| Final Report | |
MARIA ISABEL MORENO & CHRISTIAN DEVENISH![]() FAUNA & FLORA INTERNATIONAL 100% FUND INSTITUTO DE INVESTIGACIÓN DE RECURSOS BIOLÓGICOS ALEXANDER VON HUMBOLDT BECAS PARA ESPECIES AMENAZADAS UNIVERSIDAD NACIONAL DE COLOMBIA, SAN ANDRÉS BOGOTÁ, COLOMBIA 2003 |
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CONTENTS
METHODS Ecology of the San Andres Vireo Study area Census Questionnaires Community work RESULTS Census Ecology Community Questionnaires Names Importance of birds Vireo caribaeus Project Evaluation Divulgation Painting competition Field Trips Talks Environmental Groups DISCUSSION AND CONCLUSIONS THREATS RECOMMENDATIONS FOR CONSERVATION Global Institutional Local ACKNOWLEDGEMENTS LITERATURE CITED | |
| INTRODUCTION Island species make up half the endangered bird species in the world, further knowledge of populations, ecology and distribution as well as the impacts of conservation measures will aid the conservation of similar species in similar habitats. They also play an important part in our understanding of biogeography and evolution and the same is likely to be true for our understanding of the ecology and evolution of populations that have been restricted to continental wildlife reserves (King 1985).
This project falls into Category 1, 2 and 3 of the proposed National Strategy for the Conservation of Birds in Colombia (Renjifo et al 2000). The project also ties in with the three functions of the Biosphere Reserves (UNESCO), regarding conservation, sustainable development and environmental education. (CORALINA 1998) METHODS Ecology of the San Andres Vireo The 32 species of the genus, vireo, are restricted to the Americas and the Caribbean. (Stiles & Skutch 1995). The nest, described by Barlow and Nash in 1985, is typical of the family. It is a small cup suspended from a fork of a small branch fairly close to the ground. Two eggs and two young were found in the two nests described. The predominant foraging method was gleaning arthropods from leaves and twigs generally no higher than 5 m. The vireo is one of the most active of the group. Barlow and Nash (1985) did not observe V. caribaeus eating fruit although Rosselli (1998) reported seeing the vireo eat 'black berries' and feed 'orange seeds' to its young during the breeding season. Barlow and Nash (1985) report the song of the vireo to resemble closely those of other 'white-eyed' vireos (griseus group) as well as having three different types of call. Study area San Andrés (Colombia) lies about 200 km off the coast of Nicaragua in the West Caribbean (N 12° 32' 57.6" W 81° 43' 35.7"). It has a total area of 27 km2 (Coralina 2002), the highest point on the central ridge running north-south reaches 100 m. Average temperature is 27.4ºC and average rainfall is 1900 mm although there is a marked difference between the dry season (February to April) and the wet season (June to December). The current vegetation on the island is highly fragmented as the result of a long period of human intervention, notably the cultivation of cotton and coconut (Pearson 1985). Only very small areas of forest remain, concentrated around Big Pond, the nuclear area of the Biosphere reserve. The majority of the vegetation on the island is made up of old coconut plantations and scrubland. There are also areas of mangrove on the eastern side (Figure 1). | |
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| Figure 1. San Andrés Island, showing vegetation types. | |
| The main source of income for the island's 60,000 inhabitants is tourism although unemployment rates reach 50%. The population is divided almost equally between those of Caribbean and Continental (mainland Colombian) descent. Serious social, economic and cultural conflicts exist between these two groups. The islands of San Andrés and Providence, including their extensive coral reefs, were made a biosphere reserve in 2001. We collected data during a five month study covering both dry and rainy seasons, from November 2001 to March 2002. Census We set up 42 point sites using a 750 m grid system covering the whole island except urban areas. The points were located in the field using a GPS (Garmin eTrex), occasionally points were moved to ensure that all vegetation types were adequately covered. Point counts were used because of their advantage in patchy habitats and because of the ease of data collection over rough terrain (Buckland et al 2002). The vegetation types surveyed were Dense Forest, Sparse Forest, Coconut Plantation, Crops, Mangrove, Pasture and Scrub, based on the vegetation map produced by CORALINA (2002). See MAP 1. For the purposes of analysis data were later grouped into Open (pasture, crops, scrub), Closed (dense forest, sparse forest, coconut plantation) and Mangrove habitats. At each point site we placed four radial rows of coloured tape markers at 5 m intervals to help with distance estimations. We also measured distances from the point to large landmarks such as trees, rocks, fences, hedges etc and noted them on maps of each point site. This was to help avoid 'heaping' (Buckland et al 2000) of rounded distance estimations at 20m, 25m, 35m, etc. Distance estimation was practised a week before starting data recording, we also measured the maximum carrying distance of the vireo's call using a tape recorder playing at natural volume. We carried out the census work between 0630 and 1100 visiting 6-10 points each on census mornings. Programmed census days were changed if the weather conditions did not permit fieldwork. Data recorded in heavy rain or mist were later discarded. We collected distance data using the 'snapshot' method outlined by Buckland et al (2001). We approached each point cautiously and in some cases observed the point from a short distance so as not to disturb birds at the point itself. Distances were recorded exactly in the field and were noted as visual, call, or call visual. We also collected additional data such as height of contact, weather conditions, time, in addition to other ecological information. Each point was repeated about twice a month to ensure enough contacts for reliable density estimation and to measure the effect of the changing season. We obtained climate information from IDEAM (2003) after finishing the field work and established cut off points between the wet and dry seasons according to rainfall. We analysed distance data with DISTANCE 4.0 (Thomas et al 1998). Data were truncated at certain points to prevent outliers from influencing the model fit (Buckland et al 2001). We entered the data as grouped intervals depending on the detection curve for the different habitat types, paying special attention to the fit of the curve at distances close to zero. Data were analysed by season and vegetation type. Model definitions were chosen by the lowest AIC (Akaike's Information Criteria). The fit of the model was also checked with the Χ2 test. Questionnaires We designed two questionnaires to assess the impact of the project on the local population and their knowledge of birds and ecology, in particular the San Andres Vireo. Volunteers aged between 16 and 19 from a local school carried out the questionnaires, one in December, the other in March. Prior to this we held a couple of workshops and outings to familiarise the volunteers with the project. A representative sample of the population was interviewed from all areas of the island. The data were analysed using MS Access. Community work To publicise the project and the existence of Vireo caribaeus we carried out several meetings and workshops with different members of the local community. We also took part in radio and television programmes and provided information about the project for local newspapers. Posters of the vireo were displayed around the island and leaflets detailing the project were handed out. We organised a painting competition for school children and gave prizes consisting of T-shirts, notebooks and badges with a vireo design as well as binoculars. We organised the first San Andrés Christmas Bird Count and publicised the forthcoming Caribbean Endemic Bird Festival. A booklet of activities and games on issues connected to the vireo and conservation was written and will be distributed among all the schools on the island. A cassette with the most common bird calls accompanies this publication. RESULTS Census Data were collected during 5 months from the 42 point count sites. A total of 3516 contacts were recorded, 1230 of which corresponded to Vireo caribaeus. A total of 39 species were recorded during the point counts. A further 45 species were recorded at other times on the island and neighbouring keys. Data from the dry season was collected from 28 November 2001 to 31 December 2001, dry season data were collected from 5 February to 20 March 2002 in accordance with the change in season determined by average rainfall, total hours of sunshine and cloud cover (FIGURE 2). | |
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| Figure 2. Weather Conditions - San Andres 2001-02 | |
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The data were analysed with Distance 4.0 (Thomas et al 1998). Densities were calculated by using separate detection functions for each type of habitat. Only auditory data were analysed since the most of the records were of this kind and visual data would have a different detection function. In the case of Open habitats, such as pasture, more contacts were made at zero metres if the point fell on or near a hedgerow separating the pastures, these points were left as such so that a density reflecting use of hedgerows could be attained. (Buckland 2000).
Significant differences were found between the data of the two observers during the dry season as the 95% confidence limits did not overlap, thus, the results are presented separately. The densities of Vireo caribaeus for the dry season per vegetation type and observer are shown in TABLE 2. | |
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| Table 2. Densities of Vireo caribaeus for dry season according to vegetation type and observer. Notes: 1. Area, km2; 2. Density, individuals/km2; 3. Density standard error, ind/km2. | |
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The highest densities of vireo were recorded in closed habitat such as forest or scrub, as well as in mangrove. Significant differences were found between densities in Closed, Open and Mangrove habitats using the P2 test (P < 0.001). Densities for the wet season were calculated from pooled data from both observers, due to the differences being less and the smaller number of observations. Mangrove density was calculated using a combined detection function from both seasons due to the small number of observations. Values for the population density map were calculated for the wet season only, using data from both observers (FIGURE 4). | |
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| FIGURE 4. Population density of Vireo caribaeus (red circles). 95% confidence limit shown by green and blue circles. | |
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Ecology Two active nests were found on 18 and 21 March 2003. They were both about 1.8 m above the ground, 10 cm in length and 6-7 cm in diameter. They were both built over a forked branch, the first in a bush covered in Smilax espinosa and the second in 'Wild Nony' (Morindia roicoc). In the first one individual was seen flying to and from the nest, although no eggs were inside it. The contained two naked, blind hatchlings and two adults were close by, calling. The nests were in scrub/sparse forest habitat at the southern end of the island, about 20 m apart. They were both later abandoned for unknown reasons. In Puerto Rico, the proximity of nests in fields, grassland and urban and rural areas has been found to decrease reproductive success in Vireo latimeri (Tossas 2001). Active nests of Coereba flaveola were observed from the first week of February 2003 onwards. The San Andres Vireo was observed foraging at an average height of 2.5 m over all habitats, however in mangrove, where there is little undergrowth, it was observed foraging to a maximum height of 15 m. Community The inhabitants of San Andres were largely unaware of the presence of an endemic, threatened bird on the island. Its local name, Chincherry, was known only by a handful of the older generation. No local names are given in field guides (Bond 1993; Raffaele et al 1998). They were surprised to learn that the Vireo was only found in San Andres, and in no other place in the world, including Providence. Questionnaires Names The results of the questionnaire show how some of the native names for island birds are being lost as Spanish is increasingly adopted as a first language or language of political and social power. However, 98% of the interviewees born in San Andres used some Patois or Creole names for the birds on the island. Continental Colombians living on the island used local names of birds from their regions of origin, mainly the Caribbean coast of Colombia. The results of a visual identification exercise of six of the most common birds on the island are presented in FIGURE 5 | |
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| FIGURE 5. Percentage of people visually recognising six common birds on San Andrés. | |
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One of the most recognised birds was the Green Breasted Mango humming bird (Anthracothorax prevostii) although most people referred to it as Picaflor (25%) and/or Humming Bird (2%). See Figure 6. The name given was independent of sector of residence, indicating that the native population is adopting Spanish names, given that residential sectors are strongly
divided by social or ethnic group. However, the low abundance of the Green Breasted Mango on the island could also explain the predominance of the Spanish name. It is possible that the majority of residents on the island, both islander and continental, are only aware of the humming bird through television programmes, mainly in Spanish. | |
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| FIGURE 6. Names given to Anthracothorax prevostii according a) to place of origin of interviewees and b) place of residence on San Andrés. | |
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Importance of birds The majority of people interviewed stated that the principal factor of importance concerning birds was their beauty (69%) others stated that they were a symbol for the island (23%) as well as being unique (13%). Others replied with respect to their biological significance in that they are part of nature (9%) their threatened status (9%) and their function within an ecosystem (2%). See FIGURE 7. | |
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| FIGURE 7. Importance of birds for the residents of San Andrés. | |
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Vireo caribaeus When asked about the presence of a unique bird on San Andrés, the majority of people responded negatively (83%). Some of the responses given when asked about an endemic bird during the first questionnaire included Brown Bird, Colibrí, Negrito (2%), October Bird (4%), Sinsonte (2%), Vireo (4%). During the second questionnaire, after carrying out the publicity campaign and after the project had been running for almost five months, the answers were as follows; Chincherry (23%), Vireo (17%), Wish-Wish (2%) as well as Nightingale, Old Man Bird and Sinsonte on very few occasions (see FIGURE 8). After the publicity campaign more than half the interviewees were aware of an endemic bird on the island (59%). | |
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| FIGURE 8. Results of recognition of Vireo caribaeus in November 2001 and March 2002, including place of origin of interviewees. | |
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Project Evaluation Almost 80% of those asked in the second questionnaire stated that they had seen the poster for the San Andés Vireo. A total of 70% said that they knew of the existence of the project. Divulgation In total 9 interviews were broadcast live on local radio concerning the project over 5 months. We contributed articles about the project to a local newspaper (Argos 2002) and a tourist magazine on the island. The National University Weekly Bulletin also ran an article on the project. We appeared twice on the local television programme, People and Culture, discussing the project. Two further programmes were made in connection with the project by Telecafe and Unimedios. An internet page was constructed detailing the project and showing photos of local participants. Painting competition A total of 25 schools and 519 individuals participated in the painting competition. A prize giving ceremony was held at the National University at the end of the competition. The winners (shown on the front cover of this report) were chosen by local judges and a local music group provided entertainment. Four principal prizes of binoculars were awarded as well as 50 T-shirts, notebooks, badges with a vireo design. Field Trips Twelve field trips were organised with different sectors of the population. The primary purpose of the outings was to learn to recognise the San Andres Vireo. Talks Ten talks were given during the project, ranging from EXPORB - a celebration of the first anniversary of the Biosphere Reserve - to farmers' groups, school and nursery children, students, church congregation and university staff. Environmental Groups The group of students from the Colegio Bolivariano carrying out the questionnaires also became an ad hoc environmental group, giving talks at their school and others on the vireo. An existing environmental group at the Sagrada Familia school also participated in the project and in subsequent activities related to the Caribbean Endemic Bird Festivals. DISCUSSION AND CONCLUSIONS Unfortunately, due to a large imbalance between the results of the two observers the estimate of the vireo's population density on the island is between 558.4 ± 101 - 2760.7 ± 436. However, it remains clear that the population has not decreased, as has been inferred in publications regarding its threatened status (Rosselli & Estela 2002, Hilton-Taylor 2000). The population has remained stable or increased with respect to previous estimates (Rosselli 1998, Bond 1993, Tye & Tye 1991, Barlow & Nash 1985, Russel & Barlow 1979). It appears that the distribution of the vireo has not changed since Barlow and Nash's (1985) study in 1972. If one takes the area given in this report as the southern two thirds of the island (~17 km2) rather than a third as stated, then this practically corresponds to the non-urban area of the island at present where the vireo is still amply distributed. Furthermore as much of its present habitat is in areas of low fertility in addition to the fact that agriculture does not form an important part of the traditional activities on the island, it is unlikely that this area will be used for crops. Construction, however remains a threat to habitat. The vireo appears to be the second most common bird on the island after the bananaquit (Coereba flaveola) which shows a high population density on San Andres, 2214 individuals/km2 compared to 1200 reported by Wunderele (1984) in Puerto Rico. Furthermore, the vireo has obviously adapted to the changing nature of the island's habitat over time, and is most common in the majority vegetation on the island: forest, scrub and old plantations. The distribution over the whole island and over a variety of habitats coincides with Cody's (1985) assertion that island birds tend to make wide use of habitats given that these are more limited. As reported by Rosselli (1998), hedges within fields and pastures could be vital for the survival of the vireo. These vegetation types show low densities but the hedges provide communication between other types of vegetation as well as providing suitable habitat for the vireo. The high population density of the vireo is comparable to that of the introduced Japanese White-eye (Zosterops japonicas), the most abundant species of Hawaii - 1600 ind./km2 (Scoot et al 1986). In this sense the vireo does not follow the trend that rare species tend to have low population densities, although it does have a small geographic range (Gaston & Blackburn 1996). Further factors in its favour are that it does not have a large body size and is not an old taxa, characteristics belonging to species with higher than average extinction risks (Bibby 1995, Gaston & Blackburn 1996). The distribution map shows the vireo distributed throughout the non-urban areas of the island. A general trend favouring forest and scrub vegetation is shown although there is a wide difference in densities between point counts within the same vegetation type. This may be due to the highly fragmentary nature of the island's vegetation, and essentially one is never able to sample only one type of vegetation in isolation from border effects of neighbouring habitats. In non-urban areas the vireo is not a common 'garden bird' although it is heard with some frequency in rural settlements. There are less data for the wet season than the for the dry season because of a number of sampling days being cancelled due to excessive rain. In fact, November 2001 showed almost twice the average rainfall normally expected at that time of year (IDEAM 2003). The project has showed that creating awareness among a community is an important factor in the conservation of threatened species or habitats. In this case, the majority of the population were unaware of the existence of the San Andres vireo. Before effective conservation measures can be implemented it is important that local people know and understand what they are being asked to conserve. Through the use of posters and other publicity material a significant increase in the community's awareness was brought about. The vireo took on a new identity among the islanders, it came to be seen as something belonging uniquely to the island and the inhabitants were always proud and keen to learn about their 'Chincherry'. In fact, its endemic status was compared to that of the native islanders. Interest was shown by inhabitants in participating in events such as the Endemic Caribbean Bird Festival as well as the establishment of an San Andrés and Providence Endemic Species Day. Since the completion of this project Henrietta's Foundation organised a competition highlighting endemic species of the island. The winning story was published on the internet page of the Caracol Radio (Caracol 2002). In other conservation projects these kind of activities have shown to be an effective way of gauging a project's success in transmitting ideas and concepts (Lasso 1996). Raising awareness and creating a willingness to conserve as well as the appropriation of the species by the community are important factors in the future of the vireo's conservation. Education is another important factor. It is hoped that children on the island will educate their parents and older relatives in issues regarding the vireo. After the success of the painting competition all schools on the island will be aware of the plight of the vireo. The book of games and activities is due to be published by the Universidad Nacional, San Andrés, and will be made available to all schools. Its photocopiable nature should prove popular among teachers, provided they have the means to make copies for their students. We believe this project has played an important role in instilling a permanent awareness of the vireo and the fragile environment of the island in all future generations of San Andreans. In conclusion, the outlook for the San Andres vireo is not as tragic as its Red List status, it has the capability to adapt to changes in vegetation, and has not shown a decline in population in over 30 years. However, its very restricted range is a permanent threat. With the creation of programmes and workshops by Coralina, there is genuine interest among local people to protect the environment and to use it to their benefit in programmes of eco-tourism, for example. However, the most serious threat to the San Andres Vireo and other remaining wildlife on the island may come from a lack of sustainable development, lack of education, and lack of basic acceptable living conditions on this extremely overcrowded island. Conservation cannot be separated from these aspects but must be a part of all development plans and programmes. THREATS
- Recreation: Hunting with sling shots is a favourite occupation amongst children on San Andres. In Jamaica this has led to birds being rare around rural settlements (Haynes et al 1989). - Cage bird trade: Its unique status, imparted by means of the project, may increase captures for this reason. We were once asked how much we were paying per specimen. - Subsistence: This is unlikely to be a major threat although we heard reports of children eating birds as small as the vireo. However, in other communities on mainland Colombia birds of this size are taken for food (M. Toro, pers. com.). RECOMMENDATIONS FOR CONSERVATION Global
Institutional
Local
Appendices and full report available on request from postmaster. ACKNOWLEDGEMENTS Many thanks to; LITERATURE CITED Burbano, H. 2000. Desarrollo sostenible y educación ambiental. Aproximación desde la naturaleza y la sociedad. Universidad de Nariño, Pasto. ISBN 958-9479-14-6 | |
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