Bluebird and Small Cavity Nester Conservation
Sialis - Bluebirds and other small cavity nesters


Breeding Age

Question: At what age does a bluebird mate? When do they start nesting?

Male bluebird feeds female, photo by Dave Kinneer
A male Eastern Bluebird offers a mealworm treat to his mate. Photo by David Kinneer.

Most cavity nesters like bluebirds breed the year after they were born (i.e., if they are born in 2008, they will breed in the spring of 2009.) House Sparrows are an exception. They can reach sexual maturity at 9 months, which gives them a competitive advantage. (McLoughlin) Bluebirds breed in their second year, and are generally 10-11 months old (may be 1.13 years old) the first time they breed (if they can find a mate). They will breed annually thereafter.

Older birds may start nesting ahead of younger birds (especially first-time breeders.) This may be because:

  • young males have to find and establish territories, while older males may remain in or near the territory they used the previous year. Older birds may come back to the cavity they successfully used the previous year.
  • Older birds may maintain pairs during nonbreeding season, or more quickly pair up with a mate from the previous year.
  • Older birds may be in better physical condition, because they are more experienced at finding food.
  • Older birds may be more experienced at building and defending a nest.

Earlier breeders usually produce more young, and those young are more likely to survive. They have more time to grow and develop survival skills before they have to migrate or, if they are resident, before winter sets in.

References and More Information:

We are more than birdwatchers. We are cavity nester caretakers.
- E.A. Zimmerman, 2008

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