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This research seeks to pinpoint the telencephalic structures most closely correlated with feeding flexibility, which is operationalised as feeding innovation rate per taxon. By calculating a weighted average per taxon of 1030 feeding innovations collated from five zones of the world (western Europe, North America, Australia, New Zealand and India), the study shows that relative size of the hyperstriatum ventrale and, to a lesser extent, the neostriatum , best predicts weighted innovation rate; these two structures are thought to be functionally equivalent to the mammalian neocortex. The worst telencephalic predictors of innovation rate are two structures respectively thought to be involved in primary visual projection and the control of stereotyped, species-specific behaviour, the wulst area and the paleostriatum. / A second presumed correlate of behavioural flexibility, taxonomic variation in the use of urbanised and other anthropogenically-modified habitats, shows a consistent pattern in four geographical zones (Great Britain, North America, Australia and New Guinea), as well as a qualitative association with the relative size of the forebrain. There is no linear correlation, however, between urbanisation rate per taxon and either forebrain size or innovation rate, suggesting that other variables like diet, tameness and neophilia may have to be quantified at finer taxonomic levels in future studies of opportunism in habitat use.

This thesis seeks to determine if juvenile birds preferentially select foraging information from their parents, by examining the acquisition of novel food-finding skills in juveniles of a flock-feeding species, the ringdove (Streptopelia risoria). / The first experimental examined the flock feeding behaviour of juvenile ringdoves foraging in a small aviary flock composed of kin and non-kin; frequencies of local enhancement, food begging and aggression were recorded, as well as the individuals that the juvenile associated with while searching for food. Juvenile ringdoves foraged significantly more often with their kin and were aggressed more by non-kin. The last three experiments tested juveniles on three components of foraging: novel food type, environmental colour cues associated with food and novel food-searching techniques. All three involved a choice-test where the juveniles had their father and an unrelated flock member as demonstrators. All three choice-tests showed there was no preference for selecting either demonstrator's solution. Juvenile doves in the field may appear to learn from their parents simply because they associate more with them. (Abstract shortened by UMI.)

The variable plumage characteristics of the sub-adult male cohort of the red-winged blackbird (Agelaius phoeniceus) are described. At one extreme of the plumage variation, there are a group of sub-adult males that are indistinguishable from the adult males. These birds can only be correctly aged by cloacal examination for the bursa of Fabricius in the autumn. At the other extreme, approximately 4% of the population are near perfect female-mimics. A simple scoring system based on the interspersion of dark feathers in the epaulet is presented, which permits classification of the sub-adult males into 1 of 6 plumage classes. These epaulet classes are significantly correlated with other traits of the plumage. / Age when entering the prebasic molt, and the physical condition of the sub-adult male may influence the development of the varied plumage characteristics. / The distribution of the plumage characteristics of a population of sub-adult males collected at a major blackbird roost in the province of Quebec is described for birds captured in the fall and spring. The spring plumage characteristics are more variable than the fall, a phenomenon which is not consistent with plumage wear as has been previously reported, but which may be related to a prealternate molt which the birds undergo. The prealternate molt is prevalent in some but not all of the contour feather tracts, and is restricted to females and the sub-adult male cohorts. / An age- and sex-specific spring migration of red-winged blackbirds is examined. Adult males arrive to the spring roosts first, followed by yearling males and then females. A similar pattern of dispersal to the breeding territories is described. Within the subadult male cohort, the birds with the most adult-male like plumage traits arrive at the vernal roosts first. / The characteristics of the prealternate molt and differential spring migration are discussed in relation to the pressures of sexual selection on the respective age and sex cohorts. / The adaptive significance of variable sub-adult male plumages and delayed plumage maturation in passerines is evaluated. Several competing hypotheses have been advanced to describe the phenomenon of delayed plumage maturation. These hypotheses are reviewed, and a test is proposed which unequivocally differentiates between the various alternatives. (Abstract shortened with permission of author.)

1. Cost constraints in models of territory size are based on time/activity/laboratory estimates that predict birds using larger territories will incur higher energy costs. The predicted form of the cost constraint may be linear, accelerating or decelerating depending on assumptions inherent in the models. The aim of this study was to assess the reality and form of the cost constraint by making direct measurements of the energy costs of territory use in birds that occupy territories of different size and shape; polygonal territories represented by the robin Erithacus rubecula, and linear by the dipper Cinclus cinclus. Free-living energy expenditure was measured using the doubly-labelled water technique, whilst simultaneously recording patterns of territory use by radio-tracking. 2. Territorial robins concentrated their activity in one or more foraging patches located in bushes. Range polygons containing all the foraging patches used by an individual provided estimates of territory area, and were generally of high eccentricity. A small proportion of robins was classified as non-territorial based on range polygon areas. Furthermore, while territorial robins showed high fidelity to ranges over the short term (days), non-territorial individuals were nomadic. Over the longer term (months), however, some territorial robins showed range drift. Dippers similarly used preferred core regions within ranges, although there was no selection for particular habitat features. 3. Because robins occupied territory polygons which varied from polygonal to highly linear, work was focused on this species to allow intra-specific comparison. Robins tended to commute between foraging patches by flying. It was appropriate, therefore, to describe territories in terms of a number of patches linked by a network of flight paths. This generated two further measures of territory size; the number of patches used and the total flight distance between patches. 4. The robins exploited a renewing food supply. Predictions were tested concerning the temporal scheduling of visits to foraging patches within territories. Patches tended to be separated by flight paths of similar lengths, and were visited in a regular sequence. Although the number of foraging patches used varied, all territories had similar total core areas. Robins using many small foraging patches commuted between patches more often and covered a larger total flight distance during each foraging circuit of the territory. The configurations of foraging patches were used in a highly linear manner. This was true even if the territory containing them was of low eccentricity. 5. Changes in structure and pattern of use varied predictably with territory size, and could be described mathematically. Based on this and published time/activity budgets, a suite of models was developed to predict how energy costs would vary with number of patches used and total flight distance between patches. Models were tested by directly measuring the energy expenditure of robins using different territories. The number of patches used and total flight distance between patches were both significantly correlated with energy expenditure, while territory area was not. One of the models showed a significant fit to the observed data, and suggested that the form of the energy cost constraint on territory size was linear. The effect of territory shape on energy costs was minimal. The implications of these results for models of territory size are discussed. 6. The slope and elevation of the energy cost constraint varied with the morphology of territory occupants. Based on this, an association of morphology with territory size was predicted; robins of lower mass and wing-loading using larger territories. The observed data supported these predictions, and suggested a possible genetic predisposition to particular patterns of territory occupancy in the robin.

Since European settlement, the woodlands and associated habitats, especially in the temperate zones of Australia, have been extensively cleared and converted to arable land and pastures. Much of the remaining vegetation in the agricultural zone occurs as small isolated patches prone to disturbance and degradation. Apart from habitat loss and fragmentation, altered fire regimes, periods of intense drought, and the introduction of exotic plants and animals, have contributed to the deterioration of most of the natural habitats across Australia, with a negative impact on the native wildlife, including birds. Many woodland bird species have undergone widespread declines, culminating in some local or even regional extinctions. In the mallee woodlands of south-east Australia two closely related species of whistlers (fam. Pachycephalidae) — Red-lored Whistler Pachycephala rufogularis and Gilbert’s Whistler P. inornata — have overlapping ranges, and in some areas they co-exist. These two species are morphologically and ecologically similar. However, despite the similarities, P. rufogularis has undergone greater declines in distribution and abundance than P. inornata. The ecology of these two species is poorly known, which renders adequate management impracticable. The major objectives of this thesis were to determine the key habitat requirements for the two species, to determine their habitat use, and to document the ecology and behaviour of the two species, particularly their foraging, and intra- and interspecific interactions. A sound knowledge of the ecology of the two species is needed to underpin appropriate actions for their management and conservation. Morphological features were measured from skins of P. rufogularis and P. inornata in the South Australian Museum collection, and from captured live birds, to detect if any aspect of the morphology could indicate possible niche partitioning between the two species. Also, the use of biometry as a tool for separating the sexes for P. rufogularis, for determining the species of the uncoloured immature birds and for sexing immatures, was evaluated. No morphological feature suggested niche partitioning. The biometry did not prove a very reliable tool for distinguishing sexes in adult P. rufogularis, but reliably identified the species of the uncoloured immatures. Sexing immatures based on biometrical data alone was not possible. Research was conducted in two main South Australian parks: Gluepot Reserve and Ngarkat Conservation Park. Ecological and behavioural data for P. rufogularis and P. inornata were collected by observing marked (colour-banded and radio-tagged) and unmarked individual birds of both species and sexes, over a two-year period from June 2004 to May 2006. The home ranges of P. rufogularis and P. inornata were determined by tracking the movements of birds in the landscape. Pachycephala rufogularis had much larger home ranges than P. inornata, especially when breeding. The striking differences in home range size between the two ecologically similar species might be related to differences in site fidelity. Pachycephala rufogularis at Gluepot was sedentary, being detected in the same locations throughout the year, and over several years. On the contrary, P. inornata generally showed poor site fidelity, being more mobile, and shifting home ranges between and within seasons. In the field the two species were segregated by habitat. Pachycephala rufogularis and P. inornata showed different habitat preferences, even in areas where they did not co-occur. Pachycephala rufogularis favoured low mallee with Triodia on sand dunes, while P. inornata favoured tall mallee with sparse shrub understorey in interdunes, but also other habitats, such as prickly Acacia thickets and Casuarina woodlands. However, both species used the mallee- Triodia with Callitris vegetation type. The key to coexistence in this habitat was a behavioural one, P. inornata acting as a subordinate species. Pachycephala rufogularis had strict habitat requirements, with the presence of Triodia being critical for the presence of the species. In contrast, P. inornata was more flexible in its habitat requirements, and used a broader range of vegetation types, being more of a habitat generalist. The investigation of habitat use from both a spatial and temporal perspective confirmed that both species actively selected habitat, and that the habitats they selected differed. The core areas of home ranges predominantly contained the preferred habitat for both species. In both species, core areas of home ranges of breeding individuals (where generally the nests were placed) contained preferred habitat in higher proportion than core areas of non-breeding birds. This suggests that during breeding, both species are more restricted to, and/or use more intensely the preferred habitat than when not breeding. The foraging behaviour did not differ consistently between the two species, both capturing insects mostly by snatching in canopy foliage, and also by gleaning on the vegetation, at different heights. However, the two species were already segregated by habitat. Thus the resource partitioning occurred spatially, at the macrohabitat level. In the instances when individuals of both species foraged in the same area and used the same resources, resource partitioning occurred at a temporal scale. Both species were generalists in foraging; therefore, a presumed foraging specialisation as a possible factor related to the decline of P. rufogularis was ruled out. Pachycephala rufogularis and P. inornata are unlikely to be competitors. Support for this argument came from the situation at Ngarkat, where P. inornata was absent. Despite this, P. rufogularis did not use a broader range of vegetation types in Ngarkat, as would be expected under ‘competitive release’. Instead the species maintained strict habitat requirements, specializing virtually on a single vegetation type. The rigid habitat requirements of P. rufogularis, together with its sedentary nature, render this species vulnerable to disturbances, such as wildfires. On the other hand, the apparent flexibility in habitat requirements and greater mobility may explain why P. inornata has been more successful than its sibling species. The information on habitat requirements, preference and use, and also on home ranges of P. rufogularis and P. inornata provided in this study should be included in future habitat suitability models and predictive models for these species, which will assist in their management. / http://proxy.library.adelaide.edu.au/login?url= http://library.adelaide.edu.au/cgi-bin/Pwebrecon.cgi?BBID=1374821 / Thesis (Ph.D.) -- University of Adelaide, School of Earth and Environmental Sciences, 2009