Browsing by Author "Monteiro, Hamilton"
Now showing 1 - 5 of 5
Results Per Page
Sort Options
- Deliberate poisoning of Africa's vulturesPublication . Henriques, Mohamed; Buij, Ralph; Monteiro, Hamilton; Sá, Joãozinho; Gomes Wambar, Francisco; Tavares, José Pedro; Botha, Andre; Citegetse, Geoffroy; Lecoq, Miguel; Catry, Paulo; Ogada, DarcyNão consta
- Nest-site characteristics and aspects of the breeding biology of the endangered Timneh Parrot Psittacus timneh in Guinea-BissauPublication . Lopes, Daniel C; Martin, Rowan O; Henriques, Mohamed; Monteiro, Hamilton; Regalla, Aissa Said; Tchantchalam, Quintino; Indjai, Bucar; Cardoso, Seco; Manuel, Celestino; Cunha, Manjaco; Cunha, Domingos; Catry, PauloTimneh 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.
- Not in wilderness: African vulture strongholds remain in areas with high human densityPublication . Henriques, Mohamed; Granadeiro, José Pedro; Monteiro, Hamilton; Nuno, Ana; Lecoq, Miguel; Cardoso, Paulo Eduardo; Regalla, Aissa Said; Catry, PauloVultures constitute an important functional group in many ecosystems, providing crucial ecosystem services both in natural and humanized environments. These scavengers are facing massive declines worldwide, but in several African countries virtually nothing is known on populations' status and threats, hampering the development of adequate conservation strategies. In Guinea-Bissau, globally important populations of Hooded Necrosyrtes monachus and African white-backed vultures Gyps africanus were recently reported. Using the country as a study area, we aim to characterize human-vulture interactions in West Africa applying a multidisciplinary approach. We assessed the status and distribution of vulture populations using data from 1711 km of roadside transects, examined predictors of their distribution, and produced a nationwide population estimate for the Hooded Vulture, using an innovative method based on the relationship between the size of human population in settlements and vulture numbers. We conducted 47 stakeholder interviews to assess perceived roles played by vultures, and to investigate potential anthropogenic threats. Hooded vultures were strongly associated with high human population densities, whereas no relation was found between African white-backed and Rüppell's vultures and any of the tested predictors, which included cattle density, precipitation and Normalized Difference Vegetation Index, among others. We estimate a national population of 43347 Hooded vultures, the largest population reported in the species range. Respondents were generally aware of the services provided by vultures, especially waste and carcass removal, including in urban areas. Hunting for witchcraft and traditional medicine was the most frequently recognised threat, while poisoning was ranked as having the highest impact. We hypothesise that poisoning-related mortality may be affecting African white-backed and Rüppell's vultures' distribution and explain their scarcity in apparently highly suitable habitats. Our results suggest a mutualistic rather than a commensalistic relationship between vultures and humans, with important implications for designing and implementing conservation strategies.
- Status of birds of prey in Guinea-Bissau: First assessment based on road surveysPublication . Henriques, Mohamed; Lecoq, Miguel; Monteiro, Hamilton; Regalla, Aissa Said; Granadeiro, José Pedro; Catry, PauloSeveral studies have reported marked declines in populations of birds of prey across the African continent, including West Africa. However, there are still regions of which virtually nothing is known, as is the case for Guinea-Bissau. Because birds of prey play important roles in ecosystems and several species are threatened, it is important to establish baseline knowledge on their status. This is the first study in the country focusing exclusively on birds of prey. We conducted 1 711 km of roadside transects from mid-February to the end of May 2016, covering most of Guinea-Bissau. In total 4 989 birds of 33 species were counted, of which Hooded Vultures Necrosyrtes monachus were the most common (252 birds per 100 km, the second highest abundance in all the species’ range). Observations outside transects, including during regular field trips throughout the country, particularly between 2012 and 2016, were used as complementary information adding 13 species to the list, and contributing three new species for Guinea-Bissau: Ayres’s Hawk-eagle Hieraaetus ayresii, Booted Eagle Hieraaetus pennatus and Lesser Kestrel Falco naumanni. Most species showed differences in abundance in relation to vegetation cover (based on the normalised difference vegetation index). Apart from Hooded Vultures and White-backed Vultures Gyps africanus, all other raptors in the IUCN Red List were found to be scarce, including other vultures and several medium-to-large eagles.
- The diet of two opportunistic seabirds (Caspian and Royal Terns) confirms the importance of Sardinella spp. in West African coastal food websPublication . Correia, Edna; Granadeiro, J. P.; Regalla, Aissa Said; Monteiro, Hamilton; Catry, PauloDespite their importance for fisheries, livelihoods and biodiversity conservation, shelf ecosystems in West Africa are poorly known. Caspian Tern (Hydroprogne caspia) and Royal Tern (Thalasseus maximus) are two of the most numerous and widespread nesting seabirds in the region, and an understanding of the diet of these opportunistic predators may throw light on important elements of the local food webs. This study describes and compares the prey consumed by these two species in Guinea and Guinea-Bissau collected from 2013 to 2015. Our results show that both tern species feed mostly on pelagic fish from which Clupeidae (mostly Sardinella maderensis) dominated the diet at all locations and seasons. Pristigasteridae and Polynemidae were the next most frequent prey in the diet of these two tern species. Our findings strengthen the recent suggestion of a wasp-waist ecosystem for our study area, with sardinella as the key prey for several predators, including seabirds and pelagic fishes, and potentially influencing their distribution and abundance. Moreover, our results show a higher diversity in the diet of the Caspian Tern, with this species preying on a greater range of benthopelagic fishes (e.g. Gerreidae; Mugilidae) which fits with observations of inshore foraging that seems rarer in Royal Terns. We further show that prey identification based only on otoliths from pellets, as opposed to the use of all hard structures (e.g. otoliths, vertebrae, scales), seriously underestimates the occurrence of species with fragile and small otoliths, including clupeids and other small pelagics.