Vast flocks of red-winged blackbirds are a formidable sight in marshland areas, foraging on wetland cattails and stripping cereal crops from farmers’ fields. These common marshland inhabitants are widespread residents across the United States, breeding in every state except Hawaii.
Our guide to red-winged blackbird nesting explores the preferred habitats for nest construction, and the intricate nest-weaving processes used by the female red-winged blackbird. If you’re interested in knowing more, then please read on.
Nesting sites of red-winged blackbirds are never far from a water source, and usually constructed in marshland reedbeds or lakeside rushes. Loose nesting colonies, sometimes with more than a thousand birds, form: birds breed in relatively close proximity to each other, with several females often nesting on the same male’s territory.
Female Red-winged Blackbird sat on the nest
Red-winged blackbirds construct cup-shaped nests, making full use of materials they gather from their marshland habitats, including reeds, mud and wet leaves. Mud is used to shape and hold the nest together, and finishing touches of soft grass are added as a lining.
Close up of a Red-winged Blackbird nest, with three blue eggs inside
The rough dimensions of an average red-winged blackbird’s nest are as follows:
Nesting begins from late March onwards in some parts of the United States, with eggs commonly laid between April and July (for second or third broods of a season). Laying begins between one and several days after the nest construction is complete.
Male Red-winged Blackbird perched on a reed
The incubation period of red-winged blackbirds is typically 11 to 13 days. After eggs hatch, growth and development are fairly rapid, and young birds are ready to fledge after around 10 to 14 days.
The nesting site is chosen by the female, under close observation from the male. Once construction begins, the male’s “supervisory” role continues, with the female doing the crafting herself, while the male may supply nesting materials and offer superficial assistance.
Grasses are woven around vertical reed stalks to form a platform on which the main nest cup is constructed. A base of wet leaves, coarse grasses, and decaying wood is built up, and on this, reeds and finer grasses are woven together to form a cup shape, which is molded into shape using wet mud. Finally, a soft lining of intertwined grasses is added.
The whole nest-building process takes a female red-winged blackbird between 3 and 6 days to complete.
A female Red-winged Blackbird gathering materials to build the nest
After between 10 and 14 days in the nest, juvenile red-winged blackbirds are ready to leave the nest. They continue to be fed outside of the nest by both parent birds for another 2 weeks.
Red-winged Blackbird chicks in the nest, begging for food
Recently fledged Red-winged Blackbird chick
In a typical year, red-winged blackbirds will raise one or two broods, each with between 3 and 5 young. On rare occasions, three broods will be laid, with a new nest constructed from scratch for each brood.
Red-winged blackbirds tend to return to the same breeding grounds each season, with males arriving around a month ahead of females to establish a territory. These skilled crafters will not reuse a previous nest, preferring to start afresh each time, even in the same breeding season.
However, red-winged blackbirds do not mate for life and mate with a different bird (or birds) each year – they are a polygynous species, meaning that males will mate with up to 15 females in a season.
Females too may mate with more than one male, and may end up laying a clutch of eggs with mixed paternity.
Close up of a male Red-winged Blackbird on a perch
From 3 to 5 pale blue-green eggs are laid by female red-winged blackbirds. Eggs are oval in shape and usually have darker markings around the larger end. Eggs measure roughly 24 mm (0.9 in) in length and weigh around 4g (0.04 oz).
Three Red-winged Blackbird eggs inside the nest
Red-winged blackbirds can lay up to three broods a season, but one or two is more common. Nest construction begins late March onwards, with eggs being laid shortly afterwards. April is the most common month for red-winged blackbirds to begin incubating their first clutch, and if a third brood is raised, laying can continue until late-July or even into August on rare occasions.
There are no recorded examples of red-winged blackbirds choosing to nest in nesting boxes. Their preferred habitat choices of marshland vegetation and waterside reedbeds, are not places in which nest boxes are typically placed, and they are particular about crafting their own intricately woven grassy basket-style constructions to meet their nesting needs.
This means that a nest box would likely not be considered a viable option.
Female Red-winged Blackbird feeding chicks in the nest
Large overnight roosts, formed of hundreds or even thousands of red-winged blackbirds, gather at sunset in marshlands, swampy vegetation or low tree branches. After fledging, young birds join female roosts, while males continue to roost separately. Outside of the breeding season, roosts become mixed.
Breeding territories of red-winged blackbirds found in wetlands, swamps and other marsh-like areas. If those locations are unavailable they will seek other open areas near water in which to set up home.
Backyards are not generally suitable, as they tend to lack the vegetation and conditions needed. However, if your backyard has cattails, reeds or rushes, and a swampy patch, surrounded by tall grass, then it would not be impossible for a red-winged blackbird to successfully raise a brood there.
After leaving the nest, young Red-winged Blackbirds gather in large flocks
When a nest site is disturbed, either by a predator or the presence of noise or unusual activity nearby, a red-winged blackbird may choose to abandon eggs to start again in a different, safer location.
One study of red-winged blackbird nesting success at wetlands in the Great Lakes region found that 5 percent of observed nests were abandoned during or after incubation, while 56 percent failed (largely due to predation), and 39 percent were successful.
While it is typical practice for red-winged blackbirds to nest in reeds, rushes and cattails in marshland areas, on occasion nests may be crafted in the branches of waterside willow or alder trees.
Red-winged Blackbird calling in spring
In some rare occasions, red-winged blackbirds’ nests may be built at ground level, surrounded by tall grassy vegetation. However, it is more common for red-winged blackbirds to weave their basket-style nest using upright reeds or rushes as supports. On average, nests are between 20 and 80 cm (8 to 31 in) off the ground.
Only female red-winged blackbirds incubate their eggs, with males remaining nearby on high alert to protect the nest from predators. Males frequently breed with more than one female – usually between 5 and 10, but occasionally as many as 15 in the same loose colony.
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