Unravelling feeding territoriality in the Little Blue Heron, Egretta caerulea, in Cananéia, Brazil / Desvendando territorialidade alimentar na Garça-Azul, Egretta caerulea, em Cananéia, Brasil

Habitat use by the Little Blue Heron (Egretta caerulea) and discovery of feeding territoriality are discussed here. The results showed the existence of a territorial individual defending an area (2,564.46 ± 943.56 m²) close to the mangrove, and non-territorial individuals (9.17 ± 2.54) in the rest of a demarcated area (mean area for the non-territorial: 893.25 ± 676.72). A weak positive correlation (r = 0.47, df = 46, p < 0.05) was found between the overlapping of territorial and non-territorial individuals (2.85 ± 3.07 m²) and the mean overlapped area for territorial individuals (171.41 ± 131.40 m²). Higher capture (1.52 ± 1.14 × 1.00 ± 1.37 catches/minutes) and success rates (0.45 ± 0.31 × 0.21 ± 0.27) and lower energy expenditure rates (45.21 ± 14.96 × 51.22 ± 14.37 steps/minutes; and 3.65 ± 2.55 × 4.94 ± 3.28 stabs/minutes) were observed for individuals foraging in areas close to the mangrove. The results suggest that the observed territorial behaviour is more related to a number of food parameters than to intruder pressure, and also that the observed territoriality might be related to defense of areas with higher prey availability.(AU)

Uso do habitat pela garça-azul (Egretta caerulea) e a descoberta da territorialidae alimentar são discutidos aqui. Os resultados apontaram para a existência de um indivíduo territorial defendendo uma área (2.564,46 ± 943,56 m²) próxima ao manguezal e indivíduos não-territoriais (9,17 ± 2,54) no restante de uma área demarcada (média das áreas para os não-territoriais: 893,25 ± 676,72). Uma correlação positiva fraca (r = 0,47, df = 46, p < 0,05) foi encontrada entre a sobreposição de indivíduos territoriais e não-territoriais (2,85 ± 3,07 m²) e a média de área sobreposta para indivíduos territoriais (171,41 ± 131,40 m²). Maiores taxas de captura (1,52 ± 1,14 × 1,00 ± 1,37 capturas/minutos) e sucesso (0,45 ± 0,31 × 0,21 ± 0,27 capturas/tentativas de captura) e menores taxas de gasto energético (45,21 ± 14,96 × 51,22 ± 14,37 passos/min; e 3,65 ± 2,55 × 4,94 ± 3,28 tentativas de captura/min) foram registradas para indivíduos forrageando em áreas mais próximas do manguezal. Os resultados sugerem que o comportamento territorial observado tem mais relação com alguns parâmetros alimentares do que com a pressão de intrusos. Assim como a territorialidade observada pode estar relacionada com a defesa de áreas que contém alta disponibilidade de presas.(AU)

Unravelling feeding territoriality in the Little Blue Heron, Egretta caerulea, in Cananéia, Brazil / Desvendando territorialidade alimentar na Garça-Azul, Egretta caerulea, em Cananéia, Brasil

Habitat use by the Little Blue Heron (Egretta caerulea) and discovery of feeding territoriality are discussed here. The results showed the existence of a territorial individual defending an area (2,564.46 ± 943.56 m²) close to the mangrove, and non-territorial individuals (9.17 ± 2.54) in the rest of a demarcated area (mean area for the non-territorial: 893.25 ± 676.72). A weak positive correlation (r = 0.47, df = 46, p < 0.05) was found between the overlapping of territorial and non-territorial individuals (2.85 ± 3.07 m²) and the mean overlapped area for territorial individuals (171.41 ± 131.40 m²). Higher capture (1.52 ± 1.14 × 1.00 ± 1.37 catches/minutes) and success rates (0.45 ± 0.31 × 0.21 ± 0.27) and lower energy expenditure rates (45.21 ± 14.96 × 51.22 ± 14.37 steps/minutes; and 3.65 ± 2.55 × 4.94 ± 3.28 stabs/minutes) were observed for individuals foraging in areas close to the mangrove. The results suggest that the observed territorial behaviour is more related to a number of food parameters than to intruder pressure, and also that the observed territoriality might be related to defense of areas with higher prey availability.

Uso do habitat pela garça-azul (Egretta caerulea) e a descoberta da territorialidae alimentar são discutidos aqui. Os resultados apontaram para a existência de um indivíduo territorial defendendo uma área (2.564,46 ± 943,56 m²) próxima ao manguezal e indivíduos não-territoriais (9,17 ± 2,54) no restante de uma área demarcada (média das áreas para os não-territoriais: 893,25 ± 676,72). Uma correlação positiva fraca (r = 0,47, df = 46, p < 0,05) foi encontrada entre a sobreposição de indivíduos territoriais e não-territoriais (2,85 ± 3,07 m²) e a média de área sobreposta para indivíduos territoriais (171,41 ± 131,40 m²). Maiores taxas de captura (1,52 ± 1,14 × 1,00 ± 1,37 capturas/minutos) e sucesso (0,45 ± 0,31 × 0,21 ± 0,27 capturas/tentativas de captura) e menores taxas de gasto energético (45,21 ± 14,96 × 51,22 ± 14,37 passos/min; e 3,65 ± 2,55 × 4,94 ± 3,28 tentativas de captura/min) foram registradas para indivíduos forrageando em áreas mais próximas do manguezal. Os resultados sugerem que o comportamento territorial observado tem mais relação com alguns parâmetros alimentares do que com a pressão de intrusos. Assim como a territorialidade observada pode estar relacionada com a defesa de áreas que contém alta disponibilidade de presas.

Brood size and its importance for nestling growth in the Biscutate Swift (Streptoprocne biscutata, Aves: Apodidae)

Many Apodidae, including Streptoprocne biscutata (Sclater, 1866), drop eggs from their nests during incubation. This is interpreted as nest site competition or accident. We provide evidence that egg ejection is deliberate and that this behaviour controls the brood size. Brood sizes were manipulated and nestling growth was measured to test the hypothesis that pairs can regulate brood size during incubation based on current ability to rear nestlings. Natural (control) broods with one, two and three nestlings, and manipulated (experimental) broods reduced to one and increased to two and three young were monitored. Growth rates were measured based on weight, and wing, tail and tarsus lengths of natural and manipulated broods. We compared the slopes of each measure's regression lines of the nestlings of each brood size by t-test. Nestling growth of control nests was similar and relatively little associated with brood size. In broods reduced to one nestling, weight, wing and tail had greater growth rates, and in broods increased to three nestlings growth rates were lower. Weight was most, and tarsus length least influenced by brood size. In general, nestling growth of manipulated nests was inversely proportional to brood size. The results suggest that pairs with larger clutches are in better physical conditions than others. Thus, in experimental broods, pairs are over or under-loaded because feeding activities increase or decrease and these changes affect the growth rate of the nestlings. The present study suggests that egg ejection can control brood size. This behaviour is probably stimulated by physical changes in the adult birds during incubation.

Muitos Apodidae, incluindo Streptoprocne biscutata (Sclater, 1866), derrubam ovos do ninho durante a incubação. Este comportamento tem sido interpretado como competição ou acidente. Este estudo apresenta evidências de que a expulsão de ovos é deliberada e que esse comportamento controla o tamanho da ninhada. Ninhos com diferentes tamanhos de prole foram manipulados para testar a hipótese de que os casais podem regular o tamanho da ninhada durante a incubação com base em suas capacidades de alimentar os filhotes. Ninhadas naturais (controle) com um, dois e três filhotes e ninhadas manipuladas (experimentais) reduzidas para um e aumentadas para dois e três filhotes foram monitoradas. Foram medidas as taxas de crescimento de massa, asa, cauda e tarso de proles naturais e manipuladas. As inclinações das retas de regressão do desenvolvimento de cada medida ao longo da idade dos filhotes de cada tamanho de ninhada foram comparadas pelo t-teste. O crescimento dos filhotes de ninhos controle foi semelhante e esteve relativamente pouco associado ao tamanho da ninhada. Nas ninhadas reduzidas para um filhote, a massa, asa e cauda apresentaram as maiores taxas de crescimento e nas ninhadas aumentadas para três filhotes ocorreram as menores taxas. A massa foi a variável mais influenciada pelos experimentos e o tarso a menos. De forma geral, o crescimento dos filhotes de ninhos manipulados foi inversamente proporcional ao tamanho da ninhada. Os resultados sugerem que os casais com mais filhotes estão em melhores condições físicas do que os outros. Por isso, nas ninhadas experimentais, a taxa de crescimento dos filhotes muda em virtude dos casais se encontrarem sub ou sobrecarregados na tarefa de alimentação. Sugere-se que o comportamento de expulsão de ovos possa ser uma forma de regular o tamanho da ninhada, o qual provavelmente é desencadeado por mudanças nas condições físicas das aves adultas durante o período de incubação.

Reproductive steroid hormones and ovarian activity in felids of the Leopardus genus.

Reproductive endocrine patterns were characterized in female ocelots (Leopardus pardalis; n = 3), tigrinas (Leopardus tigrinus; n = 2), and margays (Leopardus wiedii; n = 2) housed in captivity in southern Brazil. Females were maintained as singletons and exposed to natural fluctuations in photoperiod. Cyclic changes in ovarian steroids were monitored by analyzing estrogen and progestogen metabolites in fecal samples collected five times weekly for 14 to 18 months. Based on intervals between fecal estrogen peaks, mean (+/- SEM) duration of the estrous cycle was 18.4 +/- 1.6 days for the ocelots (range, 7-31 days; n = 75 cycles), 16.7 +/- 1.3 days for the tigrinas (range, 11-27 days; n = 23 cycles), and 17.6 +/- 1.5 days for the margays (range, 11-25 days; n = 32 cycles). Fecal progestogen analyses combined with two laparoscopic observations of the ovaries confirmed that ocelots and tigrinas did not ovulate spontaneously. In contrast, non-mating-induced luteal phases of 40.1 +/- 6.3 days in duration (range, 30-60 days) were observed frequently in both margays. There was no evidence of gonadal seasonality in margays in either follicular or luteal activity. In ocelots, cyclic changes in estrogen excretion were observed during each month of the year; however, only one female cycled continuously. In the other two ocelots, periods of acyclicity of several months' duration were observed. It was not possible to conclude whether tigrinas were aseasonal because estrous cyclicity was observed in only one of two individuals. In the female that cycled, a 3-month period of acyclicity was observed in the late fall/early winter. These data demonstrate similarities among three felid species of the genus Leopardus, including evidence they are polyestrous but experience unexplained periods of ovarian inactivity. Only the margays differed by exhibiting occasional spontaneous, non-mating-induced ovulations. Historically, these species have not bred well in captivity. However, it is hoped that understanding the biological similarities and differences among them could lead to improved management strategies that may one day result in increased reproductive success. Zoo Biol 20:103-116, 2001. Copyright 2001 Wiley-Liss, Inc.