The eared grebe (Podiceps nigricollis) and pied-billed grebe (Podilymbus podiceps) are two species of grebes found in North America. Though they belong to different genera, they share some similarities in appearance and behavior. However, there are several key differences between these two waterbird species.
Appearance
In terms of physical characteristics, the most noticeable difference between the eared grebe and pied-billed grebe is the color of their bills. As their names suggest, the eared grebe has a black bill while the pied-billed grebe has a bill with both black and white markings giving it a “pied” look.
Both species have red eyes. However, the eared grebe has a bright red iris while the pied-billed grebe has a duller brick red iris.
During the breeding season, eared grebes develop ornate head plumes and ear-like tufts of black feathers behind their eyes which give them their common name. Pied-billed grebes lack these ornate plumes and tufts.
In breeding plumage, eared grebes are mostly black on the head, neck, back, and flanks. Their undersides are white. Pied-billed grebes have drab gray-brown plumage on the head, neck, breast, and flanks. Their undersides are whitish.
Another difference is size. Eared grebes are larger than pied-billed grebes. Eared grebes measure 13-16 inches (33-41 cm) long with a wingspan around 23 inches (58 cm). Pied-billed grebes are 9-12 inches (23-30 cm) long with an 18 inch (46 cm) wingspan.
Behavior
Both eared grebes and pied-billed grebes are excellent swimmers and divers. However, there are some differences in their typical water behaviors.
Eared grebes tend to swim low in the water with just their long necks exposed. They dive frequently while swimming. Pied-billed grebes swim with their bodies slightly more elevated above the water and don’t dive as frequently.
While feeding, eared grebes may swim in small flocks. Pied-billed grebes are usually solitary while feeding or stay in pairs if breeding.
An unusual behavior of eared grebes is that they may pile aquatic vegetation on their backs. The function of this behavior isn’t definitively known but it may help anchor them while feeding underwater. Pied-billed grebes don’t exhibit this vegetation-carrying behavior.
Breeding
The breeding behaviors and nesting habits of these species also show some contrasts.
Eared grebes nest in colonies, often with hundreds of breeding pairs on a single water body. Pied-billed grebes are solitary nesters with each pair having their own isolated territory.
Both species build floating nests attached to emergent vegetation. However, eared grebe nests tend to be more haphazard piles while pied-billed grebes construct neater cup-shaped nests.
Clutch sizes are similar with 3-6 eggs for eared grebes and 5-10 eggs for pied-billed grebes. However, eared grebe chicks are able to swim and dive right after hatching while pied-billed grebe chicks start off riding on their parents’ backs and only swim independently after a week or two.
Range and Habitat
Though they overlap in some regions, eared grebes and pied-billed grebes have different breeding and wintering ranges in North America.
During the summer breeding season, eared grebes primarily inhabit wetlands in the western half of the continent. Pied-billed grebes have a broader breeding range extending throughout much of North America.
In winter, some eared grebes migrate to the Atlantic coast and Gulf of Mexico. But many overwinter in the Great Lakes region. Pied-billed grebes winter along the southern Atlantic and Gulf coasts as well as in parts of California and Mexico.
Both species use freshwater habitats like ponds, lakes, and wetlands. However, eared grebes have a greater tendency to nest and forage in more open water areas than pied-billed grebes which use protected emergent vegetation more.
Diet
Eared grebes and pied-billed grebes are carnivorous waterbirds that feed mainly on small fish and other aquatic prey.
Some differences in their diets include:
- Eared grebes consume more fish like minnows and suckers.
- Pied-billed grebes eat more crayfish, tadpoles, and insect larvae.
- Eared grebes occasionally take small mollusks.
- Pied-billed grebes sometimes eat amphibians and small reptiles.
- Both eat aquatic invertebrates like shrimp, leeches, and insect larvae.
Their varied diets reflect their opportunistic feeding behaviors, taking advantage of whatever small prey is abundant in their aquatic habitats.
Conservation Status
Both the eared grebe and pied-billed grebe are common species with large total populations. However, some differences exist in their conservation statuses.
Eared grebes are considered a species of Least Concern by the IUCN. Their global population exceeds 2 million individuals. Many of their breeding populations are increasing.
Pied-billed grebes are also Least Concern globally with several million individuals. But data suggests some regional declines in parts of their range. Wetland habitat loss impacts both species.
Key Identification Differences
To quickly identify whether a grebe is an eared grebe or pied-billed grebe, look for these key differences:
Trait | Eared Grebe | Pied-billed Grebe |
---|---|---|
Bill color | Black | Black and white |
Breeding head | Ear-like tufts | No tufts |
Breeding plumage | Mostly black | Drab gray-brown |
Nesting | Colonial | Solitary |
Size | 13-16 in | 9-12 in |
Conclusion
In summary, while the eared grebe and pied-billed grebe occupy similar ecological niches, they can be distinguished by differences in their plumage, bill coloration, breeding behaviors, habitat preferences, and other traits. Both species play important roles as predators in aquatic ecosystems across North America.