1,721,099 research outputs found
Establishing repeatable study plots on Sa Dragonera, Mallorca to assess population trends of the local breeding Balearic Shearwaters Puffinus mauretanicus
No full textThe Balearic Shearwater Puffinus mauretanicus is a Critically Endangered species endemic to the Balearic Islands, subject to a severe decline that could lead to the extinction of the species within three generations (Oro et al. 2004). Predation by introduced mammals is considered the main threat facing the species at its breeding grounds, and therefore conservation action is required along with subsequent monitoring in a species where such information is lacking. In order to assess the long-term impact of a rodent eradication project on the breeding success of the species on Sa Dragonera island, a series of study plots were established in April 2013. A survey was carried out to establish the minimum number of known Apparently Occupied Sites (AOS) within each plot. All potential nest sites within each plot were sampled for the presence of a bird(s) using a combination of methods: (i) tape playback, (ii) physical sighting (by eye or with an endoscope) and (iii) obvious signs of occupation. 33 AOS in 12 study plots were identified. This project was not a whole island estimate; rather it led to the establishment of a series of repeatable study plots, providing reference estimates of breeding pairs in defined areas on the island to enable monitoring of future changes in the population size following predator removal
Navigation in Procellariiform seabirds
Full text linkMuch of what is known about avian navigation results from half a century of displacement experiments with the homing pigeon, the main model in avian navigation. Whether the same processes underpinning navigation in the homing pigeon are also integral to navigation in other species remains an open question. In particular, how Procellariiform seabirds, which routinely travel huge distances over open ocean, might navigate is of interest because of the contrast in sensory environment compared to terrestrial species. In this thesis, I have three aims. First, to investigate whether the mechanisms involved in homing pigeon navigation might also guide Procellariiform seabirds over the ocean. Second, to establish whether GPS-tracked, free-ranging Procellariiform seabirds might be able to offer insights into avian navigational mechanisms. Third, to investigate some of the ecological drivers of long-distance movement facilitated by these navigational mechanisms in Procellariiform seabirds. By combining novel experimental and analytical approaches, I attempt to answer some of these questions. I find that many of the mechanisms though to guide homing pigeons also appear to underpin Procellariiform navigation. In particular, the involvement of information from the time-compensated sun-compass, central to structuring spatial representation in terrestrial species, seems to be very similar to that observed in pigeons. Furthermore, like pigeons, olfaction seems to play a specific role in Procellariiform seabirdsâ map sense. However, there are differences too. I make the tentative discovery that, perhaps unlike pigeons, shearwaters might be able to derive information exocentrically about their location at sea in the form of a vector of direction and distance from the home colony, implying a geometric cognitive representation of large-scale environmental gradients. Finally, in terms of ecological drivers of long-distance movement, I find that Manx shearwatersâ migratory phenology is probably constrained by their environment and not by their condition, in-keeping with the idea that long-distance movement comes at a low cost for Procellariiform seabirds.</p
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
At-sea behaviour in marine birds: a life-history perspective
Full text linkRecent bio-logging technology and associated techniques have uncovered the distribution, behaviour, and phenology of marine predators at remote locations, providing us with insights of not only scientific merit, but also in terms of conservation and management. This thesis explores the at-sea behaviour of marine birds using field studies and ethoinformatic approaches by using multiple data loggers, focusing on four species of free-ranging seabirds breeding in the UK. Key findings and conclusions are: Extending travel distance in central place foragers in the wild is associated with higher prey quality as estimated by an indirect method based on dive profiles. This result is consistent with a prediction of optimal foraging theory, but my results show empirically that seabirds are able to increase reward with distance at the extended scale of the marine environment. Razorbills Alca torda are capable of adjusting their foraging behaviour in response to proximate environmental conditions. The potential mechanisms underlying this adaptive behaviour are independent of breeding stage, but the magnitude of flight orientation is scale-dependent. These results suggest that Razorbills are capable of optimising their foraging adaptively, possibly reading cues from the environment or conspecifics. Diving behaviour in sympatric Atlantic Puffins Fratercula arctica and Razorbills is very similar, in contrast to the predictions of the competitive exclusion principle. They are likely to be near carrying capacity for the location and this may explain why Skomer’s Razorbill population is declining while its puffin population is stable. Differences in foraging trip duration of chick-rearing Manx Shearwaters Puffinus puffinus reflect differences in resource allocation between provisioning offspring and self-feeding. I developed a model based on patch quality and travel time to show that birds should use bimodal foraging trip durations to optimise feeding rates for their offspring. Individual reproductive performance in Manx Shearwaters can be predicted from previous breeding phenology and is linked to differences in overwintering behaviour patterns. This carry-over effect reveals the existence of a trade-off between current parental investment and future reproductive performance
Light-level geolocation reveals winter migration of the endangered Hutton’s Shearwater (Puffinus huttoni)
Full text linkThe Thesis comprises a general introduction and discussuion plus two result chapters. The first result chapter is about the correction of latitudinal error around the equinoxes in GLS loggers. The second results chapter describes the previously unknown winter migration of the endangered Hutton's shearwater (Puffinus huttoni)
Annual and individual patterns in the behavioural cycle of the Manx shearwater, Puffinus puffinus
Full text linkRecent innovations in the miniaturisation of animal tracking devices have enabled the study of species that are not amenable to direct observation. This has been particularly the case for pelagic seabirds, whose at-sea behaviour would otherwise be very difficult to observe. This thesis investigates patterns in the migration and behavioural cycle of the Manx shearwater (Puffinus puffinus) using miniature geolocators. By analysing these data with a range of computational approaches, insights are made into the otherwise cryptic behaviour and ecology of this seabird.
Chapter 1 provides a general introduction to annual cycles in animal behaviour and migration in seabirds. The ecology and behaviour of the Manx shearwater is then outlined, as are recent advances in tracking technology that have enabled the study of otherwise unmeasurable aspects of the ecology of this species.
Chapter 2 first details the core fieldwork and data processing procedures which were used to generate the data used in this thesis. Using a dataset of Manx shearwater migration tracks gathered by geolocation tracking programmes on 5 UK islands, individual consistency, colony-level, annual and sex-differences in the phenology of migrations are investigated.
Chapter 3 provides a detailed analysis of Manx shearwater migration routes. Building on previous work in this area, key differences are identified between colonies and individual birds in wintering area and the overall path along which they migrate.
In chapter 4 an unsupervised classification algorithm is trained to identify behavioural states during the Manx shearwater migration using saltwater immersion data. These behavioural states are used to identify periods of stopover during which a bird pauses its migration to rest or refuel. Areas of sea are identified which are commonly used by Manx shearwaters for stopover behaviour.
In chapter 5 a similar algorithm is used to identify behavioural states during the breeding season using light and saltwater immersion data from archival loggers. These time series of behavioural states are used to estimate the timing of major life history events such as egg laying and incubation, enabling the study of breeding behaviour and ecology in this burrow nesting seabird.
Chapter 6 draws on the results from chapters 2, 3, 4 and 5 to build up a picture of the Manx shearwater annual cycle and then goes on to investigate how the timing of key life history periods impacts on future behavioural events.
Chapter 7 provides a general discussion of the Manx shearwater behavioural cycle in light of the previous chapters, with a focus on inter-colony differences and individual consistency in behaviour, as well as implications of the research for conservation of the species
Quantifying the sociality of wild tool-using New Caledonian crows through an animal-borne technology
Full text linkNew Caledonian crows (NC crows; Corvus moneduloides) are the most prolific avian tool-users and crafters, using up to three unique tool types derived from numerous plant materials. Since the discovery that wild populations of NC crows use and manufacture different tools in different locations with no measured environmental correlates to these distributions, the process by which NC crows acquire their tool-oriented behavior has been investigated. Two major findings were discovered in 2005: NC crows have a genetic predisposition to manipulate stick like objects, and they increase their rate of manipulation when exposed to social influences. Since then, much of the research into the sociality of wild NC crows has focused on direct social influences, especially the parent-juvenile relationship, yet no social network of wild NC crows has been described. In my thesis, I characterized a new proximity-logging device, Encounternet, and outline a four-step plan to assess error in animal borne devices; uncovered drivers, such as relatedness, space-use, and environmental factors, of wild NC crow sociality, and experimentally manipulated the social network, revealing immediate changes to the number of day-time and roosting partners, the breakdown of first-order relatedness driving sociality, and an increase in the amount of time NC crows associate; and revealed an indirect pathway via tools left behind by conspecifics allowing for the transmission of tool-properties between unrelated NC crows. Altogether, I furthered our understanding of wild NC crow sociality through the use of an animal-borne device, experimental manipulation in the wild measuring the response of the NC crow social network, and demonstrated the utility of animal-borne devices in mapping the network of a population of wild birds
The at-sea behaviour of the Manx shearwater
Full text linkSeabirds are vulnerable to a wide range of impacts at sea and function as important indicators of ocean health. A detailed understanding of their movements and distributions at sea, as well as the types of behaviour in which they engage and the extent to which those activities make them vulnerable to different impacts is critical in effective conservation planning. But their elusive lifestyles and mobility have hampered studies of their at-sea behaviour. Using miniature data loggers deployed on Manx shearwaters Puffinus puffinus this thesis explores the movements, distribution and behaviour of a small-medium pelagic, procellariiform seabird during foraging trips at sea. Foraging distributions were most variable during the pre-laying period when females departed the colony to build their egg. Females foraged close to the colony when local resources were adequate, but more typically foraged in distant shelf edge waters. Males returned frequently to the colony during this period and typically foraged close by, but also in shelf edge waters when local resources were poor. During incubation and chick-rearing the foraging movements of birds tracked from up to four colonies showed considerable inter-annual variability, but were largely constrained to the Irish and Celtic Seas and the inshore waters of west Scotland. Birds from each of the colonies foraged in waters local to their own colony, but also in more distant locations, including the productive Western Irish Sea and Western Irish Sea Front where birds from multiple colonies co-foraged, presumably at high densities. At-sea behaviour was organized into three principal activities representing: (1) sustained direct flight, (2) sitting on the sea surface, and (3) foraging, comprising tortuous flight interspersed with periods of immersion and diving in pursuit of prey. Foraging was highly constrained to daylight hours during which birds engaged in bouts of diving separated by periods of flight or rest on the surface. Most dives were up to 6 m deep, lasting up to 13 s, but some much deeper dives (maximum 55.5 m) were also made. During chick-rearing the use of short and long duration trips may allow parents to control provisioning effort and their own body condition. However, reducing parents’ requirement to provision their chick (by supplemental chick feeding) did not appear to alter the at-sea movements and behaviour of parents, suggesting that at-sea behaviour probably is controlled more by foraging conditions and prey distributions than by the nutritional demands of the chick
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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