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).