Evolution of Nesting Height in an Endangered Hawaiian Forest Bird in Response to a Non-Native Predator

The majority of bird extinctions since 1800 have occurred on islands, and non-native predators have been the greatest threat to the persistence of island birds. Island endemic species often lack life-history traits and behaviors that reduce the probability of predation and they can become evolutionarily trapped if they are unable to adapt, but few studies have examined the ability of island species to respond to novel predators. The greatest threat to the persistence of the Oahu Elepaio (Chasiempis ibidis), an endangered Hawaiian forest bird, is nest predation by non-native black rats (Rattus rattus). I examined whether Oahu Elepaio nest placement has changed at the individual and population levels in response to rat predation by measuring nest height and determining whether each nest produced offspring from 1996 to 2011. Average height of Oahu Elepaio nests increased 50% over this 16-year period, from 7.9 m (SE 1.7) to 12.0 m (SE 1.1). There was no net change in height of sequential nests made by individual birds, which means individual elepaios have not learned to place nests higher. Nests ≤3 m off the ground produced offspring less often, and the proportion of such nests declined over time, which suggests that nest-building behavior has evolved through natural selection by predation. Nest success increased over time, which may increase the probability of long-term persistence of the species. Rat control may facilitate the evolution of nesting height by slowing the rate of population decline and providing time for this adaptive response to spread through the population. La mayoría de las extinciones de aves desde 1800 han ocurrido en islas, y los depredadores no nativos han sido la mayor amenaza para la persistencia de aves insulares. Las especies insulares endémicas a menudo carecen de atributos de historia natural y conductuales que reducen la probabilidad de depredación y pueden entramparse evolutivamente si no tienen la capacidad de adaptarse, pero pocos estudios han examinado la habilidad de especies insulares para responder a depredadores nuevos. La depredación por ratas no nativas (Rattus rattus) es la mayor amenaza para la persistencia del Elapaio de Oahu (Chasiempis ibidis), una especie de ave de bosque en peligro. Examiné si la ubicación de nidos de C. ibidis ha cambiado a nivel individual y de población en respuesta a la depredación de ratas midiendo la altura de los nidos y determinando si cada nido produjo crías entre 1996 y 2011. La altura