Nesting ecology of solitary‐nesting Amur Falcons (Falco amurensis) in central Mongolia

Abstract

Amur Falcons (Falco amurensis) are a migratory species that face a variety of threats across their range, but little is known about their breeding ecology. These falcons breed in forest habitats in Eastern and Central Asia using nests constructed by corvids, including Eurasian Magpies (Pica pica). We monitored nests of 21 pairs of Amur Falcons at Hustai National Park in central Mongolia in 2017. Our objectives were to describe their basic nesting ecology, estimate nest survival by modeling the daily survival rate (DSR), examine nest selection by modeling it as a function of nest and site covariates, and use a spatial simulation to test hypotheses concerning intraand interspecific avoidance. Clutch sizes averaged 4.1 eggs (N = 21 nests), and incubation and nestling periods averaged 25.7 and 26.1 d, respectively. The daily survival rate was 0.98, with young in 12 nests surviving to fledging. Nest structures were more likely to be selected as percent cover of nest bowls increased, usually in the form of a dome of sticks with multiple side entrances. Closed nests likely provide increased protection from predators. In contrast to congeneric Red-footed Falcons (F. vespertinus) that nest in large colonies, Amur Falcons nested no farther from or closer to nests of either conspecifics or congeners than expected by chance. One factor likely contributing to this difference is that Red-footed Falcons often use the nests of colonial-nesting Rooks (Corvus frugilegus), whereas Amur Falcons typically use the nests of non-colonial Eurasian Magpies. The ongoing loss of deciduous trees like white birch (Betula platyphylla) across the breeding range of Amur Falcons, probably due to climate change and increased grazing pressure, is likely to reduce the availability of nesting habitat for Eurasian Magpies which, in turn, will likely reduce availability of nests for Amur Falcons and other small falcons. RESUMEN. Ecolog ıa de la anidaci on de los halcones Falco amurensis que anidan en solitario en Mongolia central. El halc on Falco amurensis es una especie migratoria que enfrenta una variedad de amenazas a lo ancho de su rango, si bien se sabe poco de la ecolog ıa de su anidaci on. Estos halcones anidan en h abitats boscosos en Asia central y oriental utilizando nidos construidos por c orvidos, incluida la urraca Pica pica. Monitoreamos los nidos de 21 pares de F. amurensis en Hustai National Park en Mongolia central en 2017. Nuestros objetivos fueron describir la ecolog ıa b asica de su anidaci on, estimar la supervivencia de sus nidos modelando la tasa diaria de supervivencia (DSR), examinar la selecci on de nidos model andolos como funci on de covariables de nidos y sitios, y usar una simulaci on espacial para someter a prueba hip otesis relacionadas con la evasi on intra e interespec ıfica. Los tama~ nos de puesta promediaron 4.1 huevos (N = 21 nidos), y los periodos de incubaci on y de crianza de polluelos promediaron 25.7 y 26.1 d ıas respectivamente. La tasa de supervivencia diaria fue 0.98, con polluelos de 12 nidos sobreviviendo hasta la emancipaci on. Las estructuras nido fueron m as proclives a ser seleccionadas seg un el porcentaje de cobertura del nido en forma de taz on, usualmente domos de varitas con m ultiples entradas laterales. Los nidos cerrados probablemente incrementan la protecci on de depredadores. En contraste con su congen erico, el halc on F. vespertinus que anida en grandes colonias, F. amurensis anid o no m as lejos o m as cerca de conespec ıficos o congen ericos de lo esperado aleatoriamente. Un factor que posiblemente contribuye a estas diferencias es que F. vespertinus frecuentemente usa los nidos de Corresponding author. Email: [email protected] Present address: Faculty of Environmental Science and Nature Management, Norwegian University of Life Sciences, As, 1433, Norway © 2019 The Authors. Journal of Field Ornithology published by Wiley Periodicals, Inc. on behalf of Association of Field Ornithologists This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited. 266 J. Field Ornithol. 90(3):266–276, 2019 DOI: 10.1111/jofo.12307