Each year, a remarkable natural phenomenon unfolds across the globe: animal migration. Creatures of all kinds embark on epic journeys to reach their nesting grounds, driven by instinct and the cyclical rhythms of nature. While some animals undertake these migrations solo, many species travel together, forming groups that range from small family units to massive flocks numbering in the thousands. Let’s delve into the fascinating world of animals that travel together to nesting grounds, with a particular focus on waterfowl and their incredible journeys.
The Pacific Flyway: A Highway for Migratory Waterfowl
The Pacific Flyway serves as a major migratory route for birds in North America, stretching from the Arctic to Patagonia. Just as humans use highways for efficient travel, migratory waterfowl utilize flyways like the Pacific Flyway to navigate their long journeys between breeding and wintering grounds. The Bolsa Chica Ecological Reserve (BCER), located in Southern California, is a crucial stopover and wintering destination along this flyway.
Each fall, as temperatures drop and food resources diminish in their northern breeding habitats, a diverse array of waterfowl species arrives at Bolsa Chica. These birds, having completed their nesting season in locations as far north as the Arctic, seek out the reserve’s abundant resources of water, food, and shelter to sustain them through the winter months.
Geese: Family Units on the Wing
Geese are well-known for their impressive migratory journeys and their tendency to travel in flocks. Brant geese (Branta bernicla), for example, often migrate in family groups. A Brant family typically consists of a monogamous pair of parents and their offspring from the current year. These families may join together with others, forming larger flocks for migration, offering a sense of safety in numbers and potentially facilitating navigation. Canada geese (Branta canadensis) also exhibit similar social migratory behavior, often seen traveling in V-formations that are iconic symbols of migration.
These geese breed in Arctic and subarctic regions during the summer months. After the breeding season, families gather at staging sites where they undergo molting – a process of shedding old feathers and growing new ones, including flight feathers. This molting period renders them flightless for a few weeks, making the safety of a group even more crucial. Once their new feathers are in, these family units and larger flocks begin their southward journey along the Pacific Flyway towards wintering grounds like Bolsa Chica.
Dabbling Ducks: Diverse Migration Strategies
Dabbling ducks, another group of migratory waterfowl, also frequent Bolsa Chica during the fall and winter. Species like the American wigeon (Mareca americana), gadwall (Mareca strepera), green-winged teal (Anas crecca), northern pintail (Anas acuta), and northern shoveler (Spatula clypeata) undertake migrations of varying distances. While some dabbling ducks may migrate in larger flocks, others are observed in smaller groups or even individually. The social aspect of migration in dabbling ducks can be less pronounced than in geese, but they still benefit from shared knowledge of migration routes and suitable stopover locations.
Diving Ducks: Cohabitation in Wintering Grounds
Diving ducks, such as the redhead (Aythya americana), ruddy duck (Oxyura jamaicensis), bufflehead (Bucephala albeola), lesser scaup (Aythya affinis), surf scoter (Melanitta perspicillata), and red-breasted merganser (Mergus serrator), also migrate to Bolsa Chica. These ducks are adept at diving underwater to forage for food. While their migration might not always be characterized by tight-knit group travel like geese, they often congregate in large numbers at suitable wintering habitats like Bolsa Chica. The reserve provides the diverse food sources and open water they need during the non-breeding season.
Why Bolsa Chica? Habitat Restoration and Eelgrass
What makes Bolsa Chica such an attractive destination for these migratory birds? The answer lies in the reserve’s vital resources: water, food, and shelter. Specifically, the restoration of the Bolsa Chica wetlands has played a crucial role in enhancing its value to wildlife.
A significant 600-acre wetlands restoration project, completed in 2006, revitalized the tidal basin within BCER. This restoration included the re-establishment of tidal flow and the introduction of eelgrass (Zostera marina). Eelgrass is a type of submerged aquatic vegetation that forms dense underwater meadows in saltwater environments. For Brant geese, eelgrass is a primary food source, earning it the nickname “green spaghetti” among observant students.
Eelgrass beds are not only food sources but also critical components of a healthy coastal ecosystem. They support a rich food web, providing habitat and sustenance for invertebrates, fish, and other wildlife. The presence of extensive eelgrass beds at Bolsa Chica is a major draw for Brant geese and other waterfowl seeking food and refuge during migration and winter.
Banding and Conservation: Tracking Migratory Journeys
Scientists use bird banding as a valuable tool to study bird migration, lifespan, and population trends. By placing uniquely numbered bands on birds’ legs, researchers can track individual birds over time. Observations of banded Brant geese at Bolsa Chica have provided insights into their migration patterns and the importance of the reserve as a wintering location.
Reporting sightings of banded birds to organizations like the USGS Bird Banding Laboratory (www.reportband.gov) contributes valuable data for conservation efforts. This data helps researchers understand the connectivity of habitats, identify important stopover sites, and assess the impact of threats on migratory bird populations.
Threats to Migratory Waterfowl and Wetlands
Despite the ecological significance of places like Bolsa Chica, migratory waterfowl and their wetland habitats face numerous threats. Habitat loss due to coastal development, pollution, and climate change are major concerns. Rising sea levels, driven by climate change, can inundate coastal wetlands and reduce the availability of crucial foraging grounds like eelgrass beds.
Conservation efforts are essential to protect these vulnerable species and habitats. By supporting wetland restoration projects, promoting responsible coastal development, and addressing climate change, we can help ensure that migratory animals continue to have safe passage and suitable nesting and wintering grounds for generations to come. Reporting banded bird sightings and supporting conservation organizations are simple yet impactful actions individuals can take to contribute to the well-being of these incredible migratory animals.
Photos: Steve Smith, Jay Spring, Debbie Quintero, Larry Kaufman, Mark Perenchio, Robin Hoyland, Kurt Bayless, John Hannan, Babs Levitan
