Ecology and behaviour of Palm-nut Vultures Gypohierax angolensis in the Bijagós Archipelago, Guinea-Bissau

Populations of many vulture species have undergone substantial declines. In Africa, 82% are threatened and although research on vultures has increased, the biology and ecology of several species is still poorly known. The Palm-nut Vulture Gypohierax angolensis has peculiar ecological characteristics, feeding on palm fruits, associated with the aquatic environment and taking a wide variety of prey. It has been over 40 years since the last thorough study on the ecology of the species was undertaken. This study investigated several ecological and behavioural aspects of Palm-nut Vultures, using a combination of direct observations, stable isotope analysis and Bayesian mixing models. The population of this species within the João Vieira and Poilão Marine National Park is estimated to be 21–30 birds km−2. Egg laying started in November (early dry season) and some chicks were still growing in early May. A minimum of 54% of nests produced a fledgling. Observations suggest that Palm-nut Vultures moult all flight feathers annually, between January and November. Their foraging behaviour is described and cafeteria trials showed their preference for fish over oil palm fruits. However, it is estimated that oil palm fruits account for almost 50% of the assimilated diet, followed by fish, crabs and Green Turtle hatchlings or eggs, as revealed by stable isotopes and Bayesian mixing models.Résumé: Les populations de beaucoup d’espèces de vautours connaissent un important déclin. En Afrique, 82% sont menacées et malgré l’augmentation des recherches sur les vautours, la biologie et l’écologie de plusieurs espèces restent mal connues. Le Vautour Palmiste africain Gypohierax angolensis a des caractéristiques écologiques particulières: se nourrissant des fruits de palmiers, il est associé à l’environnement aquatique et se nourri d’une large variété de proies. La dernière étude approfondie sur son écologie a été effectuée il y a plus de 40 ans. Cette étude a enquêté plusieurs aspects écologiques et comportementaux du Vautour Palmiste africain, utilisant une combinaison entre des observations directes, l’analyse de la stabilité de l’isotope et la modélisation mixte de Bayesian. La population de ces espèces dans le Parc Marin National Poilão et le João Vieira est estimée à 21-30 oiseaux/km². La ponte des oeufs a commencé en Novembre (au début de la saison sèche) et quelques poussins étaient encore en cours de croissance début Mai. Au minimum 54% des nids ont produit un jeune. Les observations suggèrent que le Palmiste africain mue toutes ses plumes de vol une fois par an, entre Janvier et Novembre. Ses comportements de nourrissage ont été décrits et il a été jugé qu’ils montraient une préférence pour le poisson plutôt que l’huile des fruits de palmier. Cependant, il a été estimé que l’huile de Palme compte pour presque 50% de leur régime alimentaire, suivi pas le poisson, les crabes et les oeufs de Tortues Vertes (ou des jeunes pendant l’éclosion), comme l’ont révélé l’isotope stable la modélisation mixte de Bayesian.info:eu-repo/semantics/publishedVersio

Nest-site characteristics and aspects of the breeding biology of the endangered Timneh Parrot Psittacus timneh in Guinea-Bissau

Timneh Parrots Psittacus timneh are endemic to the moist forests of West Africa. Concerns over rapid declines in populations due to overharvesting for the pet trade and forest loss prompted the species’ categorisation as Endangered on the IUCN Red List of Threatened Species in 2016. Despite these threats, few data exist on their biology in the wild, impeding the development of effective conservation initiatives to protect populations. One of the few recorded breeding sites for this species occurs in the Bijagós Archipelago in Guinea-Bissau, where chicks have been historically harvested from nests and forest clearance for agriculture is common. We investigated the breeding ecology of Timneh Parrots in the Bijagós Archipelago focusing on two islands that harbour the densest populations. Specifically, we describe nest-site characteristics, breeding phenology and reproductive productivity. Timneh Parrots were found to use secondary nest cavities in 17 species of trees, predominantly nesting in trees between 20 m and 50 m in height. Nest cavities were generally aggregated, with a density of up to 14 nests ha−1 in some areas, although nests also occurred in isolated large trees. The distribution of nests likely reflected a heterogeneous distribution of large trees containing suitable nest cavities, emphasising the importance of protecting mature trees. Nesting efforts were initiated between early January until late March, suggesting that nest surveillance efforts to deter poaching can be efficiently focused at a small number of key sites during February to May each year, when fledgling chicks are most likely to be present. These data further suggest that the population may be limited by the availability of suitable nest cavities and that the installation of artificial nest cavities could help increase the breeding population.Fundação para a Ciência e a Tecnologia (FCT)info:eu-repo/semantics/publishedVersio

Evidence for contrasting accumulation pattern of cadmium in relation to other elements in Senilia senilis and Tagelus adansoni from the Bijagós archipelago, Guinea-Bissau

Shellfish harvesting in intertidal areas is a widespread and economically important activity in many countries across West Africa. However, in some areas, there is virtually no information concerning the levels of contaminants (and other elements related to nutritional aspects) in the harvested species. We collected sediments and several individuals of the West African bloody cockle Senilia senilis and of the razor clam Tagelus adansoni during the dry season of 2015 nearby three islands in the Bijagós archipelago, Guinea-Bissau. Aluminium, Ca, Fe, Mg, As, Cd, Co, Cr, Cu, Mn, Ni, Pb and Zn were determined in sediments and whole soft tissues of the two bivalves. Sediments showed uniformly low trace element concentrations, pointing to an ecosystem with low levels of trace element contamination. T. adansoni presented higher concentrations of most elements than S. senilis, with the exception of Cd that showed up to 40 times higher values in S. senilis than in T. adansoni from the same sites. Furthermore, Cd concentrations (25±8.7 mg kg(-1), dw) in S. senilis are clearly above the maximum level established for human consumption. Future studies should clarify whether biological factors are the major responsible for this unusual situation.Fundação para a Ciência e a Tecnologia (FCT); MAVA Foundation;info:eu-repo/semantics/publishedVersio