Northern gannets are large seabirds known for their striking white plumage and spectacular dives into the ocean to catch fish. During summer, northern gannets live in crowded breeding colonies on cliffs and rocky islands in the North Atlantic Ocean. But when winter approaches, the gannets abandon their nesting sites and head out to sea for several months. So where exactly do northern gannets go and what do they do during the winter months?
Migration Overview
Northern gannets undergo a substantial seasonal migration every year. Their breeding colonies are located in the North Atlantic between 40-60°N latitude. This includes colonies in Canada, Iceland, Ireland, Scotland, Norway, and other countries in western Europe. During spring and summer (April to September), the birds remain close to their breeding sites, foraging in nearby waters and rearing their chicks. But as autumn arrives, northern gannets begin migrating south to warmer waters for the winter.
Most northern gannets from North America migrate down the coasts of the eastern United States and Canada. Those from Iceland, Ireland, and Britain spread out across the North Atlantic, some remaining fairly far north while others journey as far south as West Africa. Some gannets, particularly young birds, simply disperse widely across the ocean rather than migrating directionally. While their wintering areas are broad, northern gannets largely avoid crossing the Equator into the Southern Hemisphere.
Wintering Areas
The wintering grounds of northern gannets span a huge geographic range across the North Atlantic Ocean:
- Northeastern Canada south to Chesapeake Bay in the United States
- Waters around Iceland and Britain
- North Sea, English Channel, Irish Sea
- Bay of Biscay, waters off Portugal, Spain, and northwest Africa
- Mediterranean Sea
- Waters off West Africa as far south as Senegal and Ghana
In these areas, northern gannets frequent both coastal and offshore regions. They tend to avoid areas close to shore where the water is quite shallow.
Winter Diet
The diet of northern gannets shifts somewhat in winter compared to their breeding period. While they continue to feed primarily on fish, the species of prey change based on availability in their wintering areas. Important winter prey includes herring, mackerel, anchovies, sardines, cod, pollack, sprat, and more. Squid may also comprise a significant portion of their diet in some regions.
Northern gannets plunge dive from heights of up to 130 feet to catch their prey. Thanks to air sacs under their skin and other anatomical adaptations, they can dive to depths over 80 feet in search of fish. Gannets have excellent underwater vision to spot and capture agile prey.
Migratory Behaviors
Northern gannets demonstrate some interesting behaviors and abilities during their migratory journeys across the Atlantic Ocean:
- They travel huge distances, sometimes over 4,500 miles between their breeding and wintering areas.
- Most migration happens over open ocean out of sight from land.
- Some gannets follow coastlines during migration while others take more direct routes across open water.
- Migratory routes show a high degree of flexibility and variation between individual birds.
- Gannets navigate and orient themselves on migration using a combination of visual landmarks, ocean currents, memory, celestial cues, and their internal compass.
- Younger birds tend to winter further south than adult birds.
- Males and females migrate separately and winter in different areas.
Northern gannets travel long distances very efficiently, sometimes covering over 500 miles in just a few days during migration. However, most of their time is spent foraging and resting rather than continuously flying long distances.
Seasonal Changes in Plumage and Appearance
Northern gannets display some interesting changes in their physical appearance between breeding plumage and non-breeding plumage:
- Breeding adults have bright white body plumage, black wingtips, and pale yellowish heads.
- Non-breeding adults have more gray-brown mottling on their head, neck, and chest.
- Immature gannets are dark gray-brown overall before gradually acquiring more white plumage each year.
- During the winter molt, adults shed all their flight feathers at once, leaving them flightless for around 5 weeks.
The changes in plumage color help distinguish between age classes and breeding status. The molt allows worn feathers to be replaced and gives the birds time to rest between breeding and migrating.
Threats and Conservation
Although northern gannet populations are currently stable, they face a number of threats on their breeding and wintering grounds:
- Oil spills – Oil spills can kill many gannets and damage their food supply.
- Fishing nets – Gannets can get caught and drown in fishing nets and gear.
- Prey depletion – Overfishing may reduce food availability.
- Habitat loss – Coastal development destroys nesting habitats.
- Pollution – Plastics and chemical pollution impact gannets through ingestion and contamination.
- Climate change – May affect prey abundance and nesting habitat.
Protecting important nesting sites and foraging areas from human impacts is crucial for gannet conservation. Sustainable fishing practices and reducing pollution in the oceans will also benefit northern gannet populations.
Location | Population Trend | Conservation Status |
---|---|---|
North America | Increasing | Least Concern |
Iceland | Stable | Least Concern |
Britain & Ireland | Increasing | Amber |
Continental Europe | Stable/Increasing | Least Concern |
This table summarizes the population trends and conservation status for northern gannets in different parts of their global range.
Research and Tracking Methods
Scientists use various research methods to study northern gannets on their breeding grounds, migrations, and wintering areas:
- Banding – Metal or colored bands placed on legs allow individual identification.
- Geolocators – Tiny light-level loggers track migration routes.
- GPS tags – Pinpoint locations and map detailed movements.
- Satellite tags – Transmit location data in near real-time.
- Stable isotope analysis – Reveals diet and foraging areas.
- At-sea surveys – Counting birds at sea monitors populations.
- Nest counts – Regular monitoring of breeding colonies.
Advanced tracking technologies like GPS and satellite tags have greatly expanded knowledge of northern gannet migration, foraging behaviors, and habitat use across their annual cycle.
Key Tracking Studies
Some landmark tracking studies on northern gannets include:
- Kubetzki et al. 2009 – Used geolocators to map migration of gannets between a German colony and West African waters.
- Fort et al. 2012 – Tracked gannets from Quebec dispersing along eastern North America for winter.
- Grecian et al. 2018 – Combined GPS and geolocator data to quantify key breeding, migratory, and wintering areas.
- Wakefield et al. 2017 – Satellite-tagged gannets from 5 colonies showing strong winter migratory connectivity.
Importance of Northern Gannets
As spectacular seabirds, northern gannets fill an important ecological role and have significance to humans as well:
- They are top ocean predators that help regulate fish populations.
- They are indicators of marine ecosystem health and environmental changes.
- Gannet behavior and migrations provide insights into seabird biology.
- Seeing gannets dive and soar inspires awe in many birdwatchers and nature-lovers.
- Gannets feature prominently in the history, culture, and folklore of many coastal peoples.
- Their nesting colonies and migratory routes generate tourism interest and income.
Continued research and conservation efforts are important to ensure northern gannets remain a thriving fixture in the North Atlantic for generations to come.
Conclusion
Northern gannets undertake a long seasonal migration between their crowded breeding colonies in the North Atlantic and dispersed wintering areas spread across a vast section of the ocean. Their journey includes coastal waters on both sides of the Atlantic but most migratory movements happen far offshore out of sight from land. Gannets demonstrate amazing fortitude and navigational capabilities as they travel thousands of miles searching for food and favorable habitat amid the ever-changing conditions of the open ocean. Learning more about where northern gannets go and how they survive through the winter provides valuable insights into the behavior and resilience of these iconic seabirds.