OUT ON A LIMB: DO HAZELNUT ORCHARDS PROVIDE HABITAT FOR CAVITY NESTING BIRDS?
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Date
2023-06
Authors
Clayton, Adam
Journal Title
Journal ISSN
Volume Title
Publisher
University of Oregon
Abstract
Cavity nesting birds are a group of high conseivation concern in the U.S. They
depend on areas with mature decaying trees in which cavities can be excavated, but few studies have examined the role of managed landscapes such as orchards in providing nesting habitat. This study assesses the suitability of hazelnut orchards for cavity nesting bird species in the Willamette Valley, where hazelnut farming is a major industry. Using field sUIVeys, I measured the density of suitable tree cavities and size of tree limbs in four commercial hazelnut orchards, three experiencing heavy fungal decay, and one with limited decay. I used observations of birds in the same orchards to determine the abundance of all cavity nesting species. When comparing between orchards, cavity density increased with average tree diameter, but was much lower in the orchard with low levels of fungal decay. Black-capped chickadees were the most abundant cavity nesting birds observed, a smaller species dependent on nest sites with soft wood. These results suggest that orchards with mature trees experiencing fungal decay may be the most valuable for cavity nesting birds, but these qualities also make orchards vulnerable to diseases that reduce crop yield. To control key diseases, many older orchards are being replaced with new blight resistant trees, altering habitat connectivity for Willamette Valley birds. A regional management strategy where some mature, decaying orchard are instead retained could benefit declining bird populations.
Description
20 pages
Keywords
cavity nesting birds, bird populations, hazelnut orchards