen transferred from other flowers. This requires that the pollinator regularly visits flowers of the same species which they may not if they are maximising their opportunities by visiting many species. Flowers can increase exclusivity by making nectar trickier to access. The presents an opportunity for some pollinator species to specialise, gaining a monopoly on particular plant species. These evolutionary pressures often lead to arms races with plant and pollinator become increasingly specialised.

The myriad of plant-hummingbird interactions have lead to diverse beak and flower morphologies. Many flowers will have multiple pollinator species whilst many hummingbirds will pollinate multiple plant species. Some hummingbirds have taken specialisation further. Hermits (Phaethornithinae) have very long, curved bills whilst sicklebills (Eutoxeres spp.) have extremely curved bills for flowers of the family Gesneriaceae. The sword-billed hummingbird (Ensifera ensifera) is the most extreme in specialisation. It uniquely has a bill longer than the rest of its body which it uses to drink from just one species: Passiflore mixta. From the perspective of both plants and pollinators, the extent of specialisation can be seen as a choice of strategies with different species (or even sexes, as above) following different evolutionary trajectories. Generalists benefit from accessing abundant yet low value nectar whilst pollinating haphazardly whereas specialists offer a more reliable service in return for a rich reward.With so many possibilities and niches to fill it is perhaps not surprising that up to 25 species can coexist in the same area.

Week 14: Barn Owls to Frogmouths

Day 55: Moluccan masked owl – Tyto sororcula

A rainforest spectre 

In almost every habitat in the world there is an owl who owns the night. Whilst the Accipitriformes and Falconiformes have dominated the diurnal predatory niches, the Strigiformes have taken the equivalent nocturnal positions. The Strigiformes comprise just two families, the Tytonidae (barn owls) and the more speciose Strigidae (true owls). The Molccan masked owl is a member of the former which are known for their heart shaped faces and sometimes ghostly appearance.

There isn’t a huge amount known about this owl species but it is part of a complex of similar species which inhabit the islands of Indonesia and Papua New Guinea. None are well described but one species, the Seram masked owl (Tyto almae), has proven especially elusive. It was first noticed from a photograph taken in 1987. It wasn’t until 2012 that a team from the Natural History Museum of Denmark and the Indonesian Institute of Sciences caught a masked owl in a mist net in Seram (an island in Indonesia) and later described it as a new species. It is still known only from these two records.

The predatory nature of owls might suggest close relatedness to other birds of prey but ornithologists may be quick to point out that owls are distantly related. However, recent research suggests that the predatory hawks, falcons and owls all share a raptorial ancestor but each lineage contains more closely related bird bird groups who have independently evolved almost every other form of dietary ecology. WARNING: below comes a taxonomic blur, not for the faint-hearted.

Traditionally, and matching the order of my work and this blog, the owls are amidst the ‘near-passerines’, the serious of groups that take us closer and closer to the passerines. This started with the soundgrouse followed by the pigeons, parrots, turacos and cuckoos and after the owls come the nightjars, swifts and hummingbirds, mousebirds, trogons, hornbills, kingfishers and woodpeckers.

Recent genomic analysis upsets this tradition remarkably. Soundgrouse and pigeons are shoved to the edge of the Neoaves (i.e. all bird but ratites and fowl) with the mesites, flamingos and grebes in the clade Columbea. The much larger clade Passerea contains, at the edge, the cuckoos, turacos, bustards, nightjars and swifts. Next comes the hoatzin, paired with the shorebirds, followed by the remaining seabirds in the rough order we covered them. The rest of the orders are land birds containing the Afroaves (raptors, owls, mousebirds, trogons, hornbills, kingfishers and woodpeckers). Finally, the nearest birds to the passerines are the two seriemas, the falcons and the parrots. Congratulations if you have followed this, I certainly find it very confusing. For a superior explanation see Jarvis et al (2014).

Day 56: Snowy owl – Bubo scandiacus

Call me Hedwig one more time!

This gorgeous white owl may be famous for being Harry Potter’s companion but reality is far more interesting. As one might predict, the snowy plumage indicates the owl’s circumpolar distribution where it breeds in the northerly reaches of the Arctic tundra. The snowy owl might look cute and cuddly but it is a proficient hunter of a variety of Arctic wildlife. Although the diminutive lemming is its main food source, the snowy owl can hunt large rodents, rabbits and hares as well as ducks, geese, waders and gulls. The females have even been known to take other owls and raptors. Like other owls, snowy owls have very large gapes enabling them to swallow prey whole. All the non-digestible parts of the prey are coughed up as pellets of hair, bone and teeth. Pellets are useful for biologists who wish to characterise the diet of owls. As for the raptors, female owls are the larger of the two sexes. 

As well as being smaller, male snowy owls are more uniformly white and thus a better choice for the Harry Potter films despite playing a female owl!

The snowy owl is a more unusual character in the genus Bubo which comprises the horned owls and eagle-owls. The Eurasian eagle-owl is one of the largest, with a wingspan over 6 ft. By comparison, the elf owl (Micrathene whitneyi ) would easily fit in your pocket. The Strigidae are a large family of owls which include most of the owl species you might be familiar with.

Day 57: Short-eared owl – Asio flammeus

Silent but deadly

Two owls down and yet I haven’t discussed some of the fantastic adaptations that unite the owls. Well, what better way to do it than with one of my favourite British birds, the stunning short-eared owl. As we know, owls evolved for the night. As it happens the shorties are observable during the day, as I have seen them over the grassy fields of Portland Bill, however the majority of their hunting occurs at night when a battery of adaptations come into effect.

In the blackness of night, owls must be able to navigate effectively and hunt small prey which may skulk, unseen, in the undergrowth. To accomplish this, owls have fantastic night vision. They have very large eyes with wide pupils which maximise the amount of light passing to their sensitive rod cells. Furthermore, an advanced neural mechanism extracts a superior amount of information from the retina. Owl’s eyes face forward enabling excellent binocular vision so that they can judge distance and depth efficiently (this eye placement gives them their anthropomorphous, ‘wise’ face). Fitting such large eyes into a relatively small head results in their tubular shape. ‘Eyetubes’ cannot be swivelled as eyeballs can, so owls must rotate their heads. They famously do this rather well, being able to rotate the head through up to 270°.

The other sense which owls have mastered is hearing. Don’t be fooled by their ‘short ears’. The ears of the ‘eared owls’ (Asio) are simply tufts of feathers, thought to break up the outline of a roosting bird. The real ears are set on either side of the head, beneath the feathers. Here, we encounter another case of asymmetry as owls’ ears are placed at slightly different heights. This allows owls to pinpoint sounds in three dimensions. We (and many other animals) are good at locating sound horizontally but vertical pinpointing is quite difficult (hence why I sometimes put my head on my side to find singing skylarks). The ears are aided by a ruff of stiff feathers that form a facial disk which collects sound waves and directs them to the ears. Even the beak is designed to minimise sound loss. What was striking when measuring the owls was how small the skeleton was beneath the feathers and how structurally different the facial feathers were to achieve their function.

Owls are excellent at detecting prey but they also need not to be detected. Thus, owls are literally deathly silent. Large, broad feathers allow owls to float around with minimal flapping. Along the leading edge of the wing feathers, serrations disrupt the turbulence that would cause sound in a normal bird whilst velvety down absorbs some of the sound that is still produced. As this silent spectre descends, with talons spread, an unsuspecting vole stands little chance.

Day 58: Papuan frogmouth – Podargus papuensis

Why the wide face?

The frogmouth is a bizarre looking bird - that is, if you were able to spot it as they exhibit impressive cryptic plumage and behaviour. They roost motionless with their necks outstretched which, coupled with their mottled-brown plumage, makes them resemble a branch, complete with a stick-like head tuft. All frogmouths have extremely wide gapes (hence the name) and the Papuan frogmouth has the largest of them all. Like the owls before them, the frogmouths are nocturnal foragers however their foraging mode is slightly more ungainly. They hunt around the ground for insects but will take prey as large as rodents, lizards and frogs. A huge mouth helps the frogmouth to grab prey in the dark without needing the finesse of an owl.

The frogmouths (Podargidae) are part of the nightjar order Caprimulgiformes. The species of this order are characterised by their nocturnal, insectivorous habits and their cryptic plumage. A morphological perspective placed the Caprimulgiformes between the owls and the swifts and it is easy to see why. Since then they have been affiliated with various ‘near-passerine’ groups and genetic evidence has confused matters although there was strong support for a monophyletic clade uniting the nightjars, owlet-nightjars (Aegotheliformes) and the swifts (Apodiformes). This is corroborated in the most recent whole-genome analysis however this clade (the Cypselomorphae or Caprimulgimorphae), is placed nowhere near the owls. Instead, they are located with cuckoos, bustards and turacos on the periphery of the Neoaves. I’m still trying to get my head around this new, counter-intuitive world order of bird.

Week 13: Parakeets to Cuckoos

Day 51: Ring-necked parakeet - Psittacula krameri

Little green men

The large, natural range of this small, long-tailed parrot is a band of sub-Saharan Africa and the Indian Subcontinent yet you probably know it better as the brightly-coloured alien that flocks around the parks and gardens of London and the surrounding counties.

As a popular pet, the ring-necked parakeet found its way into many urban localities where a combination of escapes and deliberate releases has lead to a number of stable feral populations in cities around the world including in South Africa, Japan, Turkey and North Africa. There are even more parakeets in Europe with populations in Belgium, the Netherlands, Germany, Italy and Spain. The biggest feral population is centred on south-west London.

The origin of the 'Kingston parakeets' is a bit of a mystery. Some suggest that they escaped from an aviary after the storm of 1987 or from the set of The African Queen whilst others believe Jimi Hendrix to have released a pair from Carnaby Street in the 1960's. In a city with many green spaces but few predators, the parakeets probably had little problem establishing a population but it would have taken some time for sufficient numbers to build up and become apparent. The population really began to expand during the 1990's, growing exponentially. Currently their numbers are difficult to estimate but there could be as many as 50,000 birds with flocks 6,000 birds strong.

It seems reasonable that such a large population of alien birds would have some impact on the wildlife of London and its environs. One study has found that typical garden birds are avoiding the large, noisy parrots who frequent the bird feeders of the masses. Parakeets also nest in tree holes which necessarily means that other species such as starlings or woodpeckers are loosing prime nesting habitat.

The ring-necked parakeet is just one of many invasive alien species to have reached our shores over the decades and centuries. Successfully invasive 'candidates' must occupy a niche which means either taking a vacant place in the ecosystem or pushing out a native equivalent. Vacant niches are hard to come by so our native flora and fauna tends to take a beating via competition for resources or apparent competition mediated by shared natural enemies such as Squirrel parapoxvirus and crayfish plague. Moreover, invasives are often released from the predation or parasitisation of their native lands allowing unchecked population growth. Grey squirrels, signal crayfish, American mink, harlequin ladybirds and Japanese knotweed are all well-known scourges of British wildlife and the list is growing.    

Day 52: Hoatzin - Opisthocomus hoatzin

The crested claw

The hoatzin is a pretty odd bird to look upon. With maroon eyes set in a naked, pink face, a large, orange crest at the end of a long, slender neck and broad, rounded wings and tail the hoatzin resembles the most ancient ancestors of the birds. Furthermore, the chicks possess two clawed fingers on each wing bearing a striking similarity to the feathered arms of the small, Jurassic raptors. The uniqueness of this species meant its placement in its own order: the Opisthocomiformes. However, placement of this order on the bird tree has been very difficult with suggested relatedness to tinamous, gamebirds, rails, bustards, sandgrouse, doves and cuckoos. It took whole-genome sequencing to resolve the issue so that the hoatzin is now paired with the clade comprising Gruiformes (cranes and rails) and Charadriiformes (shore birds).

The hoatzin lives among the dense, luscious vegetation bordering the rivers of the Amazon basin. They are herbivores and their diet requires special fermenting ability akin to cows. Unlike cows (and other ruminants) they do not possess a rumen but have an enlarged crop which they use to digest the vegetation. This decomposition leads to an unpleasant smell, giving the hoatzin the alternative name of stink-bird. The hoatzin is a gregarious nester and does not need to fly far to find food. The chicks are obviously unable to fly immediately after hatching so their claws are used to scramble through the branches. This is especially important for when hawks appear as the chicks drop into the water and swim to safety before climbing out when the coast is clear. The claws of chicks lead early taxonomists to conclude that hoatzins where more closely related to Archeopteryx and its kin but the claws are actually a secondarily derived trait.

Day 53:  Great spotted cuckoo - Clamator glandarius

The expert freeloader

Here we have a handsome representative of the Cuculiformes i.e. the cuckoos. You will all be familiar with our own common cuckoo (Cuculus canorus) with the famous song that gives it its onomatopoeic name. You, hopefully, will also know that the common cuckoo is a brood parasite meaning it lays its eggs in the nests of other bird species. What you may not know is that brood-parasitism is actually present in many cuckoo species in both the Old World (56 species) and the New World (three species). The common cuckoo had already been measured so I could not choose it for discussion however the great spotted cuckoo is a worthy stand-in for a discussion on cuckoos and brood parasitism.

Brood parasitism is a fascinating subject with many interesting processes. To go through these ideas it might be easy to start at the beginning. Rearing offspring is costly but many organisms do it to maximise the survival of their young. However if one could avoid that cost one could have more offspring. Many species engage in extra-pair matings so that others might rear their young. The goldeneye (Bucephala clangula) is a duck that has specialised in laying eggs in the nests of fellow females. Interspecific brood-parasitism is just one step further for a species used to pushing its eggs on others.

One might think that that when the first cuckoos began laying eggs in the nests of other species, those hosts would immediately respond. However for an unwitting host, the oblong objects in her nest have, for millions of years, always been her eggs and so she is not primed to notice if even a conspicuously different egg is added to the brood. Moreover, when the chick hatches along with the others, its loud, begging call and bright gape illicits the same instinctive feeding response as the host's actual offspring.

Clearly it is costly for the host species to expend so much energy feeding a chick that isn't its own so their is an evolutionary pressure on the host to act. The host can avoid parasitism by nesting in less accessible places and earlier in the year or it could learn to recognise the cuckoo and harass it until it flees. If this fails, hosts can learn to asses the number of eggs in the nest or to distinguish the cuckoos egg from her own. The host might respond to parasitism by evicting or piercing the new egg or abandoning the nest entirely. However, once host parents begin to evict parasitic eggs, there is a pressure for the cuckoo's eggs to resemble the host. Thus, an evolutionary arms race ensues as the hosts' powers of discrimination increase hand-in-hand with the mimicry of the cuckoo.

Mimicry requires specialisation on the part of the cuckoo and some species do not bother, preferring to have many, infrequent hosts which never cotton on to the cuckoos' ploys. Other species are able to focus on one, sufficiently abundant host species. However there are a few species, including the common cuckoo, which are able to mimic multiple hosts. This was perplexing for biologists as specialisation has a genetic basis yet members of the same cuckoo species could interbreed without messing up the different specialisations. For this to be possible, egg mimicry should be coded by genes which are only passed down the female line such as mitochondrial genes or genes on the female-determining W chromosome. This would allow females to form specialised gentes (singular gens) whilst males can mate indiscriminately as their genes will not affect the mimicry ability of their offspring.

In addition to egg mimicry, cuckoos have developed many other tactics to maximise the chances of their eggs and chicks. Some cuckoo males resemble hawks and lure aggressive host parents away allowing female cuckoos to stealthily lay an egg (the common cuckoo somewhat resembles the sparrowhawk, Accipiter nisus).Some cuckoo species have short incubation times allowing the chick to hatch before the host's. As soon as the cuckoo hatches, it instinctively rolls the host's eggs, one at a time, into a cleft in its back before thrusting them out of the nest. Whether or not to kill one's step-siblings is an interesting question. Research into brood-parasitic cowbirds suggests that when one's host has large chicks its better to evict them early to avoid later competition whereas, when the host's chicks are small, the cuckoo chick can high-jack the collective begging power of the nestmates before stealing the lions share of food.

Who wins this evolutionary arms race? Well there are many reasons why cuckoos should always be one step ahead. Firstly, cuckoos have much more at stake. Every cuckoo necessarily must outwit a host in order to succeed in reproducing. The hosts, however, are far more numerous and therefore parasitism is unlikely for any given couple, reducing the strength of the pressure. Secondly, as cuckoos' eggs become near exact replicas of the hosts' eggs, the hosts must have incredible powers of discrimination or else suffer the risk of accidentally rejecting their own eggs. Thirdly, it is suggested that some cuckoos have strategies which force hosts to comply. The brilliantly named Mafia hypothesis suggests that if a host rejects a cuckoo egg or chick, the cuckoo parents trash the host nest meaning that the risk of defection is greater then the cost of rearing the cuckoo. Evidence for this startling strategy has been put forward for two species, one of which is the great spotted cuckoo which parasitises magpies and is less likely to predate the nests of compliant hosts. #thuglife

Day 54: Little bronze cuckoo  - Chrysococcyx minutillus

Cuckoo jewel

This gorgeous little cuckoo was a regular and welcome presence during my sampling in the riparian rainforests of Cape Tribulation, Queensland. I liked this species because it had a simple yet pleasant descending call and catching a sight of its metallic green back and red eye was always nice, especially when the bird in question was bashing away at a thick, juicy caterpillar. The little bronze cuckoo was a regular attendant of mixed species flocks. These loose groups of insectivores move through the understory, sallying and rummaging for bugs amongst the foliage. When any given species is locally rare, safety in numbers is provided my members of different species including spectacled monarchs(Symposiachrus trivirgatus), rufous fantails (Rhipidura rufifrons), fairy gerygones (Gerygone palpebrosa) and little shrikethrushes (Colluricincla megarhyncha).

Hearing little bronze cuckoos and the other species of the rainforest was not only a pleasantry but a necessity for the purposes of fieldwork. From day one of sampling I needed to be able to identify the species I heard to get an accurate representation on of the presence and absence of the jungle denizens. This meant learning the calls of up to 100 species in advance with only a week or so in the field to actually hear and see them in real life. Thus, much time was devoted to sitting in front of an Australian bird app, playing calls until my partner and I could ID successfully. By the end of sampling, some species were so familiar I could ID them in my sleep but rarer individuals such as the congeneric shining bronze cuckoo (Chrysococcyx lucidus), still required the playback of our digital recordings.

This process of learning bird song in advance gave a real appreciation for its necessity in fieldwork and in birding in general. In the rainforest, most identification is based on song as small, skulking birds at some distance through the dense foliage can be difficult to observe. I'm pretty good at identifying British birds by song or call but that is from years of passive (and sometimes active) learning, one species at a time. However I had never attempted the songster crash course before on other international trips (which would have been especially useful in Honduras). From now on I will make an effort to get to know the birds of a new country in advance, by sight and by sound.

The little bronze cuckoo is another brood-parasitic cuckoo but there are many members of the Cuciliformes which are neither brood-parastic nor especially cuckoo-like including the charismatic roadrunners (Geococcyx spp.).