A Variable Circular-Plot Method for Estimating Bird Numbers

Reynolds, Richard T.; Scott, James M.; Nussbaum, Ronald A.

doi:10.2307/1367399

Cited by 510 publications

(309 citation statements)

References 13 publications

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“…We instead calculated population density using the inflection-point-per-species method (described in Reynolds et al 1980). We plotted the number of detections of each species within 10-m concentric bands and determined the distance from the observer at which its rate of detection begins to decline (the inflection point).…”

Section: à2mentioning

confidence: 99%

Avian population survey in the Floreana highlands: is Darwin’s Medium Tree Finch declining in remnant patches ofScalesiaforest?

O’Connor

Sulloway

Kleindorfer

2010

Bird Conservation International

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SummaryIsland species typically exist in pathogen and predator sparse environments before human settlement, and are particularly vulnerable to the impacts of invasive species. In this study, we used the variable circular-plot method to estimate the density of birds in the highlands of Floreana Island, Galápagos Archipelago, where introduced parasites, predators, and habitat degradation are a known threat to endemic species. We recorded the number of birds seen and heard at 15 locations near Cerro Pajas Volcano in 2004 and 2008, an area that harbours the largest expanse of highland Scalesia forest on Floreana Island. We estimated the change in population density for nine bird species, including five species of Darwin’s finches. We specifically address changes in population density for the locally endemic Medium Tree Finch Camarhynchus pauper, which only occurs on Floreana Island and has a small population size. Comparing 2004 and 2008, our study found lower population density in the Medium Tree Finch, but stable population density in Small Tree Finch C. parvulus and Large Tree Finch C. psittacula. Based on data from three additional highland sites surveyed in 2008, we estimate that the maximum size of the Medium Tree Finch population is 1,620 individuals. In addition to the survey data, we observed breeding males in 2006 and 2008. We found: (1) low nesting success (six out of 63 nests produced fledglings) and high Philornis downsi parasite intensity, and (2) a biased age structure of the breeding population. No breeding males were one year old in 2006, and no males were five years old in either study year, indicating low reproductive success as well as limited lifespan. This research has contributed to the recent re-evaluation by IUCN, which has changed the Red List status of the Medium Tree Finch from ‘Vulnerable’ to ‘Critically Endangered’.

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Section: à2mentioning

confidence: 99%

Avian population survey in the Floreana highlands: is Darwin’s Medium Tree Finch declining in remnant patches ofScalesiaforest?

O’Connor

Sulloway

Kleindorfer

2010

Bird Conservation International

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“…The Variable Circular Plot method (Reynolds et al 1980) was used to assess bird numbers in the three studied forest disturbance types between October and Figure 1. Map of the research area in Borneo.…”

Section: Bird Surveysmentioning

confidence: 99%

Bird Community Changes in Response to Single and Repeated Fires in a Lowland Tropical Rainforest of Eastern Borneo

Slik

Balen

2006

Biodivers Conserv

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Abstract. Our current understanding of bird community responses to tropical forest fires is limited and strongly geographically biased towards South America. Here we used the circular plot method to carry out complete bird inventories in undisturbed, once burned (1998) and twice burned forests (1983 and 1998) in East Kalimantan (Indonesia). Additionally, environmental variables were measured within a 25 m radius of each plot. Three years after fire the number of birds and bird species were similar for undisturbed and burned forests, but species diversity and turnover were significantly lower in the burned forests. The bird species composition also differed significantly between undisturbed and burned forests, with a strong decline of closed forest preferring bird species accompanied by a strong increase in degraded forest preferring species in burned forests. These differences were strongly related to differences in environmental conditions such as shifts in vegetation cover and layering and differences in ground and understorey vegetation structure. We also found significant shifts in body mass distribution, foraging height and feeding guilds between the bird communities in unburned and burned forests. Surprisingly, repeated burning did not lead to increasing impoverishment of the avifauna, and both once and twice burned forests still contained most of the bird species that were also present in undisturbed forest, even though their densities were considerably lowered.

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“…La intensidad de pastoreo fue de 127 animales por hectare. Para el estudio de las aves, se utilizó el método de parcelas circulares propuesto por Reynolds et al (1980). Dentro de cada uno de los cuartones de todos los años de siembra (1995)(1996)(1997)(1998), se ubicaron al azar 2 parcelas con un radio fijo de 10 m, de forma tal que no existiera solapamiento entre una y otra, para un total de 28 parcelas circulares en todo el sistema, y los muestreos se realizaron una vez por período climático, durante un año (junio del 2001 a mayo del 2002) en el horario de la mañana.…”

Section: Materials Y Métodosunclassified

Diversidad zoológica asociada a un silvopastoreo leucaena-guinea con diferentes edades de establecimiento

Lazo¹,

Valdés²,

Sampaio

et al. 2007

Pesq. agropec. bras.

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Resumen -El objetivo de este trabajo fue evaluar la diversidad zoológica asociada a un silvopastoreo con leucaena-guinea, por medio de la caracterización de la composición y estructura de las aves, insectos y la macrofauna del suelo, en cuatro edades de establecimiento (3, 4, 5 y 6 años de explotación). Con las especies registradas en cada uno de estos grupos zoológicos, se calcularon los índices ecológicos: número de individuos, riqueza, diversidad y abundancia de especies, en diferentes edades del sistema. En todos los grupos, se apreció el aumento significativo en la riqueza de especies y en el índice de diversidad biológica de Shannon, en la medida que se desarrolló el sistema. Se observó incremento en la abundancia de insectos biorreguladores y, en relación con las aves, el horario de muestreo no mostró interacción con los distintos años de siembra. La macrofauna se incrementó, observándose dominancia de anélidos al 6 o y 7 o año de explotación, caracterizado por Polyferetrina elongata y Oligochaeta elegans. El desarrollo del silvopastoreo leucaena-guinea logra sistemas productivos pecuarios que aumentan la producción de biomasa y de otros componentes biológicos y contribuir para crear un sistema sostenible y compatible con el ambiente.Términos para indexación: Leucaena leucocephala, Panicum maximum, aves, insectos, macrofauna, sostenibilidad. Zoological diversity associated to a silvopastural system leucaena-guinea grass with different establishment timesAbstract -The aim of this work was to evaluate the associated zoological diversity of a silvopastural system leucaena-guinea grass, by characterizing the composition and structures of the birds, insects and the macrofauna of the soil, in four establishment times of the silvopastural systems (3, 4, 5 and 6 years of exploitation). For the species recorded in each zoological group, the following ecological indices were determined: number of individuals, richness, diversity and abundance of species, in each establishment times of the system. A significant increase, in all the zoological groups, was observed for the richness of species and for the index of biological diversity of Shannon, as the system developed. An increase in the abundance of bioregulator insects was observed, and for the birds, the sampling time showed no interaction with the different sowing years. The macrofauna of the soil increased during the management of the system, and a dominance of annelids (Polyferetrina elongata and Oligochaeta elegans) was noted during the 6 th and 7 th year of exploitation. The silvopastural system leucaenaguinea grass increases the biomass production and other biological components, and contributes to create a sustainable system which is compatible with the environment.

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A Variable Circular-Plot Method for Estimating Bird Numbers

Cited by 510 publications

References 13 publications

Avian population survey in the Floreana highlands: is Darwin’s Medium Tree Finch declining in remnant patches ofScalesiaforest?

Avian population survey in the Floreana highlands: is Darwin’s Medium Tree Finch declining in remnant patches ofScalesiaforest?

Bird Community Changes in Response to Single and Repeated Fires in a Lowland Tropical Rainforest of Eastern Borneo

Diversidad zoológica asociada a un silvopastoreo leucaena-guinea con diferentes edades de establecimiento

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