RESUMO
The masked booby (Sula dactylatra dactylatra) colony at Middle Cay, Pedro Bank, 60 miles south of Jamaica, has been affected by challenges resulting from anthropogenic disturbances. Despite habitat degradation, the colony displays resilience by remaining extant on the cay. Between June 2008 and June 2009 we investigated the colony’s health (mainly breeding success). Data were collected once per month for twelve months and included one day, seven day and 24 hour (day and night continuous observational) sojourns. Forty-four nests were marked and monitored using a novel method for marking seabird nests based on painted seashells. Data collected from the colony included: the presence/absence/number of egg(s)/chick(s) in nests, offspring maturity, adult attendance at nests and the time of data collection. An average of 227 adult birds constituted the colony. Using the Mayfield Method and the “Naïve Estimator” for comparison, the colony’s breeding success was determined to be 37.20% despite a hatching success of 40% and a fledgling success of 93%. This is less than the estimated 45.77% success typical of healthy colonies of sulids such as the masked booby elsewhere. Based on the breeding success calculations the long term survival of this colony is at risk and needs active conservation.
La colonis del alcatraz enmascarado (Sula dactylatra dactylatra) en Cayo Middle, Banco de Pedro, 60 millas al sur de Jamaica, ha sido afectada por una serie de desafíos resultantes de disturbios antropogénicos a su hábitat. A pesar de la degradación excesiva del hábitat, la colonia muestra resilencia al permanecer en el cayo. Entre junio de 2008 y junio de 2009 realizamos una investigación de la salud de la colonia (principalmente éxito reproductivo). Los datos fueron recogidos una vez al mes durante doce meses e incluyó un día, siete días y 24 horas (día y noche de continua observación). Cuarenta y cuatro nidos fueron marcados y monitoreados utilizando un método novedoso para marcar nidos de aves marinas. Los datos recogidos de la colonia incluyen: presencia/ausencia/número de óvulos/polluelos en nidos, madurez de crías, asistencia de adultos en los nidos y el tiempo de recolección de datos. Un promedio de 227 aves adultas constituían la colonia. Usando el método de Mayfield para analizar los datos y el “estimador Naïve” para la comparación, el éxito reproductivo de la colonia se determinó de un 37.20% a pesar de un 40% de éxito de eclosión y un éxito de pichones del 93%. Esto es menos que el éxito estimado de 45.77% en colonias saludables como la del alcatraz enmascarado en todo el mundo. Basado en los cálculos de éxito la supervivencia a largo plazo de esta colonia está en riesgo y necesita se ejecute conservación activa.
Assuntos
Desastres Provocados pelo Homem , Aves/anatomia & histologia , Aves/classificação , JamaicaRESUMO
Polystictus superciliaris (Wied, 1831) is a small tyrant-flycatcher endemic to mountaintops in the highlands of eastern Brazil. In this paper we present the first description of the breeding biology of P. superciliaris and estimate its reproductive success from a population inhabiting rocky outcrops. This study was conducted during 2005 in the Parque Estadual da Serra do Rola Moça, municipality of Nova Lima (20°03'S, 44°00'W), state of Minas Gerais, southeastern Brazil. Fourteen pairs of P. superciliaris were banded and monitored. The onset of the breeding season in 2005 was assumed to have been sometime before the 26th of July, while it was assumed to have ended on the 23rd of November based on the last observation of a successful brood. Clutch size was invariably two eggs (N = 21), the incubation period averaged 17.7 ± 1.3 days (N = 9), and the nestling period averaged 16.4 ± 1.3 days (N = 8). We estimated the probability of reproductive success for P. superciliaris to be 41.3%, during this particular breeding season. Of the 12 (57.1%) unsuccessful nests, eight (66.7%) had eggs and four (33.3%) had nestlings when they failed. In nine (42.8%) of these cases, the nests were lost to predation, two to parasitism by botflies, and one due to abandonment. This study suggests that the reproductive success of P. superciliaris is intermediate compared to the other species of Tyrannidae that have been studied and closer to the lower limit of the 40%-80% range which is characteristic of tyrant _ flycatcher species that breed in temperate regions.
RESUMO
The nesting success of three colonies of Streptoprocne biscutata (Sclater, 1866), and the influence of clutch and brood size on nesting success of species were studied. Overall, apparent nesting success was 58% and Mayfield nesting success was 53%. Nest survival during incubation (64%) was lower than during the nestling period (83%). During incubation, clutches were lost to rain, desertion, predation, egg ejection, egg damage, and egg disappearance. During the nestling period, losses occurred due to offspring disappearance, nestling death by starvation, predation and falling. During both incubation and nestling periods, predation was low, while egg ejections and nestling starvation were the main causes of nest failure. Nest survival during incubation was directly proportional to clutch size, while during the nestling period it was inversely proportional to the brood size. Apparently, there seemed to be an advantage to having more eggs during incubation. However, if all eggs were to hatch during unfavorable weather the nest success could be low. These results suggest that when the breeding pairs face adversity during incubation, they control the brood size by ejecting part of the clutch.
RESUMO
Polystictus superciliaris (Wied, 1831) is a small tyrant-flycatcher endemic to mountaintops in the highlands of eastern Brazil. In this paper we present the first description of the breeding biology of P. superciliaris and estimate its reproductive success from a population inhabiting rocky outcrops. This study was conducted during 2005 in the Parque Estadual da Serra do Rola Moça, municipality of Nova Lima (20°03'S, 44°00'W), state of Minas Gerais, southeastern Brazil. Fourteen pairs of P. superciliaris were banded and monitored. The onset of the breeding season in 2005 was assumed to have been sometime before the 26th of July, while it was assumed to have ended on the 23rd of November based on the last observation of a successful brood. Clutch size was invariably two eggs (N = 21), the incubation period averaged 17.7 ± 1.3 days (N = 9), and the nestling period averaged 16.4 ± 1.3 days (N = 8). We estimated the probability of reproductive success for P. superciliaris to be 41.3%, during this particular breeding season. Of the 12 (57.1%) unsuccessful nests, eight (66.7%) had eggs and four (33.3%) had nestlings when they failed. In nine (42.8%) of these cases, the nests were lost to predation, two to parasitism by botflies, and one due to abandonment. This study suggests that the reproductive success of P. superciliaris is intermediate compared to the other species of Tyrannidae that have been studied and closer to the lower limit of the 40%-80% range which is characteristic of tyrant _ flycatcher species that breed in temperate regions.
RESUMO
The nesting success of three colonies of Streptoprocne biscutata (Sclater, 1866), and the influence of clutch and brood size on nesting success of species were studied. Overall, apparent nesting success was 58% and Mayfield nesting success was 53%. Nest survival during incubation (64%) was lower than during the nestling period (83%). During incubation, clutches were lost to rain, desertion, predation, egg ejection, egg damage, and egg disappearance. During the nestling period, losses occurred due to offspring disappearance, nestling death by starvation, predation and falling. During both incubation and nestling periods, predation was low, while egg ejections and nestling starvation were the main causes of nest failure. Nest survival during incubation was directly proportional to clutch size, while during the nestling period it was inversely proportional to the brood size. Apparently, there seemed to be an advantage to having more eggs during incubation. However, if all eggs were to hatch during unfavorable weather the nest success could be low. These results suggest that when the breeding pairs face adversity during incubation, they control the brood size by ejecting part of the clutch.
RESUMO
The nesting success of three colonies of Streptoprocne biscutata (Sclater, 1866), and the influence of clutch and brood size on nesting success of species were studied. Overall, apparent nesting success was 58% and Mayfield nesting success was 53%. Nest survival during incubation (64%) was lower than during the nestling period (83%). During incubation, clutches were lost to rain, desertion, predation, egg ejection, egg damage, and egg disappearance. During the nestling period, losses occurred due to offspring disappearance, nestling death by starvation, predation and falling. During both incubation and nestling periods, predation was low, while egg ejections and nestling starvation were the main causes of nest failure. Nest survival during incubation was directly proportional to clutch size, while during the nestling period it was inversely proportional to the brood size. Apparently, there seemed to be an advantage to having more eggs during incubation. However, if all eggs were to hatch during unfavorable weather the nest success could be low. These results suggest that when the breeding pairs face adversity during incubation, they control the brood size by ejecting part of the clutch.
RESUMO
Polystictus superciliaris (Wied, 1831) is a small tyrant-flycatcher endemic to mountaintops in the highlands of eastern Brazil. In this paper we present the first description of the breeding biology of P. superciliaris and estimate its reproductive success from a population inhabiting rocky outcrops. This study was conducted during 2005 in the Parque Estadual da Serra do Rola Moça, municipality of Nova Lima (20°03'S, 44°00'W), state of Minas Gerais, southeastern Brazil. Fourteen pairs of P. superciliaris were banded and monitored. The onset of the breeding season in 2005 was assumed to have been sometime before the 26th of July, while it was assumed to have ended on the 23rd of November based on the last observation of a successful brood. Clutch size was invariably two eggs (N = 21), the incubation period averaged 17.7 ± 1.3 days (N = 9), and the nestling period averaged 16.4 ± 1.3 days (N = 8). We estimated the probability of reproductive success for P. superciliaris to be 41.3%, during this particular breeding season. Of the 12 (57.1%) unsuccessful nests, eight (66.7%) had eggs and four (33.3%) had nestlings when they failed. In nine (42.8%) of these cases, the nests were lost to predation, two to parasitism by botflies, and one due to abandonment. This study suggests that the reproductive success of P. superciliaris is intermediate compared to the other species of Tyrannidae that have been studied and closer to the lower limit of the 40%-80% range which is characteristic of tyrant _ flycatcher species that breed in temperate regions.