Diet
The diet of black wheatears was very diverse, with 337 prey items of 96
families and 29 orders (Table S3). Arthropods were detected in all
samples and belonged to 5 classes and 22 orders, of which 17 orders were
Insecta. The main prey belonged to the order Hymenoptera (Frequency of
Occurrence: 83%), mainly ants (family Formicidae; 75%). Frequent
animal orders that were detected in more than half of the samples
included Lepidoptera (67%), mainly belonging to families Noctuidae
(30%), Pterophoridae (25%) and Geometridae (15%); Coleoptera (62%),
mainly Tenebrionidae (28%) and Carabidae (13%); Orthoptera (54%),
mainly Acrididae (42%); and Diptera (51%), with 10 families identified
but none detected in more than 10% of droppings. There were also other
important arthropods as Hemiptera (40%), mainly from the family
Pentatomidae (16%); and Araneae (34%), mainly Salticidae (11%). The
only vertebrates found were lizards (Squamata) detected in two
droppings. The vegetal component of the diet was less diverse, but also
very common (60% of the droppings), with Solanum nigrum (order
Solanales, family Solanaceae) being the most frequently detected (35%)
(Figure 1; Table S3).
We found no differences between sexes in the average number of prey
items detected per sample, irrespective of taxonomic resolution: highest
prey item resolution ( = 8.344; LR Chisq = 0.232, df = 1, p = 0.630),
families ( = 5.739; LR Chisq = 0.130, df = 1, p = 0.718) or orders ( =
5.226; LR Chisq = 0.083, df = 1, p = 0.773). However, the overall prey
richness was higher for males than females for the analysis carried out
at the highest prey item resolution (even if a 95% confidence interval
was considered), while no significant differences between sexes were
detected for analysis based on identifications at the family or order
levels (Figure 2).
Regarding diet composition, we found a significant difference between
sexes at the highest prey item resolution (Res. Df = 91, Deviance = 427,
p = 0.006), family level (Res. Df = 90, Deviance = 139.9, p = 0.021),
but not at the order level (Res. Df = 91, Deviance = 44.52, p = 0.054).
The univariate tests showed that the differences found were due to 11
prey items and 6 families (Table S3). The prey item most important for
compositional differences was one unidentified Myrmicinae species, that
was also the prey most often detected in black wheatear droppings. This
ant species was detected in 58% of females’ droppings, while in males
it was only detected in 29% of droppings (Table S3). At the highest
resolution level, all other prey had differences in frequency of
occurrence between sexes smaller than 10% (Table S3). At the family
level, the differences were mainly due to the families Pentatomidae,
Formicidae, Tettigoniidae, that were preyed 24%, 21% and 11%,
respectively, more often by females, while males preyed 23% more often
on Tenebrionidae (Figure 1; Table S3). There were also 2 orders that
differed between sexes (Hymenoptera and Santales), despite the overall
effect of sex being non-significant when analysing prey composition at
the order level (Table S3).