Mean Body Mass of Birds Known to Perform Broken-Wing Display
| Bird | Mean body mass (grams) |
|---|---|
| Pied-billed grebe | 409 |
| Common ringed plover | 60 |
| Common snipe | 126 |
One antipredator defense that the grey-headed lapwing uses to protect its nest and young chicks is called “broken-wing display”; this form of deceptive defense involves an adult bird pretending to be injured and unable to fly in order to distract an approaching predator. Broken-wing display has been documented in 285 bird species from 13 different avian orders. A student predicts that bird species with mean body masses greater than 150 grams do not use deceptive defenses because larger birds tend to be more effective than smaller birds at using aggressive defenses to protect nests from predators, making deceptive defenses unnecessary.
Which choice most effectively uses data from the table that weakens the student’s prediction?
Explanation
Context: A student predicts that bird species with mean body masses greater than 150 grams do not use deceptive defenses (like broken-wing display) because larger birds can use other defenses. The table shows three birds known to perform broken-wing display: pied-billed grebe (409g), common ringed plover (60g), and common snipe (126g).
Answer: B) The pied-billed grebe has a mean body mass of 409 grams and is known to perform broken-wing display.
Why? The student predicts that birds over 150g don't use deceptive defenses. The pied-billed grebe is 409g — well over 150g — and DOES perform broken-wing display. This directly contradicts the prediction.
Traps:
- A) "The common ringed plover uses broken-wing display, but the pied-billed grebe does not" → this contradicts the actual data in the table (the grebe IS in the table as a broken-wing display performer) and wouldn't weaken the prediction if the grebe truly didn't use this display
- C) "The common snipe uses broken-wing display even though it is larger than the common ringed plover" → the snipe is 126g (under 150g), so this doesn't challenge the >150g prediction
- D) "The common snipe and the common ringed plover both have a mean body mass under 150 grams" → confirms they're under the threshold; doesn't challenge the prediction about birds over 150g