RESULTS
Our dataset consisted of a total of 855 captures from 588 individual
nightjars that had been examined for limb damage and loss at least once
during 97 nocturnal surveys conducted in 2021-2023 (Table 1). Sampling
effort, measured as either the total number of captures (range: 282-287)
or as the number of different individuals examined (range: 207-225), was
uniform across the three years of systematic study (Table 1). No
evidence of severe damage (i.e., toe amputation) was observed in any of
the 219 juveniles examined, although one of the juveniles caught in 2023
had a full (ant) head attached to the claw of the central toe (Figure
1c). Of the 369 different adults captured during 2021-2023, only three
missed a toe: a 1-year-old male captured for the first time in 2021 (toe
still attached to the foot by a thin piece of skin; Figure 1b), a
5-year-old male captured in both 2021 and 2022 (first caught as a
second-year bird in 2017), and a 1-year-old female captured in 2023
(first caught as a non-injured juvenile the year before). The estimated
frequency of damage in adults across the three years of study was 1:123
(0.81%), although annual estimates differed as much as 2-fold (Table
1). Four additional adults missing one or more phalanges in one or more
toes were recorded during non-systematic checks in previous years (Table
1). Despite the lack of records of toe amputations in juvenile
nightjars, there is insufficient statistical support to conclude that
there is a greater incidence of damage in adults (Fisher’s exact test, P
= 0.299).
Damage generally consisted of total amputation (80% of cases) or
incomplete excision (20%) of one or two toes. The most severe damage
was recorded for an adult female captured in 2015, which missed three
toes of the right foot and one lateral toe and the claw of the medial
toe on the left foot (Figure 1a).
The encountered left mandible (year 2021) measured 2.3 mm in length by a
maximum width of 0.8 mm, was dark brown in colour and ended in a
bifurcation, with a robust central tooth. It was identified as belonging
to a worker ant of the army ant genus Dorylus (Fabricius, 1793).
Some 20 species of Dorylus ants have been listed for Mali and
Guinea (antsmap.org), where the captured nightjars spend the winter. It
is currently impossible to identify the attacker at the species level,
even if we had retrieved the entire individual, and the entire genus is
currently under taxonomic revision (Kiko Gómez, pers. comm.).
The full head attached to the juvenile (year 2023) caused no apparent
damage to the bird, apart from nicking one of the teeth of the
characteristic pecten (comb) of the medial toe of nightjars (Figure 1c).
The full head was identified as belonging to a worker of Messor
barbarus , an easily identifiable species that can be distinguished from
other species of the genus in the Iberian Peninsula by the unique
reddish colouration on the head (Lebas et al., 2017).