SEABIRDS AND SHOREBIRDS
Last week we explored urban birds, who they are, what they eat, and where they live. We learned a little about mallard ducks, a bird that spends a lot of its time on water, but we didn’t get into all the other birds that spend the majority of their time out at sea or use the shore as a feeding ground. These are our seabirds and shorebirds.
There are a few distinguishing characteristics between seabirds and shorebirds. The main difference is that seabirds are pelagic, meaning they spend most of their life out at sea, while shorebirds are migratory birds that run along the shore looking for food.
Since seabirds spend most of their life out at sea, they have different adaptations that help them survive their native habitats. Some seabirds have webbed feet that help them move throughout the water. This adaptation also helps to provide traction when the birds take off for flight from the water. Other seabirds have claws to help them grab hold of fish under water. Seabirds also tend to have more feathers than other birds that help with insulation and waterproofing. The feathers on their back are dark and the feathers on their underside are light. This is an adaptation known as countershading, which is common in many mammals, reptiles, birds and fish. Countershading is a type of camouflage that helps the animals avoid detection from predators as well as prey.
Seabirds have different strategies when feeding. Some seabirds do what is called surface feeding and dunk their heads into the water to capture prey below. Seabirds such as penguins have the ability to dive underneath and pursue their prey called “pursuit diving.” Some seabirds try plunge diving. This is when they dive from high in the air, building enough momentum on the way down to plunge into the water and go deeper than normally allowable due to air between their feathers that makes them more buoyant. This is a highly skilled tactic that not all seabirds have mastered. Gannets, boobies, tropicbirds, some terns and brown pelicans all specialize in plunge diving. Seagulls and skuas try the plunge dive but are less skilled and successful at it.
Shorebirds, also known as wading birds, spend less time in the water but rely on the sea and other wetlands for food. Common shorebirds are avocets, black skimmer, oystercatchers, plover, sandpiper, and stilt. These birds have longer legs and pointed beaks allowing them to wade in the water and poke their bills into the sand for food. Most shorebirds are migratory and are known for their distant travel each year. Some shorebirds travel an astonishing 15,000 miles each year, while others can reach altitudes of 10,000 feet and reach speeds of 50 miles per hour. Almost two-thirds of the shorebirds that breed in North America journey from their arctic nesting grounds and go all the way to Central and South America for winter. In the following spring they return to the Artic.
One of the most common enemies to these birds, other than their predators are what are called “introduced species.” These are species that aren’t necessarily native to the habitat but have been introduced to the environment and are able to survive. The survival of these introduced species throws off the life cycle of native species. An example of an introduced species that poses a threat to these birds are feral cats. A feral cat is a domesticated cat that has returned to the wild, usually left behind by travelers and then breeds on the land. Other introduced species can have a different affect, such as goats, rabbits and other herbivores. These animals aren’t predators, but eat the vegetation that would otherwise help them to protect their young.
Birds are an incredible species, with so many different adaptations to help them survive. The slightest increase in length of their legs and bills allows them to strategically plant themselves in shallow waters to feed, while the adaptation of webbed feet or more feathers helps them survive conditions presented by the sea. As climates change, and habitats evolve, new adaptations will occur in order for these seabirds and shorebirds to survive.