Aloe marlothii is a winter-flowering succulent that is widespread in the savanna biome of northern and north-eastern South Africa. Plants grow up to 8 m in height and are commonly found on rocky north-facing slopes. Nectar production occurs through a 24 h period with flowers producing copious amounts (c. 250 µl) of dilute nectar (c. 12%). This abundant nectar supply, that is available for a 5-10 week period during June-August, is utilised by numerous opportunistic avian nectarivores. At a study site in Suikerbosrand Nature Reserve, 60 km south-east of Johannesburg, at least 59% (38 species) of birds recorded during census transects fed on nectar; throughout the range of A. marlothii at least 85 species feed on nectar. This diversity surely far exceeds the number of species ever recorded feeding on nectar of a single plant. During the flowering period an influx of birds at the aloe forest occurred, with an overall increase in abundance and diversity. Pollinator exclusion experiments supported the hypothesis that A. marlothii is pollinated by generalist birds; specialist nectarivores are possibly excluded as inefficient pollinators by the nectar of low concentration and high volume. Fruit set was higher in plants that had avian visitors and very low when pollinators were absent. Stable carbon isotope analysis of whole blood was used to quantify the importance of nectar sugars for opportunistic nectarivores. During flowering there was an enrichment in the δ13C isotopic signature of whole blood of nectar-feeding birds towards that of nectar (δ13C = -12.6‰). This shift was most prominent in frugivores, insectivores and omnivores that typically fed on a diet depleted in 13C when nectar was not available. The C4 grass seed diet of granivores was similar to the isotopic signature ofA. marlothii nectar, so we were unable to determine to what degree granivores benefitted from nectar. Stable nitrogen isotopes in whole blood may suggest that many nectar-feeding birds shift their trophic position during flowering. However, we interpret these results with caution because of insufficient knowledge on diet-tissue fractionation factors of wild birds and/or temporal changes in vegetation isotopic values. Stable carbon isotope analysis of breath samples was used to show that A. marlothii nectar is a readily available income energy source for nectar-feeding birds. Because A. marlothii nectar is so dilute we expected it to be an important water source for many opportunistic nectar-feeding bird species. There was no correlation between the enrichment of δ13C of breath CO2 (representing metabolised nectar sugars) and the δ18O in breath CO2 (representing a highly evaporated water source in nectar); for most birds the δ18O in breath CO2 was more similar to that of free-standing water sources. However, because our knowledge on the relationship between δ18O of ingested water and body water, and fractionation processes when CO2 is exhaled is limited, we were unable to quantify water obtained from nectar. The sugars of A. marlothii nectar are probably more important, as a food source for opportunistic nectarivores during dry winter months when insect abundance is low, than the water in nectar, because birds are able to source water from other drinking sites. / Thesis (PhD)--University of Pretoria, 2010. / Zoology and Entomology / unrestricted

Made available in DSpace on 2015-03-05T16:19:37Z (GMT). No. of bitstreams: 0 Previous issue date: 27 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Atividades de mineração causam alterações nas paisagens, acarretando mudanças na vegetação e nas propriedades e topografia do solo que acabam por afetar a fauna. Para minimizar os efeitos da mineração, empresas mineradoras freqüentemente implementam procedimentos de recuperação ambiental exigidos por lei. O presente estudo aborda o efeito e a influência da estrutura da vegetação nas comunidades de aves em áreas recuperadas após processos de mineração em florestas no município de São Mateus do Sul, sudeste do Estado do Paraná e em áreas de campo em Candiota no Rio Grande do Sul No Paraná selecionei quatro áreas para as amostragens: três delas, com 5, 10 e 20 anos de recuperação vegetal (A05, A10 e A20, respectivamente) encontram-se na Unidade da Petrobrás (Superintendência de Industrialização de Xisto) e a quarta área de estudo é um fragmento florestal que não sofreu interferências de mineração (A50). Em Candiota selecionei três áreas com vegetação nativas nunca antes mineradas e três áreas recuperadas. Nos do / Mining activities cause severe alterations in natural landscapes, changing the vegetation and the properties and topography of the soil, and thus altering habitats and the associated fauna. To minimize the effects of mining, mining companies implement procedures of environmental recuperation demanded by law. The present study investigates the influence of vegetation structure on bird communities in reclaimed areas after mining in forest and grassland habitats in south Brazil. Forested areas were studied in the State of Paraná, while grasslands were studied in the Pampa biome in Rio Grande do Sul. In Paraná I sampled four areas, three of them (with 5, 10 and 20 years of vegetation recuperation named, respectively, A05, A10, and A20), were located in the Unit of Petrobrás, and the fourth was a forest fragment that did not suffer mining interferences (A50). In Rio Grande do Sul I selected six areas, three with native vegetation never mined before and three reclaimed areas. I sampled the avifauna using the point

Thesis (Ph. D.)--University of Toronto, 1997. / Two chapters co-authored with Kathy Martin. Includes bibliographical references.

Renewable energy is a promising alternative to alleviating fossil fuel-based dependencies, but its development can require a complex set of environmental trade-offs for bird communities in the area, ranging from effective and physical habitat loss to direct collision-related mortality. The wide variation in the nature and significance of predicted impacts of utility-scale photovoltaic (PV) facilities on birds, and the low levels of confidence attending these predictions, has emphasised the need for scientific research. This study assesses the risks to bird populations and guilds at one of South Africa's largest PV developments. Firstly, in order to identify functional and structural changes in bird communities in and around the development footprint, bird transect data were gathered, representing the solar development, boundary, and untransformed landscape. Secondly, to assess the risk of collision mortality with solar-related infrastructure, representative samples (core vs. edge) were surveyed for bird carcasses and other signs of collision for three months covering 20-30% of the facility at search intervals of 4, 7 and 14 days. In order to account for potential biases in carcass detection, searcher efficiency and carcass persistence trials were conducted. The distribution of birds in the landscape changed, from a shrubland to open country and grassland bird community, in response to changes in the distribution and abundance of habitat resources such as food, water and nesting sites. These changes in resource availability patterns were detrimental to some bird species and beneficial to others. Shrubland specialists, such as the black-chested prinia (Prinia flavicans) and chestnut-vented tit-babbler (Parisoma subcaeruleum), appeared to be negatively affected by the presence of the PV facility. In contrast, open country/grassland and generalist species, especially species such as the Cape sparrow (Passer melanurus) and familiar chat (Cercomela familiaris), were favoured by its development. Utility-scale PV facilities inevitably will not substitute for the natural habitats they have replaced, but might offer opportunities for climate protection that do not necessarily conflict with nature conservation. Monitoring success of avian mortality was significantly influenced by variation in detection rates by size class (60 and 95% for birds <100 g and >100 g, respectively) and the location of carcasses relative to the solar panel units (65 and 90% for birds adjacent and under the units, respectively) as well as decreasing persistence rates per search interval (57, 53, and 40% after 4, 7, and 14 days, respectively). Only injuries associated with non-fatal collision of large-bodied birds with the underside of the panels and entrapment between fencing could be concluded with reasonable certainty. An extrapolated fatality estimate of 4.53 fatalities.MW⁻¹.yr⁻¹ (95% CI 1.51-8.50), short study period, and lack of comparable results from other sources made it difficult to provide a meaningful assessment on avian mortality at PV facilities. Despite these limitations, the few bird fatalities that were recorded might suggest that there is no significant link with collision-related mortality at the study site. In order to fully understand the risk of solar energy development on birds, further collation and analysis of data from solar energy facilities across spatial and temporal scales, based on scientifically rigorous research designs, is required.

Depuis le début du 20ième siècle, les changements d'usage des terres, la disparition des prédateurs et les régulations de la chasse ont provoqué une augmentation des populations de cervidés dans les forêts tempérés et boréales. Ce phénomène, qui est un grand succès de la conservation de ces espèces, a toutefois conduit à des surabondances qui ont entrainé des effets négatifs en cascades sur la végétation et les communautés animales qui en dépendent.J'ai utilisé l'expérience naturelle qu'est l'introduction du cerf à queue noire sur l'archipel d'Haïda Gwaii pour étudier les conséquences de sa surabondance sur un écosystème tempéré peu perturbé par les activités anthropiques. J'ai ainsi pu mettre en évidence les contrôles descendants directs et indirects qu'exerce l'herbivore sur les Bryophytes (positifs), les plantes vasculaires (négatifs) et sur l'avifaune (négatifs) quand il n'est pas limité par les prédateurs ou la chasse.J'ai complété ces résultats par une analyse régionale sur 20 ans pour montrer que la perte de biodiversité enclenchée par la surabondance de ces cerfs était un phénomène d'érosion continu se prolongeant bien au-delà de l'impact initial. A l'échelle de l'Amérique du Nord, j'ai ensuite pu montrer, conformément aux prédictions faite à partir des études locales, qu'il existait une relation entre surabondance des populations d'ongulés et déclin de l'avifaune du sous-bois du continent. Enfin, j'ai analysé les suivis d'une expérience de réduction des densités de cerfs entamée sur deux îles il y a 13 ans. La végétation et l'avifaune se sont partiellement reconstituées démontrant qu'il est possible (1) de restaurer les réseaux trophiques fortement modifiés et (2) qu'une telle restauration si elle est possible prendra du temps et ne convergera pas (rapidement) vers un état initial. Afin de limiter les conséquences dommageables provoquées par la surabondance des cervidés, la conservation des prédateurs et l'augmentation de la chasse doivent être favorisés. / Since the past century land use changes, elimination of predators and hunting regulations triggered an increase of deer populations in temperate and boreal forests. This remarkable conservation success, lead to deer overabundance and to a cascade of negative effects on vegetation and on animal communities depending on it. I used the natural experiment provided by the introduction of black-tailed deer to Haida Gwaii to analyze the consequences of overabundant herbivore populations on temperate ecosystem only slightly modified by human activities. This unique situation allowed me to demonstrate the direct and indirect top-down effects that herbivores uncontrolled by predation or hunting exert on Bryophytes (positive) and Vascular plants (negative) as well as on songbirds (negative).I used an analysis of regional trends spanning over 20 years to show that biodiversity erosion caused by overabundant deer extends far beyond the initial impact. At the North-American scale I was able to establish a relationship between expanding deer populations and continent wide declines in understory birds. Finally I analyzed the results of an experimental reduction in deer populations initiated 13 years ago on two islands. The understory plants and songbirds responded positively and we show that (1) it is possible to restore trophic networks even after their dramatically modification, (2) that such a restoration while possible takes time and does not (rapidly) converge towards an identified initial state. From a practical standpoint I recommend that to mitigate negative effects of overabundant deer, predator conservation and hunting have to be promoted.

<p>Abstrakt: Jag har undersökt hur älvreglering påverkar mängden knott (Tvåvingar: <i>Simuliidae</i>) längs flera norrlandsälvar och vilka konsekvenser denna påverkan får för den landlevande fågelfaunan. Studien visar att utbyggnad av älvar har en negativ effekt på mängden knott. Det fanns sju gånger högre tätheter av knott längs "orörda älvar" jämfört med utbyggda älvar.</p><p>Skillnaden i antal knott mellan älvtyperna var mycket större för knotthanar än för knotthonor, vilket förklaras av att honorna är rörligare eftersom de flyger och letar efter blod. Knott lever av blod från ett flertal däggdjur och fåglar och visar en stor variation i värd-specificitet mellan olika arter. Jag fann en högre frekvens av haemosporida blod parasiter (<i>Leucocytozoon</i>) i fåglar längs "orörda" Vindelälven jämfört med den reglerade Umeälven. Detta mönster stämmer väl överens med tätheten fågelparasiterande knott som är lägre längs Umeälven. Knott attackerade främst värdar som var stora och vanliga. Fågelsamhällets sammansättning skiljde sig mellan orörda och utbyggda älvdalar. Tätheten av icke insektsätande fåglar tenderade att minska, efter häcksäsongen, längs orörda älvar medan den ökade längs utbyggda älvar. Den insektsätande fågeln svartvit flugsnappare (<i>Ficedula hypoleuca Pallas</i>) uppvisade större häckningsframgång längs orörda älvar jämfört med utbyggda älvar. Detta är förmodligen en effekt av den större mängden insekter som finns längs orörda älvar.</p> / <p>The effects of river regulation on blackfly (Diptera: <i>Simuliidae</i>) abundances and consequences for the avifauna in terrestrial environments were studied along multiple rivers in northern Sweden. I found that impoundment of rivers has detrimental effect to blackfly abundances. The densities of large-river breeding blackfly species were several-fold higher along free-flowing than along regulated rivers. The difference in abundances was much larger in males than blood-seeking females. Blackflies attacked a variety of mammalian and avian hosts and showed different levels of host-specificity between species. I found higher prevalence of haemosporidian blood parasites (<i>Leucocytozoon</i>) in birds along the free-flowing Vindel River in comparison to the regulated Ume River, where the lower densities of ornithophilic blackflies were reduced. Blood-seeking blackflies predominantly attacked large and/abundant hosts.</p><p>Assemblages of birds differed between valleys of regulated and free-flowing rivers. Densities of noninsectivorous birds tended to decrease along free-flowing rivers in the post-breeding season, but increased along regulated rivers at the same time. Insectivorous European pied flycatcher (<i>Ficedula hypoleuca Pallas</i>) showed greater fledging success along free-flowing than regulated rivers, which probably reflects the higher insect abundances found along freeflowing rivers.</p>

Abstrakt: Jag har undersökt hur älvreglering påverkar mängden knott (Tvåvingar: Simuliidae) längs flera norrlandsälvar och vilka konsekvenser denna påverkan får för den landlevande fågelfaunan. Studien visar att utbyggnad av älvar har en negativ effekt på mängden knott. Det fanns sju gånger högre tätheter av knott längs "orörda älvar" jämfört med utbyggda älvar. Skillnaden i antal knott mellan älvtyperna var mycket större för knotthanar än för knotthonor, vilket förklaras av att honorna är rörligare eftersom de flyger och letar efter blod. Knott lever av blod från ett flertal däggdjur och fåglar och visar en stor variation i värd-specificitet mellan olika arter. Jag fann en högre frekvens av haemosporida blod parasiter (Leucocytozoon) i fåglar längs "orörda" Vindelälven jämfört med den reglerade Umeälven. Detta mönster stämmer väl överens med tätheten fågelparasiterande knott som är lägre längs Umeälven. Knott attackerade främst värdar som var stora och vanliga. Fågelsamhällets sammansättning skiljde sig mellan orörda och utbyggda älvdalar. Tätheten av icke insektsätande fåglar tenderade att minska, efter häcksäsongen, längs orörda älvar medan den ökade längs utbyggda älvar. Den insektsätande fågeln svartvit flugsnappare (Ficedula hypoleuca Pallas) uppvisade större häckningsframgång längs orörda älvar jämfört med utbyggda älvar. Detta är förmodligen en effekt av den större mängden insekter som finns längs orörda älvar. / The effects of river regulation on blackfly (Diptera: Simuliidae) abundances and consequences for the avifauna in terrestrial environments were studied along multiple rivers in northern Sweden. I found that impoundment of rivers has detrimental effect to blackfly abundances. The densities of large-river breeding blackfly species were several-fold higher along free-flowing than along regulated rivers. The difference in abundances was much larger in males than blood-seeking females. Blackflies attacked a variety of mammalian and avian hosts and showed different levels of host-specificity between species. I found higher prevalence of haemosporidian blood parasites (Leucocytozoon) in birds along the free-flowing Vindel River in comparison to the regulated Ume River, where the lower densities of ornithophilic blackflies were reduced. Blood-seeking blackflies predominantly attacked large and/abundant hosts. Assemblages of birds differed between valleys of regulated and free-flowing rivers. Densities of noninsectivorous birds tended to decrease along free-flowing rivers in the post-breeding season, but increased along regulated rivers at the same time. Insectivorous European pied flycatcher (Ficedula hypoleuca Pallas) showed greater fledging success along free-flowing than regulated rivers, which probably reflects the higher insect abundances found along freeflowing rivers.

Biological invasions are one of the most important threats to global biodiversity and they were also found to negatively affect some bird species. Despite relatively large number of scientific studies dealing with the impacts of invasive plants on bird communities, their results are inconsistent, especially it is not clear how birds respond to increasing levels of expansion of invasive species in native species stands. Moreover, bird responses to plant invasions seem to depend on the ecological characteristics of individual bird species. This study contributes to elucidation of this problem; I investigated the impacts of black locust (Robinia pseudoacacia) invasion on bird communities in three types of forest stands with different levels of invasion: in stands containing solely the native oak (Quercus spp.), in partially invaded stands with different proportions of black locust and oak (mixed stands) and in pure black locust stands. Previous studies that examined birds in pure oak and pure black locust stands have found that they differ markedly in vegetation structure, but not in the total number of bird species. However, habitat specialists were associated with the oak stands, while generalists with the black locust stands. Therefore, I predicted that (1) the total species richness will be...

As florestas tropicais contêm mais da metade de todas as espécies terrestres existentes, mas sofrem com a crescente influência das atividades humanas. A destruição e a degradação de habitats são, atualmente, as principais ameaças à biodiversidade. Embora exista uma extensa literatura sobre extinção de espécies em paisagens antropizadas, muitos aspectos ainda foram pouco estudados. Desta forma, buscamos contribuir para o entendimento sobre: i) o atraso e as taxas de extinções locais de espécies após a perda e a fragmentação do habitat florestal; e ii) como as interações entre variáveis de fragmentação e de degradação do habitat (perda de qualidade do habitat) podem agravar a taxa de extinção local de espécies. Para responder a estas questões, amostramos grupos de aves em uma paisagem intensamente fragmentada ao norte do Estado do Mato Grosso, no Arco do Desmatamento Amazônico. Para quantificar o débito de extinção, inventariamos as espécies de papa-formigas em dez pontos de escuta, durante três dias, em 29 localidades amostrais, durante dois períodos separados por quase uma década. Avaliamos o legado do histórico de fragmentação da paisagem na extinção local de espécies por meio de um modelo que considera o tamanho do fragmento e o tempo desde o seu isolamento. Para investigar o papel das interações entre a degradação e a fragmentação de habitats na extinção de espécies, consideramos a assembleia de aves de sub-bosque, inventariadas por redes-de-neblina durante 14.400 horas em 30 localidades amostrais. Utilizamos a seleção de modelos para determinar quais interações e variáveis de degradação e de fragmentação são melhores preditoras do número de espécies, abundância e a composição da avifauna nos fragmentos. Nossos resultados revelaram que há duas etapas para a extinção de espécies: a extinção imediata e a extinção com atraso. Mesmo considerando a extinção com atraso, mais da metade das espécies desaparece em menos de duas décadas nos fragmentos, independentemente do tamanho do fragmento. Encontramos que a grande maioria das espécies nos fragmentos pequenos (<150 ha) foi extinta localmente logo após o isolamento, enquanto que nos fragmentos grandes, a perda de espécies ocorre com o tempo e as taxas de extinção local são mais elevadas. Ademais, os efeitos das interações entre as variáveis de degradação e fragmentação de habitat contribuem para a extinção local de espécies na paisagem estudada. Identificamos que o sinergismo entre o tamanho do remanescente florestal e a incidência de fogo é a principal causa da extinção de espécies nos fragmentos. No entanto, a abundância e a composição de espécies na comunidade foram, principalmente, influenciadas pelas interações aditivas entre o tamanho do fragmento e a presença de gado. Observamos também que as alterações causadas pela presença do gado nos fragmentos resultam na substituição de espécies especialistas de habitat florestal e típicas de sub-bosque por espécies que habitam o dossel, bordas e áreas perturbadas. As implicações de nossos resultados para a conservação são: o intervalo de oportunidade para mitigação dos efeitos da fragmentação e perda de habitat, sobre os papa-formigas, devido ao débito de extinção, mesmo que ainda presente, é muito curto para a implementação de ações eficazes para conservação, especialmente para os fragmentos pequenos, onde a perda da maioria das espécies ocorre imediatamente após o isolamento do fragmento. Portanto, ações de conservação deveriam otimizar seus esforços em fragmentos grandes (>150 ha), onde há maior chance de resguardar as espécies já comprometidas com a extinção. Além disso, as espécies nos fragmentos pequenos são negativamente e de forma mais intensa influenciadas pelos efeitos interativos com a incidência de fogo e penetração do gado. Concluímos que a preservação apenas dos remanescentes florestais não é suficiente para conservação da biodiversidade. Assim, as políticas públicas devem ser direcionadas à coibição de novos desmatamentos e queimadas, além do incentivo para a utilização de cercas ao redor dos remanescentes florestais em propriedades privadas / Tropical forests contain over half of all terrestrial species on Earth, but are succumbing to the growing impact of human activities. Habitat destruction and degradation are the main current threats to biodiversity. While there is an extensive literature on species extinction in human-modified landscapes, many aspects are yet to be explored. This study aims to contribute to our understanding of (i) the rates of time-lagged local extinctions of species in the aftermath of habitat loss and fragmentation; and (ii) the combined effects of habitat fragmentation and degradation (i.e. reduction in habitat quality) in aggravating rates of local extinctions. To develop this research, we sampled different functional groups of forest birds within an intensively fragmented landscape representative of the Arc of Deforestation of southern Brazilian Amazonia. To quantify the magnitude of extinction debt we inventoried antbirds at 29 forest sites during two periods, separated by nearly a decade. At each site, we carried out ten standardized point-counts over three days, which were validated with simultaneous digital recordings. We examined species extinction rates induced by historical landscape fragmentation using a model that considers forest fragment size and time since their isolation. In relation to interactions between habitat degradation and fragmentation, we considered all understorey birds inventoried by mist-nets during 14,400 hours at 30 sampling locations. We used model selection to determine which metrics and interactions of forest degradation (intensity of fires, selective logging and cattle presence within the forest remnants) and fragmentation (fragment size, amount of surrounding forest cover) best predicted the number, abundance and composition of species in the fragments. Our results revealed that there are two main stages for species extinctions: immediately after and time-lagged forest isolation. Even where there is a delay in species extinctions, over half of all species disappeared within less than two decades post-isolation, regardless of forest fragment size. We also found that the majority of species in small fragments (<150 ha) disappear immediately after isolation, whereas species losses in large fragments occur over time and they present higher local extinction rates. Moreover, interactions between habitat degradation and habitat fragmentation contributed to the local species extinctions in the studied landscape. Forest patch size operated synergistically with fire incidence as the main cause of local extinctions in fragments. However, the composition and abundance of species was influenced by the additive interactions between fragment size and cattle intrusion, which resulted in the replacement of understorey forest specialists with generalist species typically found in disturbed areas. The conservation implications of our results include: there is a narrow window of opportunity for mitigating the effects of habitat loss and fragmentation on antbirds, especially for small fragments, where most species were lost immediately after isolation. Conservation actions should be focused on large fragments (> 150 ha) where there is greater potential for retaining species committed to extinction. Also, species in small fragments were more affected by the detrimental effects of fire incidence and cattle intrusion. We therefore conclude that the preservation of remaining forest fragments in itself is not enough for forest biodiversity conservation; public policy should be directed to fire suppression and fencing to deter cattle access to remaining forest fragments within private proprieties

Because of the scarcity of information for bird communities at the major mainland rivers of southeastern Alaska, the main objective of this study was to provide baseline information including distribution, status, and habitat associations of breeding birds. I conducted a meta-analysis of all known reports (including the current study) conducted at major mainland rivers during the breeding season. I described bird species composition, distribution, abundance estimates, status, habitat associations, and guild membership for all birds recorded at 11 major mainland rivers. Based on incidental observations, 170 species were recorded by all studies. Of these, 134 species were known or suspected to breed, accounting for 50% of all birds known from Alaska and 80% of all birds known from southeastern Alaska. In addition, I provided information on species of management concern as well as management implications and recommendations. I used point counts to survey birds within deciduous riparian vegetation at 6 major mainland rivers during 2000-2002. I compared bird species composition, abundance, richness, and diversity among four main vegetation types of deciduous riparian vegetation: shrubland, young deciduous forest, mature deciduous forest, and mixed deciduous-coniferous forest. Species richness was similar among all habitat types; however, relative abundance and diversity of birds was highest in mixed forest stands. Mature forests had the greatest number of species associated with the Canadian interior. I also used point counts to compare bird species composition, abundance, richness, and diversity among 6 major mainland rivers consisting of three trans-mountain and three coastal rivers. Latitude, connectivity, and availability of mature and mixed forests were the major factors thought to cause differences in bird communities among rivers. Contrary to our predictions, coastal rivers had higher bird species richness, diversity, point abundance , and point richness than trans-mountain rivers. Of the 10 species associated with the Canadian interior recorded during point counts, 8 occurred at both trans-mountain and coastal rivers.