Nest Survival in Dusky Canada Geese (Branta Canadensis Occidentalis): use of Discrete-Time Models
Dates
Year
2006
Citation
Grand, James B., Fondell, Thomas F., Miller, David A., and Anthony, R. M., 2006, Nest Survival in Dusky Canada Geese (Branta Canadensis Occidentalis): use of Discrete-Time Models: Auk (American Ornithologists Union), v. 123, no. 1, p. 198-210.
Summary
The Dusky Canada Goose (Branta canadensis occidentalis) population that breeds in the Copper River Delta, Alaska, has declined substantially since the late 1970s. Persistent low numbers have been attributed to low productivity in recent years. We examined patterns in survival rates of 1,852 nests to better understand ecological processes that influenced productivity during 1997-2000. We compared 10 nonparametric models of daily survival rate of nests (DSR) that included variation among years, calendar dates, nest initiation dates, and nest ages with equivalent models based on parametric functions. The unequivocal best model included patterns of DSR that varied among discrete periods of years, calendar dates, and nest ages. Generally, [...]
Summary
The Dusky Canada Goose (Branta canadensis occidentalis) population that breeds in the Copper River Delta, Alaska, has declined substantially since the late 1970s. Persistent low numbers have been attributed to low productivity in recent years. We examined patterns in survival rates of 1,852 nests to better understand ecological processes that influenced productivity during 1997-2000. We compared 10 nonparametric models of daily survival rate of nests (DSR) that included variation among years, calendar dates, nest initiation dates, and nest ages with equivalent models based on parametric functions. The unequivocal best model included patterns of DSR that varied among discrete periods of years, calendar dates, and nest ages. Generally, DSR was low early in the nesting season and higher midseason. Across years, patterns in DSR were most variable early and late in the nesting season. Daily survival rates of nests declined between the first and second week after initiation, increased until the fourth week, and then declined during the last week before hatch. Nest survival probability estimates ranged from 0.07 to 0.71 across years and nest initiation dates. Mean rates of nest survival ranged between 0.21 and 0.31 each year. We suggest (1) considering models that do not limit estimates of daily nest survival to parametric forms; (2) placing greater emphasis on sample size when nests are rare, to obtain accurate estimates of nest survival; and (3) developing new techniques to estimate the number of nests initiated. (English) ABSTRACT FROM AUTHOR]; Las poblaciones del ganso Branta canadensis occidentalis que crían en el delta del Río Copper, Alaska, han declinado substancialmente desde el final de los 70s. Estos números persistentemente bajos han sido atribuidos a una baja productividad en los últimos años. Examinamos los patrones en las tasas de supervivencia de 1,852 nidos para comprender mejor los procesos ecológicos que influenciaron la productividad entre 1997 y 2000. Comparamos 10 modelos no paramétricos de tasas de supervivenda diaria de nidos (TSD) que incluyeron variación entre años, fechas de calendario, fechas de iniciación de los nidos y edad de los nidos con modelos equivalentes basados en funciones paramétricas. El mejor modelo incluyó patrones de la TSD que variaron entre periodos discretos de años, fechas de calendario y edad de los nidos. De modo general, la TSD fue baja al principio de la estación de cría y mayor en el medio de la estación. Entre años, los patrones de la TSD fueron más variables al principio y al final de la estación de cría. Las tasas de supervivencia de los nidos disminuyeron entre la primera y la segunda semana posterior al inicio de los nidos, incrementaron hasta la cuarta semana y luego disminuyeron durante la última semana antes de la eclosión. Las estimaciones de la probabilidad de supervivencia de los nidos variaron entre 0.07 y 0.71 entre los años y las fechas de inicio de los nidos. Las tasas medias de supervivencia de los nidos variaron entre 0.21 y 0.31 cada año. Sugerimos (1) considerar modelos que no limiten las estimaciones de supervivencia diaria de los nidos a formas paramétricas; (2) poner mayor énfasis al tamaño de muestreo cuando los nidos son raros, para obtener estimaciones exactas de la supervivencia de los nidos; y (3) desarrollar nuevas técnicas para estimar el número de nidos iniciados. (Spanish) ABSTRACT FROM AUTHOR]; Copyright of Auk (American Ornithologists Union) is the property of American Ornithologists Union and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)