Journal Article

Anthropogenic threats to owls: Insights from rehabilitation admittance data and rodenticide screening in Texas

Prestridge, Heather L., Smith, Jennifer A., Gomez, Eres A.

2023

Overview

Owls (Strigiformes) provide myriad ecosystem services and are sentinels for ecosystem health. However, they are at continued risk from anthropogenic threats such as vehicle collisions, entanglement with human-made materials, and exposure to anticoagulant rodenticides (ARs), a widespread pesticide known to affect owls. Texas is an important region for numerous migratory and non-migratory owl species in the United States (US), yet assessments of threats owls face here are lacking preventing the development of informed conservation strategies. This study coupled assessment of admittance data from two wildlife rehabilitation centers in Texas with AR liver screening to (1) identify which species of owls are commonly admitted, (2) evaluate seasonality of admittance, and (3) assess causes of admittance for owls in Texas. Between 2010 and 2021, 1,620 owls were admitted into rehabilitation, representing eight species of which the Great-horned Owl ( Bubo virginianus ) was the most common. For all owls combined admittance rates were highest in the spring, driven by an influx of juveniles (n = 703, 43.40%). The leading cause of admittance amongst species was ‘no apparent injury’ (n = 567, 34.94%). Where clear diagnoses could be made, the leading causes of admittances were ‘entrapment in human infrastructure’ (n = 100, 6.11%) and ‘collision with vehicles’ (n = 74, 4.56%). While the admittance data did not reveal any cases of AR poisoning, liver screening demonstrated high incidences of AR exposure; of 53 owls screened for ARs, 50.94% (n = 27) tested positive with 18 showing exposure to multiple ARs. Brodifacoum was the most frequently detected AR (n = 19, 43.18%) and seven owls (25.93%) tested positive within lethal ranges. Our results suggest that owls in Texas are at risk from myriad anthropogenic threats and face high exposure rates to ARs. In doing so, our results can inform conservation strategies that mitigate anthropogenic threats faced by owls in Texas and beyond.

• Publisher: Public Library of Science
• Subject: Anthropogenic factors / Anticoagulants / Biological control / Biology and Life Sciences / Bubo virginianus / Conservation / Datasets / Diagnostic tests / Ecosystem services / Electrical impedance / Entanglement / Entrapment / Exposure / Identification and classification / Liver / Medicine and Health Sciences / Migratory species / Nontarget organisms / Owls / People and places / Pesticides / Pests / Physical Sciences / Poisoning / Rehabilitation / Rodenticides / Screening / Seasonal variations / Strigiformes / Threat evaluation / Vehicles / Wildlife / Wildlife conservation