European starlings are a common sight in many urban and rural landscapes. These adaptable birds exhibit complex patterns when it comes to choosing and reusing their breeding sites. Understanding these behaviors provides insight into their success.
Starling Nesting Habits
Starlings are cavity nesters, preferring enclosed spaces like holes in trees, crevices in buildings, or human-made structures such as nest boxes. They also frequently use utility poles, eaves, window ledges, attics, and even vents, typically building nests 6 to 60 feet off the ground. Nests are loose, cup-shaped accumulations of materials like bark, grasses, twigs, and leaves, often supplemented with feathers, moss, or human discarded items.
The male starling typically initiates nest construction, filling the chosen cavity with bulkier materials, and the female then completes the structure, adding finer linings. Starlings are prolific breeders, beginning their nesting season around mid-April. They usually lay between four to six eggs, which are incubated for approximately 12 to 13 days, with young birds typically fledging around 20 to 23 days after hatching. Many starling pairs will raise one to two broods within a single breeding season.
Do Starlings Revisit Previous Nests?
Starlings frequently demonstrate nest site fidelity, often returning to the same general breeding area or even the exact cavity used in previous seasons. However, this return is not guaranteed, as various factors can prompt them to choose a different spot.
While starlings may return to the same location, they typically build a new nest within the cavity or thoroughly refurbish the old one. This practice is important because old nest material can harbor parasites, making the site less desirable. Starlings remove old material to deepen the nesting site, reducing parasite loads and vulnerability.
Factors Influencing Nest Site Choice
Several conditions guide a starling’s decision to return to a former nesting location or select a new one. A primary influence is a successful breeding history; if a previous attempt resulted in healthy fledglings, starlings are more inclined to return. The availability of essential resources nearby, such as food sources like insects, fruits, grains, and water, also plays a significant role. Starlings seek areas with open, grassy patches for foraging.
Predation pressure is another factor. Starlings prioritize safety from predators, selecting elevated locations or secluded nooks difficult for intruders to access. The presence of other starlings or competing bird species can also affect site choice, as starlings are aggressive and compete for desirable cavities. The condition of the old nest is also considered. Human disturbance at a previous site can deter their return, yet proximity to human structures can also be appealing due to additional nesting opportunities and foraging areas.
Management of Old Nests
Old starling nests, especially within human structures, can pose several concerns. They are known to harbor parasites such as mites and fleas, and accumulate debris over time. Higher ectoparasite loads in older nests can negatively affect clutch size and fledgling production. This potential for infestation and accumulation is a significant reason why starlings often build new nests or thoroughly clean existing sites.
When nests are located in undesirable areas like vents or attics, their bulky construction can cause blockages, create fire hazards due to flammable materials, and lead to structural damage. If starlings have finished nesting and the site is empty, it is advisable to remove the old nesting material and seal access points to prevent future re-occupancy. In North America, European starlings are considered an introduced species and are not protected under the federal Migratory Bird Treaty Act. This means their nests and eggs can be legally removed, although it is always recommended to ensure no eggs or young are present before removal, or to seek professional assistance.