The Red-winged Blackbird (Agelaius phoeniceus) is one of North America’s most recognizable and abundant bird species, frequently inhabiting marshes and wetlands. The glossy black male, with his distinctive red and yellow shoulder patches, is a familiar sight across the continent. The nesting process begins long before the physical construction of the nest, following a carefully orchestrated timeline central to the species’ success.
Establishing Territory and Mate Attraction
The nesting season begins with the early arrival of males in late winter or early spring, before females return from wintering grounds. Males immediately establish and defend a territory centered around quality wetland habitat. They use loud, trilling songs and visual displays, such as flashing their bright red shoulder patches, to advertise their presence and warn off rivals.
The quality of the territory is the primary factor dictating reproductive success, as it must contain sufficient food, water, and safe nesting sites. This species is highly polygynous; a single male may attract up to 15 females to nest within his boundaries. Females arrive later in the spring and choose their mate based on the resources and protection offered by the territory.
Seasonal Timing and Site Selection
Nest construction begins once the female has arrived and selected a territory. Peak timing for nest building generally starts in mid-March and continues through May, depending on the bird’s latitude. Females require a high-protein diet of insects for egg production, and their arrival often coincides with the increase in available insect populations. The nesting period can extend into July if the pair raises a second or third brood.
The Red-winged Blackbird is strongly associated with wet environments, and most nests are constructed low to the ground or just above standing water. The female selects a site offering stability and concealment, often weaving the nest between the vertical stalks of emergent marsh vegetation like cattails or reeds. Nests are anchored to multiple sturdy stems to withstand fluctuating water levels and wind.
Materials and Nest Construction
The female is solely responsible for building the nest, a process that typically takes between three and seven days to complete. She constructs a bulky, cup-shaped nest that is structurally layered for both durability and comfort.
The outer layer is built first, consisting of coarse, stringy plant material, such as cattail leaves or willow bark, which is woven around the vertical supports of the chosen plant stems. This outer structure provides the necessary platform and attachment point.
The second, middle layer is composed of wet leaves, coarse grasses, and decaying wood, which the female uses to form the cup shape. She may plaster the inside of this layer with mud or wet plant fragments to help shape and strengthen the structure. Finally, the female lines the inner cup with fine, dry materials like soft grasses, hair, or feathers to create a smooth, insulated surface for the eggs.
The Laying and Incubation Period
Once the nest construction is complete, the female moves quickly into the egg-laying phase, usually beginning within one to several days. The typical clutch size is three to four eggs, though the number can sometimes range from two to six. These eggs are distinctively colored, featuring a pale blue-green base with dark markings, such as black, brown, or purple speckles, which are often concentrated toward the larger end.
Incubation is performed exclusively by the female and lasts for a period of about 10 to 12 days. After the altricial young hatch, they remain in the nest for another 11 to 14 days before fledging. While the female is the sole incubator, both the male and female participate in feeding the nestlings, ensuring their rapid growth during this vulnerable stage.