Abstract
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.