ChapterPDF Available

Avian Personality

January 2013

DOI:10.7208/chicago/9780226922065.003.0004

In book: Animal Personalities: Behavior, Physiology, and Evolution (pp.66-95)
Publisher: University of Chicago Press
Editors: Carere C, Maestripieri D

Authors:

Kees van Oers

Wageningen University & Research

Marc Naguib

Wageningen University & Research

.1. A noncomprehensive species overview with studies on the assessment of avian personality traits.

…

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Avian Personality

KEES VAN OERS AND MARC NAGUIB

Introduction

Birds are widely distributed and highly diversiﬁ ed, and also generally more

conspicuous and observable in natural environments than many other ver-

tebrates. Birds also exhibit complex behavior and social processes. Because

of these attributes, birds are key model organisms that have allowed behav-

ioral biologists to address a wide range of ecological and evolutionary ques-

tions (Konishi et al. 1989; Danchin et al. 2008; Davies et al. 2012). Moreover,

owing to the contributions from a diverse group of ornithologists ranging

from amateur bird-watchers to professional scientists, the knowledge of bird

behavior under natural conditions is more extensive than for any other ver-

tebrate taxa. Many avian species are diurnal, conspicuous, and resilient, and

also permit relatively invasive investigations. In consequence, they are well

suited for experimental ﬁ eld research using a wide range of methods such as

manipulation of breeding conditions (Tinbergen and Boerlijst 1990), bioa-

coustic analyses (Marler and Slabbekoorn 2004; Catchpole and Slater 2008),

capture and marking procedures (Lebreton et al. 1992), and analyses of en-

ergy expenditure and of endocrine and immune function (Wingﬁ eld 2005).

Birds are also excellent study organisms for experimental investigations of

behavioral adaptations to changes in environmental conditions, a topic that

has become of particular interest in recent years (Visser 2008). Furthermore,

captive bird populations proved to be extremely valuable in studies on the

genetics of behavior (Berthold and Querner 1981; Jones and Hocking 1999;

Price 2002; Drent et al. 2003; Van Oers et al. 2005a), the neurological cor-

relates of behavior (Konishi 1985; Gil et al. 2006), physiological mechanisms

underlying behavior and its variation (Wingﬁ eld 2005; Soma et al. 2008), and

developmental inﬂ uences on behavior (Naguib and Nemitz 2007), as well as

in studies on sexual selection (Andersson 1994). Even in more applied ﬁ elds

such as conservation, animal welfare, and animal husbandry, birds have

been shown to be good models for studying behavior, both in the ﬁ eld and

in captivity (Sutherland 1998; Dawkins 1999; Rodenburg and Turner 2012).

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Kees van Oers and Marc Naguib | 67

Considering all of the above, it is not surprising, therefore, that the majority

of studies on animal personality have been conducted on birds. The study

of personality traits in birds can be framed into an ecological context more

easily than in other taxa, allowing analyses of ecological and evolutionary

aspects of personality. Birds of resident species can be followed individually,

often throughout their lives, their behavior can be measured both under

standardized conditions in captivity and in their natural environment, and

ﬁ tness can be quantiﬁ ed. The opportunity to conduct behavioral tests in the

laboratory also allows researchers to effectively document consistent differ-

ences in individual behavior within and across contexts (Dingemanse et al.

2002; Van Oers et al. 2005b; Martins et al. 2007; Schuett and Dall 2009).

The aim of this chapter is to provide a broad overview of studies on avian

personality, including those that address genetic variation linked to person-

ality (Van Oers et al. 2005a; Fidler et al. 2007; Gil and Faure 2007; Bell and

Aubin-Horth 2010; Van Oers and Muller 2010), the behavioral and ﬁ tness

consequences of personality in natural populations (e.g., Dingemanse et al.

2004; Dinge manse and Wolf 2010; Wolf and Weissing 2010), mathematical

models that investigate possible scenarios for the evolution of personal-

ity (Wolf et al. 2007; Amy et al. 2010; Dingemanse and Wolf 2010; Houston

2010), and the physiological substrate of personality (e.g., Carere et al. 2005a;

Kralj-Fiser et al. 2007; Fucikova et al. 2009; Coppens et al. 2010; Baugh et al.

2012). We also provide a historical background of personality research in

birds and discuss recent studies from a historical perspective.

Historical overview of avian personality research

Darwin wrote extensively on animal behavior (Darwin 1872) and, after him,

scientists working on animal behavior could be separated into two differ-

ent ﬁ elds, namely, comparative psychologists and ethologists. There was

one camp of ethologists such as Douglas Spalding (1841–1877), who studied

imprinting in chicks (Gray 1967), and another camp of mainly animal psy-

chologists such as Lloyd Morgan (1852–1936), who wrote a book, very inﬂ u-

ential at the time, introducing the ﬁ eld of comparative psychology (Lloyd

Morgan 1923). Wallace Craig, Oskar Heinroth, and Charles Otis Whitman

contributed to the emergence of ethology as a major separate biological

discipline in the study of behavior. Although both comparative psychology

and ethology address basic principles of animal behavior, these disciplines

have been separated for a long time. Interestingly, however, the study of in-

dividuality in the behavior of birds, and their personality, has found its way

in research both by ethologists and by comparative psychologists, and also

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68 | Avian Personality

has emerged in publications by semiprofessional bird banders. A crucial fac-

tor for recognizing individual differences in behavior is spending sufﬁ cient

time observing the individuals. Yet, a larger part of ornithological research

up until the ﬁ rst part of the twentieth century was done in museums so that

few data were available on behavioral differences among individuals (Arm-

strong 1947).

The ﬁ rst published use of the word personality to describe characteristics

of individual birds was probably by Talbot in 1922. Talbot (1922) described

inter- and intraspeciﬁ c differences in the motivation to ﬂ y through a hole

that was situated at the entrance of a gathering cage, when birds were caught

for banding. In the Manual of Bird Banders, Lincoln and Baldwin (1929) even

stated that documenting bird personality, deﬁ ned as the individual pecu-

liarities in appearance, habits, and manners (Baechle 1947), is one of the

main achievements of bird banding. A nice example that recognizing indi-

vidual personality differences requires spending sufﬁ cient time with these

individuals is provided by Gwendolen (Len) Howard, a musician who kept

birds in captivity as hobby. Most of her birds were tame, or at least habitu-

ated to human presence, and in a book called Birds as Individuals, Howard

(1953) describes in great detail the lives of great tits, black birds, robins, and

other birds in her garden or inside her house. Most remarkable about this is

that she recognized the birds not only by their individual plumage charac-

teristics, but also by their “characteristic mannerisms and poses and their facial

expressions.” She states that great tits especially were easily recognized since

“their whole bearing and personality was too individual for confusion to arise when

I had them at close quarters” (Howard 1953).

While the early descriptions of personality-like behavior in birds were

largely anecdotal, it was probably Lack (1947) who made the ﬁ rst scientiﬁ -

cally based description of individual differences in aggressiveness in robins,

when he tested several males and their reaction to a model. Some males were

hardly interested in the model, while others vigorously attacked it. Another

series of papers related to individual differences in behavior came from

Burtt (1967), a psychologist who combined his interest in bird banding with

the scientiﬁ c study of personality. While banding over 17,000 blackbirds for

the Federal Wildlife Service, he studied bird behavior for several years from

a psychological perspective (Thayer and Austin 1992). In his book The Psy-

chology of Birds, he made the connection between personality traits, such as

extroversion, dominance, and emotional stability, and the behavior of indi-

vidual birds (Burtt 1967). Together with Giltz, he investigated, for instance,

the importance of personality in the interpretation of bird behavior (Burtt

and Giltz 1969b). In connection with a banding program at a decoy trap,

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Kees van Oers and Marc Naguib | 69

the pair measured the personality traits “complacency” and “aggression” in

common grackles (Quiscalus quiscula), red-winged blackbirds (Agelaius phoe-

niceus), brown-headed cowbirds (Molothrus ater), and starlings (Sturnus vul-

garis). They deﬁ ned what they called the complacency-agitation continuum as

the way an individual bird behaved in a small cage, directly after banding.

Complacent birds moved more compared with agitated birds. Aggression

was assessed while birds were held in a hand; birds were threatened with

a ﬁ nger and the tendency to bite was measured on a scale from zero to ten

(Burtt and Giltz 1969a). Both traits showed within- and between-species

variation and were found to be highly repeatable. They found cowbirds to

be the most complacent and starlings the most agitated species, while grack-

les and cowbirds were the most aggressive, and starlings and red-winged

blackbirds the least aggressive species (Burtt and Giltz 1969a; 1969b). They

also found that grackles had the greatest tendency to re-enter the trap, and

that they were the most resident species compared with the other species

(Burtt and Giltz 1973).

As suggested by this brief historical overview, recognizing consistent in-

dividual differences in bird behavior has a long history, dating back to the

roots of ethology. Scientiﬁ c research focusing on such differences, however,

has ﬂ ourished mainly in the last decade (Table 1), after individual differences

in behavior were framed into the well-deﬁ ned concepts of personality, be-

havioral syndromes, and coping styles.

Recent advances in avian personality research

behavioral consistency and behavioral tests

Many recent studies on behavioral consistency in birds have been inspired

by the work of Verbeek, Drent, and coworkers in the early 1990s on great tits

(Verbeek et al. 1994; 1996; 1999). This work was based on earlier studies on

the individual consistency in the response toward changes in the environ-

ment in mice (e.g., Van Oortmerssen and Bakker 1981; Benus et al. 1987) and

studies on foraging and exploratory behavior in great tits (Parus major) (e.g.,

Krebs et al. 1972; Krebs and Perrins 1978). Individual differences in explor-

atory behavior had been noticed in several studies on foraging behavior in

great tits (Partridge 1976; Kacelnik et al. 1981), so the expansion of research

with a focus on such behavioral differences could be built on a substantial

body of knowledge of this topic. The behavioral tests developed by Verbeek

and coworkers to investigate novel object and novel environment explo-

ration (Verbeek et al. 1994) are now used as standard tests in most studies

on great tits (e.g., Dingemanse et al. 2002; Van Oers et al. 2008; Hollander

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70 | Avian Personality

et al. 2008; Titulaer et al. 2012) and also on other bird species (e.g., Fox and

Millam 2007; Martins et al. 2007; Kurvers et al. 2009; Schuett and Dall 2009).

Since the behavioral response to a novel object or novel environment might

be species-speciﬁ c, some caution is required when comparing studies of

different species. A test that might be very meaningful in the life-history

of one species might be less suitable for another one, thus resulting in be-

tween-species differences in the consistency of a trait (Mettke-Hofmann

et al. 2005). Hence, although exploratory behavior is now considered one

of the major animal personality traits (Réale et al. 2007; Sih and Bell 2008),

species-speciﬁ c tests to validate this and other behaviors are very important.

Related to exploratory behaviors are boldness or risk-taking behaviors (Ré-

ale et al. 2007; but see chapter 6). Whereas the exploration of a novel object

is likely to reﬂ ect a mixture of curiosity and fearfulness, risk-taking behav-

iors are often related to predation risk and foraging (Van Oers et al. 2004b).

Therefore, these behaviors are more closely linked to stress responses (Mar-

tins et al. 2007). Social relationships (Stowe et al. 2006; Stowe and Kotrschal

2007) and the behavior of unrelated ﬂ ock mates (Marchetti and Drent 2000;

Van Oers et al. 2005b; Kur vers et al. 2009) might also be important factors.

The behavior of a group of birds as a whole can, therefore, be affected by

the mix of personality types present within the group (Kurvers et al. 2009;

Schuett and Dall 2009; Amy et al. 2010).

Apart from exploratory behavior, several other traits have been investi-

gated in birds as personality traits (see table 3.1 for some examples). One

trait that has been widely used in bird research is agonistic behavior, which

has been shown to be individually consistent and to have a genetic correlate

in mice (Benus 1988) and ﬁ sh (Bakker 1994). Aggression toward a conspeciﬁ c

is a crucial part of the life-history of social animals such as birds. Especially

for social dominance (Verbeek et al. 1996; Dingemanse and De Goede 2004)

and in territorial behavior (Duckworth 2006b; Garamszegi et al. 2009; Amy

et al. 2012), agonistic behavior is an important personality trait determining

the outcome of an interaction and subsequent access to resources. In great

tits, Verbeek and coworkers (1996) investigated whether individual differ-

ences in exploratory behavior were related to agonistic behavior and how

this, in turn, related to dominance. In an experimental set-up, two males

were placed in a cage, with an opaque partition between them. After remov-

ing the partition, the authors noted which of the two males attacked ﬁ rst.

They found that this measure of aggressive behavior was consistent over

time and that fast explorers started more ﬁ ghts than slow explorers, inde-

pendent of sex and morphological traits. Individuals that initiated a ﬁ ght

were also more likely to win that ﬁ ght.

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Table 3.1. A noncomprehensive species overview with studies on the assessment of avian personality traits.

Author Year Species Personality traits

Anseriformes

Kurvers et al. 2009 Barnacle goose (Branta bernicla) Boldness

Kralj-Fiser et al. 2007 Greylag goose (Anser anser) Reaction to handling

Ciconiiformes

Blas et al. 2007 European white stork (Ciconia ciconia) Reaction to handling

Falconiformes

Costantini et al. 2005 European kestrel (Falco tinnunculus) Feeding habits

Galliformes

Richard et al. 2008 Japanese quail (Coturnix japonica) Boldness

Uitdehaag et al. 2008 Jungle fowl (Gallus gallus) Boldness

Faure 1980 Jungle fowl (Gallus gallus) Exploration

Passeriformes

Guillette et al. 2009 Black-capped chickadee (Poecile atricapillus) Exploration

Arnold et al. 2007 Blue tit (Cyanistes caeruleus) Boldness

Burtt and Giltz 1973 Brown-headed cowbird

Common grackle Red-

winged blackbird Starling

(Molothrus ater)

(Quiscalus quiscala)

(Agelaius phoeniceus)

(Sturnus vulgaris)

Aggressiveness

Complacency

Harvey and

Freeberg

2007 Carolina chickadees (Poecile carolinensis) Aggressiveness

Sociability

Quinn and

Cresswell

2005 Chaﬃ nch (Fringilla coelebs) Risk-taking

Garamszegi et al. 2009 Collared ﬂ ycatcher (Ficedula albicollis) Boldness

Aggressiveness

Risk-taking

Stöwe and

Kotrschal

2007 Common raven (Corvus corax) Boldness

Mettke-Hofmann

et al.

2005 Garden warbler

Sardinian warbler

(Sylvia borin)

(Sylvia melanocephala)

Exploration

Boldness

Verbeek et al. 1994 Great tit (Parus major) Exploration

Boldness

Verbeek et al. 1996 Great tit (Parus major) Aggressiveness

Van Oers et al. 2004b Great tit (Parus major) Risk-taking

Hollander et al. 2008 Great tit (Parus major) Exploration

Quinn et al. 2009 Great tit (Parus major) Exploration

Fucikova et al. 2009 Great tit (Parus major) Reaction to handling

Fox et al. 2009 Mountain chickadee (Poecile gambeli) Exploration

Boldness

Marchetti and

Zehtindjiev

2009 Sedge warbler (Acrocephalus

schoenobaenus)

Exploration

Minderman et al. 2009 Starling (Sturnus vulgaris) Exploration

Duckworth 2006a Western bluebird (Sialia mexicana) Aggressiveness

(continued)

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72 | Avian Personality

Author Year Species Personality traits

Beauchamp 2000 Zebra ﬁ nch (Taenopygia guttata) Exploration

Martins et al. 2007 Zebra ﬁ nch (Taenopygia guttata) Exploration

Boldness

Schuett and Dall 2009 Zebra ﬁ nch (Taenopygia guttata) Exploration

Psittaciformes

Fox and Millam 2004 Orange-winged Amazon (Amazona amazonica) Neophobia

Mettke-Hofmann

et al.

2004 10 species Boldness

Sphenisciformes

Ellenberg et al. 2009 Yellow-eyed penguin (Megadyptes antipodes) Reaction to handling

Struthioniformes

De Azevedo and

Young

2006 Greater Rhea (Rhea americana) Boldness

Table 3.1. (continued)

Agonistic behavior in birds is linked to the ability to obtain and maintain

a breeding territory (Stamps and Krishnan 1997; Naguib 2005). In studies

on agonistic behavior in relation to territorial competitiveness (Duckworth

2006a) and parental behavior (Duckworth 2006b) in Western bluebirds (Sia-

lia mexicana) it was shown, for instance, that agonistic behavior is repeatable

and costly (Duckworth 2006b). Moreover, Duckworth (2006a) showed ex-

perimentally that more aggressive males compete more effectively for territo-

ries in areas with a higher density of nest boxes. As a consequence, aggressive

and nonaggressive males occurred in breeding habitats that differed in the

strength of selection on morphological traits. These results show that aggres-

sion can affect selection on a local scale by determining individual settlement

patterns, thereby also providing opportunity for correlational selection.

Tests of agonistic behavior are, by deﬁ nition, conducted in a social con-

text, and the consistency in behavior could also be dependent on the con-

text (Van Oers et al. 2005b). To test whether males of black-capped chicka-

dees (Poecile atricapillus) behaved consistently with different mates, they

were paired to a female and several aspects of their behavior were observed

(Harvey and Freeberg 2007). After being paired with a new mate, the males

showed behavior that was consistent with the behavior previously shown

with their former mate, indicating that agonistic behavior is consistent also

when the social context has been changed (Harvey and Freeberg 2007).

A crucial issue in assessing personality traits is the identiﬁ cation of con-

texts that are most suitable for revealing consistent differences in behavior

among individuals. Exploration tests in artiﬁ cial environments, such as

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Kees van Oers and Marc Naguib | 73

a novel room or cage, and novel object tests, provide standard situations.

The artiﬁ cial nature of such a context has the advantage that behavior can

be tested in the absence of a speciﬁ c resource value, which may confound

any measurement of intrinsic behavioral traits. Resources vary in their value

to different individuals so that in tests conducted in natural situations it is

difﬁ cult to separate individual differences in behavior from differences in

resource values. Individuals may behave differently not as a result of per-

sonality but as a result of differences in resource values. Conducting tests

in the natural habitat could potentially reveal a more meaningful varia-

tion in behavior compared with the standard tests done in captivity, and

therefore yield results with high ecological and evolutionary relevance. Yet,

when testing birds for personality traits during resource defense in the ﬁ eld,

one needs to be careful in developing tests so that the recorded behavior is

not primarily related to the resource value rather than to their personality

traits. Demonstrating consistencies in behavior in contexts that are inde-

pendent of resources crucial for reproduction, thus remains a powerful tool

in research aimed at unraveling the evolutionary signiﬁ cance of personality

traits.

Causes of personality variation: genes and physiology

genetics

The majority of our knowledge of the genetic background of traits such

as exploratory behavior, aggressiveness, and fearfulness comes from stud-

ies on domestic birds. Selection experiments on chicken, turkey, ducks,

and Japanese quail have shown that the observed variation in open ﬁ eld,

pair-wise, and novel object tests has a substantial genetic basis (e.g., Brown

and Nestor 1973; Francois et al. 1999; Jones and Hocking 1999; Arnaud et al.

2008). Although the presence of a genetic component is an important factor

to consider in studies on evolutionary change of personality traits, genetic

studies of animal personality traits in natural populations are scarce (Bell

and Aubin-Horth 2010). Most quantitative genetic and molecular analyses

of bird personality traits have been conducted with the great tit (quantita-

tive: Van Oers et al. 2005a; Quinn et al. 2009; molecular: Fidler et al. 2007;

Van Bers et al. 2010; Korsten et al. 2010). In this species it is apparent that

personality traits typically have moderate levels of additive genetic varia-

tion (Dingemanse et al. 2002; Drent et al. 2003; Van Oers et al. 2004b; Quinn

et al. 2009) and of genetic dominance (Van Oers et al. 2004c), and that traits

are genetically correlated (Van Oers et al. 2004a). An important gene has

been identiﬁ ed for great tit personality: the dopamine receptor D4 gene

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74 | Avian Personality

( Fidler et al. 2007) explains between 5% and 8% of the phenotypic variation

in some but not all European great tit populations (Korsten et al. 2010). This

and other genes are thereby likely not only to affect behavioral responses

early in life (i.e., temperament traits), but also to affect learning and plastic-

ity later in life.

One difﬁ cult question is to assess the extent to which the underlying ge-

netic and physiological mechanisms are a constraint on the evolution of be-

havioral traits vs. the extent to which they are the product of variation and

selection (Bell 2005; Dingemanse et al. 2007). An important issue here is how

the word constraint is used. In a biological context, the word can refer to a

factor that impedes but does not necessarily prevent evolution in particular

directions, or it can indicate that speciﬁ c evolutionary trajectories are un-

available to selection (Roff and Fairbairn 2007). Therefore, determining the

role of genetic constraints in the evolutionary change of personality will re-

quire not only more detailed ecological studies, but also better knowledge

than we currently possess of the relevant genes and their importance in nat-

ural populations (Blows and Hoffmann 2005; Van Oers et al. 2005a). A more

comprehensive overview of the current knowledge of the genetic basis of

personality variation in captive and wild animals is provided in chapter 6.

hormonal correlates

Many vertebrate species are characterized by the ﬂ exibility with which they

cope with stressors, and birds provide good examples of this. When birds

are under conditions of low environmental predictability, they experience

stress (Wiepkema 1992). Behavioral and physiological efforts to master the

situation (coping strategies) can be important determinants of health and

disease both in humans and in animals (Koolhaas et al. 1999). Moreover, in-

dividuals often show different physiological responses in these situations,

also referred to as coping styles. Individuals appear to cope with stressors

in a predominantly sympathetic or parasympathetic way. Individual varia-

tion in agonistic behavior can be considered as an example of more general

variation in coping with environmental challenges, where highly aggressive

individuals adopt a proactive coping style and submissive individuals adopt

a more passive or reactive style (Koolhaas et al. 2007). Therefore, most

physiological research relevant to avian personality involves stress physi-

ology and coping (see chapter 12). In mammals, it has been suggested that

individual differences in stress responses reﬂ ect variation in personality or

coping styles (Korte et al. 2005). Passive copers are expected to have higher

hypothalamic-pituitary-adrenal (HPA) responses to stressors, a lower sym-

pathetic adrenomedullary reactivity, a higher humoral immunity, but also a

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Kees van Oers and Marc Naguib | 75

higher vulnerability to stress-induced illnesses compared with active copers

(Ellis et al. 2006).

In birds, fast exploration, high risk-taking, and high responsiveness to a

novel object appear to be associated with high corticosterone levels during

the test (Martins et al. 2007; Richard et al. 2008). Birds also show individual

consistency in the secretion of stress hormones. Kralj-Fisher and cowork-

ers (2007) have shown in greylag geese that corticosterone levels measured

in fecal samples collected after repeated handling episodes were consistent

within individuals. This repeatability was especially pronounced when indi-

viduals were feeding in low competition areas; in high competition areas in-

dividuals were less consistent. Whether these individual differences in stress

responses reﬂ ect genetic personality differences remains unclear. Yet, some

support for this possibility has been found in other avian species where se-

lection experiments have shown that the stress response has an additive ge-

netic background (Brown and Nestor 1973; Edens and Siegel 1975; Satterlee

and Johnson 1988). Moreover, great tit genetic lines selected for different

personalities (Drent et al. 2003) differed in the level of stress hormone secre-

tion after being in a social contest with a conspeciﬁ c (Carere et al. 2003).

Birds of the less aggressive and more cautious line (slow explorers) showed a

trend for a higher response compared with birds of the more aggressive and

bolder line (fast explorers), which could be taken to suggest a physiological

basis of different coping strategies in birds (Carere et al. 2003). Alternatively,

personality types might differ in the perception of the stressor, causing in-

direct differences in stress response to a standard stressor (Sapolsky 1994).

Most likely both mechanisms play a role. However, the extent to which one

or the other is more important in shaping variation in personality needs to

be studied in more detail. Studies in great tits have shown that exploratory

behavior is related to stress responses in both juvenile (Fucikova et al. 2009)

and adult birds (Carere and Van Oers 2004). Adult birds that explore a novel

environment more quickly (fast explorers) show a lower stress response af-

ter being handled, but nestlings that become fast explorers in adulthood

show an increased response after being socially isolated as nestlings. This

indicates that differences in personality traits measured just after indepen-

dence might act as a predictor of individual variation in the stress response

in adulthood, and as a result of variation in responsiveness as juveniles. A

more direct way of measuring the link between variation in personality and

stress is through stress hormones. In birds, corticosterone is the major glu-

cocorticosteroid hormone secreted in response to stress, and many studies

have shown that individual birds differ in their hormonal response to stress.

This response varies not only with intrinsic factors such as sex and age, but

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76 | Avian Personality

also in relation to behavioral types, and it is modiﬁ ed by factors such as body

condition (Schwabl 1995; Silverin 1998; Cockrem and Silverin 2002; Cock-

rem 2007). These modiﬁ cations may allow the adjustment of physiological

and behavioral responses to adverse environmental circumstances and help

explain individual differences in responses.

Glucocorticosteroid responses are seen as an evolutionary mechanism

that maintains physiological homeostasis within an adaptive range. Only

recently, however, have studies raised the question of how to explain the

consistent individual differences in these responses that are unrelated to

age or size (Cockrem 2007). It will be interesting to develop this and de-

termine whether individual variation in short-term elevation of circulating

glucocorticosteroids also explains ﬁ tness differences, and whether ﬁ tness

consequences vary for different behavioral types. A ﬁ rst step in that direc-

tion was made by the work of Blas et al. (2007) on European white storks

(Ciconia ciconia). This study showed that the magnitude of the adrenocorti-

cal response to a standardized perturbation during development is nega-

tively correlated to survival and recruitment (Blas et al. 2007). The next step

would be to investigate whether these ﬁ tness consequences differ for dif-

ferent behavioral types. Blas et al. (2007) discuss this possibility, by arguing

that the success of proactive vs. reactive types varies as a function of popula-

tion density and predictability of food resources. If this is associated with

differences in glucocorticosteroid responses, it could provide an explana-

tion for varying success of the behavioral types. Direct measurements and

experimental changes, however, are needed to test this hypothesis. More on

this subject can be found in chapter 12, on neuroendocrine and autonomic

correlates of personalities.

Developmental aspects of personality

plasticity

Although it has been shown that the genetic and physiological structure of

personality is relatively rigid (Koolhaas et al. 1999; Van Oers et al. 2005a),

personality nevertheless has substantial phenotypic plasticity and can be

affected by environmental factors, speciﬁ cally when they act during early

development (Carere et al. 2005b; Arnold et al. 2007; Krause et al. 2009;

Stamps and Groothuis 2010a; 2010b; Naguib et al. 2011). Such environmen-

tal factors include changes in the context in which a trait is expressed, for

example, and the social factors that will change the adaptive value of a cer-

tain behavioral response (e.g., Schuett and Dall 2009). More subtle factors

include maternal effects acting during embryonic development, such as the

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Kees van Oers and Marc Naguib | 77

amount of hormones transferred to the egg by the female (Schwabl 1993; Gil

2008; chapter 11), circulating hormones that inﬂ uence habituation and sen-

sitization to stressful events, and learning how to cope with certain stressors

(Kant et al. 1985; Stam et al. 2000). Avian personalities are therefore open

to change, though within certain boundaries, and traits such as shyness or

boldness are therefore highly consistent within an individual. Individu-

als that are classiﬁ ed as being one or the other personality type, however,

may still ﬂ uctuate in their behavior (Carere et al. 2005a), and repeatability

of behavioral traits is typically moderate (Bell et al. 2009). Phenotypic cor-

relations between personality traits may be strong in some environments

but weak in others. For example, in great tits, both males and females of

genetic lines selected for fast exploratory behavior return more quickly to

the feeding table after a startle (risk-taking behavior). Lines selected for

risk-taking behavior also differ in their exploratory tendency, such that a

positive genetic correlation of 0.84 exists between the two traits (Van Oers

et al. 2004a). In a follow-up study investigating the context generality of

this correlation, fast- or slow-exploring great tits were tested for their risk-

taking behavior in a nonsocial context followed by a social context (Van

Oers et al. 2005b). Van Oers and coworkers found that the relation between

exploratory behavior and risk-taking behavior depended on the social con-

text. Females in general returned later in the social test, while the reaction

of males to the presence of a companion was dependent on their behavioral

type. Slow males came back sooner with faster companions and fast males

did not react to the companion (Van Oers et al. 2005b). Similar results were

found in a study on zebra ﬁ nches (Schuett and Dall 2009): males and females

differed in how consistently they behaved across social and nonsocial con-

texts. Schuett and Dall (2009) also tested whether males and females dif-

fered in their inﬂ uence as companions, and found that individuals of both

sexes inﬂ uenced each other’s exploratory behavior in a similar way within

the social context: the more exploratory the companion, the more explor-

atory the focal individual. In great tits, birds of different personality type

differ in their foraging strategy (Marchetti and Drent 2000). Moreover, the

presence and strategy of a conspeciﬁ c can affect the foraging strategies of

individuals differently, depending on their personality. As a result, birds of

different exploration types differ in their tendency to copy a tutor’s forag-

ing decision (Marchetti and Drent 2000; see below).

maternal hormones

Since birds lay eggs, embryos are separated from the mother before they

start to develop. Females are, however, able to inﬂ uence embryonic devel-

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78 | Avian Personality

opment by transferring nutrients and hormones to the yolk and albumen of

their eggs (Gil 2008). Although it is not completely clear how females can

actively vary the amounts of nutrients and hormones, these substances can

exert short- and long-term effects on the offspring (Schwabl 1993; Eising

et al. 2001; Groothuis et al. 2005; Eising et al. 2006; chapter 11). It is pos-

sible that maternal hormones in the egg may inﬂ uence personality varia-

tion by modulating genetic differences or physiologically programming

the offspring in certain ways. These maternal effects, however, may have a

genetic basis, as individual differences in the deposition of maternal hor-

mones in eggs have been shown to be, in part, genetically determined. Ge-

netic variation in yolk hormones has been found in lines of domesticated

species (Daisley et al. 2005; Gil and Faure 2007). In lines selected for fast and

slow exploratory behavior in great tits, Groothuis et al. (2008) found that

females of the slow line deposited lower amounts of testosterone in the yolk

of their eggs compared with females from the fast line. This was especially

true for the eggs laid early in the laying sequence (see chapter 11). This could

indicate that females of different personality types have different strategies

in rearing offspring. In this view, fast females would aim at rearing all off-

spring, whereas slow females invest less in those offspring that have lower

chance of surviving (Tobler and Sandell 2007). Not only can maternal hor-

mones inﬂ uence behavioral differences, they can also affect the persistence

of certain behaviors. In an experiment, the behavior of birds that came from

testosterone-injected (T-treated) and control eggs were compared for their

behavior toward a novel food source (Tobler and Sandell 2007). Birds from

T-treated eggs did not differ in their latencies to approach and eat novel

food during their ﬁ rst encounter. However, testosterone treatment affected

subsequent encounters with the novel food source. Owing to habituation,

latencies decreased in both groups over a period of 5 days, but considerably

more so in T-offspring (Tobler and Sandell 2007). Whether this is different

for offspring hatched from eggs at the beginning or end of the laying se-

quence is still unknown.

early development

Environmental factors acting during ontogeny have been shown to signiﬁ -

cantly affect a whole range of morphological (Tinbergen and Boerlijst 1990),

physiological (Kitaysky et al. 2001; Naguib et al. 2004; Verhulst et al. 2006),

behavioral (DeKogel and Prijs 1996; Nowicki et al. 1998; Naguib and Nemitz

2007; Krause et al. 2009), and life history traits (DeKogel 1997; Naguib et al.

2006) and therefore may also play a role in personality development. It is

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Kees van Oers and Marc Naguib | 79

well established that conditions experienced during early development are

important in shaping the behavior of an animal against the background of

the reaction norm (Mason 1979; Metcalfe and Monaghan 2001). Such factors

can involve a wide range of stressors, such as low-quality food (Krause et al.

2009), brood size (Neuenschwander et al. 2003), and parasites ( Tschirren and

Richner 2006). Yet, relatively little is known about how conditions experi-

enced during early development affect personality (Stamps and Groothuis

2010a; 2010b). One trait, used as a proxy for personality, boldness in response

to novel objects, has been studied by Fox and Millam (2004), who investi-

gated the effects of rearing condition on the reaction to novel objects in

orange-winged Amazon parrots (Amazona amazonica). Hand-reared, parent-

reared, and parent-reared/human-handled birds, which were handled ﬁ ve

times a week for 20 minutes, were tested for their latency to feed in the pres-

ence of ﬁ ve different novel objects between 4.5 and 6 months after hatching.

At an age of 12 months the response to a novel object in their home cage

was measured. They found that handling birds did not inﬂ uence the reac-

tion to novelty, but whether an individual was reared by their own parents

or hand-reared did. They concluded that the development of neophobia in

orange-winged Amazon parrots may be related to novelty the chicks experi-

ence during early life (Fox and Millam 2004). Moreover, we recently showed

in great tits that personality is affected by the sex ratio in the nest. Birds that

grew up in female-biased nests became faster explorers than birds that grew

up in male-biased nests. These ﬁ ndings that early social interactions shape

personality in animals but future research is required to unravel the precise

behavioral mechanism leading to this effect.

Another important inﬂ uence on behavior during early development is

the quantity, quality, or composition of food (e.g., see Birkhead et al. 1999).

Variation in food characteristics can be caused by parental choice, sibling

competition, or habitat quality but also by differences in the parents’ ability

to search and ﬁ nd suitable food. Experiments on birds investigating the in-

ﬂ uence of food during ontogeny can be conducted relatively easily in altri-

cial species compared with precocial species. Carere et al. (2005b), for exam-

ple, manipulated the early rearing condition in two great tit lines selected

for fast and slow exploratory behavior by a food rationing protocol. Birds

from both fast and slow exploration lines, but also control chicks, decreased

their growth rate and increased their begging behavior compared with

unmanipulated chicks within the same nests. This resulted in slow chicks

becoming much faster than their parents, but without any changes in ag-

gressiveness. In contrast, fast chicks had exploration scores similar to their

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80 | Avian Personality

parents but an increased level of aggressiveness. As a consequence, there

was no apparent line difference in exploration behavior at independence.

The effect, however, turned out to be partly temporary: although the off-

spring of the slow line were still relatively fast six months later, birds of the

fast line became even faster, restoring the line differences again. A side ef-

fect of the treatment on the experimental birds was that control chicks also

begged more. To rule out these effects of sibling competition, the authors

conducted a second experiment with experimental and control siblings in

separate nests. Here, only the food-rationed chicks became faster in explo-

ration, indicating that the shift in the controls in the within-nests design

was indeed due to enhanced sibling competition. Krause et al. (2009) also

showed that the feeding conditions experienced during early development

affect exploration behavior in zebra ﬁ nches. They showed that female zebra

ﬁ nches raised as nestlings under low-quality food conditions were more ex-

plorative in a novel environment than females that had been raised under

high-quality food conditions. The same individuals were also more sensi-

tive to short periods of food deprivation by losing more weight than those

raised under high-quality food, underlining the link between behavioral

differences in personality with physiological differences in responses to a

stressor.

Aside from the amount of food, its quality may also be very important

for the development of behavioral consistency. Essential amino-acids are

known to be limiting factors during development (Murphy and Pearcy

1993) and are also relatively scarce in the bulk food of many passerines

(Izhaki 1998; Ramsay and Houston 2003). Several tit species therefore sup-

ply their nestlings with a high proportion of spiders early during develop-

ment (Ramsay and Houston 2003). Spiders contain a relatively high amount

of taurine. To investigate whether taurine has a developmental effect on

personality variation in blue tits (Cyanistes caeruleus), Arnold and coworkers

(2007) conducted a feeding experiment in which they supplemented tau-

rine to blue tit nestlings during the period of maximum growth. Juveniles

that had received additional taurine as nestlings were signiﬁ cantly bolder

when investigating novel objects, and also were more successful at a spatial

learning task than controls. They concluded that prey selection is a mecha-

nism by which parents can alter the behavioral phenotype of their offspring.

Further experiments in natural settings should be conducted to see whether

parents indeed use this mechanism to prepare their offspring for the future.

Taken together, these ﬁ ndings suggest that personality traits may well be

shaped by the conditions experienced during early development, a topic

that is worth exploring more in the future.

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Kees van Oers and Marc Naguib | 81

cognition and learning

A question arises as to the extent to which individuals differing in person-

ality also differ in learning abilities or learning strategies. Individuals that

differ in environmental exploration are likely to also differ in the way they

acquire, process, recall, and use environmental information (Guillette et al.

2010; Cole and Quinn 2012; Amy et al. 2012; Titulaer et al. 2012). Animals have

to learn to ﬁ nd food, possibly from successful conspeciﬁ cs, and to remember

food locations. Marchetti and Drent (2000) found that, in great tits, slow

and fast explorers differ in their routines to revisit known feeding sites and

in using information they obtain by observing conspeciﬁ cs when foraging.

Birds were ﬁ rst trained to ﬁ nd food at a speciﬁ ed feeder, which during the

experiment was then left without food. When tested alone, fast explorers

kept on visiting the now unrewarded feeder they had previously learned to

visit. Slow explorers, in contrast, were quicker in ﬁ nding new food locations

and did not revisit the previously rewarded feeder as often. In other words,

fast birds were less ﬂ exible in ﬁ nding food locations and expressed more be-

havioral routines than did slow explorers. Interestingly, when subjects had

the opportunity to observe a tutor bird to explore a speciﬁ c food source

(colored feeder), then slow and fast explorers behaved in opposite ways. Fast

explorers were faster in copying the tutor’s behavior (and in feeding from

the feeder indicated by the tutor) whereas slow explorers did not learn to

explore the rewarded feeder from the tutor. In other words, slow explorers

were better in ﬁ nding new food sources on their own, whereas fast explor-

ers did better in exploring new food sources when given the opportunity to

learn from others. Such differences in foraging strategies may explain in part

why slow and fast explorers perform differently under natural conditions

depending on food availability. Alternatively, this could be mediated by dif-

ferential susceptibility to stress, where differential stress levels may alter the

way information is processed. In a recent experiment, Titulaer et al. (2012)

further showed that personality affected learning only in difﬁ cult tasks, but

in a sex-speciﬁ c way. Such effects presumably are related to selection act-

ing differently on the sexes with respect to behavioral strategies in terms of

space use, foraging, and social behavior. Such relations between cognition

and personality have also been addressed in a number of other recent stud-

ies (Guillette et al. 2010; Cole and Quinn 2012; Amy et al. 2012).

Animal husbandry and welfare

Obviously, research on personality is not restricted to natural contexts. Per-

sonality has been a key issue in studies on animal welfare and husbandry (We-

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82 | Avian Personality

melsfelder et al. 2000; Bolhuis et al. 2005; Würbel 2009; see chapter 14) and is

of emerging relevance in the development of nature conservation programs

that deal, for instance, with habitat defragmentation and reintroduction

of animals to new areas (see chapter 13). Although researchers with more

applied interests have often studied behavioral consistency, their concepts

and terminology are often different from those used by behavioral ecolo-

gists. Studies investigating personality in quail and chicken, for example,

often use the terms fear and fearfulness (Boissy 1995), where fearfulness is

measured as the emergence into a larger compartment, the reaction to novel

food or objects, or the response to a predator (Miller et al. 2005; 2006).

One of the central problems in applied bird ethology is feather pecking, a

common behavior in laying hens, with substantial economic and welfare im-

plications. Feather pecking has a genetic component but is also affected by

various social and housing factors (Van Krimpen et al. 2005; Van de Weerd

and Elson 2006; Rodenburg et al. 2008). Research has shown that individuals

are consistent in this behavior, reﬂ ecting a potential personality trait. Under-

standing the causes of feather pecking is thus of high applied signiﬁ cance as

it will contribute to develop rearing strategies and selection processes that

will reduce this problem. With the new regulations of housing laying hens

in larger groups, feather pecking needs to be monitored carefully, and iden-

tifying behavioral and genetic correlates of this behavior will help to ﬁ nd

optimal solutions that balance welfare and economic interests.

Personality differences also might be of great importance in reintroduc-

tion of individuals reared in captivity into wild populations or in transfer-

ring wild individuals to new locations. Before reintroduction, individuals

of many species, for example, have to learn to avoid predators. Training in-

dividuals in these capacities is therefore a crucial factor for increasing the

probability of postrelease survival (Box 1991). The ability to learn to avoid

certain dangers might, however, be dependent on the personality type of

an individual. That this can be the case is nicely shown in a study on greater

rheas (Rhea americana) (De Azevedo and Young 2006). Captive individuals

were tested for their response to several novel objects, before and after be-

ing trained to avoid predators. Birds were less bold after training compared

with before training, and the responses to the novel object before the train-

ing sessions were a good predictor of how the bird would react during train-

ing. Bolder birds behaved more calmly than shy birds. Similar results were

obtained studying the natural antipredator behavior of chafﬁ nches (Frin-

gilla coelebs): calm individuals were better able to assess the risk of a hawk

ﬂ ying over compared with very active individuals. They showed greater be-

havioral plasticity in high-risk versus low-risk situations, while hyperactive

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Kees van Oers and Marc Naguib | 83

individuals in general showed more ﬂ eeing behavior (Quinn and Cresswell

2005), possibly because of differences in the risk perception between the ac-

tivity types (Butlers et al. 2006). As dispersal, territorial, and foraging strate-

gies can be linked to personality (Dingemanse et al. 2003; Amy et al. 2010;

see below; chapter 7), including information about personality in decisions

made about when to release individuals may affect the success of a reintro-

duction project (Bremner-Harrison et al. 2004; Merton 2006).

Field studies and ﬁ tness correlates

The growing interest in research on animal personality in part has been

driven by the ecological and evolutionary signiﬁ cance of personality—

that is, that personality matters in the dynamics of wild populations. Even

though the origin and nature of individual variation in itself is interesting,

the ecological and evolutionary framework adds another reason for inter-

est, as it shows that personality affects selection while at the same time being

under selection itself. Ecologically relevant personality correlates include

nest defense behavior (Hollander et al. 2008), song (Garamszegi et al. 2008;

Amy et al. 2010; Naguib et al. 2010), social dominance (Dingemanse and De

Goede 2004), feeding behavior (Costantini et al. 2005), as well as dispersal

and mating behavior (Dingemanse et al. 2003; Van Oers et al. 2008).

Dingemanse et al. (2003) showed, for instance, that natal dispersal dis-

tance (i.e., the distance between place of origin and the place of breeding)

was linked to personality in great tits. In their study population of great tits

with known personalities (assessed under standard laboratory conditions

using a novel environment test), they found that the personality of the fa-

ther mattered. Offspring from males that were fast explorers in the novel

environment test dispersed farther from their original nest box than did

slow explorers. Furthermore, immigrants into the population had higher

exploration scores than resident birds. Such effects presumably resulted

from genetic differences and environmental effects acting during develop-

ment. Indeed, as personality has a considerable heritable component (Van

Oers et al. 2005a), personality-related differences in dispersal strategies may

affect the genetic variance of a population, depending on the extent to

which residents and immigrants succeed in breeding.

Dingemanse et al. (2004) found in great tits that personalities had differ-

ential ﬁ tness effects, that these effects were different for males and females,

and that they were reversed in different years depending on food availabil-

ity. Studying local survival across three years, they found that slow males

did better in the two years with limited food availability in winter than they

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84 | Avian Personality

did in the year with high winter food availability. Females over the same pe-

riod were affected in the opposite way. These results suggest that fast males,

being more aggressive and dominant over females (Krebs and Perrins 1978;

Drent 1987; Verbeek et al. 1996), do better in poor years than females, as the

limiting resource is the food over which they compete. In good years, the

higher winter survival results in higher competition among males for ter-

ritories so that slower and less aggressive males do relatively less well than

females. Indeed, Amy et al (2010) showed that territorial behavior is affected

by personality, with faster males being more aggressive at the site of intru-

sions while slower males follow a different strategy by singing more from the

distance and exploring more the boundaries of their territory. Dingemanse

et al. (2004) also found that in the poor year, pairs of individuals with simi-

lar personality produced more local recruits than pairs in which the male

and female had different personalities; these effects, however, may have

been caused by differential survival or differential dispersal (Dingemanse

et al. 2003). Along this line, Both et al. (2005) reported that pairs with simi-

lar personality have a higher reproductive success, measured as offspring

condition. These ﬁ ndings may explain the production of more recruits by

pairs with similar extreme personality, as shown by a different study for

the same population (Dingemanse et al. 2004), as ﬂ edgling condition has

been shown to predict survival (Tinbergen and Boerlijst 1990). While the

nature of one’s own and the partner’s personality appears to have ﬁ tness

consequences measured as offspring condition, recruits, and survival, per-

sonality also can also affect more immediate reproductive decisions. Mo-

nogamous animals are known to produce extra-pair offspring in addition

to the offspring produced with their social partner (Petrie and Kempenaers

1998; Grifﬁ th et al. 2002). Decisions about extra-pair matings most com-

monly have been linked to the expression of sexually selected traits of the

social mate and the extra-pair mate (Kempenaers et al. 1992; Hasselquist

et al. 1996). Apparently, decisions about extra-pair matings also depend on

within-pair personality differences in great tits, as pairs with more extreme

similar personality (slow-slow and fast-fast pairs) are more likely to raise

extra-pair offspring (Van Oers et al. 2008). In other words, females are more

likely to engage in extra-pair copulations when their social mate is similar

in personality compared with her own personality. Such disassortative deci-

sion making in reproduction may ensure high offspring variability and also

contributes to maintaining high variation in personality within a popula-

tion, in a similar way as has been argued for links between mate preferences

for partners with different immune characteristics (Wedekind et al. 1995;

Milinski 2006).

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Kees van Oers and Marc Naguib | 85

Conclusions

Birds are excellent model organisms for studying the causes and conse-

quences of personality in descriptive and experimental ways in the ﬁ eld

and in the laboratory. Integrating information obtained from studies un-

der controlled experimental lab conditions with experimental studies in

the ﬁ eld and analyses of ﬁ tness-relevant traits under natural conditions has

generated multifaceted insights into principles of personality. So far, much

of the ﬁ eld research addressing evolutionary and ecological questions has

been conducted on great tits, which remain the species in which the study

of causation and consequences of personality under natural conditions has

been best integrated. With research on personality now gradually expand-

ing to other avian species, the opportunity to obtain comparative data sets

allowing us to link basic species differences in life history to our current un-

derstanding on personality is becoming available.

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CHANGES IN TISSUE TROPISM OF MYCOPLASMA GALLISEPTICUM FOLLOWING HOST JUMP

Article

Oct 2022
J WILDLIFE DIS

Mycoplasma gallisepticum, a pathogen of worldwide economic importance in poultry, is recovered in chickens, especially from the respiratory tract. Some strains, however, are specialized to other tissues and because it jumps from poultry to wild birds, the new strains also cause severe conjunctivitis in new hosts. Nevertheless, most studies of M. gallisepticum in wild birds use choanal swabs or combine choanal and conjunctival swabs to quantify bacterial load. Because the clinical signs associated with M. gallisepticum infection differ markedly between poultry and House Finches (Haemorhous mexicanus), we compared the bacterial load in choanal and conjunctival samples following experimental inoculation of House Finches with M. gallisepticum isolates originating from poultry or from House Finches. This allowed us to test two hypotheses: M. gallisepticum changed tissue tropism, or M. gallisepticum simply expanded its within-host niche. By comparing bacterial loads from choanal and conjunctival swabs in birds inoculated with one of a suite of M. gallisepticum isolates, we found support for hypothesis 2. The choanal loads in House Finches did not differ between isolates, while the conjunctival loads of birds inoculated with poultry isolates were lower than in birds inoculated with House Finch isolates. When measuring the bacterial load of M. gallisepticum in birds, it is important to sample and analyze separately choanal and conjunctival swabs, as quantifying bacterial loads in pooled samples may not provide reliable information on differences in virulence.

Coping with novelty across an urban mosaic: Provisioning latency increases closer to roads and is associated with species-specific reproductive success in two urban adapters

Article

Full-text available

Jul 2022
SCI TOTAL ENVIRON

Most research on urban avian ecology has focused on population- and community-level phenomena, whereas fewer studies have examined how urbanization affects individual behavioral responses to a sudden and novel stimulus, and how those translate to fitness. We measured between-individual variation in provisioning latency in two urban adapters - great tits and blue tits - in response to an infrared camera installed in the nestbox, encountered when offspring in the nest were at the peak of food demand (9–10-days old). For each nestbox, we quantified urbanization as intensity in human activity, distance to road and proportion of impervious surface area. In both species, provisioning latency increased significantly closer to roads. Moreover, increased provisioning latency when exposed to a novel object was associated with higher reproductive success in great tits whose nestboxes were surrounded by high amounts of impervious surface. In contrast, increased provisioning latency was consistently associated with lower reproductive success in blue tits. Our results suggest that provisioning latency changes in relation to the environment surrounding the nest, and may be context- and species-specific when exposed to a novel stimulus, such as a novel object in the nest. To better understand the role of initial behavioral responses towards novelty across an individual's lifetime and, ultimately, its impact on fitness in the urban mosaic, further research explicitly testing different behavioral responses across the entire breeding cycle in wild model systems is needed.

Personality assessment of headstart Texas horned lizards (Phrynosoma cornutum) in human care prior to release

Article

Full-text available

Jul 2022
APPL ANIM BEHAV SCI

The study of animal personality is a growing field that has applications for welfare of animals living in captive settings. We measured personality traits (activity, exploration, and neophobia) in Texas horned lizards (Phrynosoma cornutum) living in human care before they were released to their natal habitat as part of a headstart program. We found evidence of consistent inter-individual differences in activity and exploration, but not neophobia. We also identified a positive correlation between activity and exploration, such that more active lizards were also more likely to explore a novel environment. These results suggest that Texas horned lizards have individual differences in response to their environment, which can inform husbandry decisions. Extensions of this work could also have implications for conservation of Texas horned lizards and for headstart programs focused on reptiles.

Coping with Novelty Across an Urban Mosaic:Provisioning Latency Increases Closer to Roads and is Associated with Species-Specific Reproductive Success in Two Urban Adapters

Article

Jan 2022

Science of The Total Environment Volume 847, 15 November 2022, 157450 Coping with novelty across an urban mosaic: Provisioning latency increases closer to roads and is associated with species-specific reproductive success in two urban adapters Author links open overlay panelMichelaCorsiniabMartaSzulkina https://doi.org/10.1016/j.scitotenv.2022.157450 Get rights and content Under a Creative Commons licenseOpen access Highlights • Two urban birds occupying similar habitat niches responded differently to a novel object. • Provisioning latency was longer when installing a new object in nests close to roads. • Provisioning latency at each nest is not associated with humans or impervious areas. • Provisioning latency towards a novel object reflects species-specific reproductive strategies. Abstract Most research on urban avian ecology has focused on population- and community-level phenomena, whereas fewer studies have examined how urbanization affects individual behavioral responses to a sudden and novel stimulus, and how those translate to fitness. We measured between-individual variation in provisioning latency in two urban adapters - great tits and blue tits - in response to an infrared camera installed in the nestbox, encountered when offspring in the nest were at the peak of food demand (9–10-days old). For each nestbox, we quantified urbanization as intensity in human activity, distance to road and proportion of impervious surface area. In both species, provisioning latency increased closer to roads. Moreover, increased provisioning latency when exposed to a novel object was associated with higher reproductive success in great tits whose nestboxes were surrounded by high amounts of impervious surface. In contrast, increased provisioning latency was consistently associated with lower reproductive success in blue tits. Our results suggest that provisioning latency changes in relation to the environment surrounding the nest, and may be context- and species-specific when exposed to a novel stimulus, such as a novel object in the nest. To better understand the role of initial behavioral responses towards novelty across an individual's lifetime and, ultimately, its impact on fitness in the urban mosaic, further research explicitly testing different behavioral responses across the entire breeding cycle in wild model systems is needed.

Experimental Planning and Experimental Design

Chapter

Dec 2023

The various considerations that must be taken into account before embarking on an animal behaviour study differ depending on whether the study is descriptive or experimental. In descriptive or correlative studies, the naturally occurring behaviour of animals is observed without influence from the researcher. In an experimental study, an experimenter tests animals under controlled conditions, typically in an environment in which the animals are exposed to specific stimuli, tasks, or conditions.

General Principles

Chapter

Dec 2023

Observing the behaviour of animals so often leads to the questions: “What?”, “How?”, “Why?”, “When?”, “Who?” and “Where?”. Through formulating such questions in a scientific manner, we generate hypotheses and predictions about their possible answers. Clear hypotheses, and the steps of scientific methodology based on them, are a basic foundation of scientific work.

Female great tits ( Parus major ) reproduce earlier when paired with a male they prefer

Article

May 2023

Mate choice is a key component of reproductive biology. Females often prefer certain males but do females modulate their reproductive investment depending on whether they are mated with their preferred partner? We investigated this question in great tits ( Parus major ) where we subjected 36 females to a six‐choice mate preference test. Male morphological traits and the female's own characteristics did not influence the preference females expressed. We however found that females spent more time near more exploratory males. We then paired females with one of the males in indoor aviaries, and subsequently monitored their reproductive investment (through measurement of plasma 17β‐oestradiol concentrations, first egg date, clutch size and egg size). Females that were mated with a male for which they had a strong preference laid their first clutch significantly earlier in the season than females paired with a male they less preferred. Our results show that mate preference influences reproductive investment in great tits, thereby linking mate choice to bird reproductive decisions.

Kluiver et al. - 2022 - Personality as a Predictor of Time-Activity Budget

Article

Full-text available

Jun 2022

Time-activity budget, i.e., how a population or an individual divides their day into various behaviours and activities, is an important ecological aspect. Existing research primarily focused on group-level time-activity budgets, while individual variations have only been reported recently. However, little is known about how consistent inter-individual differences or personalities influence time-activity budgets. We examined the personalities of lion-tailed macaques (Macaca silenus) and investigated their influence on individual time-activity budgets. The resulting personality traits, namely persistence, sociability, affiliation, and anxiety, were used to predict the three broad categories of the time-activity budget—food-related, active, and resting behaviours. We found that persistence and sociability positively predicted the time spent being active. Food-related behaviours were positively predicted by persistence, while anxiety was found to influence them negatively. The time spent resting was negatively predicted by persistence. We did not find an effect of affiliation on the time-activity budgets. We discuss these findings in light of the ecology of lion-tailed macaques. Our study highlights the importance of a novel approach that uses animal personality traits as predictors of individual time-activity budgets and offers insights regarding the use of personality assessments in conservation and welfare activities.

Inter-individual differences in laboratory rats as revealed by three behavioural tasks

Article

Full-text available

Jun 2022

Stable inter-individual differences in behaviour and personality have been studied for several decades now. The aim of this study was to test the repeatability of behaviour of the Long Evans strain of laboratory rats in order to assess their inter-individual differences. Male laboratory rats (n = 36) were tested in a series of tasks (Open field test, Elevated plus maze test, and modified T-maze test) repeated over time to assess their personality traits. To evaluate the temporal stability of the behaviour, we calculated repeatability estimates of the examined traits. We also checked for a link in behavioural traits across these experiments, which would suggest the existence of a behavioural syndrome. We found stable inter-individual differences in behaviour. Interestingly, no link emerged between the tasks we studied and therefore we did not find support for a behavioural syndrome. The lack of behavioural correlations between these experiments suggests that the results derived from these tasks should be interpreted carefully, as these experiments may measure various behavioural axes. Moreover, the animals habituate to the apparatus. Consequently, behaviour in the Open field test and Elevated plus maze test is not fully consistent and repeatable across subsequent trials.

Prior territorial responses and home range size predict territory defense in radio-tagged great tits

Article

Full-text available

Mar 2022
BEHAV ECOL SOCIOBIOL

Territorial animals often use signals to advertise territorial occupancy within their larger home ranges. Songbirds are among the best-studied territorial signaling taxa, and when competitors start singing during a territorial intrusion, residents usually show elevated spatial and vocal responses. These responses could be used by intruders and distant eavesdroppers to predict future responses or to compare responses across competitors. Yet, the extent to which responses of a resident to a territorial intrusion predict its future responses and its overall spatial behavior (home range) within a neighborhood is less well understood. We used wild great tits ( Parus major ) as a model species in repeated song playback trials, simulating territorial intrusions combined with radio-tracking before and during playback trials. The time spent close to the loudspeaker in response to an initial simulated intrusion predicted the same response variable during a second simulated intrusion on the next day, whereas singing activity during the first simulated intrusion did not predict singing during the second simulated intrusion. We also show that more explorative males (as determined by a novel environment test) and males with smaller home ranges sang more and spent more time near the loudspeaker in response to both simulated intrusions. Thus, by probing residents, intruders can obtain reliable information about subsequent response probabilities, while eavesdroppers from a distance, who can use auditory information only, would not receive sufficient predictive information. Our findings also suggest that males with larger home ranges are more tolerant toward intruders, which could reflect a trade-off between tendencies to respond strongly and to range widely. The lack of predictability of singing activity with regard to responses to future intrusions might explain why territorial animals continuously exchange vocal signals and regularly foray into neighboring territories, as a way to obtain regular information updates. Significance Statement Animals use experience from interactions with conspecifics in their future decision making, such as mate choice and strategies for conflict resolution. The value of such information depends in part on the predictability of the future behavior of that conspecific. In songbirds, territorial individuals respond to intruders by approach and signaling. Here, we tested in radio-tagged great tits ( Parus major ) if territorial responses are predictable and are affected by individual and environmental factors. We show that the time spent near the simulated intruder was more predictable than singing activity and that birds with larger home ranges showed weaker responses. These findings suggest that information based on such spatial responses is more useful for future decision making, as compared to vocal information, and that distant eavesdroppers will thus receive less reliable information. Limited predictability may explain why territorial animals continuously exchange vocal signals and foray into neighboring territories, providing opportunities for regular information updates.

The expression of the emotions in man and animals

Article

Jan 1993

C. Darwin

Individual variation of the acute adrenocortical response to stress in the white-throated sparrow

Article

Jan 1996

Hubert G Schwabl

Nature's music: The science of birdsong

Book

Oct 2004

The voices of birds have always been a source of fascination. Nature's Music brings together some of the world's experts on birdsong, to review the advances that have taken place in our understanding of how and why birds sing, what their songs and calls mean, and how they have evolved. All contributors have strived to speak, not only to fellow experts, but also to the general reader. The result is a book of readable science, richly illustrated with recordings and pictures of the sounds of birds. Bird song is much more than just one behaviour of a single, particular group of organisms. It is a model for the study of a wide variety of animal behaviour systems, ecological, evolutionary and neurobiological. Bird song sits at the intersection of breeding, social and cognitive behaviour and ecology. As such interest in this book will extend far beyond the purely ornithological - to behavioural ecologists psychologists and neurobiologists of all kinds.

The Kakapo: some highlights and lessons from five decades of applied conservation

Article

Aug 2006

D. Merton

Corticosterone stress responses and avian personalities

Article

Aug 2006

John Cockrem

The importance of nestboxes for territory settlement, survival and density of the great tit

Article

Jan 1987

P.J. Drent

Territory settlement by juvenile male Parus major in September, the crucial period for territory density in years with a seed food supply in winter, appeared to be independent of the presence of nestboxes. Density of newly settled territories was determined by the density of adult territory owners and juvenile nonterritorial males. Occupation of vacant areas during winter and spring depended on the presence of nonterritorial birds. Marked shifts in the position of the area were only observed in males with territories in subareas without nestboxes and were directed towards areas with an excess of nestboxes. Earlier experiences with these boxes for breeding and roosting seemed to be important. Most territory owners in areas without boxes roosted from October onward outside cavities in their territories. While in areas with nestboxes all territorial pairs used them for breeding, most of the territorial pairs from areas without nestboxes made breeding attempts in nestboxes outside territories and outside the area. Local survival rate of territory owners was markedly lower in areas without nestboxes, due to emigration in summer and winter and to mortality in winter caused by predation, competition for nestboxes and unfavourable weather conditions. -from Author

Ontogeny of Social Behavior

Chapter

Jan 1979

William Mason

Social ontogeny is the process of becoming social. If all organisms sprang into the world Minerva-like, complete and fully equipped with adult forms and functions, social ontogeny as a discipline could not exist. If all organisms moved from conception to maturity as though every detail in their individual careers was determined from the outset by the inexorable unfolding of some grand primordial plan, it would exist as a legitimate field of inquiry, but one that held little interest for the behavioral scientist. All is not ordained, however. What makes the study of social ontogeny an absorbing and challenging field for behavioral research is the presence of ordered variability in process and outcome. Becoming social is a matter of individual history—part of the unending dialogue between the organism and its environment that is characteristic of all life processes. More than that, it is the development of competences and skills, of deficiences and aberrations, the realization of potentials whose nature can be discerned only after the fact.

Training for life after release: Simian primates as examples

Article

Jul 1991

Hilary O BOX

Using simian primates as an example, the paper outlines the variety of skills required to adjust adequately to a natural environment after release from captive conditions. Specific examples are given from wild-born individuals which have been rehabilitated by release programmes after periods in captivity. Examples are also taken from programmes of environmental enrichment in captivity which encourage natural behaviour in various species of primates that have been bred in captivity, and thus maximize the chances that their subsequent re-introduction into the wild will succeed. In addition, a number of issues are raised with reference to differences among species in their behavioural and physiological responsiveness to changes in their environments. It is argued that these issues are an important source of hypotheses in the development of training programmes for species with different predispositions, as in their social organization.

Long-term effects of brood size manipulation on morphological development and sex-specific mortality of offspring

Article

Mar 1997

CH DeKogel

1. Little is known about long-term effects of brood size on fitness components of offspring. This is unfortunate because such information is needed to predict optimal brood size. Furthermore, ontogenetic circumstances are potentially important in explaining the large individual differences in lifetime reproductive success documented in many species. 2. In a laboratory study the long-term effect of brood size manipulation on mortality and morphological development of offspring was investigated. Young zebra finches Taeniopygia guttata were reared in small or large broods. Young were exchanged in such a way that natural siblings from different rearing conditions could be compared. 3. Manipulated brood size affected offspring morphology permanently (measurements were taken up to the age of 12 months). Individuals reared in small broods were heavier, had longer tarsi and wings, higher beaks, were in better condition, and males had redder beaks. The experiment did not affect beak length or female beak redness. Individuals from large broods had caught up on wing length and males from large broods on beak redness by 6 months of age, which may reflect priority of investment in traits important to fitness. 4. Mortality of offspring raised in large broods was higher both before and after independence. After independence the effect of manipulated brood size on mortality was sex specific; females were most likely to die. This suggests that the optimal sex ratio of offspring may depend on brood size. 5. The effect of brood size on mortality after independence was probably partly mediated by size and condition during the nestling phase and possibly by peer aggression among adult offspring. Sex-linked mortality could not be explained by a sex difference in morphological development. Why females are more vulnerable remains to be discovered.

Birds As Individuals

Article

Jan 1953

Avian Personality

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