Temporal space use dynamics and full breeding cycle survival rates of eastern whip-poor-wills in Illinois

The eastern whip-poor-will (Antrostomus vociferus) is a migratory, aerial insectivore which breeds in eastern North America. Although it is widespread across the region, its cryptic plumage and crepuscular foraging patterns make it difficult to observe, leaving many aspects of its life history understudied. These knowledge gaps must be filled to elucidate variables contributing to the species’ population decline. Because whip-poor-will activity is restricted to crepuscular periods, we examined how fine-scale temporal variables such as time of day and moon illumination influenced space use over the course of a breeding season. We collected location estimates from 49 VHF-tagged adult whip-poor-wills using an automated telemetry system and used these to calculate core areas and home ranges for each study bird. We found that whip-poor-wills held larger core areas and home ranges and overlapped with neighbors more during crepuscular than nocturnal periods and under greater moon illumination relative to darker nights. Used areas including high proportions of foraging habitat (fields and forest edges) tended to be smaller than those containing nonpreferred foraging habitat (pine forests). These increases in space use during crepuscular periods and concentration on open, edge-rich habitats appear to allow the species to exploit limited feeding opportunities. We also investigated survival within three separate stages of whip-poor-will development, the egg, chick, and post-fledging stage, to identify when broods experience greatest mortality risk. Whip-poor-wills are ground nesters, leaving nests vulnerable to terrestrial predators, but will brood and provision young for up to 3 weeks past their fledge date. We monitored 99 egg clutches, 103 chicks, and 51 fledglings over four breeding seasons and found that egg and chick survival was moderately low (51% – 54% cumulative survival) and fledgling survival was high (96% cumulative survival). Elevated post-fledging survival and the parental care strategy which underlies it offsets predation of eggs and chicks, but recruitment may be a source of population decline in years with exceptionally high pre-fledging mortality. Collectively, these results suggest that the whip-poor-will possesses unique life history traits which help them maximize both foraging efficiency and breeding productivity under profound temporal and survival constraints.

Name thesis:degree_name

M.S.

Level thesis:degree_level

Thesis

Discipline thesis:degree_discipline

Natural Res & Env Sciences

Grantor

University of Illinois at Urbana-Champaign

Year dc:date

2023

Author dc:creator

• Stewart, Sarah Haley

Contributors dc:contributor

• Ward, Michael P
• Benson, Thomas J
• O'Keefe, Joy

• Avian Ecology
• Conservation
• Nightjars
• Illinois
• Space Use
• Breeding Ecology

Statement dc:rights

• Copyright 2023 Sarah Stewart

Language dc:language

en, eng

Handle dc:identifier

https://hdl.handle.net/2142/120236

OAI record oai:identifier

https://www.ideals.illinois.edu/oai-pmh?verb=GetRecord&metadataPrefix=etdms&identifier=oai%3Awww.ideals.illinois.edu%3A2142%2F120236