A interação envolvendo artrópodes e plantas é uma das mais antigas e importantes interações ecológicas da natureza. As estratégias adotadas pelos artrópodes para reconhecer a sua planta hospedeira são bastante variáveis e pistas químicas desempenham um papel importante nessa relação. Opiliões (Arachnida, Opiliones) são altamente dependentes de quimiorrecepção para encontrar recursos e são particularmente dependentes de umidade. O opilião Jussara sp. possui uma clara preferencia por repousar em Psychotria suterella (Rubiacea), uma planta com uma arquitetura foliar complexa com folhas sobrepostas. Nada se sabe sobre como o opilião chega a ela ou quais as vantagens que ela proporciona ao opilião. Neste trabalho verificamos quais pistas são utilizadas pelo opilião para encontrar P. suterella e ainda quais os possíveis benefícios para o opilião nessa interação. Para verificação de como o opilião encontra a planta, partimos de duas hipóteses não excludentes: 1 - pistas de co-específicos são utilizadas; 2 - pistas químicas provenientes da planta são utilizadas. Para a primeira hipótese, montamos um experimento em campo com um grupo de plantas de P. suterella contendo químicos de Jussara sp. e um grupo sem químicos de Jussara sp. no caule principal e comparamos como os tratamentos afetaram o número de opiliões nas plantas de cada grupo. Para a hipótese da utilização de químicos da planta, realizamos dois experimentos visando verificar a preferência do opilião pelos voláteis de P. suterella. No primeiro utilizamos extratos de químicos voláteis de P. suterella e de mais dois controles em uma arena triangular com os 3 estímulos oferecidos simultâneamente. No segundo experimento utilizamos a própria planta P. suterella, pareada com uma planta controle ou um controle branco em um olfatômetro em Y. Para verificar os benefícios da associação também partimos de duas hipóteses não exludentes relacionadas a possíveis diferenças microclimáticas geradas por P. suterella em relação às demais plantas do local: 1- as folhas de P. suterella oferecem maior umidade do que outras plantas; 2 - as folhas de P. suterella fornecem um microambiente mais sombreado do que o de outras plantas. Para primeira hipótese, quantificamos o fluxo de transpiração foliar de P. suterella e mais 3 espécies de plantas do habitat do opilião. Já para segunda hipótese, quantificamos o bloqueio à passagem de luz através das folhas em P. suterella e das mesmas 3 espécies do teste anterior. Não obtivemos evidências claras de que os opiliões Jussara sp. utilizem químicos de co-específicos para selecionar P. suterella. Pistas químicas olfativas não parecem ser utilizadas de forma isolada para atrair Jussara sp., mas nossos resultados sugerem que talvez em combinação com outras plantas o odor possa ser utilizado. Em relação aos benefícios fornecidos por P. suterella, nós não encontramos evidências de que a transpiração foliar seja importante na interação. Contudo, o maior bloqueio de passagem de luz através da folha em comparação às demais espécies aliado a arquitetura foliar de P. suterella pode gerar microclimas benéficos para os opiliões que geralmente são altamente sensíveis a umidade / Interactions between arthropods and plants are among the oldest and important ecological interactions in nature. Strategies adopted by arthropods to recognize its host plant are very variable and volatiles often mediate the encounter between both parts. Harvestmen (Arachnida, Opiliones) are arachnids highly dependent on chemicals to find resources and particularly dependent on high humidity. The harvestman Jussara sp. clearly prefers to rest on Psychotria suterella (Rubiacea), a plant with a complex architecture with overlapping leaves. We know nothing about how the harvestmen find the plant or the advantages that such plant offers to the harvestmen. In this paper we investigate the cues used to find P. suterella by these harvestmen and how the harvestman benefits from this interaction. To test how the harvestman finds the plant, we raised two non-excludent hypotheses: 1 - conspecific chemicals are used; 2 - plant chemicals are used. For the first hypothesis, we conducted a field experiment with a group of P. suterella with chemicals of Jussara sp. and another without chemicals of of Jussara sp. on the main stem and compared how that affected the number of harvestmen on them. To test the importance of plant chemicals, we conducted two experiments to test the use of volatiles of P. suterella. We first used volatile extracts of P. suterella and two other plants in a triangular arena with the three stimuli offered simultaneously. In the second experiment, we used actual individuals of P. suterella paired with either a control plant of a white control in a Y maze. To investigate how Jussara sp. benefits by choosing P. suterella, we raised two non-excludent hypotheses related to microclimatic conditions potentially offered by P. suterella in comparison to other plants of the area: 1 - The leaves of P. suterella offer higher humidity than those of other plants; 2 - The leaves of P. suterella provide a better shadow that that of other plants. For the first hypothesis, we quantified the transpiration rate of the leaves of four local species including P. suterella. For the second hypothesis, we quantified how much light passes through the leaves of these four species. We did not find clear evidences that Jussara sp. uses conspecific chemicals to select P. suterella. Plant volatiles do not seem to be used at least isolated to attract Jussara sp., but our results suggest that maybe in combination with other plants such volatiles may be used. As for the benefits provided by P. suterella, we did not find evidence that the transpiration rate is important. However, the leaves of P. suterella do provide better shadows in comparison with the other plants, which in combination with the complex architecture with overlapping leaves may provide better microclimatic conditions to these very humidity sensitive animals

<p>The Corncrake <em>Crex crex</em> is classified as vulnerable in Sweden according to the Red List of Swedish species. The number of Corncrakes is generally declining and this has been observed in few countries for more than 100 years. In the province of Värmland in Midwestern Sweden, the Corncrake is seldom seen, but more often heard. A national inventory of the Corncrake was made during 2008 and many volunteer ornithologists in the province of Värmland were involved in the work. Observations of singing Corncrakes were done during nights in the agricultural landscape. Totally 64 singing male Corncrakes have been observed during May, June and July. The results of this study show that the Corncrakes in the province of Värmland do not choose a certain habitat type to establish on. Neither do they choose a certain part of the province geographically. The size of the field seems important when choosing a suitable field and in average a Corncrake had an area of 450 ha to utilize. Different habitat elements have been investigated near the observation locations of the Corncrakes. Roads nearby the fields do not prevent the Corncrakes from settling and singing. The distribution of days when different individuals were singing or silent revealed six possible matings in three different individuals (twice each) and also one probable move from one location to another. There is more than one way to promote the Corncrakes existence in the province of Värmland, and one of them is to delay the mowing of the field or to mow in a different manner.</p> / <p>Kornknarren <em>Crex crex</em> är klassificerad som sårbar i Sverige enligt Rödlistan. Antalet kornknarrar håller på att minska i Sverige och liknande tendens är noterat i andra länder sedan mer än 100 år tillbaka i tiden. I landskapet Värmland är kornknarren en sällan sedd, men något oftare hörd besökare. Riksinventering av kornknarren utfördes i hela landet år 2008 och många volontärornitologer i Värmland deltog i inventeringen. Observationer av sjungande kornknarrar gjordes under nattetid på landsbygden. Totalt observerades 64 hanar från maj till juli. Studien visar att kornknarrar inte väljer någon specifik typ av habitat för att sjunga i. Individerna tycks fördela sig i relation till habitattillgång. Kornknarrar verkar inte heller föredra en viss geografisk del av landskapet. Storleken på fält verkar relevant för deras val av lokal och i genomsnitt har en hane 450 ha som sin potentiella användningsyta. Olika habitatelement karterades och det visade sig att vägar inte är ett förhinder för en kornknarr att välja ett fält att etablera sig på. Dagar när kornknarrar spelade och var tysta noterades och detta visade på sex möjliga parningar för tre individer (två vardera) samt en möjlig flytt från ett fält till ett annat. Det finns fler än ett sätt att gynna kornknarren i landskapet Värmland och några av dem är att inte slå vissa fält, att slå vissa fält senare eller att slå inifrån och ut istället för tvärtom.</p>

The Corncrake Crex crex is classified as vulnerable in Sweden according to the Red List of Swedish species. The number of Corncrakes is generally declining and this has been observed in few countries for more than 100 years. In the province of Värmland in Midwestern Sweden, the Corncrake is seldom seen, but more often heard. A national inventory of the Corncrake was made during 2008 and many volunteer ornithologists in the province of Värmland were involved in the work. Observations of singing Corncrakes were done during nights in the agricultural landscape. Totally 64 singing male Corncrakes have been observed during May, June and July. The results of this study show that the Corncrakes in the province of Värmland do not choose a certain habitat type to establish on. Neither do they choose a certain part of the province geographically. The size of the field seems important when choosing a suitable field and in average a Corncrake had an area of 450 ha to utilize. Different habitat elements have been investigated near the observation locations of the Corncrakes. Roads nearby the fields do not prevent the Corncrakes from settling and singing. The distribution of days when different individuals were singing or silent revealed six possible matings in three different individuals (twice each) and also one probable move from one location to another. There is more than one way to promote the Corncrakes existence in the province of Värmland, and one of them is to delay the mowing of the field or to mow in a different manner. / Kornknarren Crex crex är klassificerad som sårbar i Sverige enligt Rödlistan. Antalet kornknarrar håller på att minska i Sverige och liknande tendens är noterat i andra länder sedan mer än 100 år tillbaka i tiden. I landskapet Värmland är kornknarren en sällan sedd, men något oftare hörd besökare. Riksinventering av kornknarren utfördes i hela landet år 2008 och många volontärornitologer i Värmland deltog i inventeringen. Observationer av sjungande kornknarrar gjordes under nattetid på landsbygden. Totalt observerades 64 hanar från maj till juli. Studien visar att kornknarrar inte väljer någon specifik typ av habitat för att sjunga i. Individerna tycks fördela sig i relation till habitattillgång. Kornknarrar verkar inte heller föredra en viss geografisk del av landskapet. Storleken på fält verkar relevant för deras val av lokal och i genomsnitt har en hane 450 ha som sin potentiella användningsyta. Olika habitatelement karterades och det visade sig att vägar inte är ett förhinder för en kornknarr att välja ett fält att etablera sig på. Dagar när kornknarrar spelade och var tysta noterades och detta visade på sex möjliga parningar för tre individer (två vardera) samt en möjlig flytt från ett fält till ett annat. Det finns fler än ett sätt att gynna kornknarren i landskapet Värmland och några av dem är att inte slå vissa fält, att slå vissa fält senare eller att slå inifrån och ut istället för tvärtom.

A interação envolvendo artrópodes e plantas é uma das mais antigas e importantes interações ecológicas da natureza. As estratégias adotadas pelos artrópodes para reconhecer a sua planta hospedeira são bastante variáveis e pistas químicas desempenham um papel importante nessa relação. Opiliões (Arachnida, Opiliones) são altamente dependentes de quimiorrecepção para encontrar recursos e são particularmente dependentes de umidade. O opilião Jussara sp. possui uma clara preferencia por repousar em Psychotria suterella (Rubiacea), uma planta com uma arquitetura foliar complexa com folhas sobrepostas. Nada se sabe sobre como o opilião chega a ela ou quais as vantagens que ela proporciona ao opilião. Neste trabalho verificamos quais pistas são utilizadas pelo opilião para encontrar P. suterella e ainda quais os possíveis benefícios para o opilião nessa interação. Para verificação de como o opilião encontra a planta, partimos de duas hipóteses não excludentes: 1 - pistas de co-específicos são utilizadas; 2 - pistas químicas provenientes da planta são utilizadas. Para a primeira hipótese, montamos um experimento em campo com um grupo de plantas de P. suterella contendo químicos de Jussara sp. e um grupo sem químicos de Jussara sp. no caule principal e comparamos como os tratamentos afetaram o número de opiliões nas plantas de cada grupo. Para a hipótese da utilização de químicos da planta, realizamos dois experimentos visando verificar a preferência do opilião pelos voláteis de P. suterella. No primeiro utilizamos extratos de químicos voláteis de P. suterella e de mais dois controles em uma arena triangular com os 3 estímulos oferecidos simultâneamente. No segundo experimento utilizamos a própria planta P. suterella, pareada com uma planta controle ou um controle branco em um olfatômetro em Y. Para verificar os benefícios da associação também partimos de duas hipóteses não exludentes relacionadas a possíveis diferenças microclimáticas geradas por P. suterella em relação às demais plantas do local: 1- as folhas de P. suterella oferecem maior umidade do que outras plantas; 2 - as folhas de P. suterella fornecem um microambiente mais sombreado do que o de outras plantas. Para primeira hipótese, quantificamos o fluxo de transpiração foliar de P. suterella e mais 3 espécies de plantas do habitat do opilião. Já para segunda hipótese, quantificamos o bloqueio à passagem de luz através das folhas em P. suterella e das mesmas 3 espécies do teste anterior. Não obtivemos evidências claras de que os opiliões Jussara sp. utilizem químicos de co-específicos para selecionar P. suterella. Pistas químicas olfativas não parecem ser utilizadas de forma isolada para atrair Jussara sp., mas nossos resultados sugerem que talvez em combinação com outras plantas o odor possa ser utilizado. Em relação aos benefícios fornecidos por P. suterella, nós não encontramos evidências de que a transpiração foliar seja importante na interação. Contudo, o maior bloqueio de passagem de luz através da folha em comparação às demais espécies aliado a arquitetura foliar de P. suterella pode gerar microclimas benéficos para os opiliões que geralmente são altamente sensíveis a umidade / Interactions between arthropods and plants are among the oldest and important ecological interactions in nature. Strategies adopted by arthropods to recognize its host plant are very variable and volatiles often mediate the encounter between both parts. Harvestmen (Arachnida, Opiliones) are arachnids highly dependent on chemicals to find resources and particularly dependent on high humidity. The harvestman Jussara sp. clearly prefers to rest on Psychotria suterella (Rubiacea), a plant with a complex architecture with overlapping leaves. We know nothing about how the harvestmen find the plant or the advantages that such plant offers to the harvestmen. In this paper we investigate the cues used to find P. suterella by these harvestmen and how the harvestman benefits from this interaction. To test how the harvestman finds the plant, we raised two non-excludent hypotheses: 1 - conspecific chemicals are used; 2 - plant chemicals are used. For the first hypothesis, we conducted a field experiment with a group of P. suterella with chemicals of Jussara sp. and another without chemicals of of Jussara sp. on the main stem and compared how that affected the number of harvestmen on them. To test the importance of plant chemicals, we conducted two experiments to test the use of volatiles of P. suterella. We first used volatile extracts of P. suterella and two other plants in a triangular arena with the three stimuli offered simultaneously. In the second experiment, we used actual individuals of P. suterella paired with either a control plant of a white control in a Y maze. To investigate how Jussara sp. benefits by choosing P. suterella, we raised two non-excludent hypotheses related to microclimatic conditions potentially offered by P. suterella in comparison to other plants of the area: 1 - The leaves of P. suterella offer higher humidity than those of other plants; 2 - The leaves of P. suterella provide a better shadow that that of other plants. For the first hypothesis, we quantified the transpiration rate of the leaves of four local species including P. suterella. For the second hypothesis, we quantified how much light passes through the leaves of these four species. We did not find clear evidences that Jussara sp. uses conspecific chemicals to select P. suterella. Plant volatiles do not seem to be used at least isolated to attract Jussara sp., but our results suggest that maybe in combination with other plants such volatiles may be used. As for the benefits provided by P. suterella, we did not find evidence that the transpiration rate is important. However, the leaves of P. suterella do provide better shadows in comparison with the other plants, which in combination with the complex architecture with overlapping leaves may provide better microclimatic conditions to these very humidity sensitive animals

No description available.

The objective of this thesis was to examine whether forest structure and ground vegetation could explain the habitat choices of the reindeer within similar forest stands. The field work was carried out on 60 sites scattered across a part of the winter grounds for Vilhelmina Norra reindeer herding district. All sites were situated within so-called core and key areas, i.e. areas which the herding district sees as necessary for the reindeer husbandry in the area. Information from GPS-collared reindeer were used to create RIVO (by the Reindeer Identified [as] Important Areas) maps, where areas the reindeer preferred were shown. The results showed that the core and key areas were not significantly different from each other regarding the forest structure, nor the vegetation, but there were some differences in terms of the habitat choice of the reindeer and when the core and key areas were combined with RIVO. The differences concern mainly the coverage of ground lichens, epiphytic lichens and moose presence. Results from other studies suggest that the reindeer habitat selection is dependent on the weather and snow conditions, and looks very different from year to year. The snow conditions are in turn affected by the forest structure, so it is important that the grazing grounds have a heterogeneous forest landscape, including areas which under normal circumstances would not be seen as important for the reindeer husbandry.

Made available in DSpace on 2015-03-05T16:20:40Z (GMT). No. of bitstreams: 0 Previous issue date: 27 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / O aumento das bordas florestais é parte da influência da fragmentação nos remanescentes de mata e pode afetar as comunidades de pequenos mamíferos. Para avaliar tal efeito, amostrei cinco áreas representativas das florestas da região sul do Brasil. Em cada uma delas amostrei a abundância e riqueza e diversidade de pequenos mamíferos, na matriz (> 60 m da floresta), borda (até 15 m para o interior da floresta), zona intermediária (60 m para o interior) e interior florestal (150 m). Avaliei ainda a disponibilidade de recursos alimentares e características estruturais do hábitat em todos esses ambientes. Para um total de 446 indivíduos (20 espécies) capturados, os dados não indicaram efeitos de borda evidentes para nenhuma das métricas utilizadas. Talvez isso se explique pelas características estruturais da borda não serem claramente distintas dos outros habitats. Além disso, não detectei também diferenças na disponibilidade de recursos (frutos e invertebrados) entre os três habitats florestais amostrados. No e / The increase of forest edges is part of the influence of the fragmentation on forest remnants and may affect small-mammal communities. For evaluating such effect I sampled five areas representative of South-Brazilian forests. In each of them I sampled the abundance, richness, and diversity of small mammals, in the matrix (> 60 m of the forest), edge (up to 15 m to the forest interior), intermediate zone (60 m to the interior), and forest interior (150 m). I also evaluated the availability of food resources and structural characteristics of the vegetation at these habitats. For a total of 446 individuals (20 species) captured the results did not indicate evident edge effects for any of the community metrics. Such pattern may be explained by the lack of differences in structural characteristics between edges and the other forest habitats. Besides, I did not detect differences in resource availability (fruits and invertebrates) among the three forest habitats, either. However, rarefaction curves indicated s

Hypothesised causes of the observed world-wide decline of amphibian populations are varied and in some cases contentious. Insufficient information relating to the autecology of many amphibian species can cause erroneous speculations regarding critical habitat requirements and hence management programs designed to enhance population viability are often unsuccessful. Most amphibians display a bi-phasic life history that involves occupation of an aquatic breeding habitat and terrestrial habitats that are used for foraging, and shelter from predation and environmental stress. However, the focus of most amphibian research is centred on the breeding habitat, with limited research being conducted into the terrestrial habitat requirements of most amphibian species. Barakula State Forest is a large continuous area of open woodland situated in the semi-arid region of Queensland. The forest supports 21 species of endemic anurans, many of which use ephemeral waterbodies for breeding. This area is, therefore, an ideal location to test the relative importance of terrestrial habitat on the distribution of a suite of frogs that display different morphological and physiological characteristics. On the landscape scale, the attributes of the terrestrial environment at three survey areas within Barakula were similar. However, at the patch scale, ground truthing showed there were considerable variations in vegetation and ground cover attributes within and between each survey site. Measured properties of the soil also tended to vary within and between sites. Soil texture ranged from sandy to heavy clay, soil pH ranged from 3.9 to 6.4 and soil moisture varied considerably. Agar models, used for testing evaporative moisture loss at different microhabitats, retained significantly higher levels of moisture when positioned in the buried microhabitat during summer, but in winter, models that were placed under leaf litter retained higher levels of moisture. Variations in levels of moisture loss at the five different microhabitats were evident within and between the survey sites. Despite a prolonged drought, 1844 native frogs representing 17 species were pitfall trapped. Members from the family Myobatrachidae comprised 94% of these captures, and burrowing species accounted for 75% of total captures. Species were not randomly distributed within or between the survey sites. Vegetation attributes and soil properties played a significant role in influencing the catch rates and traplines that supported similar vegetation and soil attributes also tended to catch similar species. Capture rates of six of the seven burrowing species were significantly influenced by soil properties. When given a choice of four different microhabitats created in enclosures, individuals from five species showed varying responses to habitat choice during night time activity. During daylight all species tended to avoid bare areas and burrowing species tended to burrow under some form of cover. Pseudophryne bibronii metamorphs showed a significant avoidance to soils with high pH. The number of Limnodynastes ornatus metamorphs was significantly and positively correlated with moisture levels surrounding a breeding area. Limnodynastes ornatus metamorphs tended to avoid areas that did not support some form of cover. Embryos from the terrestrial egg laying P. bibronii translocated to sites with varying levels of soil pH, suffered increased mortality where the soil pH was &gt4.8. In the laboratory, embryonic survival was not significantly different between the four pH treatments. There was a significant influence of fungal infection on survival rates and ranked fungal infection was significantly different between the four pH treatments. The terrestrial environment at the three survey sites has provided sufficient protection from environmental elements to allow a large diversity of anurans to persist for long periods without access to permanent water. Management must consider the importance of the non-breeding habitat when defining buffer zones, restoration programs and conservation strategies to ensure that the complete set of ecological requirements for frog species are provided.

Fiskar kan drabbas av många olika parasiter tillhörande ett brett spektrum av organismgrupper. Parasiter kan påverka värdens fysiologi, morfologi och beteende, vilket kan ha negativa effekter på värden.  Den starkt hotade flodpärlmusslan (Margaritifera margaritifera) parasiterar under sitt tidiga liv som glochidielarver på fiskgälar, i Sverige främst på öringen (Salmo trutta). I tidigare studier har man sett såväl negativa som inga effekter av parasiteringen på värdfisken. Syftet med min studie var att undersöka effekten av musslans parasitering på öringens rörelse, habitatval och tillväxt i Älgån i Arvika kommun, Värmland. Resultaten visade att höginfekterad öring förflyttade sig längre sträckor och hade lägre tillväxt än låginfekterad öring. Det var ingen skillnad mellan hög- och låginfekterade öringars habitatval med avseende på djup, vattenhastighet eller substrat. Sammanfattningsvis kan höginfekterade öringar ha högre mortalitetsrisk än låginfekterade, lägre tillväxt och sämre konkurrensförmåga, vilket kan ha negativa konsekvenser för musslans rekryteringsframgång. / Fish are affected by various parasites, belonging to many different taxonomic groups. Parasites can affect the host’s physiology, morphology, and behaviour, which may have negative effects for the host. The critically endangered freshwater pearl mussel (Margaritifera margaritifera) lives parasitically as glochidia larvae on the gills of fish, and in Sweden this occurs mainly in the gills of brown trout (Salmo trutta). During their parasitic stage, which lasts for almost one year, the mussel grows up to four or five times their initial size.  Previous studies have reported both negative and no effects of the parasite on the host fish. The aim of my study was to analyse the effect of the freshwater pearl mussel parasitation on the brown trout’s movement, habitat choice, and growth in the stream Älgån in Arvika municipalty, Värmland. The results show that highly infected brown trout moved greater distances and had lower growth than less infected trout. There was no difference in habitat choice in terms of depth, velocity, or substrate between high or low infected trout. In summary, highly infected trout may have high energy costs, low growth, and poor competitive ability, which can have negative consequences for the mussel’s recruitment.

Animal community structures, life histories and individual foraging behaviour are all an outcome of a trade-off between competition for resources (and thus the risk of starvation) and survival (and thus the risk of predation). The relative importance of these factors however, differs between ecosystems, and especially when comparing temperate to tropical ones, we usually find marked differences. The seasonality of tropical ecosystems is much reduced compared to temperate ones, and weather conditions are less extreme. Accordingly tropical systems are characterised by higher species diversity, and different life history traits have been found between temperate and tropical birds. However, how the different environmental factors interact, and how predation and starvation risk vary to cause these differences still remains largely unknown. We studied the feeding behaviour of several granivorous Estrildid finches in scrub savannah habitat in central Nigeria to test how they respond to varying degrees of starvation and predation risk. During field observations and aviary experiments we investigated whether there is seasonal variation in the birds’ foraging behaviour correlating with the abundance of grass seeds and tested how they respond to different group sizes and differing distances from cover (representing a difference in predation risk). Further we also carried out field observation on the natural feeding behaviour of several closely related sympartic Estrildid finches to investigate inter-specific and seasonal differences in competition and microhabitat choice to see if this could explain their coexistence. Finally we studied habitat choice, movement behaviour and breeding biology of the potentially threatened endemic Rock Firefinch (Lagonosticta sanguinodorsalis) between the wet and the dry season via radio-tracking to establish its habitat requirements and gain the first information in its life history traits and population trends. We found little seasonal variation in the species’ foraging behaviour, and parameters that varied did not do so in a consistent manner. Thus, we found little evidence for a seasonal change in the risk of starvation. However, the abundance of several bird species varied widely between seasons and species leaving during periods of food shortage might have released competition for remaining resources. Birds did not show a strong response in their feeding behaviour with respect to cover in either intake rate or timing of feeding. However, intake rate increased with group size, which we believe to be due to scramble competition rather than risk dilution. We therefore conclude that predation did not shape the foraging behaviour of tropical granivorous passerines as markedly as that of temperate ones. Rock Firefinches were found to breed between the late rainy and the early dry season. They selected inselberg habitat, where most nests were found between rocky boulders. During the dry season, when water sources in inselberg habitat had dried out, they had to fly distances of up to 700 m to the gallery forest to get water and this led to the inclusion of more scrub savannah and gallery forest within their home ranges. Daily egg survival was 0.89 ± 0.03 calculated after the Mayfield analysis and most failing nests were depredated probably mainly by lizards. We suggest that in addition to nest predation, water availability might limit breeding time and thus reproductive output of Rock Firefinches. Predation risk did not seem to be of high importance in shaping the birds’ feeding behaviour because there was no seasonal variation in the risk of starvation. We found some suggestive evidence that competition might be important and it is likely that bird populations constantly stay close to carrying capacity. In contrast to temperate regions the need to conserve water might be of higher importance in shaping the birds’ feeding behaviour. High adult survival rates might be due to reduced seasonality in the risk of starvation thereby leading to reduced predation risk on adult birds. High nest predation might also be of higher importance in shaping the life history traits of tropical passerines, but at present this suggestion remains speculative. The results fit into the general framework that there is a trade-off between starvation and predation risk, and in the absence of starvation risk for some species in tropical areas, predation risk is also relatively unimportant.