The Science of Spring

For the nature watcher, spring is the premier time to explore the diverse woodlands surrounding Sidmouth. From the riverside woods at Margaret’s Meadow to the iconic Bluebell Wood on Soldier’s Hill, each area offers a unique glimpse into the season’s "opening sequence".

A walk through Harpford Wood along the disused railway line is particularly rewarding, revealing a mass of wildflowers and early insects.

What is Phenology?

Phenology is the study of periodic biological events—essentially "nature's calendar". It tracks the timing of specific life stages, known as phenophases, and how they are influenced by weather and climate.

What Phenologists Record:

• Plants: First bud burst, first flower date, and "peak bloom".

• Animals: Arrival of migratory birds and the first calls of frogs.

• Insects: The emergence of pollinators like bees, which must remain "in sync" with the flowers they rely on.

Nature’s Alarm Clocks: Cues for Growth

Different species respond to different environmental signals to decide when to wake up. This is critical for survival but can lead to complications as the climate changes.

1. The "Risk Takers" (Temperature-Driven)

Most early-spring flowers are triggered by rising soil and air temperatures. They are flexible enough to enjoy an early spring but vulnerable to sudden "false spring" frosts.

• Lesser Celandine: Petals stay closed until the air hits approximately 10°C.

• Wood Anemone: Their flowering date can advance by several days for every 1°C increase in temperature.

• Snowdrops: Their opening is tied to the cumulative warmth of January and February.

• Insects: Brimstone and Peacock butterflies emerge from hibernation on the first warm, sunny days of March to find nectar.

2. The "Calendar Keepers" (Day Length-Driven)

These species rely on photoperiodism (daylight length). They are conservative and will not bloom or emerge until the days reach a specific length, regardless of the temperature.

• Wild Garlic (Ramsons): Lengthening days in April are the primary signal for their mass-flowering.

• Garlic Mustard: While it needs a cold winter to "reset," its final push in April/May is influenced by day length.

• Orange-tip Butterflies: These generally wait for the longer days of April to emerge, aligning perfectly with their food source, the Garlic Mustard.

3. The "Mixed Signals" (Bluebells)

Bluebells are a complex case. They use temperature to start growing leaves, but day length to regulate their flowering. If leaves emerge too early due to heat but flowers wait for the "correct" day length, the tree canopy might close and block their light before they finish blooming.

Woodland Birds: Sight and Sound

Spring is the best time for bird watching because species are more abundant and noticeable.

• The Golden Rule: Move as little as possible. Find a favorable spot and remain still to see birds acting naturally—nesting, displaying, or feeding young.

• Bird Song: Mostly performed by males to attract mates and defend territory. In Sidmouth’s woods, you will likely encounter fewer than twenty species, making them easy to master.

• New Arrivals: Listen for the chiffchaff and blackcap alongside residents like the robin, wren, and blue tit.

Safety Note: If you hear sharp, penetrating "alarm calls," you may be too close to a nest. Move away quietly to prevent the parent from deserting their young.

The Threat of Phenological Mismatch

When plants and insects respond to different cues, they can drift "out of sync". If a warm February triggers flowers to bloom early, but their pollinators are waiting for the day length of April, the flowers may die without being pollinated, and the insects may emerge to find no food.