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University of Arizona (1971)

THE EFFECTS OF HEAT AND ARIDITY ON REPRODUCTIVE SUCCESS OF THE CURVE-BILLED THRASHER

Smith, Ernest Linwood

Titre : THE EFFECTS OF HEAT AND ARIDITY ON REPRODUCTIVE SUCCESS OF THE CURVE-BILLED THRASHER

Auteur : Smith, Ernest Linwood,

Université de soutenance : University of Arizona

Grade : Doctor of Philosophy (PhD) 1971

Résumé
A study of the effects of increasing heat and aridity on nesting success in Curve-billed Thrashers (Toxostoma curvirostre) was conducted during the breeding seasons of 1969-1971 at Saguaro National Monument, east of Tucson, Arizona. In 1970 and 1971 data were also collected from three other areas along a 130 mile east-west gradient characterized by increasing mean daily high temperatures and decreasing winter precipitation. Low or sporadic winter rainfall appears to delay initiation of spring breeding until a period coincident with the blooming of the saguaro cactus. Heat appears to be a factor limiting reproductive success. It may contribute to high levels of hatching failure of eggs and may limit foraging activities of. adults, resulting in nestling loss through starvation. Probabilities of whole nest success and total reproductive success (young fledged per pair of breeding adults) were highest in the hottest, driest study area and in the coolest, wettest one. Fewer young fledged per pair in areas with the highest population densities. The number of young fledged per acre was almost idential in each study area. There appeared to be no correlation between bird densities and temperature and precipitation on the gradient.

Mots clés : Water — Physiological effect. ; Heat — Physiological effect. ; Birds — Arizona. ; Birds — Physiology. ; Thrashers (Birds)

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