The European Starling, Sturnus vulgaris, is a widespread and adaptable bird that often nests near human structures, utilizing any available cavity. As obligate cavity nesters, they must find an enclosed space—like a tree hollow, an old woodpecker hole, or a crevice in a building—to build their nest. This need for a secure space leads to the question of whether a starling pair returns to a successful location in subsequent breeding seasons. Starlings exhibit a high degree of attachment to previously used breeding sites.
The Strength of Starling Site Fidelity
Starlings demonstrate a pronounced tendency to return to the exact cavity or a very nearby location where they previously nested. Research has shown that a significant percentage of banded females, around 30%, utilize the same nest box in successive years, and the vast majority, approximately 90%, will breed within a kilometer of the prior site. This strong attachment to a geographical area is known as site fidelity, and it is a powerful driver in their annual nesting decisions.
The male starling is primarily responsible for selecting and claiming the nest site, often beginning to fill the cavity with nesting material before a female is even present. This initial investment and defense of the territory is a major factor contributing to the male’s strong fidelity to the location. Selecting a familiar spot saves considerable energy and time that would otherwise be spent searching for a new, suitable cavity, which can be a limiting resource.
A prior successful breeding season significantly reinforces the decision to return, as the location has already proven its quality in terms of safety and proximity to foraging grounds. Returning to a known area ensures familiarity with local food and water sources, which supports the energy-intensive process of raising one or two broods each year. This preference for known, successful sites helps the birds maximize their reproductive output.
Factors That Lead to Nest Site Abandonment
While the drive to return is strong, certain negative experiences can override a starling’s site attachment, causing them to abandon a location. The primary cause for abandonment is a major disruption or a failed nesting attempt at the site. Severe predation of eggs or nestlings, particularly if the parents experience the loss firsthand, can make a previously safe spot seem dangerous.
Another common factor is intense competition from other cavity-nesting species, such as native woodpeckers or bluebirds, which may successfully displace the starlings before the breeding season starts. Starlings are aggressive, but if another bird or even a small mammal manages to claim the cavity first or destroy the initial nest material, the starling pair may move on.
Human intervention can also force abandonment, especially when people seal up the cavity used by the starlings, such as a dryer vent or a hole in a building. If the entrance is completely blocked, or if a nest is repeatedly removed during the early stages of building, the birds must seek a new, undisturbed location. A high perception of nest predation risk can also lead to a site being avoided.
The Condition and Reuse of Old Nests
When starlings return to a nest site, they typically do not clean out the old nesting materials from the previous year. Instead, they build a new nest cup and lining directly on top of the old, compacted debris. This practice of adding new material over the old can eventually fill the cavity, making it shallower and potentially more vulnerable to predators.
The main consequence of this reuse is the accumulation of ectoparasites, particularly mites and fleas, that overwinter in the old nest material. Studies have found that nests built on top of old material harbor a greater number of these blood-sucking parasites. The resulting high parasite load can negatively affect the health of the new brood, sometimes by increasing the transmission of disease or causing anemia in the young.
To counteract the parasites, male starlings weave fresh green plant material into the nest during the building phase, a behavior thought to be a form of self-medication. These herbs often contain volatile compounds that may help improve the nestlings’ condition, potentially by stimulating their immune system to better cope with the parasites.
Although the plants do not always reduce the parasite count itself, this behavior is significant. The buildup of old nests is often the reason people seek to remove starling nests from human structures between seasons, to mitigate the risk of pest and disease issues.