ISSN (impresso) 0103-5657 ISSN (on-line) 2178-7875
Revista Brasileira de Ornitologia www.ararajuba.org.br/sbo/ararajuba/revbrasorn
Publicada pela
Sociedade Brasileira de Ornitologia São Paulo - SP
Volume 19 Número 4 Dezembro 2011
Revista Brasileira de Ornitologia, 19(4), 535‑538 Dezembro de 2011
nOTA
Foraging behavior of Hudsonian Godwit Limosa haemastica (Charadriiformes, Scolopacidae) in human-disturbed and undisturbed occasions in the Atlantic coast of Brazil César Cestari1,2 1. Programa de Pós-Graduação em Zoologia, Universidade Estadual Paulista “Júlio de Mesquita Filho” (UNESP), Campus de Rio Claro. CEP 13506‑900, Rio Claro, SP, Brasil. 2. Current address: Departamento de Zoologia, Universidade Estadual Paulista “Júlio de Mesquita Filho” (UNESP), Campus de Rio Claro. CEP 13506‑900, Rio Claro, SP, Brasil. E‑mail: [email protected] Recebido em: 04/03/2011. Aceito em: 01/09/2011.
Resumo: Comportamento de forrageio do maçarico-de-bico-virado Limosa haemastica (Aves, Scolopacidae) em ocasiões com perturbação e sem perturbação humana na costa Atlântica do Brasil. O maçarico-de-bico-virado, Limosa haemastica é considerado uma das aves pernaltas mais pouco estudadas que se reproduzem na América do Norte. Durante a migração, esta espécie utiliza poucas escalas até alcançar áreas de invernada no sul da América do Sul. Desta forma, estudos biológicos no decorrer de sua rota de migração são escassos. O foco deste artigo foi analisar o comportamento de forrageio de três indivíduos migrantes do maçarico-de-bico-virado que fizeram escala em áreas de entre-marés da costa sul do estado de São Paulo. Eu utilizei uma câmera digital para filmar e quantificar precisamente as técnicas de forrageio, o tempo de forrageio em hábitats e as distâncias percorridas pelas aves. Estas mesmas variáveis foram quantificadas em situações com e sem perturbação causadas por pessoas andando próximas das aves em forrageio. Os maçaricos-de-bico-virado utilizaram mais freqüentemente a técnica de “bicar superficialmente” em solo do que a técnica de “enterrar o bico” em solo. Eles forragearam a maior parte do tempo em solo úmido; alimentaram-se em média 31.91 ± 15.48 vezes por minuto e andaram em média de 4.40 ± 2.29 m por minuto. Os maçaricos-de-bico-virado andaram distâncias similares em ocasiões com perturbação e sem perturbação humana, porém eles forragearam menos em ocasiões com perturbação. Os resultados obtidos ressaltam a vulnerabilidade desta espécie durante os períodos de coexistência com humanos em locais com atividades recreação durante a migração. Palavras-Chave: América do Sul; ave neártica; escala filmagem; migração. Key-Words: South America; Nearctic bird; stopover; filming, migration.
The Hudsonian Godwit Limosa haemastica breeds from May through July in the tundra of North America from Alaska to the Hudson Bay, EUA, and spend the nonbreeding season in southern South America. While in the south hemisphere, godwits rely on a few, very important wintering sites (Senner 2010). The majority of individuals concentrate on Chiloé Island, southern Chile and in Tierra del Fuego, southern tip of Argentina/Chile (Morrison and Ross 1989, Andres et al. 2009, Senner 2010). In Brazil, godwits mainly stop at Lagoa do Peixe, state of Rio Grande do Sul while migrating to their breeding grounds (Morrinson and Ross 1989, Belton 1994). In other states (e.g., Amapá, Sergipe, São Paulo, Paraná, and Santa Catarina), the species has been recorded as individuals or small groups, especially along the Atlantic coast (Olmos and Silva 2001, Willis and Oniki 2003, Barbieri 2007).
The Hudsonian Godwit is one of the most poorly studied North America-breeding shorebird. Basic information of the species, such as migration routes, breeding and non-breeding places, and precise population estimates require research (Senner 2010). Previous studies in South America have presented data on relative abundance, habitat use, and feeding ecology of godwits (e.g., Hayes and Fox 1991, Blanco 1998, Brayton and Scheneider 2000, Hernández et al. 2008, Andres et al. 2009, Lizarralde et al. 2010). In this paper, I focus on the foraging behavior of three Hudsonian Godwits that used stopover sites on the southern coast of the state of São Paulo (southeast Brazil) during their southbound migration. Additionally, I compare feeding rates and walking distance of foraging godwits between sporadic periods of human disturbance (mainly caused by tourists on foot) and periods without disturbance. Several studies indicate
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Foraging behavior of Hudsonian Godwit Limosa haemastica (Charadriiformes, Scolopacidae) in human-disturbed and undisturbed occasions in the Atlantic coast of Brazil César Cestari
that human recreational activities affect the behavior of migratory birds using coastal environments (e.g., Burger 1981, Burger and Gochfeld 1991, Burger et al. 2004). Therefore, I hypothesize that godwits decrease their feeding rate and increase their distance walked while foraging due to human disturbance. Hudsonian Godwits were found in two intertidal sites: Grajaúna River at Juréia Ecological Station (24°31.4’S; 47°11.1’W) and a beach at Itanhaém municipality (24°13.3’S; 46°51.1’W). During the first occasion (19‑20 October 2010), one individual foraged in a temporary lake connected with the Grajaúna river mouth. During the second occasion (15‑17 November 2010), two individuals foraged on the shoreline of a severely disturbed sandy beach, mainly due to tourists walking along the beach. Both areas have soft sandy sediments, low declivity (4‑6°) and tidal influence of 87 ± 9 m. The Hudsonian Godwit is a medium-sized wader (37‑42 cm in length) with a long, slightly up-curved bill from the middle to the tip (culmen of 7.35‑7.55 cm in males, and 8.8‑9.0 cm in females; Sutton 1968, Hayman et al. 1986). This bill length enables the bird to capture prey at a variety of depths. According to Baker (1977), Kinsella et al. (2007) and Hernández et al. (2008), godwits may feed primarily on benthic invertebrates from coastal environments. Hence, considering the above circumstances, I quantified the feeding rate per min of the three foraging godwits and detailed the foraging tactic they used to capture prey, according to the proportion of their bill inserted into soil substrate: ‘Pecking’ was defined as fast movement of the bill toward the sand surface to capture prey. ‘Mid-probing’ was defined as when the bird buried its bill in the sand up to half its length (3.5‑4.5 cm). ‘Deep-probing’ was defined as when the bird buried its bill in the sand more than a half of its total length. In the latter, a bird may insert its entire head
in the water to probe. In addition to the feeding rate, the time and the distance walked by individuals while foraging on the wet sand (saturated sand or with surface layer of water) and dry sand (without wetness) were also recorded. The walking distance was calculated using the average distance of the species pace (= 4.60 cm, estimated from footprints in wet sand) multiplied by the number of steps. I used a digital Sony DSC H50 camera to precisely record foraging godwits. To avoid influence birds behavior, all the recordings were taken at distance about 10 m. The above ecological traits (feeding rate, foraging time in each habitat, and walking distance) were later quantified for further analysis. I defined a sample as recording of one minute of foraging. The samples of time foraging and feeding rate with different foraging techniques between habitats (wet and dry sand) were compared using a Student’s T‑test with the Bioestat 4.0 software (Ayres et al. 2004). The same statistical analysis was used to compare the species’ ecological traits (feeding rate and walking distance) during instances of human disturbance and without disturbance. Human disturbance was defined as when a person, or group of people, approached a bird to within less than five meters. Hudsonian Godwits spent more time foraging on wet (50.76 ± 16.72 s) than on dry sand habitats (9.19 ± 16.68 s) (t = ‑12; df = 92; P