Evaluating nest box addition as a population augmentation strategy for tree swallows, Hirondelle bicolore, in interior British Columbia, Canada Pokorny, Stanley
Tree swallow populations across North America are exhibiting negative annual trends. An exception to the broader trend is interior BC, Canada where tree swallow populations are growing. Augmentation of successful populations by the addition of nest boxes to cavity poor landscapes may be an appropriate strategy to mitigate or reverse the national decline. This was evaluated through an analytical comparison of the reproductive performance (clutch size and hatchlings) of tree swallow breeding pairs nesting in natural cavities and nest boxes in the William’s Lake region of BC, Canada. For the 2001-2003 breeding seasons mean clutch size (means ± SE, nest boxes: 5.94 ± 0.199 eggs (n=83), cavities: 4.2 ± 0.204 eggs (n=74)) and number of living hatchlings (means ± SE, nest boxes: 4.51 ± 0.265 chicks(n=83), cavities: 2.51 ± 0.27 chicks(n=74)) detected were significantly higher (clutch size: p-value=0.0001, hatchlings: p-value 0.0001, alpha=0.05) for pairs using nest boxes. Nest boxes provide tree swallow breeding pairs with additional nesting territories and result in higher reproductive rates. Nest box addition has the potential to be a long term population augmentation mechanism but further studies on long term impacts at the community level are necessary before it can be implemented as a management plan.
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