Responses of avian predators to polymorphic harlequin ladybird (Harmonia axyridis)

Harlequin ladybird (Harmonia axyridis) shows high level of colour
polymorphism. Particular forms differ in their colour combination, pattern
and abundance. We tested the willingness of native, wild-caught passerines
to attack and eat particular forms. We predicted that those forms that are
more abundant in the wild are better protected, as they are more familiar
to the predators. We compared the forms novemdecimsignata and spectabilis,
which represent 97 % of individuals in the wild population, but
importantly differ in their visual appearance (mostly orange vs. mostly
black). Further, we examined three intermediate forms: axyridis, which is
very scarce in the wild, and two forms not occurring in the wild –
originating from laboratory breedings: suturalis and aninkae. As
predators, we used great tit (Parus major), which is very aversive towards
ladybirds, and tree sparrow (Passer montanus), which is quite willing to
attack and even eat ladybirds. We compared their responses to particular
ladybird forms, with artificially brown-painted ladybird to test for the
effect of visual signal. We showed that both bird species attacked all
forms of ladybird equally and usually very scarcely. The brown-painted
novemdecimsignata form was attacked more often, showing that the visual
appearance prevents birds from attacking any conspicuous colour
combination. Sparrows tended to eat the attacked ladybirds of forms
novemdecimsignata, spectabilis and brown painted. Scarce axyridis form and
laboratory forms were very well protected from the attack, very likely due
to neophobia.