FROM NEST TO HOME RANGE: EXPLORING THE NESTING BEHAVIOR, CHICK DEVELOPMENT, AND SPATIAL ECOLOGY OF EASTERN WHIP-POOR-WILLS BREEDING IN RHODE ISLAND, USA

Author

Liam Corcoran, University of Rhode IslandFollow

Date of Award

2025

Degree Type

Thesis

Degree Name

Master of Science in Biological and Environmental Sciences (MSBES)

Department

Biological Sciences

First Advisor

Scott McWilliams

Abstract

Aerial insectivore populations are declining across North America at a steeper rate than many other bird groups, likely driven by loss of breeding habitat and declines in the abundance and quality of insect prey available during the breeding season. For effective conservation of declining species, understanding fundamental aspects of their life history and habitat use is especially important. The Eastern Whip-poor-will (Antrostomus vociferus, hereafter Whip-poor-will) is a species of nocturnal aerial insectivore in the nightjar family (Caprimulgidae) that breeds throughout the eastern United States and southeastern Canada. Whip-poor-will populations have declined by approximately 70% since 1970, which is thought to be primarily caused by the loss of early successional habitat and reductions in flying insect prey throughout their breeding range. Like other nightjars, Whip-poor-wills are understudied. The four primary objectives of my thesis were (1) to describe behavioral interactions of adults with the nest, between paired males and females, between adults and chicks, and between adults and predators during the incubation and chick rearing stages, and provide estimates of sex-specific incubation constancy, (2) to quantify chick growth trajectories from morphometric measurements, and then generate predictions of chick size that estimate chick age from a subset of these morphometric measurements, (3) to quantify the diurnal home ranges of breeding adults, (3) to quantify the space use sharing of neighboring adult males and paired males and females, and (4) to quantify home range-scale habitat selection of adults across two study sites.

In chapter 1, I described the behavior of breeding pairs during incubation and chick rearing and quantified chick growth. I used trail cameras to monitor 14 whip-poor-will nests during May-August 2023 in Rhode Island, USA. I estimated sex-specific incubation constancy (number of minutes per day on the nest) and observed behavioral interactions of adults with the nest, between paired males and females, between adults and chicks, and between adults and predators during the incubation and chick rearing stages. Additionally, I quantified chick growth trajectories (n = 12) for nine morphometric measurements, and growth rates for the four most informative measurements. Females spent 92 ± 2% of the 24 h period incubating, while males only assisted with incubation 4 ± 4% of the time. Paired males and females displayed a rarely documented courtship-like behavior at the nest. I also observed incubating females singing the male song, an anti-predator defensive behavior, and a slug (Gastropoda) as a predator of an egg. I provide the first published estimates of chick growth for the species and generated predictions of chick size that estimated chick age to a range of 1-2 days based on four measures (mass, tarsus length, humerus length, and wing chord). Whip-poor-will growth rates were like those of similar sized nightjars (Fiery-necked Nightjar Caprimulgus pectoralis and Common Pauraque Nyctidromus albicollis) and other aerial insectivores (flycatchers, Tyrannidae; swallows, Hirundinidae). Our growth models provide a baseline for assessing the effects of habitat quality on whip-poor-will chick growth, and a valuable tool for estimating nesting phenology and enhancing survival analyses through precise age-specific survival estimates.

In chapter 2, I quantified Whip-poor-will home range size, space use sharing between neighboring males and paired males and females, and habitat selection. We tracked 10 adult Whip-poor-wills from May-August 2022 at two state management areas, Big River and Great Swamp, and five adult Whip-poor-wills (four of which were also tracked in 2022) from May-August 2023 at Great Swamp in Rhode Island, USA. We used diurnal locations to estimate home ranges for each individual, the extent of home range overlap for neighboring males, paired males and females, the same males tracked in both years, as well as habitat selection at the home-range scale. Home range sizes of males and females were not different and averaged 18.05 ha (95% CI: 10.23, 26.11). Home ranges of neighboring males minimally overlapped while paired males and females had a high degree of home range overlap. The four males that were tracked at Great Swamp in both years used very similar home ranges across years, suggesting that at least some individuals show site and home range fidelity. We found no support for selection for distance to any land cover types at the population level; however, 10 of 11 individuals selected for at least one land cover type and eight of 11 individuals selected for early successional forest openings (e.g., scrub and grassland), although the pattern of selection varied between individuals. These findings, when considered along with other published works on Whip-poor-will habitat selection and occupancy, underscore the importance of active forest management to maintain habitat mosaics on known Whip-poor-will breeding grounds.

Comments

Additional Files Descriptions:

Video_S1 - Female Whip-poor-will incubation movements.

Video_S2 - Female Whip-poor-wills singing on nest.

Video_S3 - Paired male and female Whip-poor-will courtship-like display at the nest.

Video_S4 - Whip-poor-will anti-predator defensive display.

Video_S5 - Raccoon flushing female Whip-poor-will off nest.

Video_S6 - Additional anti-predator defensive display.

Video_S7 - Slug predation of a Whip-poor-will egg.

Video_S8 - Adult Whip-poor-will call to chicks.

Video_S9 - Adult Whip-poor-wills feeding chicks.

Video_S10 - Male Whip-poor-will defending nest against a shrew.

Video_S11 - Female Whip-poor-will defending nest against a chipmunck.

Recommended Citation

Corcoran, Liam, "FROM NEST TO HOME RANGE: EXPLORING THE NESTING BEHAVIOR, CHICK DEVELOPMENT, AND SPATIAL ECOLOGY OF EASTERN WHIP-POOR-WILLS BREEDING IN RHODE ISLAND, USA" (2025). Open Access Master's Theses. Paper 2632.
https://digitalcommons.uri.edu/theses/2632