How do you keep starlings and sparrows out of purple martin houses?

Purple martins are swallow-like songbirds that nest in cavities, and they readily take to nest boxes provided for them. However, two invasive species – house sparrows and European starlings – often compete with purple martins for those nesting sites. This competition can prevent martins from successfully breeding and establishing colonies. As such, properly managing nest boxes to exclude sparrows and starlings is crucial for attracting and maintaining purple martins.

There are several effective techniques for keeping sparrows and starlings out of purple martin houses and allowing martins to nest unimpeded. The key strategies include:

• Proper nest box placement and design
• Using entrance hole guards and openings tailored to martins
• Regular monitoring and swift removal of sparrow/starling nests
• Installing perches away from the nest boxes
• Using wire mesh to cover ventilation holes
• Considering automated bird exclusion systems

Proper implementation of one or more of these methods requires some effort and diligence, but doing so encourages martins to move in and successfully raise young. Continue reading for expanded explanations of these techniques.

Nest Box Placement and Design

Where and how you install nest boxes for purple martins can make it harder for starlings and house sparrows to access them.

Martins prefer their housing high up, typically 15 feet or more above ground. Mounting boxes on tall poles or placing them atop buildings helps deter the sparrows and starlings which prefer lower nesting sites.

You should also space multiple nest boxes/compartments at least 6-7 feet apart horizontally. This spacing decreases competition, as starlings and house sparrows are more likely to congregate in denser colonies.

Proper box placement also means situating them in open areas away from trees and shrubs. Martins like wide flyways for approaching their sites, while shrubbery offers cover and food for sparrows and starlings.

In addition to location, the size and design of nest boxes can assist with excluding the unwanted species:

• Use nest compartments at least 6 inches high x 6 inches wide x 12 inches deep
• Have entrance holes 1 15/16 inches to 2 1/8 inches wide to prevent larger starlings from entering
• Make sure drainage and ventilation is sufficient to keep the box cool and dry
• Include a porch/landing pad extending out 4-6 inches
• Paint boxes white to reflect heat and mount on a metal pole or stand

Following these nest box specifications takes advantage of the purple martin’s preferences, making the sites more attractive to them than to sparrows or starlings.

Entrance Guards and Modified Openings

Installing specialized guards around nest box entrance holes is an excellent way to deter larger-bodied starlings while still allowing martins to enter. Crescent-shaped metal guards, often called “excluders”, can be purchased or handmade to fit around the circular entrance. Keyhole guards perform a similar function.

The size of the entrance hole itself can also be managed to favor martins. Keeping holes on the smaller end of their preferred range – 1 15/16″ to 2″ wide – will prevent most starlings from entering.

You can further modify openings by making the hole an oval or rectangular shape. This allows martins to get through, while excluding round-bodied starlings. Just ensure the height and width of modified slots do not exceed martin hole size limits.

Entrance modifications like these limit access to nest boxes for invasive species, reducing direct competition with martins for breeding sites. However they do not prevent sparrows and starlings from building their own external nests that could still impact martins, so additional exclusion techniques are recommended.

Monitoring and Nest Removal

Diligent monitoring of nest boxes paired with swift removal of unwanted sparrow and starling nests is key for maintaining martin housing.

Make sure to check nest boxes at least weekly during the crucial spring nesting season. Immediately knock down and dispose of any nests built by sparrows or starlings in martin boxes. Persistence is important, as they may repeatedly try to rebuild.

You can make removal easier by coating interiors with slick surfaces or placing wire mesh across box floors to prevent nest establishment while still allowing martins to perch.

Quickly eliminating foreign nests in martin housing deprives sparrows and starlings of desired breeding sites. This constant human disruption will discourage them from competing with martins.

Be extremely careful when inspecting and removing nests once martins have laid eggs or have young. Avoid disturbing their intact nests until late in the season when martin chicks have fledged.

Put Up Perches Away From the Boxes

Another tactic is to provide adjacent perching sites on structures separate from the nest boxes. This allows martins to socially perch and investigate nesting sites, while keeping unwanted birds away from the actual boxes.

Place vertical perching poles fitted with predator guards 10-20 feet from martin housing. Or string monofilament line between boxes to create open perches.

Having these perches nearby satisfies the martins’ desire for convenient social areas without bringing starlings and sparrows directly to the nesting cavities. It’s an easy way to discourage competition.

Cover Ventilation Holes

Sealing off ventilation holes and other openings (besides the main entrance hole) is recommended for further excluding starlings.

Starlings are known for enlarging or creating secondary holes to access nest boxes. Covering all holes with wire mesh prevents them from modifying openings but still allows for adequate air circulation.

Attach 1/4″ metal mesh or hardware cloth over ventilation gaps and any other access points into the nest compartment or gourds. This eliminates potential entry points for starlings without harming box ventilation. Just be sure the main entrance remains unobstructed.

Automated Bird Exclusion Methods

There are also automated exclusion systems that can deter nest box invaders:

Motion-activated sprinklers – These devices mount near boxes and sense movement, spraying water when activated to discourage sparrows and starlings from landing. They have adjustable sensors and intervals to minimize martin disturbance.

Motorized nest box arms – Arms that rotate or otherwise move the nest box in place make it difficult for undesirable species to build nests and lay eggs. Again, they are programmed to avoid disturbing martins.

Nest box traps – Special traps exist that allow martins to enter but then trap starlings or sparrows that follow them in. This allows easy removal of the trapped pest birds. Traps require frequent emptying and resetting during nesting season.

These active exclusion systems provide further lines of defense against nest site competition, but typically work best alongside other passive methods. Proper maintenance and adjustment is vital so they deter sparrows/starlings while not frightening off purple martins.

Conclusion

Preventing European starlings and house sparrows from overtaking purple martin nesting sites takes diligent effort. But utilizing proven exclusion techniques can successfully protect martin housing and encourage colony establishment.

The key is proactive monitoring, rapid response to any foreign nests, and maintaining properly designed and located nest boxes. Physical barriers like entrance guards and ventilation covers add critical protection. Perching poles also help keep unwanted species away.

With routine care and exclusion control in place, the desirable and threatened purple martin can successfully breed and thrive. And you’ll be able to enjoy their aerial displays and bug-eating habits, rather than battles with invasive sparrows and starlings.