This thesis aims to determine the function of howl vocalisations performed by the black and gold howler monkey, Alouatta caraya, and to examine the connections between howling, welfare and breeding in captivity. Comparisons of the behaviours performed during natural howling bouts and during howling bouts in response to experimental playbacks provide evidence for a range of howl functions including regular advertisement of the caller’s occupancy and mate defence and attraction. Detailed analyses of howl call acoustics provide the first evidence of both individuality and context-specificity in the calls of A. caraya males. These findings further support the functions of intergroup spacing, mate defence and attraction and suggest that howling may act as an honest signal of male quality. Experimental playbacks of conspecific calls stimulated howling by captive male A. caraya and affected other behaviour patterns suggesting that playbacks are an effective form of environmental enrichment to enhance captive welfare. However, the efficacy of conspecific call playbacks as a form of enrichment were not reflected in the opinions of A. caraya keepers surveyed: responses to the use of this type of enrichment were unenthusiastic, and the routine use of auditory enrichment for captive primates was limited. Analysis of the European studbook found that individuals housed in a family group rather than a pair, and those which are regularly exposed to the calls of conspecific males had higher reproductive success. Also, males who performed higher rates of howling had higher reproductive success providing the first evidence of a link between howling and breeding rates. These findings contribute to the knowledge of howl vocalisations in Alouatta species and the influence of captivity on a highly vocal primate species. From thesis results it is recommended that captive A. caraya be housed in social groups containing more than one male and one female and that the playback of conspecific male howl calls be introduced into the husbandry of groups to provide a more naturalistic auditory environment.

Food supply plays a crucial role in regulating bird populations. For many small passerines, both in the UK and globally, winter food availability is substantially increased through the provision of supplementary food. Garden bird feeding is a popular and growing phenomenon. Yet there remains a distinct lack of understanding of the ecological impacts this may be having on wild bird populations. Using a three year landscape-scale study I have investigated the carry-over effects of winter supplementary feeding on the health and productivity of resident blue tit populations (Cyanistes caeruleus) during the breeding season. Replicating the diffuse nature by which food is provisioned in gardens, I have examined the importance of energy (fat) and antioxidants (vitamin E) as carry-over effect mediators. Females showed greater resource allocation through a proportional increase in yolk mass, whilst males exhibited an improved oxidative status during the brood-rearing period in response to vitamin E provisioning. But in addition, significantly lower feather carotenoid concentrations were seen in individuals from vitamin E fed woodlands, suggesting that birds of poorer condition prior to feeding were able to survive winter and recruit into breeding populations as a result of antioxidant provisioning. This indicates that winter supplementary feeding has the capacity to perturb natural selection and alter the phenotypic quality of breeding populations. Furthermore, over-winter provisioning led to a reduction in fledging success across both treatments, which suggests that it may give birds false cues as to natural food availability and encourage them to make an unsustainable investment in nestling numbers, thereby acting as an ecological trap. With garden bird feeding promoted as a method for conserving declining wild bird populations, these new insights suggest much more needs to be done to fully understand its impacts.

Oxidative stress may provide a proximate link mediating the trade-offs between the allocation of resources to growth and/or reproduction and investment in self-maintenance. Dietary antioxidants, such as carotenoids and vitamin E, provide potentially important roles in regulating these trade-offs. Recent work suggests that carotenoids may have important synergistic effects in combination with non-pigmentary antioxidants (e.g. vitamin E) on the expression of sexually-selected traits at adulthood. However, these studies involved the supplementation of antioxidants to adults and did not take into account early life-history effects. In this thesis, I test the independent and combined roles of supplementation of carotenoids and vitamin E during early growth in regulating the expression of traits at adulthood, in ring-necked pheasants, Phasianus colchicus. Individuals supplemented with a combination of carotenoids and vitamin E were larger at adulthood than individuals receiving other treatment diets (including vitamin E or carotenoids alone), but there were no differences in ornament expression, immune function or levels of oxidative damage. In addition, there were no effects of early antioxidant supplementation on primary sexual traits and I found no relationship between primary and secondary sexual traits to support the phenotype-linked fertility hypothesis. This suggests that the allocation of limited antioxidant resources is prioritised towards traits that increase competitive ability rather than sexual attractiveness or primary reproductive traits in this strongly sexually-selected species. I also measure male ornament expression to test the ‘parasite-mediated sexual signalling’ hypothesis that predicts that ornamentation could provide a signal to females of a male’s ability to resist parasites. Allocation of dietary-derived carotenoids to sexual ornaments may trade-off with allocation to immune and/or antioxidant functions mediated by the oxidative status of individuals. In this thesis I test whether supplementation with dietary antioxidants (vitamin E) can mitigate the effects of early exposure to parasites (the nematode, Heterakis gallinarum), via the alteration of the oxidative status of individuals, and positively affect the expression of sexual ornaments at adulthood. I find that vitamin E mediated the effect of early exposure to parasites on levels of oxidative damage at 8 weeks of age and reduced the parasite load of individuals at adulthood as predicted. However, the expression of sexual ornaments, immune function, and growth were unaffected by either early vitamin E supplementation or manipulation of parasite load. In contrast to predictions, the intensity of sexual ornament expression was not related to either the parasite load or oxidative status of individuals. Finally, I present the data from a novel experiment showing that feather odour changes in response to antioxidant status, but not intestinal parasite levels, at adulthood and in light of these results describe a potential role for feather odour in mate choice.

No description available.

No description available.

A study was conducted on the ecology of larval gadoids in the Northern North Sea during April 1974 and late April/ early May 1975 with particular emphasis on the feeding ecology and separation of feeding niches of the five closely related species of larvae in the area. Food was shown to be a limiting resource for which the larvae competed, with larval mortality increasing with reduced food supply, and growth rates apparantly independent of food. Although shortage of food at first feeding was implicated in the very low densities of larval haddock, whiting and cod at the start of the 1975 cruise, it was apparent that food supply could become critical for survival at later stages in the larval phase. Hence no particular stage could be ascribed major importance in controlling subsequent recruitment, the process depending on the dynamic balance of larvae and food throughout the larval phase. Daily food intake was shown to be similar for four of the species, namely saithe, Norway pout, whiting and cod larvae, as was their gross feeding-efficiency. Haddock larvae, - on the other hand, appeared to consume a greater quantity of less nutritious food. Distributional, temporal and behavioural mechanisms were implicated in feeding niche separations such that there appeared to be little direct competition for food. However, recruitment data showed how saithe, whiting and cod tended to be negatively correlated with one another, and how haddock, Norway pout and to a lesser degree whiting showed positive cox-relations. Hence survival during the larval phase has been ascribed to the-pattern of -zooplankton productivity and its species composition.

This thesis reports a study of the temporal patterns of feeding behaviour in the Barbary dove or Blonde Ring dove, Streptopelia risoria. The normal diurnal distribution of feeding in the intact, freely feeding bird is described, as is the way in which this pattern may be altered by,a. surgical manipulation which removes much of the sensory inflow from the trigeminal nerve. On the basis of the observation of the effect of this sensory trigeminal nerve section in the doves, an alternative interpretion of the role of this nerve in the control' of feeding behaviour and food intake in birds to that presented in the literature, is offered. In line with this interpretation, it is shown that a manipulation of the physical nature of an offered food material will produce a change in the temporal patterning of food intake in a way similar to that brought about by trigeminal nerve section, and that the past feeding experience of a bird has an effect on the probability that nerve section will produce a noticeable disruption in gross food intake. The fine structure of feeding behaviour is described to demonstrate the principle that the feeding control system of these birds acts so that future needs are anticipated, and it is shown that environmental cues giving information about future deprivation are used by them to feed in advance of such deprivation. In addition, the feeding behaviour of the birds in a continiousy fixed ratio operant situation is described, to show how the means of observing a behaviour can alter the pattern of that behaviour, and also how this alteration can give information about the operation of the underlying control system.

The overall aim of this thesis is to provide a clear descriptive account of pair formation and bond maintenance in the Zebra Finch. Factors important in the processes involved are assessed and the hope, explained at the outset, is to provide a clear grounding upon which future work can be based. The first three sections of the work review and analyse the background to this bird species. Types of pair bonding in birds are discussed and the general biology of the Zebra Finch is explained in detail. Section 3 deals with the behavioural displays observed during the course of the present study and reviews such observations as have been made in the light of the literature. One display, described probably for the first time, is an 'intense head-forward threat' posture which was previously thought to be absent from the behavioural repertoire of this species.

No description available.

Bitterling are a group of freshwater fishes that lay their eggs on the gills of living freshwater mussels, using the mussel as a protective environment for embryo development and utilising the mussels own respiration to ensure fertilisation. This unusual spawning mechanism, using a spawning site that can be easily manipulated, makes bitterling ideal of reinvestigating sperm competition and making system evolution. Here, using a range of bitterling species, a series of aquarium experiments were conducted, as well as morphological and histological studies of the sperm and testes. It was shown that males were highly sensitive to sperm competition, ejaculating at a higher frequency and subsequently becoming more sperm depleted where sperm competition was high. There were few differences between mating tactics except in relative testis size, where larger males had proportionally larger reproductive apparatus, but ejaculates were of a similar size. The timing of ejaculates was found to be crucial, with a peak in sperm concentration within the mussel mantle cavity 30 seconds after ejaculation. The spatial clustering of fertilisation opportunities and OSR were found to affect ejaculate frequency, ejaculate distribution among mussels, the dominance of gender males and subsequently the opportunity of subordinate males to sneak fertilisations. Significant differences in the spermatogenic strategy and the structure of the reproductive apparatus among species were identified, as well as significant differences between species in the morphology of spermatozoa.