Reading focus
Syllabus: How Does Evolution Help Explain Behavior?
Compare species controls, the barring manipulation, and responses during and after presentation.
Why you’re reading it. Apply the critique to an experimentally tractable claim about resemblance and receiver behavior.
A question to consider. Which result supports a role for barring, and what further evidence would connect that result to selection on cuckoo plumage?
Why this reading
Resemblance is an observation; mimicry is an explanation that needs evidence about a receiver's response. Davies and Welbergen manipulate the appearance of bird mounts and measure how small birds respond at feeders. The experiments turn a proposed adaptive resemblance into comparisons with alternative predictions.
Before you read
Brood parasites lay eggs in other birds' nests. Great and blue tits are unsuitable cuckoo hosts because of their nesting habits, making them useful receivers for this question. Barring means the striped pattern on the underparts. A mounted specimen permits control of appearance but cannot reproduce a live bird's movements or interactions.
Read for
- Identify what comparisons among cuckoos, sparrowhawks, and doves establish before the barring manipulation is introduced.
- Compare responses during exposure and feeder attendance afterward. Does adding or removing barring have the same effect in every species and time window?
Consider afterwards
- What result would support a general response to stripes rather than a response to a cuckoo's overall hawk-like appearance?
- What additional outcome would connect a receiver's fear to an advantage for a reproducing cuckoo?
Editorial context
The study tests receiver responses in particular small birds, including winter presentations, rather than cuckoo reproductive success or historical selection directly. A later host study extends the question to mobbing by reed warblers. Distinguish that extension from this experiment: neither a resemblance nor one receiver species establishes a universal effect across hosts and environments.