Question 2: Explain Merit

Practises Navigation over long distances

The indigo bunting (Passerina cyanea) makes a long journey every year, and migrates only at night. It flies roughly 2000 km each way between its breeding grounds in eastern North America and its wintering grounds, which stretch from southern Florida to southern Central America; the paper shows both on a map.

Explain a navigation method for the bunting’s night migration, and how the yearly journey helps the bunting.

The 2022 paper, page 5 ↗ Marking schedule, page 3 ↗

Work it out

Try it on paper first. Stuck? Take one hint at a time.

1 The describe answer said migration escapes the winter. Explain why the round trip pays.
By moving south for the northern winter and back north for summer, the bunting is in good conditions, warm with plenty of food, all year round.
2 Why must its navigation method work without the Sun?
It flies only at night, so a sun compass is no use; it needs a cue available in the dark.
3 How do the stars give it a direction?
The night sky turns around the celestial pole, near the Pole Star in the northern sky, which stays still while the other stars move round it. Young buntings learn that point and use it as north. Because the stars move through the night, the bird also needs its internal clock to allow for their rotation.
4 What triggers the journey, and what senses it?
Day length, which is the same on a given date every year, so it is a dependable trigger. In birds the pineal gland senses light through the skull and releases melatonin through the dark, so its output tracks the length of the night. Timing and navigation therefore combine internal parts (the pineal gland, the clock) with external cues such as the stars.
5 Why use more than one method?
If cloud hides the stars, the magnetic field still works, so with several methods it is less likely to end up lost.
6 What is one real difficulty of the journey, and how does migration still raise success?
A 2000 km flight each way uses huge energy and risks predators and getting lost. Even so, spending the year in good conditions means more birds survive and breed, increasing reproductive success.

Answer Migrating south for the northern winter and back for summer keeps the bunting in warm conditions with plenty of food all year. It flies only at night, so it cannot use the Sun; it uses the stars instead, steering by the celestial pole near the Pole Star, the still point the other stars turn around, with its internal clock allowing for the sky’s rotation. Its timing is set by day length, the same on a given date every year, which the pineal gland tracks through the melatonin it releases in the dark: internal and external cues working together. The magnetic field works when cloud hides the stars, so with several methods it is less likely to end up lost. The 2000 km journey costs a lot of energy and risks predators and getting lost, but more birds survive and breed, increasing reproductive success.

What the marker wanted

Achieved The describe points: migration, circannual rhythm, the cue, a night navigation method, and a benefit.
Merit Explains: migration avoiding bad conditions, the round trip giving good conditions all year; why the bunting’s navigation must work at night; navigation and timing using internal (pineal gland) and external (star) cues; using several methods so it is less likely to end up lost; how the celestial pole or the magnetic field is used; migration increasing reproductive success; and a real difficulty of the journey. Three make M6.

One answer, N0 to E8. Merit points sit above the Achieved ones: two give M5, three M6.

In our words, from NZQA’s 2022 marking schedule.

Common mistake

Naming stellar or magnetic navigation without explaining how it works. NZQA’s 2022 report says many answers stopped there.

How did it go?

Got it moves it further out. Review brings it back tomorrow.