The nightjar and the ant: Intercontinental migration reveals a cryptic interaction

• Published in: Ecology and evolution Vol. 14; no. 5; pp. e11113 - n/a
• Main Authors: Camacho, Carlos, Vidal‐Cordero, J. Manuel, Sáez‐Gómez, Pedro, Hidalgo‐Rodríguez, Paula, Rabadán‐González, Julio, Molina, Carlos, Edelaar, Pim
• Format: Journal Article
• Language: English
• Published: England John Wiley & Sons, Inc 01-05-2024; John Wiley and Sons Inc; Wiley
• Subjects: Adults; Amputation; amputations; Ants; Behavioural Ecology; Bird migration; Birds; Body parts; Caprimulgus; Community Ecology; Damage; Dorylus; Feet; Females; Fingers & toes; Injuries; Injury analysis; Insect bites; Insects; interspecific interactions; Mandible; migration; Mutualism; Nature Notes; Predation; Sepsis; Taxonomy; Teeth; Terrestrial ecosystems; Tropical environments; Zoology; Spain; Dorylus; migration; amputations; Caprimulgus; interspecific interactions
• ISSN: 2045-7758; 2045-7758
• DOI: 10.1002/ece3.11113

Birds and ants co‐occur in most terrestrial ecosystems and engage in a range of interactions. Competition, mutualism and predation are prominent examples of these interactions, but there are possibly many others that remain to be identified and characterized. This study provides quantitative estimates of the frequency of toe amputations resulting from ant bites in a population of migratory red‐necked nightjars (Caprimulgus ruficollis) monitored for 15 years (2009–2023) in S Spain, and identifies the attacker(s) based on taxonomic analyses of ant‐mandible remains found on injured toes. Less than 1% of examined adults (N = 369) missed one or more toes. The analysis of ant remains identified African army ants (Dorylus sp.) as the primary cause of toe amputations in nightjars and revealed that body parts of the attacker may remain attached to the birds even after intercontinental migration. No cases of severe damage were observed in juveniles (N = 269), apart from the mandible of a Messor barbarus – a local ant species – attached to one of the teeth of the characteristic comb of the medial toe of nightjars. The incidence of ant‐bite damage may appear unimportant for nightjar populations, but this might not be true if only birds that manage to survive their injuries and potential complications (e.g. severe bleeding and sepsis from opportunistic infections) return from the tropics. More field studies, ideally in tropical areas, that incorporate routine examination of ant‐induced injuries into their protocols are needed to understand the true incidence and eco‐evolutionary implications of antagonistic ant‐bird interactions.
Nightjars are migratory birds that spend most of their time on the ground and are exposed to accidental contact with army ants on their tropical non‐breeding grounds. Damage from ant bites results in toe amputations in at least 1% of individuals. Mandible remains of the ants may still be found attached to the toes of nightjars breeding in Europe even after migration from tropical areas, enabling determination of the cause of injury and identification of the attacker.