Nest-site competition between invasive and native cavity nesting birds and its implication for conservation

Area of Science:

• Ecology
• Conservation Biology
• Ornithology

Background:

• Nesting cavities are a limited resource crucial for many bird species.
• The impact of invasive cavity-nesting birds on native populations is a significant conservation concern.
• Experimental data on resource competition between invasive and native birds is scarce.

Purpose of the Study:

• To experimentally determine if invasive cavity-nesting birds affect native cavity breeder occupancy and breeding success.
• To assess the role of nest box entrance size in mediating competition between native and invasive birds.
• To provide data for effective nest box management strategies in urban parks.

Main Methods:

• Field experiment over three breeding seasons in a Tel Aviv urban park.
• Nest boxes with manipulated entrance hole sizes (large vs. small) were used.
• Occupancy rates and breeding success of native and invasive bird species were compared between treatments.

Main Results:

• Large-entrance boxes were dominated by invasive common mynas and rose-ringed parakeets (77.5% occupancy).
• Small-entrance boxes favored native species (36.5% occupancy), excluding invasive birds.
• Native great tits in large-entrance boxes experienced significantly lower breeding success due to usurpation by common mynas.

Conclusions:

• Invasive alien species reduce native cavity breeders' potential by exploiting limited nest cavities and direct usurpation.
• Competition for nest boxes, particularly larger ones, negatively impacts native species' breeding success.
• Modifying nest box entrance size is a practical management strategy to reduce competition and benefit native cavity breeders.