Ecologia espacial de bandos mistos de aves em um trecho da floresta atlântica do sul do Brasil
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Data
2021-10-15
Autores
Brandt, Claudia Sabrine
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Universidade Estadual Paulista (Unesp)
Resumo
Tem sido cada vez mais evidente que o conhecimento sobre o comportamento e as interações sociais em algumas espécies são importantes para compreender a dinâmica das populações e comunidades. No caso das aves, a proteção de bandos mistos de florestas tropicais é importante para a conservação de comunidades, por incluir, em diversos casos, espécies que dependem dessas associações para permanecerem em uma determinada área. No entanto, a despeito da composição, pouco se conhece sobre a dinâmica interna de bandos mistos de floresta atlântica. Considerando que existe um consenso de que a espécie Habia rubica seja a espécie nuclear nos bandos em que participa, nesse estudo buscou-se compreender: 1. a área de ocupação de H. rubica enquanto a espécie participa de bandos mistos; 2. o grau de sobreposição entre as áreas de ocupação de H. rubica com a de outras quatro espécies participantes de bandos mistos (Automolus leucophthalmus, Philydor atricapillus, Basileuterus culicivorus e Xiphorhynchus fuscus); 3. quais variáveis ambientais são determinantes no uso do habitat por Habia rubica. Foram selecionadas cinco áreas de estudo localizadas nos municípios de Blumenau, Timbó e Brusque, Santa Catarina, Brasil, onde indivíduos das cinco espécies foram capturados e marcados com anilhas coloridas. Posteriormente, partindo da premissa de que os indivíduos de H. rubica são fiéis a um mesmo bando misto, foi pré-determinado um esforço amostral de ~40 horas de acompanhamento de um mesmo indivíduo/grupo de H. rubica enquanto associado a um bando misto em cada área de estudo. Os indivíduos tiveram a sua localização determinada em intervalos de 10 minutos com o auxílio de um GPS de mão acoplado ao pesquisador que acompanhou os bandos mistos. Utilizando a Análise de Densidade de Kernel Autocorrelacionada - AKDE, foi observado que enquanto participaram de bandos mistos, os indivíduos de H. rubica apresentaram uma área de ocupação de ~11 ha. Os indivíduos de A. leucophthalmus, P. atricapillus e X. fuscus apresentaram uma grande sobreposição com a área de ocupação de H. rubica, o mesmo não ocorrendo com B. culicivorus. A análise Função Integrada de Seleção de Passos - iSSF mostrou que a distância em linha reta até o ponto onde ocorre de escoamento preferencial de água no terreno (distância de drenagem) foi a única variável selecionada da mesma forma para todos os indivíduos de H. rubica, com o deslocamento ocorrendo em áreas onde ocorre o escoamento preferencial da água. Os resultados indicam que para que seja mantida a ocorrência de bandos mistos com H. rubica na porção sul da floresta atlântica é necessário preservar remanescentes não-isolados, em condições relativamente boas de conservação, de tamanho ~11 ha. Essas áreas devem também incluir fundos de vales e/locais onde ocorra o escoamento preferencial da água, variável que parece determinante na movimentação de H.rubica enquanto participa de bandos mistos. A observação de um fluxo de entrada e saída de indivíduos de H. rubica dos bandos mistos estudados, cujo parentesco é desconhecido, demonstra a necessidade de estudos futuros para a melhor compreensão da dinâmica populacional da espécie. Por fim, permanece desconhecido o padrão de movimentação da espécie quando não está associada aos bandos. Considerando que o seu padrão de movimentação pode ser totalmente diferente do que ocorre quando associada a outras espécies, os requerimentos de área para indivíduos de H. rubica podem ser ainda maiores. Sendo assim, são recomendados estudos focando esse aspecto da ecologia espacial da espécie.
It has become increasingly evident that knowledge about behavior and social interactions in some species is important to understand the dynamics of populations and communities. In the case of birds, the mixed flocks of tropical forests have an important role in biodiversity conservation as some bird species depend on these associations to remain in the area. Although some studies have been done on the flock composition, little is known about the internal dynamics of mixed Atlantic forest flocks. Considering that there is a consensus that the species Habia rubica is the nuclear species in the flocks it participates, this study aim to understand: 1. the area of occupancy of H. rubica when the species participates in mixed flocks; 2. the degree of overlap between the areas of occupancy of H. rubica and other four species (Automolus leucophthalmus, Philydor atricapillus, Basileuterus culicivorus and Xiphorhynchus fuscus) participating in mixed flocks; 3. the environmental variables determinant in habitat use by H. rubica. Five study areas located in the municipalities of Blumenau, Timbó and Brusque, Santa Catarina, Brazil, were selected and, individuals of the five species were captured and marked with colored rings. Subsequently, assuming that individuals of H. rubica remain in the same mixed flock, we predetermined a sampling effort of ~40 hours for tracking the same individual/flock of H. rubica while associated with a mixed flock in each study area. The individuals had their location recorded every 10-minute using a handheld GPS carried by the researcher who followed the mixed flocks. Using Autocorrelated Kernel Density Analysis - AKDE, it was observed that while participating in mixed flocks, H. rubica individuals occupy an area of ~11 ha. The individuals of A. leucophthalmus, P. atricapillus and X. fuscus have great overlap with the area of occupancy of H. rubica. We did not observe the same pattern in B. culicivorus. The Integrated Step Selection Function - iSSF analysis showed that the distance, in a straight line, to the point where preferential runoff of water occurs on the ground (drainage distance) was the only variable selected in the same way for all individuals of H. rubica. The displacement of individuals occurs in areas where there is preferential water flow. The results indicate that, in order to maintain the occurrence of mixed flocks with H. rubica in the southern portion of Atlantic Forest, it is necessary to preserve nonisolated remnants in relatively good conservation conditions, with a size of ~11 ha. These areas should also include valley bottoms and/or places where preferential water flow occurs, a variable that seems to be determinant to the movement of H. rubica while participating in mixed flocks. The observation of an inflow and outflow of individuals of H. rubica from the mixed flocks studied, whose kinship is unknown, demonstrates the need for future studies to better understand the population dynamics of the species. Finally, the movement pattern of this species remains unknown when it is not associated with flocks. Considering that H. rubica movement patterns can be totally different from what occurs when associated with other species, the area requirements for individuals of H. rubica can be even higher. Therefore, studies focusing on this aspect of the spatial ecology of the species are recommended.
It has become increasingly evident that knowledge about behavior and social interactions in some species is important to understand the dynamics of populations and communities. In the case of birds, the mixed flocks of tropical forests have an important role in biodiversity conservation as some bird species depend on these associations to remain in the area. Although some studies have been done on the flock composition, little is known about the internal dynamics of mixed Atlantic forest flocks. Considering that there is a consensus that the species Habia rubica is the nuclear species in the flocks it participates, this study aim to understand: 1. the area of occupancy of H. rubica when the species participates in mixed flocks; 2. the degree of overlap between the areas of occupancy of H. rubica and other four species (Automolus leucophthalmus, Philydor atricapillus, Basileuterus culicivorus and Xiphorhynchus fuscus) participating in mixed flocks; 3. the environmental variables determinant in habitat use by H. rubica. Five study areas located in the municipalities of Blumenau, Timbó and Brusque, Santa Catarina, Brazil, were selected and, individuals of the five species were captured and marked with colored rings. Subsequently, assuming that individuals of H. rubica remain in the same mixed flock, we predetermined a sampling effort of ~40 hours for tracking the same individual/flock of H. rubica while associated with a mixed flock in each study area. The individuals had their location recorded every 10-minute using a handheld GPS carried by the researcher who followed the mixed flocks. Using Autocorrelated Kernel Density Analysis - AKDE, it was observed that while participating in mixed flocks, H. rubica individuals occupy an area of ~11 ha. The individuals of A. leucophthalmus, P. atricapillus and X. fuscus have great overlap with the area of occupancy of H. rubica. We did not observe the same pattern in B. culicivorus. The Integrated Step Selection Function - iSSF analysis showed that the distance, in a straight line, to the point where preferential runoff of water occurs on the ground (drainage distance) was the only variable selected in the same way for all individuals of H. rubica. The displacement of individuals occurs in areas where there is preferential water flow. The results indicate that, in order to maintain the occurrence of mixed flocks with H. rubica in the southern portion of Atlantic Forest, it is necessary to preserve nonisolated remnants in relatively good conservation conditions, with a size of ~11 ha. These areas should also include valley bottoms and/or places where preferential water flow occurs, a variable that seems to be determinant to the movement of H. rubica while participating in mixed flocks. The observation of an inflow and outflow of individuals of H. rubica from the mixed flocks studied, whose kinship is unknown, demonstrates the need for future studies to better understand the population dynamics of the species. Finally, the movement pattern of this species remains unknown when it is not associated with flocks. Considering that H. rubica movement patterns can be totally different from what occurs when associated with other species, the area requirements for individuals of H. rubica can be even higher. Therefore, studies focusing on this aspect of the spatial ecology of the species are recommended.
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Palavras-chave
Ecologia espacial, Avifauna, Bandos mistos, Floresta Atlântica, Mixed species bird flocks, Habia rubica, Atlantic forest, Spatial ecology