Little blue herons (Egretta caerulea) are small wading birds that are found in wetlands throughout much of North America. As their name suggests, they have blue-gray plumage and are on the smaller side compared to other heron species. The little blue heron’s coloration can vary between light blue and dark slate-gray depending on the season and age of the bird. Young little blue herons start out completely white and gradually gain their blue-gray plumage over a period of 1-2 years.
One feature that often gets asked about little blue herons is whether or not they have ornamental plumes like some other heron species, such as the great egret. The answer is that little blue herons do not develop long specialized plumes during the breeding season like their larger relatives. They have more uniform plumage over their body and lack the dramatic wispy breeding plumes that great egrets display. However, little blue herons do grow elongated feathers on the back, chest, and head to a small degree during breeding.
Plumage Differences Between Heron Species
To understand why little blue herons lack extensive plumes, it helps to look at how breeding plumage varies among different heron species:
Great Egret
The great egret (Ardea alba) develops very long specialized plumes on its back during breeding season. These plumes can reach up to 30 inches in length! The plumes emerge from the back and the breast area and cascade down over the body dramatically. In addition to the back plumes, great egrets also grow long ornamental plumes from the head area. These breeding plumes are bright white in great egrets.
Great Blue Heron
Great blue herons (Ardea herodias) also develop plumes as breeding ornamentation but not to the degree that great egrets do. The plumes are shorter and fewer in number compared to a great egret. Great blue herons have plumes that emerge from the back, chest, and head. The plumes are blue-gray and white in coloration.
Little Blue Heron
Little blue herons do not grow such elongated plumes during breeding. They develop some elongated feathers on the chest, back, and head – but these plumes are quite short and not very ornamental compared to other species. The plumes are barely noticeable compared to the striking breeding plumes of egrets and larger herons. Little blue herons lack eye-catching ornamental plumes.
Why Don’t Little Blue Herons Have Prominent Plumes?
So why don’t little blue herons develop impressive plumes like their larger relatives? There are a few possible explanations:
Size and Energy Constraints
Growing elaborate breeding plumes takes a lot of energy for herons and egrets. Little blue herons are much smaller in body size compared to great egrets and great blue herons. The smaller size of the little blue heron likely places constraints on the amount of energy that can be invested into growing ornamental feathers. The plumes require a lot of calories and nutrition to develop – the smaller little blue heron may not be able to meet those needs compared to larger heron species. Maintaining and displaying prominent plumes also requires energy, and the greater surface area to body size ratio of little blue herons may make carrying elaborate plumes more challenging.
Reduced Sexual Selection Pressures
One theory for why herons and egrets grow showy breeding plumes is that the plumes are selected for through sexual selection. The size and ornamentation of plumes may signal male quality and fitness to female birds. Larger, more elaborate plumes suggest a male has good genes and lots of resources to grow the feathers. However, such sexual selection pressures appear lower in little blue herons compared to larger heron species. The lack of elaborate plumes suggests they are not as important for mate selection and attracting females in little blue herons. The breeding plumage is likely serving other functions besides just mate attraction.
Need for Camouflage
Because of their small size, little blue herons may face higher predation risks from birds of prey and other predators. Thus, there may be selective pressure for their breeding plumage to provide camouflage and crypsis benefits. Bright white plumes could make little blue herons more conspicuous to predators. So the more subdued blue-gray and less ornamental plumage may help little blue herons stay cryptic and evade predation during the breeding season. Drabber plumage provides better camouflage in wetland environments.
No Juvenile White Phase
Related to camouflage needs, little blue herons lack the striking white juvenile plumage seen in many heron species like great egrets, reddish egrets, and tricolored herons. Those species go through a white juvenile phase in the first 1-2 years before gaining their adult coloration. Little blue heron juveniles instead have blue-gray plumage from a young age. This suggests reduced needs for the white ‘crypsis coat’ in young little blue herons, likely due to their smaller size and different foraging behaviors. The lack of white juvenile plumage may relate to why little blue herons also lack bright white breeding plumes as adults.
Male Versus Female Plumage
In little blue herons, both males and females have similar plumage patterns year-round. Little sexual dimorphism or differences exist between the sexes with regards to plumage. This contrasts with some of the larger heron species where males and females can look quite different from each other, especially during breeding season.
For example, male great egrets develop more elaborate plumes on the back and breast region compared to females. Male great blue herons likewise grow somewhat longer head and back plumes than females on average. Both male and female little blue herons grow short non-ornamental plumes, so there are no major differences in breeding plumage. Their monomorphic plumage suggests reduced sexual selection pressures related to mate choice and attraction.
Species | Male Plumage | Female Plumage |
---|---|---|
Great Egret | Longer back plumes | Shorter back plumes |
Great Blue Heron | Slightly longer head and back plumes | Slightly shorter head and back plumes |
Little Blue Heron | No major differences | No major differences |
Changes in Plumage Over the Year
While little blue herons do not display major differences between male and female plumage, individuals of both sexes do go through seasonal plumage changes.
During the breeding season, little blue herons grow darker blue-gray feathers on the head, chest, and back. These darker feathers include the short plumes. Outside of breeding, little blue herons moult and replace those ornamental feathers. Their plumage returns to a lighter blue-gray hue over the body.
Juvenile little blue herons look very different than adults, as mentioned previously. Hatchlings are covered in white down. As they grow, juveniles transition to entirely white plumage, unlike the blue-gray appearance of adults. Over the course of 12-24 months, juvenile birds gradually replace those white feathers with the blue-gray definitive plumage that marks adulthood. This molt to adult plumage occurs through a series of partial moults.
By their second breeding season, little blue herons generally have full adult plumage. However, some individuals may retain some white feathers into their second year before gaining full blue-gray coloration.
Age | Plumage |
---|---|
Hatchling | White downy feathers |
Juvenile | All white plumage |
1-2 years old | Mixed white and blue-gray; molting to adult plumage |
Adult | Definitive blue-gray plumage year-round; darker breeding plumage |
Role of Plumage in Heron Ecology and Evolution
While little blue herons do not sport the ornamental plumes seen in larger heron relatives, their more subdued plumage patterns still play important roles in their biology and ecology:
Camouflage
Their blue-gray hues help little blue herons blend in among shore vegetation as they forage and nest. This conceals them from potential predators but also helps them stealthily stalk small aquatic prey.
Thermoregulation
The light coloration may aid with reflecting heat and keeping cool. Darker pigmentation during breeding may allow better heat absorption for incubating eggs.
Breeding Signals
Though not as showy as other herons, the breeding plumage likely still serves social signaling functions related to courtship and breeding condition.
Mate Attraction
While reduced, some sexual selection based on plumage ornaments may occur, just not to the degree seen in larger heron species.
Species Recognition
The definitive little blue heron appearance helps with species identification and recognition, which is important for coordinating breeding and social behaviors.
So while they lack prominent plumes, the plumage of little blue herons is still an important adaptation. Their breeding plumage has likely evolved to balance natural and sexual selective pressures, resulting in more subdued ornamentation compared to larger heron species.
Conclusion
In summary, little blue herons do not display the long, showy ornamental plumes seen in other heron species such as great egrets and great blue herons. They instead have more uniform blue-gray plumage over the body that becomes darker during breeding season. A number of factors may contribute to little blue herons lacking dramatic plumes, including energy constraints from their small size, reduced sexual selection pressures, and greater needs for camouflage. Both male and female little blue herons develop short non-ornamental plumes on the neck, back, and head for breeding season. Outside of breeding, their plumage returns to a lighter blue-gray appearance. While not overly showy, the plumage patterns of little blue herons still serve important functions related to their life history and ecology. Their breeding plumage shows subtle ornamentation that likely represents an evolutionary balance between natural and sexual selective factors.