Springtime bird use of agricultural landscapes examined by using autonomous recording units

Abstract

Autonomous recording units (ARUs) emerged as a novel technology for avian acoustic monitoring in the 2000s. They have since been primarily used as a substitute for human observers during the breeding season. Autonomous recording units have potential uses in springtime soundscapes, such as to study spring departure or arrival of migratory birds and territory establishment of resident breeding birds. We described springtime bird communities of agricultural landscapes based on data collected between 1 April and 15 May 2015-2019, from ARUs deployed at 32 locations across 13 counties in Iowa, USA. We compared bird communities across site types, analyzed trends in migrant arrival dates and detection rates, and examined springtime occupancy of five species that commonly use grassland cover: Common Yellowthroat (Geothlypis trichas), Field Sparrow (Spizella pusilla), Grasshopper Sparrow (Ammodramus savannarum), Savannah Sparrow (Passerculus sandwichensis), and Vesper Sparrow (Pooecetes gramineus). We made 4029 detections of 86 bird species. The most frequent detections were of common farmland species, including Red-winged Blackbird (Agelaius phoeniceus), American Robin (Turdus migratorius), Brown-headed Cowbird (Molothrus ater), Ring-necked Pheasant (Phasianus colchicus), and Eastern Meadowlark (Sturnella magna); however, detections also included 18 species of greatest conservation need. Sites with reconstructed prairie vegetation, conventionally grown corn (Zea mays) and soybean crops (Glycine max), crops with prairie strips, and crops with terraces had similar species richness. We found that, in addition to documenting species richness and departure/arrival times of migratory species, ARUs generated species-level detection probabilities similar to or higher than existing studies on breeding season occupancy. Detection probabilities of five focal species ranged from 0.36-0.89. Occupancy models revealed significant springtime land cover associations for Common Yellowthroats, Field Sparrows, Savannah Sparrows, and Vesper Sparrows. We conclude that springtime deployment of ARUs can provide valuable information on phenological patterns and springtime habitat use of birds.RESUMEN. Las unidades de grabación autónomas (ARUs, por sus siglas en inglés) surgieron como una tecnología novedosa para el monitoreo acústico de aves en la década de 2000. Desde entonces, se han utilizado principalmente como un sustituto de observadores humanos durante la temporada de reproducción. No obstante, las unidades de grabación autónomas tienen aplicaciones potenciales en paisajes sonoros de primavera, como el estudio de la salida o llegada de aves migratorias y el establecimiento de territorios de aves residentes. Este estudio se centra en las comunidades de aves en paisajes agrícolas durante la primavera, basándose en datos recopilados entre el 1 de abril y el 15 de mayo de 2015-2019, a partir de ARUs desplegadas en 32 ubicaciones en 13 condados de Iowa, EE. UU. La comparación de comunidades de aves entre tipos de sitios, el análisis de tendenci...