ORIENTATION AND MICROCLIMATE OF HORNED LARK NESTS: THE IMPORTANCE OF SHADE

Abstract Across their range, Horned Larks (Eremophila alpestris) consistently construct their nests adjacent to and north of a conspicuous object such as a tuft of grass, shrub, or rock. We studied the relative importance of a northern nest orientation to nest microclimate in Horned Larks breeding in northeastern California. Nests showed a significant northern bias in orientation angle and were 49% shaded in the early afternoon, the hottest part of the day. Artificial nests of eastern, western, and southern orientations exhibited little to no shade during this time. A northern nest orientation also allowed nests to face prevailing winds during the day and avoid them in the evening. The Horned Larks' preference for a northern nest orientation offers multiple advantages for regulation of nest microclimate. Orientación y Microclima en Nidos de Eremophila alpestris: La Importancia de la Sombra Resumen. De forma consistente a lo largo de su rango de distribución, Eremophila alpestris construye sus nidos adyacentes a y al norte de objetos conspicuos, como parches de pasto, arbustos o rocas. Estudiamos la importancia relativa de la orientación de los nidos hacia el norte para el microclima de éstos en individuos de E. alpestris que se reproducen en el noreste de California. El ángulo de orientación de los nidos presentó un sesgo significativo hacia el norte y éstos tuvieron un 49% de sombra durante las primeras horas de la tarde, el período más caliente del día. Nidos artificiales con orientación hacia el este, oeste y sur exhibieron poca o ninguna sombra durante esa parte del día. La orientación hacia el norte también permitió a los nidos orientarse hacia la dirección predominante del viento durante el día y evitar los vientos durante el atardecer. La preferencia de E. alpestris por la orientación de los nidos hacia el norte ofrece múltiples ventajas para la regulación del microclima del nido.

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