The word viṣikara is formed with suṭ optionally when denoting a kind of bird, the other form being vikāra,
Verse
सर्वे शकुनयो भक्ष्या विष्किराः कुक्कुटादृते ।
This word is formed by adding the affix क (III. I. 135) to कृ with the preposition वि and the augment सुट् ॥ The word विकिर also refers to birds only, a kind of cock. The phrase शकुनिर्विकिरा वा is added from the Vartika and is no part of the original sutra. Thus सर्वे शकुनयो भक्ष्या विष्किराः कुक्कुटादृत ॥ Though the sutra विष्किरोवाशकुनौ would have given the optional form विकिर, the specific mention of this form in the sutra indicates that विकिर always means 'bird' and nothing else. Otherwise विकिर would have referred to some thing other than a bird.,