Robert L Thomson

Robert L Thomson
University of Cape Town | UCT · FitzPatrick Institute of African Ornithology

PhD in Animal Ecology

About

94
Publications
25,332
Reads
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2,470
Citations
Citations since 2017
50 Research Items
1550 Citations
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2017201820192020202120222023050100150200250300
2017201820192020202120222023050100150200250300
Additional affiliations
August 2015 - present
Percy FitzPatrick Institute of African Ornithology
Position
  • Professor (Associate)
September 2008 - July 2015
University of Turku
Position
  • Researcher
February 2007 - August 2008
Wildlife Conservation Society
Position
  • AI surveillance team leader

Publications

Publications (94)
Article
Old world vultures are the most threatened group of raptors globally. Supplementary feeding sites (SFS) are a popular conservation tool, widely used to assist vulture populations. Despite their popularity, the impact of SFS on vultures remains largely unstudied. A lack of knowledge on the number, distribution and management of SFS is a key factor h...
Article
Eavesdropping on community members has immediate and clear benefits. However, little is known regarding its importance for the organization of cross-taxa community structure. Furthermore, the possibility that eavesdropping could allow species to coexist with a predator and access risky foraging habitat, thereby expanding their realized niche, has b...
Article
Full-text available
“Islands of fertility” result from the focussing of water and nutrients around many shrub or tree species due to plants foraging for resources. Plant–animal feedbacks may amplify the development of such islands through environmental modification due to, for example, faunal deposition of nutrients and seeds. Fauna residing within vegetation clumps a...
Article
The decline of numerous bird species worldwide has been attributed to increased nest predation pressure often associated with anthropogenic factors. Identifying effective management strategies to reduce nest predation is therefore a conservation priority, but tests of management strategies often lack appropriate control treatments. Conditioned Food...
Article
Animal distribution in a landscape depends mostly on the availability of resources. This can be facilitated by other species that have positive effects on local species diversity and impact community structure. Species that significantly change resource availability are often termed ecosystem engineers. Identifying these species is key but predicti...
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Full-text available
Birds of prey are apex predators and understanding their life history can serve as a valuable baseline for investigating their ecological role. Pygmy Falcons ( Polihierax semitorquatus ), Africa’s smallest diurnal raptor, have evolved to be obligate associates of Sociable Weaver ( Philetairus socius ) colonies throughout their southern African rang...
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The African Bird Atlas Project (ABAP) is a citizen-science bird-monitoring programme that relies on a robust, repeatable protocol (BirdMap) and allows insights into the distributions of African birds and their conservation. The protocol involves collecting bird lists within spatial sampling units called pentads (5 × 5 minutes of latitude by longitu...
Article
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Breeding habitat choice based on the attraction to other species can provide valuable social information and protection benefits. In birds, species with overlapping resources can be a cue of good quality habitats; species with shared predators and/or brood parasites can increase joint vigilance or cooperative mobbing, while raptors may provide a pr...
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1. In vertebrates, thyroid hormones (THs) play an important role in the regulation of growth, development, metabolism, photoperiodic responses and migration. Maternally transferred THs are important for normal early‐phase embryonic development when embryos are not able to produce endogenous THs. Previous studies have shown that variation in materna...
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The spatial distribution of animals in a landscape depends mainly on the distribution of resources. Resource availability is often facilitated by other species and can positively influence local species diversity and affect community structure. Species that significantly change resource availability are often termed, ecosystem engineers. Identifyin...
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Tissue samples are frequently collected to study various aspects of avian biology, but in many cases these samples are not used in their entirety and are stored by the collector. The already collected samples provide a largely overlooked opportunity because they can be used by different researchers in different biological fields. Broad reuse of sam...
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Telomere length and shortening rate are increasingly used as biomarkers for long-term costs in ecological and evolutionary studies because of their relationships with survival and fitness. Both early-life conditions and growth, and later-life stressors can create variation in telomere shortening rate. Studies on between-population telomere length a...
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Background Populations living in fragmented habitats may suffer from loss of genetic variation and reduced between-patch dispersal, which are processes that can result in genetic differentiation. This occurs frequently in species with reduced mobility, whereas genetic differentiation is less common among mobile species such as migratory birds. The...
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The provision of anthropogenic food undoubtedly influences urban bird fitness. However, the nature of the impact is unclear, with both benefits and costs of urban diets documented. Moreover, the influence of short-term fluctuations in food availability, linked to urban weekday/weekend cycles of human presence, is largely unknown. We explored whethe...
Article
Breeding- and nest-site choice is a behavioral strategy often used to counter negative interactions. Site choices before breeding prevent costs of predation and competition but have been neglected in the context of brood parasitism. For hosts of brood parasites, the earlier brood parasitism is prevented in the breeding cycle the lower the future co...
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The global lockdown to mitigate COVID-19 pandemic health risks has altered human interactions with nature. Here, we report immediate impacts of changes in human activities on wildlife and environmental threats during the early lockdown months of 2020, based on 877 qualitative reports and 332 quantitative assessments from 89 different studies. Hundr...
Preprint
Full-text available
Telomere length and shortening rate are increasingly used as biomarkers for long-term costs in ecological and evolutionary studies because of their relationships with survival and fitness. Telomere length can be heritable, but both early-life conditions and later-life stressors can create variation in telomere shortening rate. Studies on between-po...
Article
The use of poison to eliminate predators is causing African vulture populations to collapse. To understand the prevalence and motivations of this practice we conducted an extensive survey with South African commercial farmers. Using a specialised questioning technique and ad hoc quantitative methods we found that an estimated 22% and 31% of farmers...
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The primary role of nests as structural support for eggs, nestlings, and incubating parents is well established, but our understanding of their secondary roles and their adaptive features is still limited. Nests can serve a particularly important role in protecting or buffering birds from weather. In hot, arid environments, maximum daily temperatur...
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Effects of tracking devices on survival are generally considered to be small. However, most studies to date have been conducted over a time‐period of only one year, neglecting the possible accumulation of negative effects and consequently stronger negative impacts on survival when the individuals have carried the tracking devices for longer periods...
Article
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Under the current African vulture crisis, supplementary feeding sites (SFS), which provide carrion resources, have become a popular conservation tool to address vulture declines. In South Africa, this practice is unregulated and the context in which SFS operate and their adherence to best management practices is currently unknown. In this study, we...
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Breeding habitat choice and investment decisions are key contributors to fitness in animals. Density of individuals is a well-known cue of habitat quality used for future breeding decisions, but accuracy of density cues decreases as individuals disperse from breeding sites. Used nests remain an available information source also after breeding seaso...
Article
Among birds, pronounced heterothermy tends to be used by small species belonging to phylogenetically older taxa and inhabiting environments with unpredictable and/or seasonally scarce food resources. Previous evidence suggests that a small arid-zone raptor, the pygmy falcon (Polihierax semitorquatus), enters torpor and decreases its body temperatur...
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Context: Conversion of natural ecosystems into anthropogenic landscapes can result in biotic homogenization, whereby differences in species composition among sites are diminished through colonization or local extinction. This may reduce the resilience of assemblages to further perturbation and the range or quality of ecosystem services they offer....
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Following on from the 2016 SAFRING ringing summary, the SAFRING database has grown to 2,677,367 ringing records (initial, retrap, resightings and recoveries). This number is increased to 2,698,821 records when foreign scheme records stored in the database are included.
Article
Biometrics form a key characteristic of a species. Here, we provide a summary of biometrics held by the South African Bird Ringing Scheme (SAFRING), which was initiated in 1948, including measures of mass and lengths of the tarsus, head, culmen, tail and wing. We include all species in southern Africa for which there was sufficient data. Accordingl...
Article
Mothers may vary resource allocation to eggs and embryos, which may affect offspring fitness and prepare them to future environmental conditions. The effects of food availability and predation risk on reproduction have been extensively studied, yet their simultaneous impacts on reproductive investment and offspring early life conditions are still u...
Preprint
Full-text available
Animals' life-history traits vary largely along many continuums across species and several physiological parameters have been proposed as possible mediators that drive the life-history variation, such as metabolic rates, glucocorticoids, and oxidative stress. Interestingly, thyroid hormones (THs), despite closely interacting with these physiologica...
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Predation risk is vital in determining habitat quality. But landscapes of fear are complex and dynamic, such as temperate deciduous forests characterized by intermittent, synchronized production of large seed crops (mast peaks). These “resource pulses” elevate the magnitude of predation risk via direct or indirect effects, possibly altering also pr...
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Supernormal clutches are found across bird species. Such clutches often result from more than one female laying eggs in the same nest and can reflect different behaviours from parasitism to laying mistakes. Enlarged clutches are readily visible among waders due to a maximum maternal clutch size of four eggs, yet surprisingly little is known about t...
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Universal predictions on the occurrence of cooperative breeding are still elusive. This breeding strategy is strongly linked to phylogeny; therefore, studies on species within groups where cooperative breeding is more prevalent could improve our understanding. Many diurnal raptors exhibit cooperative breeding, although occurrence rates are mostly b...
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Background: Breeding site choice constitutes an important part of the species niche. Nest predation affects breeding site choice, and has been suggested to drive niche segregation and local coexistence of species. Interspecific social information use may, in turn, result in copying or rejection of heterospecific niche characteristics and thus affec...
Article
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The use of poison by farmers to control livestock predators is a major threat to vulture populations across Eurasia and Africa. While there is now some understanding of poison use on freehold farmland regions in southern Africa, the prevalence and drivers of this practice are still unknown in communal farmlands. We surveyed 353 communal farmers in...
Article
Depositing faeces at the nest should be expected to carry risks such as increased parasite loads and disease exposure. This perplexing behaviour is unusual in birds but is consistently shown by a handful of species, and has been demonstrated to function in predator deterrence, thermoregulation and prey attraction. Pygmy Falcons Polihierax semitorqu...
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Leucism is the total or partial lack of melanins in the skin and associate structures (i.e. hair or feathers). Little is known about the factors influencing this chromatic aberration although some local studies suggest that there is an effect of habitat, age and sex. To test these hypotheses and expand our knowledge on leucism, we carried out a lar...
Article
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Ecosystem services are cited as one of the many reasons for conserving declining vulture populations in Africa. We aimed to explore how communal farmers in Namibia perceive vultures and the ecosystem services they provide, with special focus on cultural and regulating ecosystem services. We surveyed 361 households across Namibia’s communal farmland...
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Urbanization, one of the most extreme human-induced environmental changes, represents a major challenge for many organisms. Anthropogenic habitats can have opposing effects on different fitness components, for example, by decreasing starvation risk but also health status. Assessment of the net fitness effect of anthropogenic habitats is therefore d...
Article
A growing number of studies have demonstrated that heterospecific individuals with overlapping resource needs – putative competitors – can provide information to each other that improves the outcomes of decisions. Our studies using cavity nesting resident tits (information provider) and migratory flycatchers (Ficedula spp., information user) have s...
Article
Migration during spring is usually faster than during autumn because of competition for breeding territories. In some cases, however, the costs and benefits associated with the environment can lead to slower spring migration, but examples are quite rare. We compared seasonal migration strategies of the endangered Baltic population of the dunlin (Ca...
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Brood parasitism incurs severe fitness costs for hosts. Diverse host adaptations to avoid parasitism exist at various stages of the host breeding cycle, but the literature suggests that egg-stage defenses are the most evolved. Fitness costs of parasitism would be minimized if hosts avoided parasitism prior to egg laying, but it remains unclear whet...
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The presence of conspecifics is a social cue frequently used by songbirds in breeding-site selection. In migratory species, conspecific attraction is not possible for individuals that arrive first to breeding grounds, but these individuals may use information from ecologically similar heterospecifics. Resident tits (Paridae) are known to provide cu...
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Predator presence and shortage of food resources can alter behavior and cause chronic physiological stress, with long-term detrimental effects on the prey. Recently, it has been hypothesized that cellular damage via oxidative stress could be associated with such effects. Variation in food availability and predation risk could modify the oxidative/a...
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Intraspecific killing by birds while competing for resources should only occur when individuals have severely limited breeding alternatives. The requirement of such extreme circumstances is supported by the paucity of reported incidents. Here we add to this small body of literature by describing mortal combat between two male African Pygmy Falcons....
Article
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Being an obligate parasite, juvenile common cuckoos Cuculus canorus are thought to reach their African wintering grounds from Palearctic breeding grounds without guidance from experienced conspecifics but this has not been documented. We used satellite tracking to study naïve migrating common cuckoos. Juvenile cuckoos left breeding sites in Finland...
Data
Number of ringed common cuckoos per country and country where southernmost recovery was obtained. Ringing periods are shown in the country column. Information obtained from European bird ringing atlases. (DOCX)
Data
Timing and duration of the autumn migration periods of satellite-tracked juvenile and adult cuckoos in 2010–2014. Dates are given for arrivals and departures and the duration of each stage is given in days. ID = Bird identification with sex (F = female, M = male) followed by satellite-tag ID and last two digits of the tagging year in brackets. Age...
Data
Morphometrics and ages of the young cuckoos. Measured when tagging (N = 13). Tag activation is given as days after tagging. (DOCX)
Data
Location quality of positions included in the study. Number of locations and location quality (LQ A-B, 0–3; CLS 2007–2015) of cuckoos tracked from leaving the breeding areas to arrival on the winter grounds (as the southernmost stationary position) or end of transmission. (DOCX)
Data
Supplementary Wind Analysis. (DOCX)
Data
Fate of tagged cuckoos across studies. Logistic regression (Generalised Linear Model with logit link and binomial error distribution) of Finland post-fledging vs. UK post-fledging: parameter estimate of difference in location: 1.17; SD = 0.70; z = 1.68, P = 0.09. Finland juvenile autumn vs. UK adult autumn: parameter estimate of difference in age/l...
Article
Full-text available
Social information use in songbird habitat selection commonly involves a conspecific attraction strategy. Individuals copy the breeding-site choices of conspecifics, that is, bias their own settlement decisions towards sites (tracts of spatially limited habitat with similar structure) already occupied by others. In order to be adaptive, social info...
Article
The spatial distribution of predators is affected by intra- and interspecific interactions within the predator guild. Studying these interactions under fluctuating food availability, while taking habitat characteristics into account, offers a quasi-experimental set up to determine the relative impact of con- and heterospecifics on reproductive succ...
Article
Full-text available
Mothers may affect the future success of their offspring by varying allocation to eggs and embryos. Allocation may be adaptive based on the environmental conditions perceived during early breeding. We investigated the effects of food supplementation and predation risk on yolk hormone transfer in the pied flycatcher Ficedula hypoleuca. In a food sup...
Article
Predation risk has negative indirect effects on prey fitness, partly mediated through changes in behaviour. Evidence that individuals gather social information from other members of the population suggests that events in a community may impact the behaviour of distant individuals. However, spatially wide-ranging impacts on individual behaviour caus...
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Brood parasite - host systems continue to offer insights into species coevolution. A notable system is the redstart Phoenicurus phoenicurus parasitized by the 'redstart-cuckoo' Cuculus canorus gens. Redstarts are the only regular cuckoo hosts that breed in cavities, which challenges adult cuckoos in egg laying and cuckoo chicks in host eviction. We...
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Small light-level geolocators have revolutionized research on avian migration and breeding ecology. However, proper evaluations of their impact on the life history of individuals compared to control individuals that experience the same conditions are still rare. Geolocator effects may be species specific and depend on the type of mounting, sex and...
Article
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Nest predation is a key source of selection for birds that has attracted increasing attention from ornithologists. The inclusion of new concepts applicable to nest predation that stem from social information, eavesdropping or physiology has expanded our knowledge considerably. Recent methodological advancements now allow focus on all three players...
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Passive Integrated Transponder (PIT) tags have been widely used for ornithological research. However, only few studies have reported their impacts on individuals. We assessed the efficacy of subcutaneous PIT tag implantation in the mantel area of adult Pied Flycatchers Ficedula hypoleuca. In addition, we investigated the short-term effects of the t...
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A key tool used to assess reproductive trade-offs in birds is brood size manipulation (BSM) experiments. Most BSM studies have examined the influence on short-term measures of reproductive output. Seldom evaluated are the effects on long-term fitness proxies under temporally or spatially varying environments. Unpredictable environments may affect r...
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The way in which animals use habitat can affect their access to key resources or how they are buffered from environmental variables such as the extreme temperatures of deserts. One strategy of animals is to modify the environment or take advantage of structures constructed by other species. The sociable weaver bird (Philetairus socius) constructs e...
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Males of many species theoretically face a fitness tradeoff between mating and parental effort, but quantification of this is rare. We estimated the magnitude of the mating opportunity cost paid by incubating male Temminck’s stints (Calidris temminckii), taking advantage of uniparental care provided by both sexes in this species. “Incubating males”...
Article
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Animals should cue on information that predicts reproductive success. After failure of an initial reproductive attempt, decisions on whether or not to initiate a second reproductive attempt may be affected by individual experience and social information. If the prospects of breeding success are poor, long-lived animals in particular should not inve...
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Individuals of many taxa gather social information in order to make informed decisions with lowered unpredictability. Social information may show temporal periods of higher information value during certain events. However, the value of information is expected to decrease with time since the event and individuals accessing this information are expec...
Article
Predation risk is an environmental stressor that can induce changes in prey behavior and physiology. Perception of predation risk may indirectly aff ect off spring traits and future fi tness prospects via impacts on the condition of parents. Females may infl uence the survival of their off spring via maternal eff ects, especially when breeding in s...
Article
Full-text available
Breeding habitat selection is expected to be adaptive. Animals should respond to strong agents of natural selection, such as expected offspring mortality due to nest predators, in their settlement decisions. In birds, mammalian nest predators are a significant mortality source and birds are known to respond to their presence. However, the mechanism...