Group and family living is an integral part of many animals’ ecology. Thus the behavior became associated with plenty of advantages as well as disadvantages. However, rarely has the actual concept of the group been investigated. Questions such as, “What constitutes a ‘group’?” and “Do the individuals within these ‘groups’ associate with each other frequently enough to actually enjoy the benefits of group living?” are seldom asked. With these questions in mind, the aim of this study was to use Siberian jay (Perisoreus infaustus) individuals in their territories to explore and shed more light on the issue of the extent of group living. A working definition of a ‘group’ was made and subsequently the birds were observed in their natural habitat in northern Sweden during several seasons. Consequently, a pair-wise coherence index (CI) was created to quantify the levels of association between the individuals within each territory in order to investigate which possible factors affect the extent of the observed cohesion. Results of the study indicate that pair-wise cohesion was strongly dependent on the kinship of the birds. Moreover, it was found that the alpha and kin birds had significantly higher coherence values than the non kin birds. Thus, within a territory, it was the alpha and the kin birds that formed the core of the group with the non kin birds being much less associated with the other individuals. This was in contrast to the hypothesis, which predicted alpha birds to form the core of the group solely, with kin birds having significantly lower coherence. Interestingly, no effect of habitat type and season was found on the cohesion of the territorial group. Moreover, further evidence of sub-grouping was found even on the kinship level, thus suggesting yet more complex interplay between group cohesion and the group members.  All in all, with the non kin birds having low coherence values, the study casts light on the fact that even if individuals are present in a territory, they might not necessarily be a tight unit and as such be unable to fully benefit from group living.

Competition among individuals over shared resources reveals asymmetries in quality resulting in the formation of dominance hierarchies. These hierarchies act as a mechanism for social selection by partitioning resources among group-living animals. The following chapters describe my dissertation research which investigates the factors contributing to competitive asymmetries among broodmates as well as the short- and long-term consequences of the early social environment for the cooperatively breeding red-cockaded woodpecker (Picoides borealis). My research revealed that fledgling red-cockaded woodpeckers form male-biased, linear dominance hierarchies. Among fledgling males,, high relative nestling condition strongly predicted fledgling dominance, and this condition–rank relationship persisted through independence. Male nestlings are slightly larger and heavier than females; however, the sexual size dimorphism in mass is only present in mixed-sex broods, suggesting that the subtle structural size advantage gives males a competitive advantage over their sisters. Conflict rates among siblings increased with decreasing targeted feeding rates, and dominant fledglings were able to secure more food from provisioning adults through scramble competition. First-year survival favored males over females and dominant males over subordinates. Females were more dispersive overall than males, and subordinate males were more likely to disperse than dominants. The social environment prior to fledging influenced male dispersal decisions and subordinates delayed dispersal in the spring in situations where all dominants died over the winter. The probability of delayed dispersal in females was higher for females raised without brood-mates in one of two populations included in a long-term demographic data analysis. The availability of breeding vacancies may explain the differences in female dispersal behavior according to social environment between these populations. This research contributes to a greater understanding of the relative contribution of intrinsic benefits versus extrinsic constraints as an influence on delayed dispersal decisions in red-cockaded woodpeckers. Inter- and intra-sexual social rank is correlated with individual access to natal food resources and the probability of first-year survival. The intrabrood variation in dispersal strategies driven by social rank is sufficient to regularly produce both dispersal strategies among males and provides additional support that delaying natal dispersal is the preferred strategy for males in this system. / Ph. D.

Group-living sets the scene for complex social behaviours such as cooperative breeding, and exploring the factors that shape group-living is crucial in understanding these behaviours. This thesis explores the ecology of a population of the facultative cooperative breeding southern anteater-chat (Myrmecocichla formicivora), a group-living bird species endemic to southern Africa. It reveals a breeding system based around a breeding pair and up to three auxiliary males. Despite equal numbers of males and females produced as fledglings there was a surplus of adult males, which remained philopatric. Dispersal was strongly female biased. Females dispersed within their first year, they dispersed further than males, and they lost the benefits of the natal site. The sex skew in the population suggested that these factors drive differential mortality, with juvenile females having much lower annual survival than juvenile males. Adult survival was higher, with female survival only slightly lower than male survival. Dispersal distances suggested that males selected the breeding location, nearer to their natal site. There was no evidence of surplus non-breeding females. On the loss of a breeding female there was no replacement until new females entered the population, yet if a breeding male disappeared the female promptly re-paired with a male from another group. There was no indication of birds floating in the population, and if males were orphaned or widowed they joined other groups as unrelated helpers in preference to floating. There was no sign of inter-group or individual aggression among chats, and unrelated helpers were peacefully accepted into groups, suggesting mutual benefits. In fact all birds in a group helped raise offspring of the breeding pair, and groups with more helpers fledged more offspring, which implies that both direct and indirect fitness benefits can be gained through joining a group and helping. There was surprisingly little inheritance of breeding position by auxiliaries, and strikingly low levels of extra-pair paternity. This study suggests that the Southern anteater-chat group structure arises through male philopatry due to a shortage of breeding females, the benefits of remaining on the natal site and helping, and the potentially high costs of living alone.

The dynamics of natural populations may be influenced by a variety of factors, ranging from feeding interference and territoriality to the risk of predation and climatic effects. The relative influence of these factors may be contingent upon the quality of the habitat in which individuals reside. A factor that can largely affect population dynamics and that often covaries with habitat structure is predation risk. However, the combined effect of habitat and predation risk can vary according to the social context and intrinsic characteristics that affect individual behavioural responses. This thesis investigates the effects of habitat quality at the level of the population and the individual, and examines how it relates to the above factors in Siberian jays (Perisoreus infaustus), a territorial, group-living species in which the main cause of mortality is predation. The results demonstrate a strong effect of habitat on survival, reproduction and behaviour. Mortality was generally higher in open areas and managed forests and reproductive success decreased after forest management. Breeding females were more sensitive to environmental factors than males, possibly because of higher reproductive costs. Estimates of spatial demography suggested that there were more sinks than sources, and that they were located in open, managed forests. Behavioural decisions confirmed that open forests were associated with higher predation risks. However, decisions depended on social context; immigrants took highest risks and were the recipients of most aggression, largely an effect of social subordination. Also, parents provide their offspring with benefits that are withheld from immigrants. As a result, first-year survival was higher in retained offspring. Investigating the effects of multi-scale habitat quality on individual behaviour and population dynamics has generated an increased understanding of the effects of forest management on the dynamics of this population. This approach should facilitate development of an effective conservation management policy for this species.

<p>This thesis examines risk management in breeding Siberian jays (<i>Perisoreus infaustus</i>), which is indigenous to the northern taiga. Parent behaviour and the nest are cryptic. A new nest is built each year. It is placed on spruce or pine branches close to the trunk and well insulated with lichens, feathers and reindeer hair.</p><p>Nest failure rate was the main factor driving annual variations in jay numbers. The probability for nesting attempts to be successful ranged annually between 0.08 and 0.70. Nest predation was rampant and a main cause of nest failure. Nest predators were mainly other corvids (primarily the Eurasian jay <i>Garrulus glandarius</i>). Habitat quality was the main factor determining the risk of predation. The risk for nest failure due to predation was higher in thinned forests with an open structure and with a high abundance of man-associated corvid species (jays, crows, raven). </p><p>Siberian jay parents show several strategic adjustments in life-history and behaviour to the risk of nest predation. Parents traded reduced feeding rates for a lower predation risk and allocated feeding to low risk situations. Chick provisioning imposes a cost by drawing the attention of visually hunting predators to the location of nests, and parents adjusted their daily routines and avoided exposure by allocating provisioning to times of low activity among nest predators. These strategic adjustments of feeding efforts were estimated to reduce the exposure to nest predators by 26 percent. Also, parents adjusted their reproductive efforts to the perceived presence of predators in a playback experiment. Siberian jays reduced their reproductive investment by laying a smaller clutch size when high risk of nest predation reduced the value of current reproduction, as predicted from life-history theory.</p>

<p>Evolution is fuelled by independent reproduction events. Yet, the offspring of at least three percent of all bird species postpone dispersal and forego independent reproduction. The Siberian jay, <i>Perisoreus infaustus, </i>is such a species where some<i> </i>offspring are philopatric and remain in their natal territory for up to three years, forming family groups. The main finding of this thesis is that nepotistic anti-predator behaviour displayed by parents provided philopatric offspring benefits, which could be an incentive to stay and forego independent reproduction. Predation, (hawks - 80 % and owls - 15% of deaths observed) is the main cause of mortality. Parents increased their vigilance nepotistically; they were more vigilant against surprise predator attacks, and gave alarm calls when attacked when feeding together with offspring. However, the two parents differed in their behaviour. Mothers gave calls only when together with their offspring, while males also warned unrelated immigrants. Sitting predators were approached and mobbed more intensely by parents in the presence of philopatric offspring. The vocalisation of Siberian jays provides information about predation risk. Specific calls are given for hawks and owls, and calls also varied with hawk behaviour. The nepotistic anti-predator behaviour of parents is a benefit, which the offspring can gain only “at home”, and such behaviour appears to promote offspring to forego dispersal and independent reproduction. This was confirmed in an experimental manipulation; philopatric offspring dispersed when fathers were removed and replaced by a despotic, immigrant stepfather. From a life-history perspective, parents have an incentive to protect their reproductive investment. Nepotistic anti-predator behaviour create a safe haven in the natal territory for philopatric offspring and provides direct fitness benefits. Without such direct fitness benefits offspring may disperse and wait for a breeding opening elsewhere. </p>

This thesis examines risk management in breeding Siberian jays (Perisoreus infaustus), which is indigenous to the northern taiga. Parent behaviour and the nest are cryptic. A new nest is built each year. It is placed on spruce or pine branches close to the trunk and well insulated with lichens, feathers and reindeer hair. Nest failure rate was the main factor driving annual variations in jay numbers. The probability for nesting attempts to be successful ranged annually between 0.08 and 0.70. Nest predation was rampant and a main cause of nest failure. Nest predators were mainly other corvids (primarily the Eurasian jay Garrulus glandarius). Habitat quality was the main factor determining the risk of predation. The risk for nest failure due to predation was higher in thinned forests with an open structure and with a high abundance of man-associated corvid species (jays, crows, raven). Siberian jay parents show several strategic adjustments in life-history and behaviour to the risk of nest predation. Parents traded reduced feeding rates for a lower predation risk and allocated feeding to low risk situations. Chick provisioning imposes a cost by drawing the attention of visually hunting predators to the location of nests, and parents adjusted their daily routines and avoided exposure by allocating provisioning to times of low activity among nest predators. These strategic adjustments of feeding efforts were estimated to reduce the exposure to nest predators by 26 percent. Also, parents adjusted their reproductive efforts to the perceived presence of predators in a playback experiment. Siberian jays reduced their reproductive investment by laying a smaller clutch size when high risk of nest predation reduced the value of current reproduction, as predicted from life-history theory.

Evolution is fuelled by independent reproduction events. Yet, the offspring of at least three percent of all bird species postpone dispersal and forego independent reproduction. The Siberian jay, Perisoreus infaustus, is such a species where some offspring are philopatric and remain in their natal territory for up to three years, forming family groups. The main finding of this thesis is that nepotistic anti-predator behaviour displayed by parents provided philopatric offspring benefits, which could be an incentive to stay and forego independent reproduction. Predation, (hawks - 80 % and owls - 15% of deaths observed) is the main cause of mortality. Parents increased their vigilance nepotistically; they were more vigilant against surprise predator attacks, and gave alarm calls when attacked when feeding together with offspring. However, the two parents differed in their behaviour. Mothers gave calls only when together with their offspring, while males also warned unrelated immigrants. Sitting predators were approached and mobbed more intensely by parents in the presence of philopatric offspring. The vocalisation of Siberian jays provides information about predation risk. Specific calls are given for hawks and owls, and calls also varied with hawk behaviour. The nepotistic anti-predator behaviour of parents is a benefit, which the offspring can gain only “at home”, and such behaviour appears to promote offspring to forego dispersal and independent reproduction. This was confirmed in an experimental manipulation; philopatric offspring dispersed when fathers were removed and replaced by a despotic, immigrant stepfather. From a life-history perspective, parents have an incentive to protect their reproductive investment. Nepotistic anti-predator behaviour create a safe haven in the natal territory for philopatric offspring and provides direct fitness benefits. Without such direct fitness benefits offspring may disperse and wait for a breeding opening elsewhere.