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We describe how levels of glucose, triglyceride, fatty acids, glycerol, β-hydroxybutyrate, uric acid, and corticosterone varied in the blood of Pied Flycatchers (Ficedula hypoleuca) during three breeding cycles. Data are for egg-laying and incubating females, and adults of both sexes that were caring for nestlings. Egg-laying females had high blood levels of triglyceride, fatty acids, and uric acid. Triglyceride and fatty acids decreased steadily with the laying of each new egg, whereas uric acid increased. This pattern of change in blood lipids would be expected as the number of ovarian follicles that are loaded with yolk precursors and subsequently ovulated diminishes. The rising uric acid level probably reflects increased consumption and subsequent catabolism of dietary proteins. Corticosterone levels were low suggesting that food was readily available for the production of eggs. Incubating females used fat as fuel, most of which was probably of dietary origin given their low blood triglyceride coupled with high fatty acid, glycerol, and corticosterone levels, and stable, high body weight. None of the birds' plasma constituents varied with clutch size or the length of time the females had been incubating. Females rearing broods exhibited low triglyceride and high β-hydroxybutyrate and corticosterone levels. Blood glycerol and free fatty acids rose steadily as a function of nestling age, while glucose and body weight declined. Such a picture suggests that females underwent transient bouts of fasting while providing their chicks with food. Meanwhile males were lighter than their mates and had lower blood metabolite levels, but their blood corticosterone was elevated and correlated with uric acid levels, suggesting that they took more time to forage for themselves than females. Nonetheless, they too lost weight during this stage of the breeding cycle.

Niveles Sanguíneos de Metabolitos y Corticosterona en Adultos Reproductivos de Ficedula hypoleuca

Resumen. Describimos la variación en los niveles sanguíneos de glucosa, triglicéridos, ácidos grasos, glicerol, betahidroxibutirato y corticosterona en Ficedula hypoleuca durante tres ciclos reproductivos. Los datos son para hembras que estaban poniendo o incubando huevos y para adultos de ambos sexos que estaban criando pichones. Las hembras que estaban poniendo huevos presentaron niveles altos de triglicéridos, ácidos grasos y ácido úrico. Los triglicéridos y ácidos grasos disminuyeron regularmente con la puesta de cada huevo nuevo, mientras que el ácido úrico aumentó. Este patrón de cambio en los lípidos sanguíneos era esperable debido a la disminución del número de folículos ováricos cargados con precursores de la yema que son subsecuentemente ovulados. El incremento en el nivel de ácido úrico probablemente refleja un incremento en el consumo y posterior catabolismo de proteínas dietarias. Los niveles de corticosterona fueron bajos, lo que sugiere que existía una alta disponibilidad de alimento para la producción de huevos. Las hembras que estaban incubando utilizaron las grasas como combustible. Considerando los niveles bajos de triglicéridos, los niveles altos de ácidos grasos, glicerol y corticosterona, y el peso corporal alto y estable de las aves, la mayor parte de estas grasas fue probablemente de origen dietario. Ninguno de los constituyentes del plasma sanguíneo varió con respecto al tamaño de la nidada o al período de tiempo durante el que las hembras habían estado incubando. Las hembras que estaban criando pichones presentaron niveles bajos de triglicéridos y niveles altos de betahidroxibutirato y corticosterona. El glicerol y los ácidos grasos sanguíneos se incrementaron con regularidad en función de la edad de los pichones, mientras que la glucosa y el tamaño corporal disminuyeron. Estos resulta

Michael Kern, Wayne Bacon, David Long, and Richard J. Cowie "BLOOD METABOLITE AND CORTICOSTERONE LEVELS IN BREEDING ADULT PIED FLYCATCHERS," The Condor 107(3), 665-677, (1 August 2005).[0665:BMACLI]2.0.CO;2
Received: 16 November 2004; Accepted: 1 April 2005; Published: 1 August 2005

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