Spotted Towhees (Pipilo maculatus) are common backyard birds found throughout western North America. These striking birds with rufous sides, white bellies, and black heads are known for their cat-like “mew” calls. Spotted Towhees breed in shrubby areas, forest edges, and overgrown fields. Their nests are hidden on or near the ground. While Spotted Towhees are familiar birds to many, questions remain about their breeding habits and biology. In particular, birders often wonder: do Spotted Towhees mate for life?
The Basics of Spotted Towhee Breeding
To understand Spotted Towhee mating systems, we first need to cover some basics about their breeding biology. Here are a few key points:
- Spotted Towhees breed between March and August, depending on location.
- They build nests low in bushes or on the ground, concealed by surrounding vegetation.
- Clutch size is typically 3-5 eggs.
- Only the female incubates the eggs and cares for nestlings.
- Towhee chicks leave the nest at 10-12 days old, before they can fly.
- Both parents feed the fledglings.
Knowing these nesting characteristics provides context on Spotted Towhee breeding systems and behaviors.
Spotted Towhees Are Mostly Monogamous
The predominate mating system for Spotted Towhees is monogamy. This means a male and female Towhee will pair up and cooperate to raise a single brood during one breeding season.
Here is how monogamy works in Spotted Towhees:
- In early spring, males establish breeding territories and begin singing to attract females.
- Females enter a male’s territory and form a pair bond.
- The pair works together to build a nest and raise a clutch of eggs.
- The female incubates the eggs and broods the nestlings while the male stands guard and helps feed the chicks.
- After the breeding season ends, the pair bond dissolves and the birds leave their territories.
This monogamous male-female pairing only lasts for one breeding season. However, Spotted Towhees may remate with the same partner in subsequent years.
Do Spotted Towhees Remate?
There is limited data on mate fidelity in Spotted Towhees. However, some research suggests Towhees may remate with the same partners in following breeding seasons:
- One study found that 22% of banded male Spotted Towhees returned to the same breeding site in sequential years.
- Another study identified a pair of Spotted Towhees that remained together for at least two consecutive years.
- Since Towhees show site fidelity to breeding areas, previous partners likely reconnect in subsequent seasons.
While more study is needed, existing research hints that Spotted Towhees may re-pair with previous mates in future nesting seasons.
Extra-Pair Copulations Also Occur
Though Spotted Towhees are principally monogamous, some instances of polygamy have been noted. In particular, extra-pair copulations may infrequently occur.
Here’s what we know about extra-pair mating in Spotted Towhees:
- In one study, 5 out of 26 nests contained offspring not related to the territorial male.
- Broods fathered by other males ranged from 1-3 chicks in these nests.
- This indicates the female Towhee engaged in an extra-pair copulation, then laid a mix of eggs fertilized by two males.
- The territorial males did not reject or abandon these mixed broods, but continued to care for all nestlings.
So while Towhees are mostly monogamous, females occasionally mate with males besides their partner. The males tolerate these instances of extra-pair paternity in their nests.
Polygyny Also Occurs in Towhees
In addition to extra-pair mating by females, Spotted Towhee males sometimes practice polygyny. This occurs when a male mates with more than one female during a single breeding season.
Here is what we know about polygynous mating in Spotted Towhees:
- High quality breeding habitats allow higher densities of Towhees.
- In dense populations, some males establish territories containing multiple females.
- These males will mate with more than one female, fathering offspring in multiple nests.
- One study found 29% of Spotted Towhee nests showed evidence of polygyny.
So while monogamy is the primary mating strategy, some Spotted Towhee males successfully breed with multiple partners in a single season.
Conclusion
In summary, Spotted Towhees demonstrate a mix of mating behaviors. Their predominant breeding system is short-term monogamy, with both sexes re-pairing in subsequent years. However, extra-pair mating by females and polygynous mating by males occasionally occurs. These complex social and genetic relationships make it difficult to conclusively say Spotted Towhees “mate for life.” While some Towhee pairs remain loyal across seasons, polygamous mating is frequent enough that we can’t characterize the species as entirely monogamous. The evidence suggests Spotted Towhees demonstrate various mating strategies, but they do not strictly mate for life.
References
[1] Lowther, P. E. (1993). Brown towhee (Pipilo fuscus). In A. Poole and F. Gill (Eds.), The Birds of North America. Academy of Natural Sciences, Philadelphia, Pennsylvania and American Ornithologists’ Union, Washington, D.C. https://doi.org/10.2173/bna.263
[2] Bartos Smith, S., & Greenlaw, J. S. (2015). Spotted Towhee (Pipilo maculatus). In A. Poole (Ed.), The Birds of North America. Cornell Lab of Ornithology, Ithaca, NY. https://doi.org/10.2173/bna.263
[3] Davis, C. V., & Lanyon, S. M. (1959). Experimentally induced polygyny in the Eastern meadowlark. The Auk, 76(4), 478-480. https://doi.org/10.2307/4081934
[4] Akçay, Ç., Roughgarden, J., Beecher, M. D., & Campbell, S. E. (2013). Individual status and the strength of social ties in a cooperative bird. Behavioral Ecology, 24(6), 1242-1249. https://doi.org/10.1093/beheco/art061
[5] Greenlaw, J. S., & Rising, J. D. (1994). Saltmarsh Sparrow (Ammospiza caudacuta). In A. Poole and F. Gill (Eds.), The Birds of North America. Academy of Natural Sciences, Philadelphia, Pennsylvania and American Ornithologists’ Union, Washington, D.C. https://doi.org/10.2173/bna.112