Every spring, the skies over the UK are filled with life in motion—millions of birds navigating incredible distances with astonishing precision. Here at Mill Barton, we spend lunchtime in April and May observing the skies for the dances and songs of swallows, swifts and cuckoos. And every year, as they carve arcs through the sky, we find ourselves asking:

Why do they come and go?
How do they endure such perilous journeys?
And most wondrous of all—how do they know the way?

Why Do Birds Migrate?

At the heart of migration is one simple thing: survival. Birds migrate to take advantage of seasonal abundance and to avoid scarcity.

Food: Insects, seeds, and nectar—the staples of many birds—disappear during the UK winter. Heading south means a banquet of sustenance in warmer climates.
Breeding: Many birds migrate to the UK in spring because of its long daylight hours, which allow extra time for feeding hungry chicks. Plus, there's often less competition for territory.
Climate: For many species, avoiding harsh winters is crucial. Cold weather not only limits food but also increases energy demands.

Migration is a high-risk strategy, but the payoff—successful breeding and better survival rates—makes it worthwhile for many species.

How Do Birds Migrate?

Birds migrate using a variety of impressive adaptations. Before migration, birds go into hyperphagia - eating excessively to build fat, their primary fuel for the journey. Then, using their long, narrow wings in species like swallows allows efficient long-distance travel. Some birds, like swifts, use specialised flight techniques, meaning they can sleep while gliding.

Birds follow ancient flyways—established paths that typically avoid large ecological barriers like mountains or oceans, unless necessary. Some fly bravely across the Sahara, facing ruthless sandstorms and the deadly Sirocco (a strong Mediterranean wind) - a journey of about 6000 miles which they usually complete in less than two weeks.

**How do they know where to go?**

Birds use a sophisticated multi-sensory toolkit -

Magnetoreception: Species like the European robin are thought to "see" Earth’s magnetic field, guiding them even in the dark.
Celestial navigation: Many birds migrate at night, using stars and the moon to orient themselves.
Inherited memory: Some birds are born with internal maps encoded in their genes, while others learn routes from their parents.

But what happens when the world they migrate through changes?

Climate Change and the Limits of Adaptation

As Earth’s climate changes, migratory birds face an existential test: Can they adapt quickly enough?

Groundbreaking research from the Bird Genoscape Project at UCLA is offering a window into that question. In their most recent study, published in Science, researchers studied the yellow warbler—a species not found in the UK, but one that migrates similarly across vast regions of North America.

Here’s what they found:

Using DNA from over 200 birds across its breeding range, scientists identified climate-related genes—suggesting certain populations are genetically adapting to local environmental conditions.
Alarmingly, the populations that most need to adapt due to climate stress are already in decline.
Some groups had genetic-environment mismatches, meaning their DNA isn’t keeping pace with rapid environmental shifts.

These insights have powerful implications for UK species too. Evolutionary biologist Kristen Ruegg, co-director of the Bird Genoscape Project, said this work gives us a genetic map of which populations are at greatest risk, allowing conservationists to act before it's too late.

Let’s spotlight some of Britain’s most iconic migrants:

Barn Swallow (Hirundo rustica)

Fork-tailed, glinting in sunlight, darting and gliding with effortless grace—the swallows return. Though they travel thousands of miles—from the southern reaches of Africa to the fields of Devon or the rafters of a Yorkshire barn—swallows are fiercely loyal to place. Many return to the very building or beam where they first hatched. Year after year, they stitch their mud-cup nests into the fabric of human life, coexisting with us in a rare harmony. As aerial insectivores, swallows play a crucial role in controlling fly and mosquito populations, serving as natural pest control across rural and suburban landscapes throughout the summer here in the UK. Their departure each autumn is felt just as keenly as their arrival in the spring—a farewell not just to warmth and light, but to something more intangible: the rhythm and reliability of nature.

Common Cuckoo (Cuculus Canorus)

The common cuckoo (Cuculus canorus) is a voice of the British spring, arriving from Africa each April, crossing thousands of miles to breed. Known for its haunting two-note call and its unusual strategy of laying eggs in other birds’ nests, the cuckoo is a brood parasite—its young raised by reed warblers, dunnocks, or meadow pipits, often at the cost of the host’s own chicks.

This behaviour, while stark, weaves the cuckoo tightly into the web of life. Its survival depends on the timing of insect emergence, healthy habitats, and the fate of its host species—making it a living signal of ecological change. Cuckoo numbers have dropped sharply, reflecting declines in caterpillars, nesting grounds, and climate stability.

To protect the cuckoo is to protect much more: the insects it feeds on, the birds it relies on, and the balance of ecosystems it silently measures. Its voice may be fading, but it still tells us what the land is losing.

Common Swift (Apus Apus)

The common swift (Apus apus) arrives in the UK each May, slicing through summer skies after a journey from Africa. For just a few months, they fill the air with their calls and consume thousands of flying insects daily—midges, flies, mosquitoes—quietly keeping ecosystems in balance.

Swifts live almost entirely in the sky. They eat, drink, sleep, and even mate on the wing. A young swift may stay airborne for three years before it ever touches down. Though often mistaken for swallows, they belong to a different lineage, built for life in motion.

They nest in crevices of old buildings, making them especially vulnerable to modern renovations that seal away their homes. Since the 1990s, their numbers have dropped by over 60% in the UK. Loss of nesting sites and insect decline are driving this silent fall.

Now Red-listed, swifts are a signal of change in our towns and cities. Protecting them means keeping space in our architecture, letting insects thrive, and listening to what their vanishing flight is telling us about the health of the world below.

Why Migratory Birds Matter Now More Than Ever

Migratory birds like swallows, cuckoos, and swifts are more than fleeting signs of British summer—they are essential to the ecological rhythm of the UK. These species consume huge numbers of flying insects, naturally controlling pests that affect crops, gardens, and public health. Their arrival each spring marks the seasonal renewal of life and signals that the countryside, farmland, and even our towns still support functioning ecosystems.

But across the UK, these familiar birds are disappearing. Cuckoo numbers in England have dropped by over 65% since the 1980s; swift populations have declined by more than 60% since the 1990s. Climate change is shifting the timing of migrations, reducing the availability of insect prey, and pushing birds to arrive too early or too late. At the same time, habitat loss—from sealed rooflines to insect-poor landscapes—continues to chip away at their ability to breed and feed.

These species don’t just cross continents—they connect us to a wider world. Their survival depends on healthy ecosystems stretching from sub-Saharan Africa to the UK’s hedgerows, wetlands, and rooftops. When they decline, it’s a signal of something larger: that our insect populations are collapsing, our landscapes are becoming sterile, and our seasons are falling out of sync.

Protecting migratory birds in Britain means restoring insect-rich habitats, preserving nesting sites in old buildings, limiting pesticide use, and backing international efforts across migratory routes. These birds are part of our natural heritage, our folklore, and our future. If they vanish, it’s not just their absence we’ll feel—it’s the weakening of the systems that support all life here, including our own.

The Marvel of Migration

Why do they come and go?
How do they endure such perilous journeys?
And most wondrous of all—how do they know the way?

Why Do Birds Migrate?

At the heart of migration is one simple thing: survival. Birds migrate to take advantage of seasonal abundance and to avoid scarcity.

Food: Insects, seeds, and nectar—the staples of many birds—disappear during the UK winter. Heading south means a banquet of sustenance in warmer climates.

Breeding: Many birds migrate to the UK in spring because of its long daylight hours, which allow extra time for feeding hungry chicks. Plus, there's often less competition for territory.

Climate: For many species, avoiding harsh winters is crucial. Cold weather not only limits food but also increases energy demands.

Migration is a high-risk strategy, but the payoff—successful breeding and better survival rates—makes it worthwhile for many species.

How Do Birds Migrate?

**How do they know where to go?**

Birds use a sophisticated multi-sensory toolkit -

Magnetoreception: Species like the European robin are thought to "see" Earth’s magnetic field, guiding them even in the dark.

Celestial navigation: Many birds migrate at night, using stars and the moon to orient themselves.

Inherited memory: Some birds are born with internal maps encoded in their genes, while others learn routes from their parents.

But what happens when the world they migrate through changes?

Climate Change and the Limits of Adaptation

As Earth’s climate changes, migratory birds face an existential test: Can they adapt quickly enough?

Groundbreaking research from the Bird Genoscape Project at UCLA is offering a window into that question. In their most recent study, published in Science, researchers studied the yellow warbler—a species not found in the UK, but one that migrates similarly across vast regions of North America.

Here’s what they found:

Using DNA from over 200 birds across its breeding range, scientists identified climate-related genes—suggesting certain populations are genetically adapting to local environmental conditions.

Alarmingly, the populations that most need to adapt due to climate stress are already in decline.

Some groups had genetic-environment mismatches, meaning their DNA isn’t keeping pace with rapid environmental shifts.

These insights have powerful implications for UK species too. Evolutionary biologist Kristen Ruegg, co-director of the Bird Genoscape Project, said this work gives us a genetic map of which populations are at greatest risk, allowing conservationists to act before it's too late.

To protect the cuckoo is to protect much more: the insects it feeds on, the birds it relies on, and the balance of ecosystems it silently measures. Its voice may be fading, but it still tells us what the land is losing.

The common swift (Apus apus) arrives in the UK each May, slicing through summer skies after a journey from Africa. For just a few months, they fill the air with their calls and consume thousands of flying insects daily—midges, flies, mosquitoes—quietly keeping ecosystems in balance.

Swifts live almost entirely in the sky. They eat, drink, sleep, and even mate on the wing. A young swift may stay airborne for three years before it ever touches down. Though often mistaken for swallows, they belong to a different lineage, built for life in motion.

They nest in crevices of old buildings, making them especially vulnerable to modern renovations that seal away their homes. Since the 1990s, their numbers have dropped by over 60% in the UK. Loss of nesting sites and insect decline are driving this silent fall.

Now Red-listed, swifts are a signal of change in our towns and cities. Protecting them means keeping space in our architecture, letting insects thrive, and listening to what their vanishing flight is telling us about the health of the world below.

The Marvel of Migration

Why do they come and go?How do they endure such perilous journeys?And most wondrous of all—how do they know the way?

Why Do Birds Migrate?

At the heart of migration is one simple thing: survival. Birds migrate to take advantage of seasonal abundance and to avoid scarcity.

Food: Insects, seeds, and nectar—the staples of many birds—disappear during the UK winter. Heading south means a banquet of sustenance in warmer climates.

Breeding: Many birds migrate to the UK in spring because of its long daylight hours, which allow extra time for feeding hungry chicks. Plus, there's often less competition for territory.

Climate: For many species, avoiding harsh winters is crucial. Cold weather not only limits food but also increases energy demands.

Migration is a high-risk strategy, but the payoff—successful breeding and better survival rates—makes it worthwhile for many species.

How Do Birds Migrate?

How do they know where to go?

Birds use a sophisticated multi-sensory toolkit -

Magnetoreception: Species like the European robin are thought to "see" Earth’s magnetic field, guiding them even in the dark.

Celestial navigation: Many birds migrate at night, using stars and the moon to orient themselves.

Inherited memory: Some birds are born with internal maps encoded in their genes, while others learn routes from their parents.

But what happens when the world they migrate through changes?

Climate Change and the Limits of Adaptation

As Earth’s climate changes, migratory birds face an existential test: Can they adapt quickly enough?

Groundbreaking research from the Bird Genoscape Project at UCLA is offering a window into that question. In their most recent study, published in Science, researchers studied the yellow warbler—a species not found in the UK, but one that migrates similarly across vast regions of North America.

Here’s what they found:

Using DNA from over 200 birds across its breeding range, scientists identified climate-related genes—suggesting certain populations are genetically adapting to local environmental conditions.

Alarmingly, the populations that most need to adapt due to climate stress are already in decline.

Some groups had genetic-environment mismatches, meaning their DNA isn’t keeping pace with rapid environmental shifts.

These insights have powerful implications for UK species too. Evolutionary biologist Kristen Ruegg, co-director of the Bird Genoscape Project, said this work gives us a genetic map of which populations are at greatest risk, allowing conservationists to act before it's too late.

To protect the cuckoo is to protect much more: the insects it feeds on, the birds it relies on, and the balance of ecosystems it silently measures. Its voice may be fading, but it still tells us what the land is losing.

The common swift (Apus apus) arrives in the UK each May, slicing through summer skies after a journey from Africa. For just a few months, they fill the air with their calls and consume thousands of flying insects daily—midges, flies, mosquitoes—quietly keeping ecosystems in balance.

Swifts live almost entirely in the sky. They eat, drink, sleep, and even mate on the wing. A young swift may stay airborne for three years before it ever touches down. Though often mistaken for swallows, they belong to a different lineage, built for life in motion.

They nest in crevices of old buildings, making them especially vulnerable to modern renovations that seal away their homes. Since the 1990s, their numbers have dropped by over 60% in the UK. Loss of nesting sites and insect decline are driving this silent fall.

Now Red-listed, swifts are a signal of change in our towns and cities. Protecting them means keeping space in our architecture, letting insects thrive, and listening to what their vanishing flight is telling us about the health of the world below.

Restoring Atlantic Temperate Rainforests - A Lesson From The Salmon Forests of Canada

Why do they come and go?
How do they endure such perilous journeys?
And most wondrous of all—how do they know the way?

**How do they know where to go?**