PART I: Introduction

Easily recognizable and found in great abundance, the Red-Winged Blackbird is the most widely-known of the 5 blackbird subspecies in North America. Flying in flocks of up to the millions and flashing their bright red epaulettes, the feisty Red-winged Blackbird (Agelaius phoeniceus) is a beautiful bird to behold and is even more fascinating below the surface.

Description and Identification

As the name suggests, Red-Winged Blackbirds are easily identifiable by their brightly coloured epaulettes (shoulders). This feature is only present however in breeding males of the species, used to threaten competition and attract the attention of their brunette female counterparts. Non-breeding males lack completed red patches and instead sport a black, almost scaly look in colouration. (The Cornell Lab of Ornithology)

Though the red shoulders of the Red-winged Blackbird are recognized as a staple trait, males may often be confused with the Tricoloured Blackbird, a similar but more localized subspecies of Blackbird. The main indicator that the bird seen is truly a Red-winged, is the yellow band below the epaulette, while the band appears white in their subspecies cousin. These two species can often be seen flocking together on the west coast of Canada.

Female Red-wing Blackbirds are streaky in colour, with a yellow hue around their beaks. Females are found to be slightly smaller than males, with the species ranging between 32 to 72 grams in weight, and 17 to 23 centimetres in length. (Griff & McIntyre, 2009) However, the size and proportions can vary between different subspecies.

Red-winged Blackbirds have slender, conical beaks which they use to collect seeds and hunt insects from the marshland they inhabit. They have a stocky build and a wingspan of 31 to 40 centimetres. Belonging to the Order Passeriformes, and like many of the songbirds, the Red-winged blackbird has Anisodactyl Feet, with three digits in front and one in the back. This model of feet is designed to perch on reeds and twigs, as well as allows them to run or bounce across open fields, which is very beneficial to ground foragers such as the Red-wing. They even have the ability to hop backwards while foraging which is referred to as  “double scratch”. (Griff & McIntyre, 2009) Red-winged Blackbird eggs are typically blue-green and covered in dark spots.

Many people will recognize a Red-winged Blackbird song without realizing what bird it comes from. An everyday background trill, the song of a male consists of several introductory notes followed by a harsh “kon-ka-reeee”. There is also a common “Chek” call that is used to communicate flight to nearby birds. Lastly, the Red-winged Blackbird is able to make an alarm call that is a single high pitched note, trailing slightly down in pitch. It will use this to alert other blackbirds of the presence of nearby predators. (Sibley, 2016)

Distribution, Habitat and Nesting

The Red-winged Blackbird can be found throughout North America over the course of a year. They predominantly inhabit the United States year-round but make their way northbound for the warmer breeding season. Their migration is known to be one of the first signs of spring in Canada. Red-winged Blackbirds spend the breeding season in wetlands but fresh and saltwater. They are also known to inhabit hayfields, meadows and even wooded areas along waterways. In fall and winter, they congregate in millions, with similar species, in agricultural fields, and grasslands. The factors behind their chosen habitat include the abundance of nesting materials, food sources, and even the types of birds that live in the neighbourhood. (Griff & McIntyre, 2009)

Fun fact: Red-winged blackbirds travel as many as 800 miles south for the winter!

Red-winged Blackbirds build their nests low, near the ground or water surface among the dense vegetation. The nest consists of varying weaved plant material, filled with wet leaves and decaying wood. Next, the nest is plastered with mud and then finally lined with fine, dry grass. When the nest is complete, it measures approximately 4 to 7 inches across and 3 to 7 inches deep. This nest is simple but durable and effective, being adaptable to whatever resources are at hand. (The Cornell Lab of Ornithology)

Behaviour

The Red-winged Blackbird is a highly polygynous species, with up to 15 female partners at a time, though on average this is closer to around 5 partners per male. During the breeding season, males are extremely aggressive and territorial, even known to attack larger animals such as people and horses.

Red-winged blackbirds may have up to three broods per partner per year. Females are the main contributor to building nests and choosing the nest location within a male’s designated territory. Prior to and throughout the breeding season, male Red-winged Blackbirds can be seen sitting on a high perch over their territory and singing as a way of displaying dominance and sexual prowess. (The Cornell Lab of Ornithology)

Females lay three to five eggs and incubate them for approximately 11 to 13 days. The young red-wings then stay in the nest for 9 to 12 days. Both Female and Male Red-winged blackbirds protect the nest from predators during this time. It is even seen that other neighbouring Red-winged Blackbird males will go out of their way to defend a nest in another male’s territory. This interesting, perceived altruistic behaviour shows a more cooperative side of the otherwise highly aggressive males. (Olendorf, Getty & Scribner, 2004). Red-wing males often sound an alarm before divebombing their enemies from behind. Fearless, they repeat this for as long as necessary, often staying with the predator long after they have fled, proving they are not to be messed with. (Griff & McIntyre, 2009)

Fun Fact: Young Red-wings are capable of swimming in short distances while adult Red-wings cannot!

Conservation Status

Red-winged blackbirds are abundant in North America and also are a widely-studied species. They are considered of Low-Concern, although the Red-wing Blackbird, like many bird species, is still threatened by many things. (The Cornell Lab of Ornithology)

The main threat to a Red-wing is habitat loss due to the drainage of wetlands for development and agriculture. As with many other birds, red-winged blackbirds are vulnerable to pesticides. Predators of adult red-winged blackbirds include hawks and owls. Their eggs and young may also be preyed upon by predators such as raccoons, mink and other birds such as the marsh wren. The Red-winged Blackbird has adapted to this nesting threat through the placement of nests over water.  (Griff & McIntyre, 2009)

PART II: Current Research – Defensive Strategies

Defense as a Team: Cooperative Rivals

Red-winged Blackbirds are known for being highly territorial and aggressive, persistent and brave, going after predators that could swallow them in one bite. However, one of the most common conflicts seen leading up to, and during the breeding season, is the conflict between male Red-wings. It is common to see males staking their territory to each other by raising their epaulettes and practicing in aggressive song. This behaviour translates to sexual selection power with the females and often territories are marked clearly before females have even migrated fully over. Once nesting has occurred however, a shift in attitude occurs where neighbouring males become protective of each other’s young.

It was observed by researchers that once mates and territories were established, there became a non-biological bond between neighbouring families, where males would come to the aid of other males and defend their young just as aggressively as their own. Through the study, it was hypothesized that this was an act of reciprocal altruism, as there were no additional external motivators observed, such as resource trading, or sired offspring (biological relation to that of the neighbouring male).

It was a simple understanding that the males protected the young of those who were in the most danger, even at the risk of their own young being temporarily less protected. This “golden rule” was then passed down through multiple breeding seasons and generations. This overall was seen to cause high nesting success for contributing males. (Olendorf, Getty & Scribner, 2004).

Defense Against Brood Parasites

A brood parasite is a bird that lays its eggs in another bird’s nest, relying on other birds to take care of their young. Sometimes when doing this, the parasitic bird will destroy the host’s eggs in the process. This can be extremely destructive and have lasting damages to the local population of competing birds. A relevant example of a local brood parasite is the Brown-headed Cowbird.

In order to defend against brood parasitism, the Northern Yellow warbler developed a way to communicate between females of the species and warn them of the presence of birds such as the Cowbird. They make a distinctive alarm sound when Brown-headed Cowbirds are near called a “seet” call. (Goldman, 2020) This “seet” call is unique to the cowbird and alerts nearby warblers to return to their nest, preventing egg transfers from occurring.

During a study where researchers observed yellow warblers and this behaviour, they noticed the consistent presence of Red-winged Blackbirds in the area. It was known that the two birds often nested in similar areas, and were seemingly less territorial with each other, but, the researchers soon noticed that the Red-winged Blackbirds were actually in fact responding to this “seet” call.

As cowbirds prey upon Red-wings as well, it was theorized that there is a mutualistic relationship between Red-winged Blackbirds and Yellow warblers. When working together against a common enemy, it was seen that both species experienced less brood parasitism when nesting near each other. Yellow warblers gave early warning calls of nearby Brown-headed Cowbirds, and in response, Red-wings fought off the cowbirds with their aggressive behaviour. (Lawson & Hauber, 2020)

Conclusion

In conclusion, Red-winged Blackbirds are well populated and found all across North America. These spirited and determined birds travel hundreds of miles each migration and they can adapt to most climates given their well-rounded diet and nesting needs. Red-winged blackbirds work tirelessly to keep up their species survivability, juggling many partners and defending not only their young but that of each other. They even became bilingual in order to gain from yellow warblers and protect themselves from brood parasitism. This is a clear sign of a successful bird whose intelligence and resiliency has led it to succeed in the Law of Natural Selection

References

Christopher McPherson, XC602542. Accessible at www.xeno-canto.org/602542

Goldman, J. (2020, April 13). Red-Winged Blackbirds Understand Yellow Warbler Alarms. Retrieved November 18, 2020, from https://www.scientificamerican.com/podcast/episode/red-winged-blackbirds-understand-yellow-warbler-alarms/

Griff, D. (2009). Red-winged blackbird (1066035505 810256428 T. McIntyre, Ed.). Retrieved November 18, 2020, from https://www.hww.ca/en/wildlife/birds/red-winged-blackbird.html

Lawson, S., & Hauber, M. (2020, March 31). Yellow Warblers’ special cowbird alarm alerts blackbirds. Retrieved November 19, 2020, from https://www.birdwatchingdaily.com/news/science/yellow-warblers-special-cowbird-alarm-alerts-blackbirds/

Martin St-Michel, XC179966. Accessible at www.xeno-canto.org/179966.

Olendorf, R., Getty, T., & Scribner, K. (2004). Cooperative nest defence in red-winged blackbirds: reciprocal altruism, kinship or by-product mutualism?. Proceedings. Biological sciences, 271(1535), 177–182. https://doi.org/10.1098/rspb.2003.2586

Red-winged Blackbird Overview, All About Birds, Cornell Lab of Ornithology. (n.d.). Retrieved November 18, 2020, from https://www.allaboutbirds.org/guide/Red-winged_Blackbird/overview

Sibley, D. (2016). Red-Winged Blackbird. In Sibley birds west: Field guide to birds of western North America (2nd ed., p. 434). New York, New York: Alfred A. Knopf.

Simon Elliott, XC597738. Accessible at www.xeno-canto.org/597738.