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Nest boxes not always the best way to understand or boost bird populations

Scientists often use artificial breeding sites such as nest boxes, bat houses, and human-made burrows to study and manage numerous species of animals including bats, insects, lizards, fish, and birds. A recent study published in the journal Ecological Applications entitled “Simulations reveal the power and peril of artificial breeding sites for monitoring and managing animals” warns that the addition of human-made nest sites to an ecosystem does not always benefit populations or help researchers to monitor species such as the American Kestrel who regularly use nest boxes.

This study was a collaboration of The Peregrine Fund’s American Kestrel Partnership (AKP) and the Department of Biological Sciences and Raptor Research Center at Boise State University and has a warning for researchers: Patterns in nest box occupancy do not necessarily reflect actual population trends. Changes in the number of unmonitored, natural sites can make trends in the occupancy of nest boxes misleading if a researcher mistakenly interprets changes in occupancy as population trends. The article also shows that when new nest boxes are installed, a bird’s fidelity to a previous breeding site and slowness to move to newly installed boxes may be misinterpreted as an increasing population, even when the population has been continuously declining. Importantly, nest boxes may indeed benefit populations that need nesting sites; however, if a population is in trouble for other reasons, another nest box is not the golden ticket.

The AKP’s research has been based on collecting data from citizen scientists who place nest boxes in their communities and then monitor the activity in them. Kestrels are of particular concern because their populations have declined across North America by nearly 50% over the past 45 years and no one knows why. One of the main causes of kestrel declines is often said to be a loss of natural nest cavities. However, as Dr. Chris McClure, Director of the AKP, explains, “This study shows that when a population is declining because of a loss of natural nest cavities, nest box occupancy should actually go up as the demand for those boxes rises. Because many kestrel nest box programs across the country have declining occupancy, it’s unlikely that a loss of nest sites is the main cause of kestrel declines.” Dr. Julie Heath of Boise State University who uses nest box monitoring data for much of her research on Kestrels expands, “Nest boxes can still be used as a conservation tool if they’re being monitored and managers make sure that their nest boxes aren’t drawing birds into areas with relatively lower nesting success.” Dr. Ben Pauli, who is now an Assistant Professor at Saint Mary’s University of Minnesota, also collaborated in the study. The researchers hope that their results will help managers to understand when nest boxes might be a help or hindrance to bird populations and when to believe trends in nest box occupancy.

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To learn more about The Peregrine Fund’s American Kestrel Partnershipand how to become a partner in solving the mysterious American Kestrel decline, visit:

Article citation: 

McClure, C. J.W., Pauli, B. P. and Heath, J. A. (2017), Simulations reveal the power and peril of artificial breeding sites for monitoring and managing animals. Ecol Appl. (Early View) doi:10.1002/eap.1509

For more information, contact:

Erin Katzner
Director of Global Engagement
Main Phone:     208-362-3716
Direct Phone:     208-362-8277