Wallcreeper feeding behaviour

in the 3 days we were watching this particular Wallcreeper its feeding pattern fitted well with that described in BWP quoted below:
Food: Small insects and spiders. Prey obtained mainly on rock faces, also (especially in rainy weather) among pebbles on banks of streams and below cliffs, occasionally from trees. While foraging, frequently investigates crevices, often disappearing between rocks. In Azov Sea area (USSR), bird seen fluttering about on clay bank, entering old nest-holes of Roller Coracias garrulus. Takes prey from small cracks in rock itself as well as from small grassy patches on it; also by flycatching; Diptera often picked off substrate while bird hovers. (Hess 1925; Niethammer 1937; Dementiev and Gladkov 1954a; Kharchenko 1965; Löhrl 1988.) For locomotion, see Löhrl 1964. Prefers sunlit rock faces in early morning, more shaded sites in afternoon (Löhrl 1967a). Bird foraging on wooden church tower in Switzerland in winter flushed small insects from cracks and caught them in the air (Hauri 1970).

The images here show the bird looking into crevices and holes where it often flushed out insects or appeared to flush? larvae that dropped out of the holes the creeper then turning and chasing them in flight; most larger prey was taken to a flat ledge on the top of an overhang where it presumably found them easier to consume -- it occasionally hovered under overhangs looking into holes and crevices and appeared to defy the laws flight by flying upside down! The attached images are needless to say not great, small very active bird with a heavy lens and camera pointed skywards, hand held, while standing on a slippery slope or entwined in vegetation -- the pics of the bird upside down are genuine and not flipped over!