Stable isotope analyses are a powerful tool in understanding diets, defining trophic networks, in... more Stable isotope analyses are a powerful tool in understanding diets, defining trophic networks, inferring geographical origins of animals and in forensic tracing of the origins of deceased humans or illegally traded animal and plant material. African grey parrots Psittacus erithacus are one of the most traded animal species in the world, and the origin of confiscated illegal or deceased specimens are often unknown. We measured stable isotope values (δ13C, δ15N and δ2H) in different African grey parrots (n = 32) and determined feather type (i.e. primary, tail, breast) standardization values for comparing individuals. δ13C and δ2H values differed between known wild (n = 42) and captive (n = 50) birds when standardized for feather type, but not for δ15N. δ13C and δ2H values in feathers from a consignment of African grey parrots (n = 100), all of which were deceased, aligned significantly with that of known wild birds. We suggest that further analyses of feathers, across a range of spatial and temporal scales, will enhance stable isotope analyses as a valuable tool in monitoring and combatting the trade of African grey parrots. Furthermore, the use of stable isotope analyses may improve the monitoring of illegally traded bird species, and other wildlife, across the globe.
Breeding biology and nesting requirements of Cape Parrots in their natural habitat and in captivi... more Breeding biology and nesting requirements of Cape Parrots in their natural habitat and in captivity were investigated. Few nests were found, suggesting that nest-sites are limiting, and that the parrots have specific nesting requirements. Nests were secondary cavities in dead Podocarpus spp. (branches), high up in forest canopy trees. Breeding usually occurred from August to February, but was observed in other months, particularly in captive birds. Clutch size varied from 2–5, incubation was by the female and lasted 28–30 days, with fledging a further 55–79 days. In captive birds the ovaries are mature at 2.5 years, but age at first breeding is usually at 4–6 years.
Plant–animal interactions are key to sustaining whole communities and ecosystem function. However... more Plant–animal interactions are key to sustaining whole communities and ecosystem function. However, their complexity may limit our understanding of the underlying mechanisms and the species involved. The ecological effects of epizoochory remain little known compared to other seed dispersal mechanisms given the few vectors identified. In addition, epizoochory is mostly considered non-mutualistic since dispersers do not obtain nutritional rewards. Here, we show a widespread but unknown mutualistic interaction between parrots and plants through epizoochory. Combining our observations with photos from web-sources, we recorded nearly 2000 epizoochory events in 48 countries across five continents, involving 116 parrot species and nearly 100 plant species from 35 families, including both native and non-native species. The viscid pulp of fleshy fruits and anemochorous structures facilitate the adherence of tiny seeds (mean 3.7 × 2.56 mm) on the surface of parrots while feeding, allowing the ...
The Common Starling Sturnus vulgaris has progressively expanded its range in South Africa since i... more The Common Starling Sturnus vulgaris has progressively expanded its range in South Africa since its introduction into Cape Town in the late 19th century. In the past few decades it has extended this range into Gauteng province. Using data from the Southern African Bird Atlas Project 2, this paper examines the spread and relative abundance changes for the species across South Africa over the past 10 years, with a detailed look at the recently-colonised Gauteng. Across South Africa, the Common Starling's distribution has shifted, and grown. As it spreads north along the coastline and northwards inland, some of the former range has been lost. In Gauteng, the species has shown a range and abundance expansion over the same period. If the observed trends are to continue, this species is likely to eventually become a prominent species across the entire country, and further north into the sub-region. However, the potential impact that this species has on indigenous avifauna is unknown a...
Xylitol is an alternative sweetener to sucrose, glucose and fructose, and is available under a nu... more Xylitol is an alternative sweetener to sucrose, glucose and fructose, and is available under a number of brands in South Africa. Carbon stable isotope values (δ13C) of a selection of commercially available xylitol products (n=28) were analysed and compared with sugar samples (n=29). Sugarcane (C4) and beet sugar (C3) derived sugar samples aligned with published values of source, although two samples that indicated a sugarcane origin suggested a beet sugar origin. Control corn-derived samples defined a stepwise xylose to xylitol discrimination of +0.7‰. The distinction between C3- and C4-derived xylitol was less clear with three samples difficult to define (range = -14.8 to -17.1‰). The values for a suite of xylitol samples (-22.3‰ to -19.7‰; n=8) that aligned closely with a suspected C3-derived xylose, were ~8‰ more positive than known birch isotope values. Some xylitol samples may thus represent (1) a mixture of C3- and C4-derived products, (2) derivation from a CAM species source ...
SummaryStable isotopes (δD, δ13C, δ15N) were measured in adult and juvenile Amur Falcon Falco amu... more SummaryStable isotopes (δD, δ13C, δ15N) were measured in adult and juvenile Amur Falcon Falco amurensis feathers to understand the migratory connectivity of this species. Using the OIPC (Online Isotopes in Precipitation Calculator) and a calibration curve for American Kestrels Falco sparverius we predicted the breeding range of South African Amur Falcons in the Palaearctic. δD values for juvenile feathers (mean ± SE = -58.1 ± 2.5‰, range -83.9 to -25.7‰) and predicted Palaearctic annual precipitation values indicated that juvenile Amur Falcons in South Africa originated from across their entire Palaearctic range. This rejects the leapfrog migration hypothesis and suggests the widespread movement of birds south, with a funnelling effect into the subregion where they become concentrated over a narrower distribution range. Adult δDf values were more depleted (-37.4 ± 1.8‰, range = -71.3 to -9.3‰) than predicted annual precipitation values for sites where feathers moulted in South Afric...
We believe that we amply demonstrated the importance of Amur Falcons towards agriculture and ecol... more We believe that we amply demonstrated the importance of Amur Falcons towards agriculture and ecology in South Africa and Southern Africa. Based on our calculations and observations, it may even be considered a keystone species. Any significant reduction in falcon numbers may have significant consequences and their conservation and maintenance of numbers seem critical. Aiming for only conserving a reduced but stable population, just to keep the species from going extinct, could be a serious blow to the ecology in the breeding and non-breeding grounds, and probably also at the stop-over sites (including those in India). Maintenance of the population in toto is therefore strongly advised. Although the conservation status of this species is currently of least concern, the sensitivity of this species towards sudden reductions combined with the concomitant ecological and economic consequences should be enough motivation for a re-evaluation.
Long-distance dispersal events and their derivable increases of genetic diversity have been highl... more Long-distance dispersal events and their derivable increases of genetic diversity have been highlighted as important ecological and evolutionary determinants that improve performances of range-expanding species. In the context of global environmental change, specific dispersal strategies have to be understood and foreseen if we like to prevent general biodiversity impoverishment or the spread of allochthonous diseases. We explore the genetic structure and potential population mixing on the recently range-expanding European bee-eater Merops apiaster. In addition, the species is suspected of harbouring and disseminating the most relevant disease for bees and apiculture, Nosema microsporidia. In agreement with complementary ringing recovery data and morphometric measurements, genetic results on two mitochondrial genes and 12 microsatellites show a reasonably well-structured population partitioning along its breeding distribution. Microsatellite results indicated that not only did a few birds recently disperse long distance during their return migrations and change their natal breeding areas, but also that a group of allochthonous birds together founded a new colony. Although we did not provide evidence on the direct implication of birds in the widespread of Nosema parasites, our finding on the long-distance dispersal of bird flocks between remote breeding colonies adds concern about the role of European bee-eaters in the spread of such disease at a large, inter-continental scale.
Worldwide, there is concern about the increased prevalence of infectious diseases and their effec... more Worldwide, there is concern about the increased prevalence of infectious diseases and their effects on biodiversity. Increasing changes in the environment, particularly changes in climatic conditions as a consequence of anthropogenic-induced climate change, are some of the factors driving this increased disease prevalence. Vertebrate taxa that appear to be most affected by these diseases are amphibians and birds, though this may be a consequence of research effort. Beak and feather disease virus (BFDV) affecting psittacine bird species is the disease of concern here. Data on BFDV incidence in wild, endangered Cape parrots (Poicephalus robustus) were collected opportunistically from 1992 to 2014. Data show that the disease is prevalent naturally in the wild during extreme climatic events, including drought. This stresses the birds, which may result in the expression of pathological symptoms. Juveniles in particular appear to succumb during times of drought. This has conservation implications with the impacts of extreme climatic events associated with anthropogenic-induced climate change.
Stable isotope analyses are a powerful tool in understanding diets, defining trophic networks, in... more Stable isotope analyses are a powerful tool in understanding diets, defining trophic networks, inferring geographical origins of animals and in forensic tracing of the origins of deceased humans or illegally traded animal and plant material. African grey parrots Psittacus erithacus are one of the most traded animal species in the world, and the origin of confiscated illegal or deceased specimens are often unknown. We measured stable isotope values (δ13C, δ15N and δ2H) in different African grey parrots (n = 32) and determined feather type (i.e. primary, tail, breast) standardization values for comparing individuals. δ13C and δ2H values differed between known wild (n = 42) and captive (n = 50) birds when standardized for feather type, but not for δ15N. δ13C and δ2H values in feathers from a consignment of African grey parrots (n = 100), all of which were deceased, aligned significantly with that of known wild birds. We suggest that further analyses of feathers, across a range of spatial and temporal scales, will enhance stable isotope analyses as a valuable tool in monitoring and combatting the trade of African grey parrots. Furthermore, the use of stable isotope analyses may improve the monitoring of illegally traded bird species, and other wildlife, across the globe.
Breeding biology and nesting requirements of Cape Parrots in their natural habitat and in captivi... more Breeding biology and nesting requirements of Cape Parrots in their natural habitat and in captivity were investigated. Few nests were found, suggesting that nest-sites are limiting, and that the parrots have specific nesting requirements. Nests were secondary cavities in dead Podocarpus spp. (branches), high up in forest canopy trees. Breeding usually occurred from August to February, but was observed in other months, particularly in captive birds. Clutch size varied from 2–5, incubation was by the female and lasted 28–30 days, with fledging a further 55–79 days. In captive birds the ovaries are mature at 2.5 years, but age at first breeding is usually at 4–6 years.
Plant–animal interactions are key to sustaining whole communities and ecosystem function. However... more Plant–animal interactions are key to sustaining whole communities and ecosystem function. However, their complexity may limit our understanding of the underlying mechanisms and the species involved. The ecological effects of epizoochory remain little known compared to other seed dispersal mechanisms given the few vectors identified. In addition, epizoochory is mostly considered non-mutualistic since dispersers do not obtain nutritional rewards. Here, we show a widespread but unknown mutualistic interaction between parrots and plants through epizoochory. Combining our observations with photos from web-sources, we recorded nearly 2000 epizoochory events in 48 countries across five continents, involving 116 parrot species and nearly 100 plant species from 35 families, including both native and non-native species. The viscid pulp of fleshy fruits and anemochorous structures facilitate the adherence of tiny seeds (mean 3.7 × 2.56 mm) on the surface of parrots while feeding, allowing the ...
The Common Starling Sturnus vulgaris has progressively expanded its range in South Africa since i... more The Common Starling Sturnus vulgaris has progressively expanded its range in South Africa since its introduction into Cape Town in the late 19th century. In the past few decades it has extended this range into Gauteng province. Using data from the Southern African Bird Atlas Project 2, this paper examines the spread and relative abundance changes for the species across South Africa over the past 10 years, with a detailed look at the recently-colonised Gauteng. Across South Africa, the Common Starling's distribution has shifted, and grown. As it spreads north along the coastline and northwards inland, some of the former range has been lost. In Gauteng, the species has shown a range and abundance expansion over the same period. If the observed trends are to continue, this species is likely to eventually become a prominent species across the entire country, and further north into the sub-region. However, the potential impact that this species has on indigenous avifauna is unknown a...
Xylitol is an alternative sweetener to sucrose, glucose and fructose, and is available under a nu... more Xylitol is an alternative sweetener to sucrose, glucose and fructose, and is available under a number of brands in South Africa. Carbon stable isotope values (δ13C) of a selection of commercially available xylitol products (n=28) were analysed and compared with sugar samples (n=29). Sugarcane (C4) and beet sugar (C3) derived sugar samples aligned with published values of source, although two samples that indicated a sugarcane origin suggested a beet sugar origin. Control corn-derived samples defined a stepwise xylose to xylitol discrimination of +0.7‰. The distinction between C3- and C4-derived xylitol was less clear with three samples difficult to define (range = -14.8 to -17.1‰). The values for a suite of xylitol samples (-22.3‰ to -19.7‰; n=8) that aligned closely with a suspected C3-derived xylose, were ~8‰ more positive than known birch isotope values. Some xylitol samples may thus represent (1) a mixture of C3- and C4-derived products, (2) derivation from a CAM species source ...
SummaryStable isotopes (δD, δ13C, δ15N) were measured in adult and juvenile Amur Falcon Falco amu... more SummaryStable isotopes (δD, δ13C, δ15N) were measured in adult and juvenile Amur Falcon Falco amurensis feathers to understand the migratory connectivity of this species. Using the OIPC (Online Isotopes in Precipitation Calculator) and a calibration curve for American Kestrels Falco sparverius we predicted the breeding range of South African Amur Falcons in the Palaearctic. δD values for juvenile feathers (mean ± SE = -58.1 ± 2.5‰, range -83.9 to -25.7‰) and predicted Palaearctic annual precipitation values indicated that juvenile Amur Falcons in South Africa originated from across their entire Palaearctic range. This rejects the leapfrog migration hypothesis and suggests the widespread movement of birds south, with a funnelling effect into the subregion where they become concentrated over a narrower distribution range. Adult δDf values were more depleted (-37.4 ± 1.8‰, range = -71.3 to -9.3‰) than predicted annual precipitation values for sites where feathers moulted in South Afric...
We believe that we amply demonstrated the importance of Amur Falcons towards agriculture and ecol... more We believe that we amply demonstrated the importance of Amur Falcons towards agriculture and ecology in South Africa and Southern Africa. Based on our calculations and observations, it may even be considered a keystone species. Any significant reduction in falcon numbers may have significant consequences and their conservation and maintenance of numbers seem critical. Aiming for only conserving a reduced but stable population, just to keep the species from going extinct, could be a serious blow to the ecology in the breeding and non-breeding grounds, and probably also at the stop-over sites (including those in India). Maintenance of the population in toto is therefore strongly advised. Although the conservation status of this species is currently of least concern, the sensitivity of this species towards sudden reductions combined with the concomitant ecological and economic consequences should be enough motivation for a re-evaluation.
Long-distance dispersal events and their derivable increases of genetic diversity have been highl... more Long-distance dispersal events and their derivable increases of genetic diversity have been highlighted as important ecological and evolutionary determinants that improve performances of range-expanding species. In the context of global environmental change, specific dispersal strategies have to be understood and foreseen if we like to prevent general biodiversity impoverishment or the spread of allochthonous diseases. We explore the genetic structure and potential population mixing on the recently range-expanding European bee-eater Merops apiaster. In addition, the species is suspected of harbouring and disseminating the most relevant disease for bees and apiculture, Nosema microsporidia. In agreement with complementary ringing recovery data and morphometric measurements, genetic results on two mitochondrial genes and 12 microsatellites show a reasonably well-structured population partitioning along its breeding distribution. Microsatellite results indicated that not only did a few birds recently disperse long distance during their return migrations and change their natal breeding areas, but also that a group of allochthonous birds together founded a new colony. Although we did not provide evidence on the direct implication of birds in the widespread of Nosema parasites, our finding on the long-distance dispersal of bird flocks between remote breeding colonies adds concern about the role of European bee-eaters in the spread of such disease at a large, inter-continental scale.
Worldwide, there is concern about the increased prevalence of infectious diseases and their effec... more Worldwide, there is concern about the increased prevalence of infectious diseases and their effects on biodiversity. Increasing changes in the environment, particularly changes in climatic conditions as a consequence of anthropogenic-induced climate change, are some of the factors driving this increased disease prevalence. Vertebrate taxa that appear to be most affected by these diseases are amphibians and birds, though this may be a consequence of research effort. Beak and feather disease virus (BFDV) affecting psittacine bird species is the disease of concern here. Data on BFDV incidence in wild, endangered Cape parrots (Poicephalus robustus) were collected opportunistically from 1992 to 2014. Data show that the disease is prevalent naturally in the wild during extreme climatic events, including drought. This stresses the birds, which may result in the expression of pathological symptoms. Juveniles in particular appear to succumb during times of drought. This has conservation implications with the impacts of extreme climatic events associated with anthropogenic-induced climate change.
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Papers by Craig Symes