Personality traits in the blue tit

In order to adapt their behaviour optimally and to be able to increase fitness, individuals are assumed to respond flexibly to environmental variation they encounter. Contrasting with this classical behavioural ecological point of view is the concept of animal personality. The latter focuses on understanding the mechanisms underlying and evolutionary processes maintaining variation in the expression of a behavioural trait over time and across situations or contexts. Originating in human psychology, personality studies have recently been integrated into the fields of ecology and evolution. Studies on consistent variation in behaviour within and between individuals (personality) have resulted in numerous insights and these are still expanding. In the first chapter of this thesis I research underlying factors and possible consequences of the response (delayed hatching) of blue tits (Cyanistes caeruleus) to encountered climatic variation. I find that hatching delay (i.e. number of days hatching was delayed) is associated with early laying dates and low mean temperatures during the egg-laying phase. In addition hatching delay is negatively associated with clutch hatchability and female body condition. Using a reciprocal cross-fostering protocol on a large number of broods, I find that hatching delay may also negatively affect developmental parameters in offspring, in particular body mass of nestlings at fledging. Results from this study demonstrate that environmental conditions during egg laying can have effects lasting throughout the breeding and nestling period. In chapters II to V I investigate variation in behaviour among individuals. The focus in these four chapters is on personality traits in blue tits. I first design an experimental setup, using a bird cage, in which several behavioural traits can be measured in a quick and non-invasive manner and which can be applied in both winter and breeding season. In addition several behavioural traits are measured during handling of both adult and nestling birds. All these behavioural measures are then used to test several aspects of behaviour in a personality context in the blue tit. The behavioural traits derived from the bird cage are repeatable over time and qualify as personality traits in this species. In addition I find an association between one of the measured personality traits in the cage and a single nucleotide polymorphism in the 3rd exon of the dopamine receptor (D4) gene (DRD4), similar to what has been found in recent research on great tits (Parus major). This suggests that there is a genetic basis underlying this personality trait and that this genomic region might be involved in animal personality. I apply a reaction norm framework to assess context specificity of the traits measured in the bird cage, using measures from (partly) the same birds measured in two distinct contexts (winter and breeding season). I show that one needs to carefully consider the context under which individuals are assayed and that a recorded behaviour may or may not be repeatable in another context. Furthermore I use data from a cross-foster protocol on nestling blue tits in combination with quantitative genetics. I assess the heritability of three behavioural traits and show that these traits form a behavioural syndrome at both the phenotypic and genetic level. In addition, from the applied animal model analysis I can conclude that environmental factors, encountered by nestlings during the rearing period, may have a considerable impact on a nestling s personality. Thus, taken into account findings from the first chapter in this thesis, the development of both physical and behavioural traits in an individual seems to find its origin already in the earliest phases of life. Finally I test whether three personality traits and two immunological traits in the blue tit covary and form a syndrome which includes behavioural and immunological traits. I find that there are intrinsic correlations between behavioural and immunological traits; however there is no strong evidence for the existence of a syndrome of these traits in the blue tit.Perinteisen käyttäytymisekologisen näkökulman mukaan käyttäytyäkseen optimaalisella tavalla ja parantaakseen kelpoisuuttaan yksilöiden oletetaan reagoivan elin ympäristönsä vaihteluihin joustavasti. Uusi tutkimusala, eläinten persoonallisuustutkimus, tarkastelee asia eri tavalla. Persoonallisuustutkimus tarkastelee mekanismeja ja evolutiivisia prosesseja, joiden seurauksena tutkituissa ominaisuuksissa esiintyy ajasta ja tilanteesta riippuen yksilöllistä vaihtelua. Ekologiaan ja evoluutiobiologiaan juurtuneen eläinten persoonallisuustutkimuksen perusta on psykologiantutkimusperinteessä. Eläinten persoonallisuustutkimus on tuottanut nopeasti uusia oivalluksia ja tutkimusala laajenee jatkuvasti. Väitöskirjan ensimmäisessä osassa tutkin säätekijöiden vaikutusta sinitiaisen (Cyanistes caeruleus) hautomiskäyttäytymisen alun myöhästymiseen. Hautominen myöhästyi jos pesye oli suuri ja jos muninnan aikana oli viileää. Hyväkuntoiset naaraat pystyivät aloittamaan haudonnan viiveettä. Kun poikasia siirrettiin pesyeestä toiseen, haudonnan viivästymisen havaittiin aiheuttavan poikasten kasvun ja kehityksen huononemista. Tutkimuksen tulokset osoittavat, että muninnan aikaisilla ympäristöolosuhteilla voi olla pesäpoikasajan yli ulottuvia vaikutuksia. Väitöskirjan muissa osatöissä (II V) tutkin käyttäytymisen vaihtelua yksilöiden välillä. Näiden neljän työn keskiössä ovat sinitiaisen persoonallisuuspiirteet. Ensimmäisessä osatyössä esittelen häkkikokeen, jota voidaan käyttää monien persoonallisuuspiirteiden nopeaan ja häiriötä tuottamattomaan tutkimiseen niin kesällä kuin talvella. Koe sopii pesivien aikuisten ja pesäpoikasten tutkimiseen. Häkkikokeessa havaittavat ominaisuudet ovat yksilöllisesti säilyviä eli toistuvia, eli niitä voidaan pitää sinitiaisen persoonallisuuspiirteinä. Kuten talitiaisellakin (Parus major), eräs tutkituista ominaisuuksista on yhteydessä dopamiinireseptorigeenin (DRD4) kolmannessa eksonissa esiintyvään yhden emäksen polymoprfismiin (SNP). Tuloksen perusteella voidaan olettaa, että persoonallisuuspiirre on perinnöllinen ja että kyseinen genomin alue on yhteydessä eläinten persoonallisuuteen. Sovellan rektionormin käsitettä tutkiessani osittain samojen yksilöiden käyttäytymistä kesällä ja talvella. Tulosten perustella voi osoittaa, että tutkimusajankohta vaikuttaa tuloksiin, ja että käyttäytymispiirteestä riippuen havainnot voivat olla toistettavissa tai ne voivat olla toistumatta. Siirtämällä poikasia pesästä toiseen ja käyttämällä kvantitatiivisen genetiikan menetelmiä arvioin käyttäytymispiirteiden periytyvyyttä. Osoitan, että käyttäytymispiirteet muodostavat ns. käyttäytymissyndrooman, joka on sekä fenotyyppinen että geneettinen ominaisuus. Siirrettyjen poikasten kehityksen perusteella voi osoittaa, että poikasten kasvuympäristöllä on suuri vaikutus pesäpoikasten persoonallisuuteen. Poikasen kasvuympäristö vaikuttaa siten sekä poikasen fyysiseen kehitykseen että sen persoonallisuuteen. Viimeisessä osatyössä tutkin, vaihtelevatko sinitiaisen kolme persoonallisuuspiirrettä ja kaksi immunologista ominaisuutta samansuuntaisesti. Tulokset eivät kuitenkaan tue ajatusta, että sinitiaisella olisi persoonallisuuspiirteistä ja immunologisista ominaisuuksista koostuva käytäytymissyndrooma

Prior experience of captivity affects behavioural responses to `novel' environments

Information ecology theory predicts that prior experience influences current behaviour, even if the information is acquired under a different context. However, when individuals are tested to quantify personality, cognition, or stress, we usually assume that the novelty of the test is consistent among individuals. Surprisingly, this ‘gambit of prior experience’ has rarely been explored. Therefore, here we make use of a wild population of great tits (Parus major) to test if prior experience of handling and captivity influences common measures of exploration (open field tests in two novel contexts: room and cage arenas), social response (simulated using a mirror), and behavioural stress (breathing rate). We found that birds with prior experience of captivity (caught previously for unrelated learning and foraging experiments) were more exploratory, but this depended on age: exploration and captivity experience (in terms of both absolute binary experience and the length of time spent in captivity) were associated more strongly in young (first-winter) birds than in adults. However, there was no association of prior experience of captivity with social response and breathing rate, and nor did the measures of exploration correlate. Together our results suggest that re-testing of individuals requires careful consideration, particularly for younger birds, and previous experiences can carry over and affect behaviours differently.Peer reviewe

Exploring the genetics of nestling personality traits in a wild passerine bird: testing the phenotypic gambit

When several personality traits covary, they form a behavioral syndrome. Understanding the evolutionary dynamics of a behavioral syndrome requires knowledge of its genetic underpinning. At present, our understanding of the genetic basis of behavioral syndromes is largely restricted to domestic and laboratory animals. Wild behavioral syndromes are mostly inferred on the basis of phenotypic correlations, and thus make the “phenotypic gambit” of assuming that these phenotypic correlations capture the underlying genetic correlations. On the basis of 3 years of reciprocal cross-fostering of 2896 nestlings of 271 families within a pedigreed population, we show that the nestling personality traits handling aggression, breathing rate, and docility are heritable (h2 = 16–29%), and often have a pronounced “nest-of-rearing” variance component (10–15%), but a relatively small “nest-of-origin” variance component (0–7%). The three nestling personality traits form a behavioral syndrome on the phenotypic and genetic level. Overall, the phenotypic correlations provide a satisfactory description of the genetic ones, but significantly underestimate the magnitude of one of the pairwise genetic correlations, which mirrors the conclusion based on domestic and laboratory studies.Peer reviewe

Experimental manipulation of Blue Tit nest height does not support the thermoregulation hypothesis

Birds show immense variation in nest sizes within species. At least six different hypotheses have been forwarded to explain intraspecific variation in nest size in cavity nesting species, but very few of those hypotheses have been tested experimentally. In our study, when nestlings were 2 days old, we manipulated the height of 182 Blue Tit (Cyanistes caeruleus) nests to either 5 cm or 11 cm while standardising their ectoparasite load and genetic and maternal background. In line with the hypothesis that larger nests provide thermoregulatory benefits, we expected experimentally enlarged nests to show increased growth of nestlings compared to shallow nests, or to improve female somatic condition. We found that the nest height manipulation affected the tail length of 16-day old nestlings, but did not affect any other morphometric measure (tarsus length, body mass, head size and wing length). In addition nest height manipulation had no impact on nestling survival and did not affect female body condition. Our results do not therefore provide strong support for the thermoregulatory hypothesis and suggest regional differences in the relationship between nest size and reproductive success.Peer reviewe

Integrating drone-borne thermal imaging with artificial intelligence to locate bird nests on agricultural land

In conservation, the use of unmanned aerial vehicles (drones) carrying various sensors and the use of deep learning are increasing, but they are typically used independently of each other. Untapping their large potential requires integrating these tools. We combine drone-borne thermal imaging with artificial intelligence to locate ground-nests of birds on agricultural land. We show, for the first time, that this semi-automated system can identify nests with a high performance. However, local weather, type of arable field and height of the drone can affect performance. The results’ implications are particularly relevant to conservation practitioners working across sectors, such as biodiversity conservation and food production in farmland. Under a rapidly changing world, studies like this can help uncover the potential of technology for conservation and embrace cross-sectoral transformations from the onset; for example, by integrating nest detection within the precision agriculture system that heavily relies on drone-borne sensors.Peer reviewe

Reed Warbler Hosts Do Not Fine-Tune Mobbing Defenses During the Breeding Season, Even When Cuckoos Are Rare

Hosts of brood parasitic cuckoos often employ mobbing attacks to defend their nests and, when mobbing is costly, hosts are predicted to adjust their mobbing to match parasitism risk. While evidence exists for fine-tuned plasticity, it remains unclear why mobbing does not track larger seasonal changes in parasitism risk. Here we test a possible explanation from parental investment theory: parents should defend their current brood more intensively as the opportunity to replace it declines (re-nesting potential), and therefore "counteract" any apparent seasonal decline to match parasitism risk. We take advantage of mobbing experiments conducted at two sites where reed warblers (Acrocephalus scirpaceus) experience (in Italy), or do not experience (in Finland), brood parasitism. We predicted that mobbing of cuckoos should be higher overall in Italy, but remain constant over the season as in other parasitised sites, whereas in Finland where cuckoos do not pose a local threat, we predicted that mobbing should be low at the beginning of the season but increase as re-nesting potential declined. However, while cuckoos were more likely to be mobbed in Italy, we found little evidence that mobbing changed over the season at either the parasitized or non-parasitized sites. This suggests that re-nesting potential has either little influence on mobbing behavior, or that its effects are obscured by other seasonal differences in ecology or experience of hosts.Peer reviewe

Pedigree_BT

Pedigree of the blue tit population (2003-2010

Supplementary textR2

R codes used for performing quantitative genetic analyses (with asreml-R), structural equation models (with lavaan) and simulation

Data from: Breeding phenological response to spring weather conditions in common Finnish birds: resident species respond stronger than migratory species

National bird-nest record schemes provide a valuable data source to study large-scale changes in basic breeding biology and effects of climate change on birds. Using nest-record scheme data from 26 common Finnish breeding bird species from whole Finland, we estimated the laydate of the first egg for 129 063 nesting attempts. We then investigated the relationship of mean spring temperature and spring precipitation sum to changes in the onset of laying over the period 1961–2012. In addition, we examine differences in response to these climatic variables for species grouped for different life history strategies; migration, diet and habitat. Finally, we test whether body size is related to the strength of phenological response. We show that 26 common Finnish breeding bird species have advanced their laying dates over time and to an increase in the mean spring temperature over the study period. When species are grouped according life history strategies, we find that breeding phenological change is negatively associated with changes in the mean spring temperature where residents respond strongest to changes in mean spring temperature, but also short- and long-distance migrants advance laydates with increasing spring temperatures. Breeding phenological change is also associated with spring precipitation, where resident species delay and short-distance migrants advance the onset of breeding. In addition we find that omnivorous species respond stronger than insectivorous species to changes in spring temperature. In contrast to results from an earlier study, we do not find evidence that small-sized species respond stronger to spring temperature than large-sized species. As climate warming is predicted to continue in the future, long-term citizen science schemes, such as the Finnish nest-card scheme, prove to be a valuable cost-effective way to monitor the environment and allow investigation into how species are responding to changes in their environment