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1 February 2005 NOCTURNAL HYPOTHERMIA IN SEASONALLY ACCLIMATIZED MOUNTAIN CHICKADEES AND JUNIPER TITMICE
Sheldon J. Cooper, James A. Gessaman
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Abstract

We measured body temperature of Mountain Chickadees (Poecile gambeli) and Juniper Titmice (Baeolophus ridgwayi) at different times of day and under a range of ambient temperatures in order to determine the use of nocturnal hypothermia in seasonally acclimatized small passerines. Our findings show both species used nocturnal hypothermia year-round. Depth of hypothermia was inversely correlated to body mass in Juniper Titmice but not in Mountain Chickadees. In both species, depth of hypothermia did not vary seasonally but nocturnal body temperature was regulated 3–11°C lower than daytime values. Nocturnal energy savings range from 7%–50% in chickadees and from 10%–28% in titmice. These nocturnal energy savings translate into ecologically important reductions in daily energy expenditures for these two species.

Hipotermia Nocturna en Individuos de Poecile gambeli y Baeolophus ridgwayi Aclimatados Estacionalmente

Resumen. Medimos la temperatura corporal de Poecile gambeli y Baeolophus ridgwayi a diferentes horas del día y en un rango de temperaturas ambientales para determinar el uso de hipotermia nocturna en pequeñas aves paserinas aclimatadas estacionalmente. Nuestros resultados muestran que ambas especies presentaron hipotermia nocturna durante todo el año. La profundidad de la hipotermia estuvo inversamente correlacionada con la masa corporal en B. ridgwayi, pero no en P. gambeli. En ambas especies, la profundidad de la hipotermia no varió estacionalmente, pero la temperatura corporal nocturna estuvo regulada 3–11°C por debajo de los valores diurnos. El ahorro nocturno de energía varió entre 7%–50% en P. gambeli y entre 10%–28% en B. ridgwayi. Estos ahorros nocturnos de energía se tradujeron en reducciones ecológicamente importantes en los gastos diarios de energía para ambas especies.

Sheldon J. Cooper and James A. Gessaman "NOCTURNAL HYPOTHERMIA IN SEASONALLY ACCLIMATIZED MOUNTAIN CHICKADEES AND JUNIPER TITMICE," The Condor 107(1), 151-155, (1 February 2005). https://doi.org/10.1650/7597
Received: 25 May 2004; Accepted: 1 October 2004; Published: 1 February 2005
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KEYWORDS
Baeolophus ridgwayi
body temperature
energy metabolism
nocturnal hypothermia
Poecile gambeli
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