Let’s Talk About Bird Relationships

Let’s Talk About Bird Relationships 

Let’s take a closer look at reproductive behavior in birds. Their relationships are far more diverse than we often imagine. 

Most birds, more than 90 percent of species, are socially monogamous. This means a pair raises their chicks together for at least one breeding season. But social partnership does not always mean sexual exclusivity. In the 1990s, scientists discovered that many “monogamous” pairs regularly engage in extra-pair mating. As a result, birds can be socially monogamous, genetically monogamous, both, or neither. True lifelong fidelity is actually rare. 

Open Relationships 

In polygynous species, one male may mate with several females. This usually occurs when females can raise chicks on their own. In these systems, males focus on defending high-quality territories and attracting mates. This creates strong competition, where some males reproduce often while others do not reproduce at all. 

In many songbirds, females prefer males with more complex songs. Over time, this preference may help drive the evolution of elaborate vocal displays. 

Reversed Roles 

Some of the most striking exceptions to typical bird relationships are phalaropes, including Wilson’s, Red, and Red-necked Phalaropes. These species are classic examples of sex-role reversal. Females are larger, more brightly colored, and often more aggressive than males. 

Females compete for mates, defend territories, and may mate with multiple males. After laying eggs, they leave males to handle incubation and chick-rearing. This strategy allows females to maximize the number of eggs they produce. In some cases, males may even end up caring for another male’s offspring if a new female takes over a site. 

Although phalaropes are usually very social, during the breeding season, females become territorial and actively defend their mates from rival females. 

Long-Distance Relationships 

Some bird partnerships span entire continents. Hudsonian Whimbrels spend the winter on opposite coasts of South America, then reunite months later in Alaska. 

When they meet again, courtship begins in the air with high flight displays and musical calls. If the connection is right, they move to the ground for synchronized chases and graceful movements that look a lot like flirting. 

Laying Eggs in Another Bird’s Nest 

Not all birds raise their own young. Brood parasitism is a reproductive strategy in which species such as cowbirds and cuckoos lay their eggs in other birds’ nests. 

The host parents then raise the chicks, often at great cost to their own offspring. Parasites may remove host eggs, and their chicks, which usually hatch earlier and grow faster, can outcompete or even push out the host’s young. In the prairies of North America, many species of ducks breed in the shallow wetlands. Female ducks often lay their eggs in the nests of other species. Since “baby ducks” mostly care for themselves, this behavior (called brood amalgamation) isn’t particularly destructive and can lead to some adorable and diverse groups of babies following their “mother”. 

Raising Young Together 

In some species, parenting becomes a group effort. Cooperative breeding is a social system in which offspring receive care from additional group members, often called “helpers,” alongside their parents. 

In our local Eastern Bluebirds, the young from the first brood of the year often help raise their siblings from the next season’s nest! This cooperation increases the survival of the family group and strengthens long-term bonds. 

Many Ways to Build a Bond 

From lifelong partners to open relationships, role reversals, long-distance reunions, and cooperative families, birds show us that there is no single “right” way to build a relationship. 

Instead, there are countless creative solutions shaped by evolution, environment, and opportunity. 

References 

Elphick, C., Dunning, J. B., Jr., & Sibley, D. A. (Eds.). (2001). The Sibley guide to bird life & behavior. Alfred A. Knopf. 

Hatchwell, B. J. (2009). The evolution of cooperative breeding in birds: Kinship, dispersal and life history. Philosophical Transactions of the Royal Society B: Biological Sciences, 364(1533), 3217–3227. https://doi.org/10.1098/rstb.2009.0109 

Opar, A. (2023, February 21). Monogamy rare in the wild. Audubon. https://www.audubon.org/news/monogamy-rare-wild 

Snyder, K. T., & Creanza, N. (2019). Polygyny is linked to accelerated birdsong evolution but not to larger song repertoires. Nature Communications, 10, Article 884. https://doi.org/10.1038/s41467-019-08621-3