Ecosystem engineers show variable impacts on habitat availability for cavity nesters in South American temperate forests

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2024
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Abstract
Ecosystem engineers are organisms that impact their environment and co-existing species by creating or modifying habitats, and thus they play important roles as drivers of community assembly. We examined whether cavity characteristics and/or habitat attributes associated with cavities provided by 4 ecosystem engineers influence the presence of nests of 3 secondary cavity-nesting birds-Aphrastura spinicauda (Thorn-tailed Rayadito), Tachycineta leucopyga (Chilean Swallow), and Troglodytes aedon (Southern House Wren)-and whether these variations influence their reproductive success. We tested this by: (1) assessing nest presence in cavities supplied by ecosystem engineers and (2) quantifying the reproductive success of secondary cavity nesters as a function of cavity characteristics and habitat attributes supplied by ecosystem engineers. Between 2009 and 2022, we recorded 757 cavities in 546 trees in old-growth and second-growth forests in a Global Biodiversity Hotspot in the Andes of southern Chile. Insect/fungi and Pygarrhichas albogularis (White-throated Treerunner) play a key role as the primary producers of cavities. Insect/fungi generated the cavities for 82% of A. spinicauda nests and 95% of T. aedon nests; in contrast, 57% of T. leucopyga nests were cavities excavated by P. albogularis. Characteristics of cavities (size of cavity entrance, volume, and height above ground) were associated with nest presence of secondary cavity nesters and with reproductive success of A. spinicauda and T. aedon. Habitat attributes such as tree density and canopy cover influenced nest presence for A. spinicauda and T. leucopyga, but did not correlate with the reproductive success of any secondary cavity nester. Bamboo density and forest type were related to reproductive success of A. spinicauda and T. aedon. Diameter at Breast Height of trees was related to the reproductive success of T. leucopyga. This study contributes to understanding the importance of various ecosystem engineers for the conservation of secondary cavity-nesting birds in temperate forests and beyond.
center dot Ecosystem engineers are organisms that impact their environment and co-existing species by creating or modifying habitats, and thus they play important roles as drivers of community assembly.center dot We examined the presence of nests of 3 species of secondary cavity nesters and their reproductive success in cavities supplied by 4 ecosystem engineers.center dot Between 2009 and 2022, we recorded 757 cavities in 546 trees in old-growth and second-growth forests in a Global Biodiversity Hotspot in the Andes of southern Chile.center dot Insect/fungi and Pygarrhichas albogularis played a key role as the primary producers of cavities for secondary cavity nesters. The characteristics of cavities were associated with the presence of nests and showed a weaker association with the reproductive success of secondary cavity nesters.center dot Habitat attributes showed a weak association with the presence of nests and the reproductive success of 3 secondary cavity nesters.center dot This study contributes to understanding the importance of various ecosystem engineers for the conservation of secondary cavity-nesting birds.
Los ingenieros de ecosistemas son organismos que influyen en su entorno y en las especies coexistentes creando o modificando h & aacute;bitats, por lo que desempe & ntilde;an un papel importante como impulsores de la formaci & oacute;n de comunidades. Examinamos si las caracter & iacute;sticas de las cavidades y/o los atributos de h & aacute;bitat asociados con las cavidades proporcionados por cuatro ingenieros de ecosistemas influyen en la presencia de los nidos de tres aves que anidan en cavidades secundarias (Aphrastura spinicauda, Tachycineta leucopyga y Troglodytes aedon), y si estas variaciones influyen en su & eacute;xito reproductivo. Esto se comprob & oacute;: i) evaluando la presencia de nidos en cavidades suministradas por los ingenieros de ecosistemas y ii) cuantificando el & eacute;xito reproductivo de los nidificadores secundarios en funci & oacute;n de las caracter & iacute;sticas de las cavidades y los atributos del h & aacute;bitat suministrados por los ingenieros de ecosistemas. Entre 2009 y 2022, registramos 757 cavidades en 546 & aacute;rboles de bosques antiguos y de segundo crecimiento a lo largo de un Hotspot de Biodiversidad Global en los Andes del sur de Chile. Los insectos/hongos y el Pygarrhichas albogularis desempe & ntilde;aron un papel clave como principales productores de cavidades. Los insectos/hongos generaron el 82% de los nidos de A. spinicauda y el 95% de los nidos de T. aedon; en contraste, el 57% de los nidos de T. leucopyga fueron cavidades excavadas por P. albogularis. Las caracter & iacute;sticas de las cavidades (tama & ntilde;o de la entrada de la cavidad, volumen y altura sobre el suelo) se asociaron con la presencia de nidos de los nidificadores secundarios y con el & eacute;xito reproductivo de A. spinicauda y T. aedon. Los atributos del h & aacute;bitat, como la densidad de & aacute;rboles y la cobertura del dosel, influyeron en la presencia de nidos de A. spinicauda y T. leucopyga, pero no de T. aedon, y no afectaron el & eacute;xito reproductor de ninguno de los nidificadores secundarios. La densidad de bamb & uacute; y el tipo de bosque se relacionaron con el & eacute;xito reproductivo de A. spinicauda y T. aedon. El Di & aacute;metro a la Altura del Pecho de los & aacute;rboles se relacion & oacute; con el & eacute;xito reproductivo de T. leucopyga. Este estudio contribuye a comprender la importancia de varios ingenieros de ecosistemas para la conservaci & oacute;n de aves que anidan en cavidades secundarias en el bosque templado y m & aacute;s all & aacute;.
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cavity characteristics, Chile, ecosystem engineers, habitat attributes, native birds, secondary cavity nesters, Atributos del h & aacute;bitat, aves nativas, caracter & iacute;sticas de cavidades, ingenieros de ecosistemas, nidificadores secundarios de cavidades
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