Beat About the Bush: Birds

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DedicationTo Caroline – as always, your support and sacrifices have made this work possible!andTo my parents – for that life-changing first visit to the Kruger that started it all, and for instilling an appreciation for all things wild!

AcknowledgementsTo the entire Jacana team, especially Jan, Jen, Brett and Mike, who have been involved over the length of a project that has evolved many times. Thanks for the patience when confronted with delays due to my schedule, and dedication to getting the best possible product on the shelves.

A special thank you also to the many talented photographers who have helped to bring this publication to life – especially Pete Hancock, Gerrit van Egdom, Craig Carnaby, Shaun Malan, Delmaine Stoffels and Rob Lewis who have kindly allowed the complimentary use of their photographs.

And, finally again to Caroline, for helping with typing and cross-referencing and generally making the pressure bearable when deadlines seemed impossible to meet.

Published by Jacana MediaPO Box 291784, Melville 2109Johannesburg, South AfricaTel: (011) 628-3200; Fax: (011) 482-7280E-mail: [email protected]; www.jacana.co.za

Design and DTP by Jacana MediaPhotographs by Trevor Carnaby, except where acknowledged alongside photographsFront cover photograph: White-fronted bee-eaters by Chris van Rooyen Title page photograph: African jacanaPrinted by Craftprint, SingaporeJob Number 001252

No part of this publication may be reproduced, adapted, stored in a retrieval system, or transmitted in any form or by any means electronic, mechanical, photocopying, recording, or otherwise, without the written permission of Jacana Media. The publishers welcome any comments. All rights reserved.

Copyright © 2008 Trevor Carnaby1st Edition 2008Updated Edition 2010ISBN: 978-1-77009-241-9

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Beat aBoutthe Bush

Birds

BY TREVOR CARNABY


CONTENTS

INTRODUCTION 2 General historical introduction 2

Anatomical glossary 8

General glossary 12

Behavioural glossary 16

Taxonomic chart 22

The meanings of scientific names 25

Birds endemic to southern Africa 32

Birds endemic to Africa 33

Vagrants and rarities 34

Introduced species 35

Newly described species 36

Comparative bird table 37

NAME CHANGES AND BIRD AREAS 57 New bird names 60

New scientific names 63

People after whom birds are named 66

Origins of common names 69

Interesting common names and their origins 76

Southern African globally threatened species 81

FLIGHT AND DESIGN 83 Bird record holders – both in southern Africa and the world 145

BREEDING 154 Mating systems 154

Polyandrous species 160

Co-operative breeding table 163

Local co-operative breeders 167

Brood-parasite tables 171

Brood-parasite nesting details 177

Courtship 180

Species hybridisation table 194

Nesting 195

Raising of young 234

Altricial and precocial bird groups in southern Africa 241

Bird breeding details 248


DEFENCE AND SURVIVAL 260

FOOD AND FEEDING METHODS 319

GENERAL BEHAVIOUR 349 Healthmaintenance 352

Migrationandmovements 369

SouthernAfricanbirdspeciesknowntomigrate 370

Vocalisations 377

Birdspeciesthatusesong-postsinsouthernAfrica 377

SouthernAfricanmimics 383

Birdsthatduet 385

Behaviouringeneral 389

RAPTORS 411

WATERBIRDS, WADERS AND SHOREBIRDS 432

GROUNDBIRDS 457

NIGHTBIRDS 470

GENERAL BIRDS 480

TRACKS, SIGNS AND CLUES 503 Nests 504

Droppings 520

Tracksandthefeetresponsibleforthem 525

MORE ABOUT BIRDS – YOUR A TO Z 528

APPENDICES 748 Collectivenamesofbirds 748

Keytotheiconsinthesection‘Moreaboutbirds–yourAtoZ’ 749

Index 751

References 764


7

nape

crown

lateral crown stripe

pupil

iris

lores

nape (hind heck)

mantle

scapulars

back

rump

vent

tail(rectrices)

tibia

tibio-tarsal joint (ankle)

tarsus

outer toe (#4)middle toe (#3)

inner toe (#2)

flank

belly

breast-band

breast

throat

chin

bill

nostril

forehead

INTRODUCTION


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ANATOMICAL GLOSSARYThis is a list of words and phrases describing the different physical characteristics of a bird. I have tried wherever possible to keep the definitions as simple and unambiguous as possible.

Red highlighted words are anatomical features of a bird defined in this Anatomical Glossary below.Green highlighted words are behaviours or words linked to behaviours that are also defined in the Behavioural Glossary, page 16.Orange highlighted words in some definitions indicate words that are defined in the General Glossary, page 12.

Name Position on the body DefinitionAlula On the wrist of the wing Small (bastard) wing at the wrist used to prevent stalling at slow speedAnkle * (see knee) Midway up the visible leg The joint between the tibia (because of bone fusion, correctly called the tibiotarsus) and the

tarsus (because of bone fusion, correctly called the tarsometatarsus) that bends ‘backwards’ - usually mistaken for the knee

Back Along the spine Area of the body that houses the all-important bony spine enclosing the spinal cordBarb On some feathers Lateral branches from the shaft of a feather, creating the main webbing of the vane Barbule On barbs of feathers Small hooks on feather barbs used to maintain integrity of feather Beak Front of head Another name used for the bill - usually used to describe small birdsBelly Between the breast and the vent The area that houses the muscular stomach used for digesting foodBill Surrounds the mouth Highly modified mouthparts with a keratin cutting edge to replace teethBreast Between the throat and belly The upper front area of the body that houses the heart and lungs - also referred to as the chest Bristle Usually on the face at the bill or eyes Small sensory feathers with stiff shafts and (virtually) no barbs - the eyelashes of birds such as

ground-hornbills - see nasal and rictal bristlesBrood patch On the belly Vascularised patch of bare skin that develops on belly to keep eggs warm - also called the

incubation patchCarpal spur On the wrist of the wing A small bone (with or without a claw) emanating from the carpal bones in the wrist - a

vestigial digitCaruncle Usually on the head An often colourful, vascularised and fleshy growth above the bill of some birds - also called a

comb when laterally flattenedCasque On the bill (beak) or top of the head A hollow, keratinous ridge / structure (usually larger in males) along the upper mandible

of hornbills - used for resonating calls over distance OR the bony structure on the head of certain guineafowl

Cere At the base of the upper mandible A fleshy or waxy (often colourful) appendage of uncertain function at the base of the upper mandible of some birds

Cervical rib On either side of neck vertebrae Small ribs for muscle attachment on the neck vertebrae of some waterbirdsCheek On the side of the face below the eye Fleshy part of the face, often devoid of feathers and brightly coloured for use in displayChest Between the throat and belly The same as the breastChin At the base of the bottom mandible In mammals denotes the apex of the lower jaw, but in birds is at the base of the extension of

the dentary boneCloaca At the lower base of the tail Common opening used for reproduction and waste disposalComb Usually on top of the bill An often colourful, vascularised and fleshy growth above the bill of some birds - also called a

caruncle when knobblyCone cell In the retina of the eye Colour-sensitive cell in the retina used for colour perception / visionContour feather All over the body Feathers that streamline, protect, waterproof and give the body shape (contour)Covert(s) Various parts of the body Small contour feathers that cover and protect the ear openings and other sensitive parts of the

bodyCowl Around the face A ‘ridge’ of long, broad, loose feathers around the border of the face giving it a ‘dish-like’

appearanceCrest Usually on the top of the head Feathers of the head that are longer and more loose than surrounding plumage - literally

means ‘tuft’ or ‘plume’Crown On top of the head The upper domed part of the skull from above the eye to the top of the headCrown stripe Along the top of the head A black or white stripe that (usually) runs laterally along the crown from the forehead to just

above the ear or to the back of the headCulmen Part of the upper mandible The curved apex ridge of the upper mandible of the bill extending from the forehead to the tip


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GENERAL GLOSSARYThis is a list of the words and phrases that you are most likely to encounter when reading up on, discussing or describing birds. Wherever possible, an attempt has been made to keep the definitions as simple and unambiguous as possible.

Orange highlighted words in some definitions indicate words also to be found in this General Glossary.Green highlighted words are behaviours or words linked to behaviours that are defined in the Behavioural Glossary, page 16. Red highlighted words are anatomical features of a bird defined in the Anatomical Glossary, page 8.

Word or Phrase DefinitionAddled Eggs that do not hatch - they are unfertilised and often turn bad

Adult A bird that is fully grown with a final characteristic plumage and physically developed to become sexually mature

Altricial Describes chicks that are basically helpless at hatching. They are confined to the nest and need to be fed by the adults (see precocial).

Anisodactyl(ous) Describes the most common toe arrangement in the feet of birds - 3 toes facing forward (toes 2 to 4) and 1 toe facing backwards (toe number 1)

Antiphonal Describes bird song (singing) where two individuals call alternately in duet

Arboreal Spending most of the time in trees

Ascendent Describes feathers in a line (tract) being moulted individually, starting at the one furthest from the body and ending with the closest one - the opposite of descendent

Asynchronous Not at the same time - in reference to eggs hatching at different times (as in many altricial species) as opposed to synchronously (hatching together)

Brood The bird equivalent of a mammal litter. Also means to take care of young - sit on chicks to protect and keep them warm; sometimes also used (incorrectly) in place of incubating (eggs)

Brood-parasite A bird that lays its eggs in the nest of another bird and expects that bird (called the host or foster parent) to incubate the eggs and raise the chicks. See brood-parasitism

Call Generally a reference to non-musical, often singular, vocal notes uttered by birds during various interactions or when alighting and taking off

Casting A pellet or bolus of indigestible animal parts that is regurgitated and disgorged periodically by many bird species.

Centrifugal Describes moulting of the tail feathers where corresponding opposite rectrices are replaced in pairs from the centre outwards (see centripetal)

Centripetal Describes moulting of the tail feathers where corresponding opposite rectrices are replaced in pairs from the outside inwards (see centrifugal)

Chick A name that broadly defines any young bird that is still covered in down feathers. Once it attains flight feathers it is called a juvenile then moults into an immature

Class A taxonomic (scientific) classification that groups closely related Orders of animals or plants - falls between Phylum and Order in the hierarchy

Clutch A collection of eggs from a single female during a single breeding attempt

Confusion effect The phenomenon whereby birds in groups or flocks that are tightly packed become a formidable deterrent to enemies, essentially confusing them in selecting an individual as prey and thereby reducing individual mortality.

Crepuscular Being active during the twilight hours of dawn and dusk

Cryptic Colours or markings on the feathers that camouflage the bird by allowing it to match and blend with its surroundings (the substrate)

Decurved Curving downwards - usually used to describe the bill of certain birds (see recurved)

Descendent Describes feathers in a line (tract) being moulted individually, starting at the one closest to the body and ending with the furthest one - the opposite of ascendent

Dilution effect The effect created by groups of animals where the presence of the individuals is more diluted the bigger the group gets. This effectively makes them less conspicuous to enemies and reduces chances of mortality.

Dimorphic Describes a species that has two (2) distinctly different colour variations within the population (see morph)


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BEHAVIOURAL GLOSSARYThis is a list of the words and phrases pertaining to bird behaviour that you are most likely to encounter when reading up on, discussing or describing birds. An attempt has been made to keep the definitions as simple and unambiguous as possible, with general reference to those species or bird groups that exhibit each behaviour.

Green highlighted words in the ‘definition’ column are behaviours or words linked to behaviours that are also defined in this Behavioural Glossary.Orange highlighted words in some definitions indicate words that are defined in the General Glossary, page 12.Red highlighted words are anatomical features of a bird defined in the Anatomical Glossary, page 8.

Behaviour DefinitionAerial sallies When a bird flies out from a perch in a roughly circular route to either hawk prey in flight or to display before alighting in

exactly the same spot (or very close to it).

Allelomimetic behaviour When animals (either of the same or different species) imitate or mimic one another’s behaviours, be it vocalisations, foraging, maintenance activities or predator evasion tactics. See song or call mimicry.

Allofeeding The feeding of one bird (adult or juvenile) by another without simultaneous reciprocity. See courtship-feeding.

Allopreening When one bird preens another without simultaneous reciprocity. Serves to remove parasites, ‘repair’ feathers or assert dominance.

Altitudinal migration When a bird’s seasonal migratory movements are based on moving to points of different elevation to find food. This usually equates to going up in summer and down in winter.

Anting The act of using formicine ants for feather maintenance. It is thought that the acid they secrete assists with exfoliation and eradication of old oil and feather debris - as does the ants’ foraging behaviour. The ants either walk unassisted over the bird as it lies on the ground (passive anting) or they are physically picked up by the bird and vigorously rubbed through the plumage (active anting).

Apotreptic behaviour Agonistic (threat) behaviour of an adult bird in defence of its territory or its nest (or in a contest situation with another bird) whereby it aggressively approaches the threat and displays, without any thought of retreat (escape). The main drive is to ‘approach and confront’ in an effort to deter attack. See epitreptic behaviour.

Beating Describes the battering that many prey items receive against stumps, rocks or the ground after being caught. It is usually reserved for large or dangerous prey that needs to be killed or immobilised before the bird can release the grip it has with the bill in order to be safe from reprisal or to enable the bird to manipulate non-moving prey into a position (head-first) that allows easy and trouble-free swallowing.

Belly-wetting The act of adult birds sitting in the water to wet the belly feathers and then returning to the nest to sit on the eggs or chicks. Thought to cool and / or hydrate, and is used by some groundbirds. Also called belly-soaking.

Bill-clattering Occurs in many storks. Describes the activity of courting pairs hitting their bills together to make an audible sound in display.

Bill-snapping When the bill is closed forcibly and rapidly to produce a ‘snapping’ or ‘clicking’ sound as the cutting edges of the mandibles come together. Used as contact by many smaller birds while foraging or in territorial / courtship display where it is often coupled to wing-fripping.

Broken-wing display When adult birds, that have eggs or chicks in a nest of imminent discovery by a predator, in desperation act as though they are injured by dragging a wing on the ground - feigning injury - in an attempt to distract the predator and lure it away from the nest. Most predators usually opt for the easiest meal, being attracted to flailing animals, and will follow the bird which then suddenly flies off when far enough from the nest.

Brood-parasitism When a bird lays its egg/s in the nest of another bird, expecting them to be incubated and the chicks to be raised. If the eggs are laid in the nest of the same species, then it is called intra-specific brood-parasitism (as in some groundbirds and waterbirds - among others), whereas different species is referred to as inter-specific brood-parasitism as occurs in ‘typical’ brood-parasites, such as old world cuckoos and occasionally some waterbirds. See egg-dumping.

Brood reduction When the number of eggs within a clutch or chicks within a brood are reduced (killed) to reduce competition for resources. The result is fewer offspring, but they are stronger and healthier with a better chance of survival. Parents themselves may abandon, neglect or kill what they perceive to be the excess or weaker individuals. See cainism / siblicide.

Brooding When the parent (or helpers in co-operative breeders) sits on nestlings. This is done to insulate, warm or cool them because they cannot initially thermoregulate effectively. It also serves to protect them from danger and the elements. Brooding also applies to cleaning the nestlings and maintaining nest hygiene - removing parasites and faeces (at least initially).


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BIRDS ENDEMIC TO AFRICAThe following is a list of those bird Orders, Families or ‘Groups’ – not individual species – represented in southern Africa that are found only or almost entirely within the boundaries of the African continent and nowhere else. Because ‘common names’ vary so much globally (although recent standardisation of names has alleviated this problem), the list given under the categories ‘Groups’, is merely a guideline.

Coliiformes - mousebirdsMusophagiformes - turacos, go-away-birds

Endemic OrdersAkalatsAlethesApalisesBatisesBishopsBoubousBuffalo-weaversBush-shrikesCamaropterasCrimsonwingsCrombecsEremomelasFirefinchesFrancolinsHelmet-shrikesHoneybirdsHyliotasKorhaansLongclawsMannikins

Endemic ‘Groups’ (common bird type)NicatorsOxpeckersPalm-thrushesPenduline-titsPuffbacksPytiliasQueleasRobin-chatsSaw-wingsSeedcrackersSeedeatersSiskinsSparrow-weaversSpurfowlTchagrasTwinspotsWattle-eyesWidowbirdsWren-warblers

Bucorvidae - ground-hornbillsChaetopidae - rock-jumpersColiidae - mousebirdsLybiidae - african barbets, tinkerbirdsMusophagidae - turacos, go-away-birdsNumididae - guineafowlsPhoeniculidae - wood-hoopoesPromeropidae - sugarbirdsRhinopomastidae - scimitarbillsSagittaridae - secretarybirdStruthionidae - ostrichesViduidae - whydahs, indigobirds, cuckoo finch

Endemic Families

Scopidae - hamerkop

Near-endemic Families (mostly within Africa)

BrownbulsChanting goshawksFlufftailsGreenbulsLovebirdsTit-babblers

Near-endemic ‘Groups’ (mostly within Africa)

The cape shoveler, a near-endemic, gets its name from the shovel-shape of the bill that is adapted for filter-feeding plankton. Sometimes, groups of these birds will swim in a broad circle, following each other to exploit food stirred up by the bird ahead.

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INTRODUCTION


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NAME CHANGES AND BIRD AREAS

Why have so many bird names recently changed?

Change is inevitable. As with most other natural sciences, ornithology has advanced tremendously over the last few years. Our understanding of how birds live is due, in large part, to the many thousands of hours of research and experimentation conducted by field researchers and scientists, but has also been revolutionised in recent years by DNA-sampling techniques. These very intricate procedures get right down to the basic ‘blue-print’ of each species and have revealed some interesting information. Essentially, ornithology has, as a result of this data, had to undergo taxonomic revision – that is, some changes in scientific classification have been made. The reason for this was that birds had, in the past, been classified and grouped based on various physical and physiological characteristics – traits considered to be reliable indicators of lineages.

New research has revealed that a lot of the previous groupings were, in fact, spot on! There have, however, been a number of surprises, and in the interests of advancement and for the very simple reason of ‘stating facts’ and ‘making changes to correct mistakes’, revisions have had to be made. Most of these will not concern the average birder because they are all either of an obscure nature (Genera and Specific name changes – in other words, changes to the scientific names) or cases of birds’ relatives / affiliations suddenly changing. For example, batises have now moved from an affiliation with flycatchers to one with shrikes – but the bottom line is that the average birder does not actually care about such trivialities! Where the impact (and resistance) has been made, however, is where the names ‘that my granddad used’ have changed.

The world is becoming a smaller place on a daily basis. Gone are the days when isolated areas are just that – isolated! We can no longer get away with calling a species – regardless of whether it is fauna or flora – by a myriad of different names in different areas. By the same token, it is unacceptable and incredibly confusing to

Only the female chinspot batis has the characteristic brown spot below the bill. It is thought that batises, which were previously grouped with the flycatchers, are actually a type of shrike – changes also being made at Family level. Indeed, the strange ground-dwelling white-tailed shrike of Namibia is also thought to be an aberrant batis!

chinspot

Female


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refer to totally different species by the same common name. In most cases where this has happened, the name with the longest history or usage, or the most descriptive or technically correct name has been adopted. The time has come to standardise a single global bird species-list so that everybody is on the same page – and speaking of pages, I am sure there are a good many ‘life-lists’ that need adjustment, and rightfully so!

It is always equally exciting and challenging when dealing with change – we are a species of routine and do not like change – but, however slowly people accept these changes, the new names will (and have to) become a fixture. It may take most of a generation, but by then we will all wonder what the fuss was all about!

What are the new bird names?

Of the 300 or so changes to southern African bird names, the vast majority are in fact only minor or subtle in nature. In many cases, names are now preceded by african, southern, northern, eastern, etc. to denote differences in geographical range between these and very similar species elsewhere. Some subtle changes

have, in fact, only involved the addition of a hyphen. For example, redbilled hornbill is now red-billed hornbill. Then, of course, there are some major changes with entire

Three-banded plover preening. The small plovers of the Genera Charadrius and Pluvialis have retained the name ‘plover’ whereas their bigger cousins of the Genus Vanellus are now called ‘lapwings’.

The bulbuls of the Genus Pycnonotus, such as this dark-capped bulbul (previously black-eyed), are the only bulbuls to retain the name bulbul. Those of the Genera Andropadus, Chlorocichla and Phyllastrephus are now called greenbuls, except for the terrestrial bulbul (Phyllastrephus terrestris) which is now called a brownbul.


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‘groups’ of birds changing name to come into line with international convention. Examples are dikkops changing to thick-knees, some francolins to spurfowl, some plovers to lapwings, widowfinches to indigobirds, louries to turacos, bleating warblers to camaropteras and some canaries to seedeaters. On the other hand, some of these ‘group name changes’ have, in fact, not been that major with only subtle changes to parts of the name in groups such as: some robins to robin-chats, widows to widowbirds, some honeyguides to honeybirds, tinker-barbets to tinkerbirds, saw-wing swallows to saw-wings, finchlarks to sparrowlarks, some bulbuls to brownbuls and greenbuls, and some small owls to owlets.

There have of course also been a number of other individual species name changes – some minor and some major, but all have been necessary changes (see ‘Why have so many bird names recently changed?’, page 57). Although there has been a lot of negativity and resistance with regard to these changes, the overall result is far from earth-shattering, and when listed in alphabetical sequence as below, they are quite easy to learn.

The lighter-headed version of the red-billed hornbill (pictured here) that occurs in northern Namibia has recently been declared a separate species, now known as the damara hornbill.

NAME CHANGES AND BIRD AREAS


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BREEDING

1. Mating systems

What mating systems do birds have?

As with mammals, there are two major mating or breeding systems (with variations thereof) that are prevalent in birds. What follows here is a brief (ideal) outline of the two systems, which is then accompanied by a more detailed analysis and discussion of the subtle variations of each that actually occur in nature. The basic outline is as follows:

MonogamyThis is where each sex has only one dedicated partner, the so-called pair-bond. This can be either for most of a season or seasonally (most common); to lasting a few seasons (fairly common); to lasting for life (not too common). In fact, monogamy is far more common in birds than mammals, accounting for about 50% (in true terms – see opposite) of local species.

PolygamyThis occurs where one sex has many different mates in a breeding season, with no pair-bond being formed. The sex that cheats determines how polygamy is further defined. If the male is the rotten scoundrel (usual), then the system is called polygyny, and if the female is the culprit, it is called polyandry.

• Polygyny – one male with many females. These females can all be mates at the same time i.e. the stud can have a few mates, all with eggs in different nests simultaneously (called simultaneous polygyny), or he can participate in incubation and chick-rearing to a certain extent and then mate with another female, and repeat the process (called serial polygyny).

• Polyandry – this is a rare system (supposedly accounting for less than 5% of species) where the female has more than one mate. All incubation, brooding and chick-rearing is left to the male, while territorial defence falls primarily with the (usually) larger and more colourful female. She is often ably assisted by her husbands who will put up a spirited group territorial defence. Again, she can have a few nests in the territory at one time – each being presided over by a different male (called simultaneous polyandry), or she can have a few mates in succession (called serial polyandry).

Fulvous ducks are seasonally monogamous with both sexes playing a role in parental care for the first few weeks.

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The detailed discussion is as follows:

Birds, as with mammals, can generally be divided into monogamous species (those with only one partner or mate) and polygamous species (those with more than one mate).

Birds are, however, unusual when compared with mammals in that about 90% (or so it appears) of species are monogamous as opposed to polygamous. Many bird species have either sex actually being promiscuous, meaning they are pretty unselective in their mate choice and are prone to short relationships (one-night stands as it were)! This is what takes the apparent 90% of monogamous relationships down to only about 50% in real terms (as mentioned opposite).

Assuming that ‘being successful’ is a function of reproductive success – especially as far as males are concerned – it would seem odd that so many males would commit to one mate (with the limited breeding opportunities it infers) as opposed to a system where more mates mean more offspring. To answer why this may be the case, we first need to look at the definition of ‘reproductive success’. The conventional approach is to regard ‘success’ as a function of the number of offspring fledged. However, should none (or few) of these young get to breed themselves, then we can hardly say that the parent has been reproductively successful because their genetic material has not been perpetuated through more than one generation. It is far more advisable, therefore, to regard ‘breeding success’ as a function of the number of ‘grandkids’ the bird has. In other words, it is the number of young that have been raised to the extent of themselves being successfully able to breed.

It may be prudent, therefore, based on various environmental and survival criteria, for males to stick with one mate and assist with rearing of young to ensure that offspring raised have been given the best possible start in order to make finding mates possible. Helping to give chicks food means they will be in good condition, and birds in good condition attract the best mates (see ‘Why do birds sing?’, page 378).

The main diet of the zitting cisticola is grasshoppers, although they will eat any insects. When breeding, serial polygyny (a male mating with one female after the other) or simultaneous polygyny (a few females at the same time) can occur. Bonds only last for one breeding attempt.

The african black duck is very closely related to the yellow-billed duck – the bill has the same design and markings but is blue-grey instead of yellow. They have been recorded to hybridise in captivity. Unlike the yellow-billed duck, this species has pair-bonds that can persist for an entire breeding season or even for a few years.

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BREEDING


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DEFENCE AND SURVIVAL

As a general rule, during agonistic encounters – stressful conflict situations with enemy or conspecific – there are two ways in which a bird behaves. It either aggressively approaches the ‘threat’ and by various means tries to intimidate it into retreating – called apotreptic behaviour, or it can defensively withdraw from the conflict without aggression (but still displaying) – called epitreptic behaviour.

How do birds control their body temperature (thermoregulate)?

Birds do not sweat and instead have to rely on other means to stay cool. Various physiological and behavioural adaptations have evolved to make this possible. Special respiration, postures and bathing are the most commonly observed.

Apart from a short period after hatching (the period of time being dependent on the size of the bird and whether or not is is altricial or precocial), birds are ‘warm-blooded’ and able to internally regulate their body temperature. They are, therefore, said to be homeothermic, maintaining their body temperature at between 40 and 42°C. Thermoregulation or ‘temperature control’ applies to two opposite behaviours, namely to cool the body when its temperature starts to rise and to heat it up when the core temperature starts to fall.

Various mechanisms are employed to achieve ideal core temperature and are discussed separately as ‘How do birds heat / warm the body?’ (Question 1) and ‘How do birds cool the body?’ (Question 2):

1. How do birds heat / warm the body? Essentially, when cold, the bird needs to eat more because food produces energy in the form of heat. The whole idea here is to conserve heat by reducing heat loss and to increase heat gain by producing heat.

SunningThe easiest way to warm up is to sit in the sun. Birds sun themselves in many ways and will usually open the wings to expose as much of the body’s surface as possible to the warming rays. Small birds will often sun on the ground with doves and go-away-birds, for example, being well known for lying flat with outstretched wings to warm the upper body, and with a vertically held wing while leaning to one side to expose and warm the undersurface as well. Larger birds tend to sit at the top of trees or on an exposed limb and will often open the wings and arch the

This white-fronted bee-eater is taking the opportunity to warm itself while exposed to the sun on the warm ground near its nest-hole.


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trailing edge forward so that there is maximum exposure. I have seen birds such as the bateleur and african fish-eagle facing to and away from the sun in this position.

ShelterAnother way to keep warm is to look for shelter at night (or in cold rain or wind by day) when temperatures usually plummet. Simply staying under an overhang, in a nest-hole of a tree or rock or just in a closed nest constructed of plant material can go a long way to maintaining body temperature and save the bird a lot of energy by not having to use physiological mechanisms (see below). It is estimated that by staying in

a nest, birds can capitalise on temperatures that can be as much as 5 – 10°C warmer than the outside ambient temperature.

HuddlingAlso called ‘clumping’, huddling is the behaviour where birds will sit touching one another for warmth. They will do this on exposed roosts such as branches at night or in cold weather and will even clump inside communal nests as well. This is particularly common in co-operative breeders such as wood-hoopoes. During the non-breeding season (which tends to be winter), it is interesting to note that many birds will use communal single-species or multi-species roosts, (see ‘Why do birds roost communally?’, page 408). Besides the obvious safety advantages, communal roosting may also serve a thermoregulatory function as well. The collective ‘body-heat’ of the group and the mere presence of a close neighbour will buffer and protect each bird from the wind and ambient temperature – although these birds do not usually touch each other.

Pulling the legs inThe legs, invariably without the benefits of an insulatory feather covering, are one of the areas where birds lose heat the quickest. When cold, birds will either pull the legs right up into the belly, vent and tail feathers when flying or will tuck the legs in and perch or roost in a hunched posture. Some birds such as raptors, flamingos and storks may even be seen to stand and tuck one leg in at a time to reduce the cooling effects of water or wind.

Perching, roosting or resting on warm substrates – this is rare but used opportunistically (as it is in mammals). It is more prevalent in nocturnal terrestrial species (such as thick-knees, coursers and some nightjars) that will roost or rest on rocks or exposed ground between bouts of foraging. Some storks can also be seen to be resting on their tibio-tarsal joints. This is probably more a function of getting

Cold, blustery days are when large raptors, such as this african fish-eagle, can be seen with spread wings, sunning themselves by facing into the sun.

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the body closer to the warm ground in cool weather than it is a case of simply ‘resting’ as is often believed.

Fluffing the feathersBy erecting the contour feathers (see ‘What types of feathers are there?’, page 109), a layer of insulatory air is trapped in the plumage to help maintain warmth. This is generally only done when resting or roosting because, in flight, the feathers need to be ‘sleeked’ and all air expelled for streamlining.

Physiological mechanismsIf all, or some, of the above mechanisms for warmth have been used to no avail, and the body core reaches what is called the lower critical temperature (LCT), then internal mechanisms of heat production take over. The LCT is the temperature at which the brain starts to realise that body temperature needs to be urgently raised to avoid life-threatening problems. This is not a set temperature (in °C) for all birds, but varies rather with body size. Because of the high body surface area to volume ratio of small birds, they tend to heat up and lose heat quicker (reaching the LCT at a faster rate) and the LCTs for these species can be as high as 30 – 35°C. Bigger birds, however, are able to stabilise their temperature more readily because of their lower body surface area to volume ratio and some can have LCTs as low as 5 – 10°C. Once this temperature is reached, the metabolic rate will increase to generate heat. Most birds are apparently able to triple their metabolic rates when they are cold, but the downside is that this uses a lot of energy and they then need to soon eat again. The bird will then start to shiver, but as the temperature drops, it ultimately reaches what is called the lower lethal temperature (LLT). This is the temperature at which the metabolism cannot produce any more heat and hypothermia sets in when the metabolic rate starts to fall uncontrollably until the bird dies. It is interesting

This female (yellow iris) saddle-billed stork is resting on the tarsal joint – this is common in winter when the behaviour may also help with warming the legs.

Cape turtle-dove sunning with the wing underside fully exposed and the tail spread to a maximum. Parasites that start moving about on the bird during this behaviour may be easier to remove during preening afterwards than would be the case when sunning has not occurred.

rump exposed by fanned tail

underwing exposed

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MORE ABOUT BIRDS – YOUR A TO Z

Akalats

There is only the one species in southern Africa, namely the east coast akalat that is resident in a narrow belt of moist, evergreen forest between the Zambezi River and Beira in Mozambique. It specialises in moving around in the dense, tangled understorey of the forest where it preys on small beetles, crepuscular moths and small vertebrates, which it catches primarily on the ground by means of a fairly broad bill and the help of rictal bristles. It is known to commensally associate with swarms of army ants that scare invertebrate prey from the leaf litter, capitalising on these prey items. There is no sexual colour dimorphism.

These are actually robins (formerly called gunning’s robin), having the typical white supercilium, and are closely related to Old World flycatchers. They are similar in having a broad bill and rictal bristles. Concealed white supraloral spots (above the lores) contrast with the brownish crown and head – and these are erected during display in both sexes. The melodic call is typical of robins but they are not known to mimic the calls of other birds. When landing, they will flick the wings and cock the tail like a chat (which they are also related to). Monogamous pairs will demarcate territories that the male advertises by call. The nest is a partially domed structure placed at, or very close to, ground level and constructed of rootlets and other soft material such as grasses and moss. The semi-altricial chicks are covered in down.

Albatrosses

These birds favour the cold, blustery seas of the Arctic and Antarctic where they breed on islands (except for some that breed in the Galapagos near the equator). All 15 species that have been recorded in southern African waters are vagrants (the majority) or non-breeding visitors that reach their northern limits close to our coast. The largest albatrosses are among the heaviest flying birds, and some have the longest wingspan of any bird. They are adapted to life on the open seas and can fly for days with barely a wing-beat. This is achieved by virtue of having a high wing-loading (weight to wing area ratio) as well as what is termed a high aspect ratio. The latter refers to the wing’s length to width (expressed as area) ratio. So, the longer and narrower the wing, the higher the aspect ratio and the better the bird is able to glide. The long wings mean they have an unusually high secondary feather count of up to 40 – about 16 being considered average in other birds.

The details of each bird ‘group’ is briefly dealt with in this section. See page 749 for key to the icons


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MORE ABOUT BIRDS – YOUR A TO Z

Many species cannot take off from a standing start unless there is a considerable headwind. They ordinarily need to use a ‘runway’ to get airborne, running at speed into the wind with open wings and rapid flapping. The reason they cannot get off the ground from a standing start is firstly because the wings are very long with a relatively small area and they weigh a lot so the high wing-loading is a handicap; and secondly, the wings do not move past the horizontal on the upstroke and cannot therefore generate enough down-force because of the limited path the wing can travel. There is a special sheet of muscle that stretches from the sternum (breastbone) to the humerus that limits the wing moving past the horizontal, effectively locking it in place while gliding. This enables these birds to glide for hours, their body-weight keeping the wings open and locked in position. This means that they don’t tire because they don’t have to consciously hold the wings in a horizontal position. They are assisted in this type of flight by winds off the sea, and make use of two techniques called slope-soaring and dynamic-soaring (see ‘What is dynamic-soaring and slope-soaring’, page 103). They are therefore reliant to a large extent on wind, and in calm weather the energetic drain of flapping is enough to ground them at their roosts or on the sea itself. The lower legs (tarsi) are laterally compressed to offer less resistance, making the job easier for the fully webbed feet when swimming on the surface or diving (in the smaller species that plunge-dive).

The fact that they do not have a hind toe means that these birds cannot perch (probably a good thing considering their size), so they are confined to nesting and roosting on the ground in areas free from terrestrial predators (offshore islands). Because such sites are widely scattered and space is limited, all albatrosses utilising these islands for roosting and breeding do so communally. None breed within southern Africa’s waters. They form long-term monogamous pairs that either make a simple scrape or a large mound-type nest on the ground. The latter is made either entirely of mud or of plant material and may resemble the ‘turret’-type nests built by gannets and flamingos. Only a single, large egg is laid. They have one of the longest egg-development periods, sometimes taking more than a month from initial yolk formation, through fertilisation to shell development.

The chick is covered with down at hatching (possibly helping with insulation in the extreme weather of the breeding grounds) and is said to be semi-altricial, requiring extensive parental care. The nestling period is protracted and can last up to a year before the young bird finally fledges. Parental care duties are shared equally between the sexes. If they lose the egg for whatever reason, they will not lay a replacement egg (see ‘Will birds lay replacement clutches?’, page 231). Due to the protracted nestling dependency period of almost 12 months in the larger species (there is no

The black-browed albatross is a master of flight, using gliding, dynamic-soaring and slope-soaring to good effect when trying to save energy out on the open ocean.

© P

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post-fledging care due to the advanced state of the fledgling at this stage), pairs only breed at most every two years. In the smaller species where the breeding period is much shorter, breeding attempts may occur every year. The chicks are initially brooded by one adult while the other forages, but as they grow and their nutritional requirements increase (before fledging they may, in fact, become heavier than the adults), it becomes a necessity that both adults go out to forage simultaneously. The lone chick is then susceptible to attack by other birds, such as predatory skuas and giant-petrels, and also to starvation should anything happen to the parents. The latter is unfortunately a major mortality factor as adults are killed in large numbers by long-line fishing operations. When attacked, the chicks can defend themselves only by regurgitating a foul-smelling stream of oily material from the gut at their tormentor. When the adults return, the chick is fed by regurgitation.

They are reliant on having to fly long distances for extended periods to satisfy their nutritional requirements, and the primary moult is therefore continuous, taking up to four years to complete a cycle by which time the first feathers replaced are due to be renewed again. Because they spend all their time at sea with little or no access to fresh water, they are equipped with a salt gland that purges excess body salt through the enlarged and modified nostrils that run in a tube along each side of the bill – not joined on top of the bill as in storm-petrels, petrels and shearwaters. This anatomical peculiarity has led to albatrosses and their relatives, the birds just mentioned, being known as ‘tube-noses’. They have a long life-cycle, taking 4 to 6 years to reach maturity and can live for 30 years or more.

Alethes

Only the white-chested alethe, one of four species endemic to Africa, occurs marginally into southern Africa, being found in the eastern coastal region south of the Zambezi River in Mozambique. This bird is interesting because although it is called an alethe, it is not considered a ‘true’ alethe (Genus Alethe), as denoted by its Genus Pseudalethe, meaning ‘false alethe’. Although the true alethes are closely allied to the Old World flycatchers and chats, this ‘false alethe’ is probably more closely related to robin-chats. All these birds are in the same Family, namely Muscicapidae, so these affiliations are trivial. There is no sexual colour dimorphism. Preferred habitat is coastal and montane forest where it moves about in a secretive manner in the dense understorey, staying close to, or on the ground, while looking for invertebrates, small vertebrates and possibly also fruit in summer. They glean from foliage but, when on the ground, move through and toss the leaf-litter with the bill to unearth prey – much like thrushes do. They are monogamous with long-term pair-bonds and will hold suitable territories for a number of years. They will bill-snap in aggressive interactions. Nests are an open cup that is well camouflaged with moss and lichen and placed in a concealed tree fork. Very little is known about the young.


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4. Behaviour in general

What is a passerine?

‘Passerine’ is a general scientific term or name used to describe birds that have unspecialised feet. In birds, ‘normal’ feet constitute 3 toes facing forward and 1 toe backwards where all the toes are to be found at the same level (none higher up the foot than the others) and all are fixed in position, not being able to ‘swivel’ in extreme directions. These feet are said to be unspecialised because they ‘just grip’. Any departure from this formula is termed and referred to as specialised feet – either in terms of toe numbers

Typical passerines, such as this ant-eating chat, have 10 primary flight feathers and 12 tail feathers. They also have a complex syrinx (voicebox).

Even birds that spend much of their time on the ground, such as larks and pipits, are passerines. The inappropriate definition of passerines being ‘perching birds’ has led to confusion in this regard.

A typical passerine foot structure and manner of perching. The left and right legs and feet can often be widely separated – something that most perching non-passerines find difficult or impossible to accomplish.

Crows are the largest passerines. This cape crow is busy calling and is perching with a simple, unspecialised, anisodactyl (3 toe forward, 1 toe back) foot structure.

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COLLECTIVE NAMES OF BIRDSThe names in brackets are alternatives to the primary name.

Species Collective nounAuks Raft (flock, colony)Avocets ColonyBirds Flock (dissimulation, (in general) fleet, volery, parcel)Bitterns Sedge (siege)Bustards FlockBuzzards WakeChickens Peep (brood, clutch)Coots Covert (commotion,

cover, rasp)Cormorants Flight (gulp)Cranes Sedge (siege)Crows Murder (muster, hover,

parcel)Curlews Head (herd)Dotterel TripDoves Dole (dule, piteousness,

pitying)Ducks Paddling (flush, brace,

dopping, sord)Dunlins FlingEagles Convocation (eyrie)Falcons CastFinches Charm (trimming,

trembling)Flamingos StandFrancolins Covey (bevy, bew,

warren, clutch)Geese Gaggle (skein, team,

wedge)Goshawks Flight

Hawks Mews (kettle, screw, moulting)

Hens BroodHerons Siege (hedge, sedge,

rookery)Hummingbirds Charm (troubling,

drum, chattering)Ibises ColonyLapwings Deceit (desert)Larks Exaltation (ascension)Magpies Congregation (tittering,

tiding, tribe)Mallards Sord (puddling, sute)Moorhens PlumpOstriches Pride (flock)Owls Parliament (stare)Oxpeckers FlingParrots Company

(pandemonium)Peacocks Ostentation (pride)Pelicans Scoop (pod)Penguins Rookery (parcel,

colony)Peregrines CadgePheasants Bouquet (nide, nye)Pigeons Passel (flight, kit)Pintail KnobPlovers Congregation (band,

leash, wing)

Pochard Rush (knob)Poultry RunQuail Bevy (drift, covey)Ravens Unkindness (conspiracy)Rooks Building (clamour)Ruffs HillSandpipers FlingSeagulls SquabbleSnipe Walk (wisp)Sparrows Host (ubiquity, tribe,

quarrel)Starlings Murmuration

(chattering, cloud, clutter)

Storks Mustering (phalanx)Swallows Gulp (flight)Swans Herd (lamentation,

squadron, whiting)Swifts Flock Teal Spring (bunch, coil,

knob)Thrushes MutationTurkeys Raffle (dule, rafter,

posse)Turtle-doves PityingVultures WakeWaterfowl Plump (raft, knob,

bunch)Woodpeckers DescentWrens Herd

Species Collective noun Species Collective noun

A congregation of birds in one place, such as these ostriches gathering at a waterhole, does not necessarily define them as a ‘congregatory species’. This term applies mainly to migrant birds (and especially migrant aquatic species) that congregate at specific locations / waypoints along the route and at their destination for rests, nutrient-replenishment or breeding. It also applies to non-migrants that predictably congregate in large numbers for breeding and roosting. A group of ostriches is called a ‘pride’.

APPENDICES


749

In this section on pages 528 – 747, each group of birds is represented by icons as follows:

Egg shapes

KEy to thE icons in thE sEction ‘MorE about birds – your a to Z’

Round Oval Pyriform

nest designs

Scrape / depression No nest Tight cup Open bowl

Stick platform Enclosed woven structure

– suspended

Enclosed woven structure

– supported

Dome of grass or sticks

Natural hole in wood

Excavated hole in wood

Mud pellet nest under overhang

Floating platform Mud-turret – open ground near water

Excavated tunnels in sandbanks

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Nest locations

Foot structures

Anisodactyl No hind toe Zygodactyl Heterodactyl

Pamprodactyl Webbed Totipalmate Lobed

Syndactyl Pectinate 2-toed Partial webbing – rudimentary

hind toe

Partial webbing – no hind toe

Semi-zygodactyl Semi-pamprodactyl

Rocky cliffs Open ground Aquatic


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Beat About the Bush: Birds