Eurasian Sparrowhawk and Common Cuckoo by Simon Rix

For the second week running, Common Cuckoo features in Photo of the Week, but this Monday's winner by Simon Rix is a completely different kind of shot to last week's effort by Paul Wilson. The similarities between the plumages of Eurasian Sparrowhawk – a formidable predator of small songbirds – and Common Cuckoo are well known, with theories for this plumage mimicry including that it may briefly frighten songbirds from their nests, allowing cuckoos to alight and lay their eggs in the nest.

Whatever the exact reasoning for its evolution, there's little doubt that the two species do show a close resemblance. However, very few birders will have ever been afforded the opportunity to study the two side by side, let alone photograph them together to allow for study of the features. But that's what Simon Rix recently managed while out in the field near Oslo, Norway, capturing this extraordinary comparison shot of the two.

While many species might find the two species a challenge to tell apart, the apparent 'chase' taking place here suggests that this sparrowhawk didn't have any difficulty realising that the cuckoo was an imposter and therefore a potential prey item! Well done to Simon on his highly unusual winning image.

Other notable images

Great Crested Grebe, Macclesfield, Cheshire (Mike Barth).

Black-crowned Night Heron, Jeddah, Saudi Arabia (Duha Alhashimi).

Scopoli's Shearwater, Scilly pelagic, Isles of Scilly (Sam Viles).

Arctic Skua, Fair Isle, Shetland (Alex Penn).

Eurasian Curlew, Baltasound, Unst, Shetland (Robbie Brookes).

Black-winged Stilt, Frampton Marsh RSPB, Lincolnshire (John Atkins).

Common Cuckoo, Elton Reservoir, Greater Manchester (Martin Loftus).

Peregrine Falcon, Cromer, Norfolk (Rob Holmes).

Common Kingfisher, Aberford, West Yorkshire (Steve Fleetwood).

Sedge Warbler, Frampton Marsh RSPB, Lincolnshire (Chris Miles).

Red-backed Shrike, Auckley Common, South Yorkshire (Richard Pittam).