Tree Trimming Information

Tree trimmers have a delicate relationship with manu-o-Kū. If trimming isn't done with care, nesting terns or chicks may be injured or eggs destroyed. A chick that falls to the ground will likely die because either the parents won't be able to care for it or it may be attacked by a predator.

However, tree trimming can actually be beneficial to manu-o-Kū!

Trimming can lead to a scar or cup to be formed in the branch, creating an ideal nesting site that will protect the egg and chick.

It can also make it easier for adults to fly in and out and provide room for juveniles to safely practice flying from branch to branch. One of the reasons a pair might decide to abandon a nesting spot is because it has become overgrown.

Tree trimming may be one explanation for why there are so many manu-o-Kū in Honolulu, but it must be done with the utmost care to ensure no nesting sites are being destroyed.

Thoughtful tree care is essential to maintaining healthy breeding habitat for Manu-o-Kū (White Terns). These seabirds rely on strong, open branch structures that provide safe, stable places to lay eggs and raise chicks. When trees become overgrown, crowded, or structurally unsound, nesting success can decline and the risk of branch failure increases.

In 2019, a collaboration among the Aloha Arborist Association, Hawaiʻi State DLNR, the U.S. Fish & Wildlife Service, Hui Manu o Kū, and Pacific Rim Conservation produced science-based Best Management Practices (BMPs) for caring for trees that host nesting Manu-o-Kū. These guidelines are designed to protect nesting birds and public safety while also promoting long-term tree health. Training based on these BMPs is available to members of the arborist community.

These arborists have taken part in White Tern–awareness training offered by the Aloha Arborist Association, Hawaiʻi State DLNR, Hui Manu o Kū, and Hawaiʻi Audubon Society. Their training prepares them to follow established best practices when working in and around trees used by nesting Manu-o-Kū, allowing essential tree care to proceed while minimizing risk to Hawaiʻi’s beloved seabirds.

Note that inclusion on this list reflects completion of White Tern–awareness training and does not constitute an endorsement, certification, or guarantee of services by Hui Manu o Kū, the Aloha Arborist Association, Hawaiʻi State DLNR, Hawaiʻi Audubon Society, Pacific Rim Conservation, or any of the organizations that collaborated in providing the training.

Tree trimming tips for arborists and homeowners

Tree Care Best Practices Near Manu-o-Kū Breeding Sites

Plan for Manu-o-Kū: Check the Breeding Range Map at www.whiteterns.org to find out if the trees youʻre pruning have known breeding sites. Before pruning, check carefully throughout the tree crown for signs of incubating adults, eggs or chicks. Call the Manu-o-Kū Hotline (808-379-7555) for assistance in determining if Manu-o-Kū are nesting in a tree.

Buddy Up: The trained manu-o-Kū observer on the ground helps the worker aloft by watching the incubating audlt or chick for signs of distress.

Mind the Buffer Zone: The behavior-defined buffer zone is breached when the incubating adult or check gets up, moves in a nervous manner, or moves away. If this happens, back away slowly.

Right Tools: Within 20 feet of breeding activity, use electric saws. Within 10 feet of a chick, use hand tools. Avoid workinig less that 10 feet from an uncubating adult.

DO:

Practice non-threatening behavior such as turning away your eyes and body, and moving calmly and slowly.
Allow the incubating adult or chick to get used to your presence.
Retain breeding branches even if no active breeding is observed as nesting branches are very often reused.
Prune to improve crown densisty, to simultaneously allow adult access and to preserve canopy cover for eggs and chicks.
Move a fallen chick off the ground and move it to a safer location.
Downland and read the full guidlines at alohaarborist.com, then click on the Manu-o-Kū tab.

DON’T:

Approach a breeding site from above, as this will cause alarm.
Vibrate, strike of shake a branch where breeding site is located.
Drop debris onto the breeding site or a branch hosting the breeding site.
Remove a branch or tree containing a flightless chick or egg without a permit.
Keep working or keep information to yourself if a chick or egg has been harmed or killed – call one of these contacts:
- Hui Manu-o-Kū Hotline: 808-379-7555
- USFWS Office of Law Enforcement (OLE): 808-861-8525
- DLNR Division of Forestry and Wildlife (DOFAW): 808-973-9778, 808-643-3567

Use our manu-o-Kū Nest Map to find specific trees that host nests

Before heading out to a project, or even on site, you can use this map to identify specific trees that are hosting, or have hosted, manu-o-Kū nests. Please be aware that the Nest Map cannot account for every nest in Honolulu. There will be nests that we don't know about so make sure to carefully inspect every tree. If you do find an undocumented nest, please tell us about it here.