This thesis presents research into the space use of a specialist reedbed Passerine, the Bearded Reedling, or Bearded Tit, Panurus biarmicus, with a view to inform the conservation of this species and reedbeds as a whole. How a species uses space, and how space use changes between individuals or over time, can influence: the ability to forage and hunt effectively, breeding success, susceptibility to predation, genetic health, disease spread, robustness against environmental change and ultimately, colonisation or extinction. Thus, understanding the space use of animals can provide critical insight into ecological systems. Birds offer interesting models when studying animal space use, as, by being intrinsically mobile, many bird species can occupy multiple spatial scales. As a consequence of being completely dependent on patchy and ephemeral reedbed habitats, the Bearded Reedling, has a clustered, inhomogeneous distribution throughout its range. This drives the existence of distinct spatial scales upon which space use studies should be characterised. Distribution and movement within a single reedbed can be considered local-scale, while spatial processes between reedbeds can be considered wide-scale. Temporal processes may act upon both of these scales. For example, changing interactions with predators may influence nest positioning at a local-scale, while seasonal changes in resource requirements might drive processes such as migration at a wide-scale. The Bearded Reedling has a wide temperate breeding range, extending over much of Eurasia. On the IUCN’s red list, it is listed as ‘of least concern’, with an estimated European population between 240,000-480,000 breeding pairs. Despite its relatively favourable conservation status, its dependence on reedbed habitats drives a fragmented distribution, with populations being concentrated in small, isolated, stands. Over the last century reedbed wetlands have suffered rapid declines caused by drainage schemes undertaken to improve land for development or agriculture. Additionally, many remaining reed stands are subject to extensive commercial management to produce thatch or biofuel. Conversely, in other areas, management is driven by conservation motives which recognise the present threats to reedbeds, and aim to encourage the diversity of species associated with these habitats. As the Bearded Reedling is fundamentally linked to the quality and structure of a reed stand, understanding the space use of this species will offer information for the direct conservation of this specialist species, and for the effects of reedbed management as a whole. This thesis first presents studies of space use at a local-scale. All local-scale research is conducted at the Tay Reedbeds in eastern Scotland. Mist netting and bird ringing data are used within capture recapture models, which include an explicit spatial component, to gain insight into the abundance of the Bearded Reedling on the Tay. This abundance estimation approach suggests the Tay reedbeds are a stronghold for this species on the British Isles, and that, as a high latitude site, the Tay may have importance for range expansion. A combination of transect surveys and radio-tracking data are then used to establish the local-scale space use of this species during the breeding and autumnal seasons. These data are related to changes in the structure of reed caused by local management in the form of mosaic winter reed cutting. Results suggest that birds exploit young and cut patches of reed as foraging resources when they are available, and that old, unmanaged reed is critical for nesting and winter foraging. Further local-scale studies concern the spatial patterns in the nesting habits of this species. Mosaic reed cutting creates clear edges in a reedbed. Artificial nests placed in the Tay Reedbeds demonstrate increased nest predation rates closer to the edges of cut patches. Additionally, high predation rates become reduced as the cut reed re-grows, suggesting that reed cutting may increase accessibility of the stand to predators. As Bearded Reedling nests are uncommon and difficult to locate, the timing, site selection and structure of a sample of real nests from the Tay is then detailed. These demonstrate an early, and relatively rigid breeding onset in this species, the importance of dense, compacted reeds as nesting sites and a degree of flexibility in nest structure. Conservation efforts will also benefit from studies into wide-scale spatial processes. These may be important when establishing how colonisation events occur and when predicting the effects of climatic change. The Bearded Reedling has been traditionally considered a resident species which only occasionally undertakes wide-scale, between-reedbed, movements. Indeed, the ecology of this species suggests strict year round local residency to reedbeds, with distinct seasonal changes in diet allowing occupation of these habitats year round. The European ringing recoveries of this species, since the 1970s are investigated to better characterise the wider movements of specialist resident. These suggest residency in southern populations, but higher instances of movement than expected in more northerly regions. In these regions wide-scale movement patterns resemble those of partial regular migratory species. An understanding of local and wide-scale spatial processes can offer a strong foundation on which to build conservation strategies. This thesis aims to use studies of space use to provide this foundation for the Bearded Reedling and offer further insight into the ecology of reedbed habitats as a whole. The thesis concludes by proposing an effective strategy for the conservation management of reedbeds that will especially benefit the Bearded Reedling.

Biological indicator species can reveal consequences of changes in physical processes within the environment, through effects on their physiology, behaviour and population dynamics. Long-lived species tend to be positioned at the top of the food chain where they can act as indicators of environmental change occurring at lower trophic levels. During poor conditions, these long-lived top predators have been selected to prioritise their own survival above the current breeding attempt, in order to maximise lifetime reproductive success. Endocrine mechanisms involving corticosterone, the ‘stress hormone’, and possibly prolactin, the ‘parental hormone’, are involved in mediating the abandonment of breeding in response to environmental perturbations. This thesis aimed to assess what the breeding success of a top marine predator indicates about changes in the marine ecosystem and what mechanisms control changes in breeding success, using the black-legged kittiwake Rissa tridactyla as the model species. I combined population-level analyses of long-term datasets (1997–2010) of diet composition, adult body mass, breeding success and foraging behaviour from the Isle of May, National Nature Reserve, Firth of Forth, south-east Scotland (56° 11‘ N, 02° 33’ W) with an individual-level field experiment to simulate chronic stress. Kittiwakes breeding in the north-western North Sea depend primarily on adult (1+ group) lesser sandeels Ammodytes marinus at the start of the breeding season and subsequently switch to depend primarily on young of the year (0 group) sandeels. Analysis of the long-term data showed that the timing of the kittiwake breeding season has become later in recent years, whilst the timing of the switch from 1+ group to 0 group sandeels in the kittiwake diet has become earlier, which may suggest mismatches in the timing of prey availability and predator demand. Increasing proportions of clupeids (mainly sprat Sprattus sprattus) were seen in the diet and further years of study may reveal whether clupeids could be a beneficial alternative prey type for kittiwakes. Foraging trip duration was unrelated to diet composition, suggesting that the main prey types of kittiwakes do not differ in their distance from the colony. Whilst foraging trip duration during incubation was related to changes in adult body mass and hatching success, diet composition was unrelated. There was a weak effect of diet composition during chick-rearing on fledging success, mediated via changes in adult body mass. However, this effect was masked by a stronger, independent, negative effect of foraging trip duration during chick-rearing. To simulate chronic stress in kittiwakes, individuals were implanted with corticosterone, using Alzet® osmotic pumps, for a week at the end of incubation. The methodology applied to kittiwakes was based on a preliminary experiment carried out in Japanese quail Coturnix coturnix japonica. The body mass and prolactin concentrations of kittiwakes were unchanged after this treatment. Corticosterone concentrations had returned to pre-treatment values by the end of the treatment week, which may have been due to down-regulation or suppression of the stress response as a result of the treatment. Corticosterone-implanted males showed lower nest attendance than sham-implanted males but the opposite was true for females. Breeding success at the end of the season was lower in corticosterone-implanted birds, suggesting a prolonged effect of chronic stress. In order to investigate the effects of disturbance to a group or colony of birds prior to the capture of an individual, a preliminary experiment was also carried out to test the stress responsiveness of a captive bird, the Japanese quail. No increase in corticosterone concentrations was seen after a capture-restraint protocol and with increasing time since the group of birds was first disturbed. A suppressed stress response in this bird may be explained by long-term captivity or domestication. These results show that the breeding success of a top marine predator can indicate changes in the timing of prey availability and prey location, mediated through changes in adult body mass. I also found that changes occurring during the chick-rearing period contributed most to the outcome of the breeding season. Chronically elevated concentrations of corticosterone are important in the control of breeding success, whereas prolactin may only play a role close to the timing of breeding failure or after failure has occurred. This thesis demonstrates the need for continued long-term monitoring of wild populations and refining of experimental methodology to better understand the impacts of environmental change on top predators.