Peregrine Falcon Eggs: Egg Size, Hatchling Sex, and Clutch Sex Ratios

• Published in: The Condor
• Main Authors: Burnham, William, Sandfort, Calvin, Belthoff, James R.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Oxford University Press (OUP) 2003
• Subjects: Animal Science and Zoology; Ecology, Evolution, Behavior and Systematics; Ancho; Huevo; Pichón; Falco peregrinus; peregrine falcon
• Online Access: http://dx.doi.org/10.1093/condor/105.2.327; http://academic.oup.com/condor/article-pdf/105/2/327/29711616/condor0327.pdf

Abstract Eggs (n = 367) collected from wild Peregrine Falcon (Falco peregrinus anatum) nests between 1976 and 1990 in Colorado and New Mexico were artificially incubated and hatched. We retrospectively examined these data for variation in egg length, breadth, and initial mass of hatchlings to resolve questions about relationships among egg size, chick size, and sex; and egg size related to first and second clutches and years. Egg length and breadth were significantly related to chick mass at hatching. Neither egg size nor hatchling mass were related to sex. Egg breadth slightly increased and then decreased over the years eggs were collected, which possibly reflects a re-established and then aging wild falcon population or other environmental variation. We also evaluated clutch sex ratios relative to theory based on sexual size dimorphism and local resource competition. Sex ratios did not significantly differ from 1:1 within first or second clutches separately or when combined. Thus, Peregrine Falcons in this population apparently did not skew clutch sex ratios in accordance with local resource competition or Fisherian theory. Huevos de Halcones Peregrinos: Tamaño, Sexo de los Pichones y Proporción de Sexos en la Nidada Resumen. Huevos (n = 367) colectados de nidos silvestres de halcones peregrinos (Falco peregrinus anatum) entre 1976 y 1990 en Colorado y New Mexico fueron incubados artificialmente hasta eclosionar. Examinamos esos datos retrospectivamente en cuanto a la variación en la longitud y ancho del huevo y el peso inicial de los pichones para contestar preguntas sobre las relaciones entre tamaño del huevo, tamaño del pichón y sexo, y entre el tamaño del huevo con relación a primeras y segundas nidadas y años. La longitud y el ancho del huevo estuvieron significativamente relacionados con la masa del pichón al eclosionar. El tamaño del huevo y el peso del pichón no estuvieron relacionados con el sexo. El ancho de los huevos aumentó ligeramente y luego disminuyó a través de los años en que los huevos se ...