The Mexican spotted owl (Strix occidentalis lucida) is a subspecies of the spotted owl that is native to the southwestern United States and Mexico. It is listed as threatened under the Endangered Species Act and its habitat, consisting of older forests and canyonlands, is declining. As a result, the U.S. Fish and Wildlife Service (USFWS) has developed a protocol to monitor and protect the remaining Mexican spotted owl populations in the United States. This protocol provides guidelines for surveying, monitoring, and mitigating impacts to the owls and their habitat from land management activities.
Background on the Mexican Spotted Owl
The Mexican spotted owl is a medium-sized owl, approximately 16-19 inches long with brown and white mottled plumage. It has large, dark eyes and lacks ear tufts. The owl inhabits older forests, especially those with complex structure and dense canopies. Its historic range included forested mountains and canyonlands across Arizona, New Mexico, western Texas, and Mexico.
Starting in the late 19th century, habitat loss from logging, grazing, and development caused the owl’s populations to decline. By 1993, the Mexican spotted owl was listed as threatened under the Endangered Species Act. Threats to its continued existence include habitat loss, forest fires, climate change, and competition from barred owls. Surveying and monitoring are necessary to track populations and protect habitat.
Key Components of the Protocol
The USFWS Mexican spotted owl protocol provides guidance, recommendations, and requirements for managing the species on public lands. Key components include:
Surveying
– Establishes survey procedures and requirements for detecting owls and determining occupancy. Surveys involve broadcasting recorded owl calls and listening for responses.
– Designates priority protected activity centers (PACs) where owls are known to nest and roost. PACs receive a protected buffer zone up to 600 acres.
– Outlines requirements for surveying PACs, suitable habitat, and areas planned for land management activities.
Monitoring
– Provides guidelines for monitoring known owl sites to track occupancy trends over time.
– Monitoring is required for PACs and recommended for other habitat.
– Describes nesting and reproductive monitoring procedures.
Habitat Management
– Sets recommendations for Amounts of protected habitat needed per owl territory.
– Provides habitat management guidelines to maintain owl nesting, roosting, and foraging areas.
– Addresses habitat needs for prey species.
Mitigation
– Requires avoidance or minimization of impacts from activities that may disturb owls.
– Specifies mitigation actions if impacts cannot be avoided, such as habitat restoration.
– Establishes procedures if owls must be flushed from nests or roosts.
Survey Types and Timing
The protocol outlines requirements and best practices for different kinds of Mexican spotted owl surveys.
Initial Surveys
Initial surveys detect new owl sites and determine occupancy. They should cover:
– Suitable habitat in project analysis areas
– Designated protected activity centers
– Areas planned for habitat modifications
Guidelines:
– Conduct 2 surveys spaced 7-10 days apart during breeding season (March 1 to August 31).
– Revisit sites with detections at least 2 more times for confirmation.
– Use taped calls or imitation calls to elicit responses.
– Survey for 6-8 hours per site after sunset under suitable conditions.
– Survey sites should be at least 0.25 miles apart.
Occupancy Monitoring
Occupancy monitoring tracks populations over time at known sites. Protocol requires annual monitoring of PACs and recommends monitoring other nest/roost sites if possible.
– Repeat initial survey methods at known owl sites.
– For PACs, survey at least 2 years if owls not detected initially to confirm absence.
– Attempt to locate any banded owls and resight color bands.
Reproductive Monitoring
Breeding status provides insights on reproduction and nest success. Guidelines:
– Determine nest status and search for young during diurnal follow-up visits at detected sites.
– Note nesting attempts, number of young, fledging success.
– Avoid prolonged disturbances at nests.
– Do not handle/band young until ≥21 days old.
Winter Surveys
Less common winter surveys can augment breeding season efforts:
– Conduct December 15 to January 14 when owls more likely to respond during daytime.
– Used to find roosting owls in areas difficult to survey in spring/summer.
– Follow-up needed on any detections.
Protected Activity Centers
Protected activity centers (PACs) designated around confirmed Mexican spotted owl nest/roost sites are a key protective measure.
– PACs consist of a minimum of 600 acres of the best available habitat.
– Timber harvest and other major habitat alterations are not allowed within PACs.
– Restricted activities may include fuel reduction thinning and prescribed burns.
– PAC boundaries should enclose known nest/roost stands and surrounding habitat.
– Areas protected include:
– Nest stands – estimated 200 acres
– Replacement nest/roost stands – estimated 100 acres
– Foraging habitat – estimated 300 acres
– Total = 600 acre minimum PAC
Additional guidelines:
– Designate PACs at all confirmed nest and roost locations unless impracticable.
– Monitoring is required annually for all designated PACs.
– Management guidelines aim to maintain owl occupancy of PACs over time.
Habitat Management Guidelines
The protocol provides science-based habitat management recommendations to help maintain viable owl populations on public lands. These include:
General Guidelines
– Retain and promote development of older forest structure. Owls selectively occupy older forests.
– Maintain canopy closure of ≥40% at nest/roost cores. Denser understory canopy provides security.
– Conserve habitat heterogeneity and layers of vegetation structure. Provides diversity of prey and conditions.
– Prevent forest loss to permanent openings. Fragmentation degrades owl habitat.
Nest/Roost Stands
– Maintain multi-layered stands with large overstory trees, high canopy closure (>70%), and woody debris.
– Retain trees ≥18″ diameter at breast height and snags ≥12″ dbh. Large trees used for nesting.
– Allow natural processes of breakage, insects, and diseases to create nesting platforms.
Foraging Habitat
– Provide foraging habitat within 1 mile of nest/roost cores.
– Manage for ≥40% canopy cover. Higher cover increases prey.
– Retain large snags and downed logs as habitat for prey species.
– Allow wildfire to play ecological role where safe. Can benefit prey abundance.
Prey Habitat
– Manage landscapes to maintain populations of preferred prey: woodrats, mice, voles, rabbits, bats, birds.
– Leave patches of dense understory vegetation and downed wood to provide prey cover and mobility.
– Retain oak communities, riparian areas, and snags which support prey species.
Avoidance and Minimization Measures
To avoid detrimental impacts to owls, the protocol requires:
– Buffers from disturbance around active nest sites during breeding season (size based on activity).
– No habitat alterations within PACs without specific management plan and mitigation.
– Surveys prior to activities in suitable habitat with potential to disturb owls.
– Seasonal restrictions on activities March 1–July 15 within 0.25 miles of nest sites.
– Measures to minimize noise, night lighting, and other disturbances to owls.
– Worker awareness training for projects in owl habitat.
Additional impact minimization recommendations:
– Conduct road construction, vegetation treatments, recreation development etc. outside breeding season when feasible.
– Design projects to retain owl habitat elements like large trees, snags, and downed wood.
– Avoid permanent openings in canopies or fragmentation of forested areas.
– Limit disturbances within watersheds with owl sites to minimize cumulative impacts.
– Cluster developments and leave large undisturbed areas.
Mitigation
Where impacts cannot be avoided, mitigation is required to offset losses of owls or habitat. Mitigation measures specified in the protocol include:
– Temporal avoidances or spatial buffers from occupied sites.
– Acquisition and protection of replacement habitat.
– Restoration or improvement of degraded habitat.
– Artificial nest/roost structure installation if natural sites lost.
– Establishment of alternative areas to meet owl needs through vegetation treatments or prey management.
– Researchers may be required to reduce disturbances associated with monitoring.
Mitigation plans should:
– Demonstrate no net loss of owl habitat through compensatory mitigation.
– Include mitigation monitoring and effectiveness assessments.
– Be consistent with USFWS goals and approved by oversight agencies.
– Provide mitigation commitments, implementation schedules, and funding assurances.
Coordination with Other Species
Land managers should coordinate Mexican spotted owl conservation under the protocol with management of other species. Considerations include:
Northern Goshawk
– Goshawk nesting territories may overlap spatially with owl PACs.
– Goshawk guidelines generally compatible for retaining owl habitat.
– May require adjustments where nest areas overlap to meet needs of both species.
Boreal Owl
– Boreal may compete with Mexican spotted owl at higher elevations.
– Protecting occupied Mexican spotted owl habitat is the priority where they co-occur.
– Survey boreal owl sites within 0.25 miles of owl PACs and avoid impacts.
Northern and California Spotted Owls
– All spotted owls have similar nesting and roosting needs.
– Requirements may overlap in mixed conifer zones of transition between subspecies.
– Coordinate surveys, monitoring, and habitat management in these areas.
Handling and Banding
The protocol allows capture and banding but recommends passive monitoring approaches first. Banding guidelines include:
– Obtain qualified personnel and required permits.
– Follow accepted protocols for trapping, handling, and banding.
– Band nestlings when ≥14 days old; climb nests when ≥21 days old.
– Minimize disturbance and avoid banding during hot temperatures.
– Report banding activities and re-sight data annually.
Conclusion
The Mexican spotted owl protocol provides a consistent, science-based approach across agencies for conserving the threatened subspecies. Key elements include surveying and monitoring for owls, establishing protected nest/roost habitat, managing for habitat needs, minimizing disturbance impacts, and requiring mitigation of unavoidable impacts. Coordinating owl management with other species is also important. Diligent implementation of the protocol can help stabilize declining populations and retain Mexican spotted owls on southwestern public lands. By following survey protocols, monitoring owl sites, designating PACs, managing landscapes to maintain habitat and prey species, requiring impact avoidance or mitigation, and coordinating across agencies and ownerships, land managers can contribute to recovering this unique species.