77-7 SWHA TAC 2000.pdf

RECOMMENDED TIMING AND METHODOLOGY

FOR SWAINSON'S HAWK NESTING SURVEYS

IN CALIFORNIA'S CENTRAL VALLEY

Swainson’s Hawk Technical Advisory Committee

May 31, 2000

This set of survey recommendations was developed by the Swainson’s Hawk Technical Advisory Committee (TAC) to maximize the potential for locating nesting Swainson’s hawks, and thus reducing the potential for nest failures as a result of project activities/disturbances. The combination of appropriate surveys, risk analysis, and monitoring has been determined to be very effective in reducing the potential for project-induced nest failures. As with most species, when the surveyor is in the right place at the right time, Swainson’s hawks may be easy to observe; but some nest sites may be very difficult to locate, and even the most experienced surveyors have missed nests, nesting pairs, mis-identified a hawk in a nest, or believed incorrectly that a nest had failed. There is no substitute for specific Swainson’s hawk survey experience and acquiring the correct search image.

METHODOLOGY

Surveys should be conducted in a manner that maximizes the potential to observe the adult Swainson’s hawks, as well as the nest/chicks second. To meet the California Department of Fish and Game’s (CDFG) recommendations for mitigation and protection of Swainson’s hawks, surveys should be conducted for a ½ mile radius around all project activities, and if active nesting is identified within the ½ mile radius, consultation is required. In general, the TAC recommends this approach as well.

Minimum Equipment Minimum survey equipment includes a high-quality pair of binoculars and a high quality spotting scope. Surveying even the smallest project area will take hours, and poor optics often result in eye-strain and difficulty distinguishing details in vegetation and subject birds. Other equipment includes good maps, GPS units, flagging, and notebooks.

Walking vs Driving Driving (car or boat) or “windshield surveys” are usually preferred to walking if an adequate roadway is available through or around the project site.While driving, the observer can typically approach much closer to a hawk without causing it to fly. Although it might appear that a flying bird is more visible, they often fly away from the observer using trees as screens; and it is difficult to determine from where a flying bird came. Walking surveys are useful in locating a nest after a nest territory is identified, or when driving is not an option.

Angle and Distance to the Tree Surveying subject trees from multiple angles will greatly increase the observer’s chance of detecting a nest or hawk, especially after trees are fully leafed and when surveying multiple trees in close proximity. When surveying from an access road, survey in both directions. Maintaining a distance of 50 meters to 200 meters from subject trees is optimal for observing perched and flying hawks without greatly reducing the chance of detecting a nest/young: Once a nesting territory is identified, a closer inspection may be required to locate the nest.

Speed Travel at a speed that allows for a thorough inspection of a potential nest site. Survey speeds should not exceed 5 miles per hour to the greatest extent possible. If the surveyor must travel faster than 5 miles per hour, stop frequently to scan subject trees.

Visual and Aural Ques Surveys will be focused on both observations and vocalizations. Observations of nests, perched adults, displaying adults, and chicks during the nesting season are all indicators of nesting Swainson’s hawks. In addition, vocalizations are extremely helpful in locating nesting territories.

Vocal communication between. hawks is frequent during territorial displays; during courtship and mating; through the nesting period as mates notify each other that food is available or that a threat exists; and as older chicks and fledglings beg for food.

Distractions Minimize distractions while surveying. Although two pairs of eyes may be better than one pair at times, conversation may limit focus. Radios should be off, not only are they distracting, they may cover a hawk’s call.

Notes and Species Observed Take thorough field notes. Detailed notes and maps of the location of observed Swainson’s hawk nests are essential for filling gaps in the Natural Diversity Data Base; please report all observed nest sites. Also document the occurrence of nesting great homed owls, red-tailed hawks, red-shouldered hawks and other potentially competitive species. These species will infrequently nest within 100 yards of each other, so the presence of one species will not necessarily exclude another.

TIMING

To meet the minimum level of protection for the species, surveys should be completed for at least the two survey periods immediately prior to a project’s initiation. For example, if a project is scheduled to begin on June 20, you should complete 3 surveys in Period III and 3 surveys in Period V. However, it is always recommended that surveys be completed in Periods II, III and V.

Surveys should not be conducted in Period IV.

The survey periods are defined by the timing of migration, courtship, and nesting in a “typical” year for the majority of Swainson’s hawks from San Joaquin County to Northern Yolo County.

Dates should be adjusted in consideration of early and late nesting seasons, and geographic differences (northern nesters tend to nest slightly later, etc). If you are not sure, contact a TAC _ member or CDFG biologist.

Survey dates Justification and search image

Survey time Number of Surveys

I. January-March 20 (recommended optional) All day 1

Prior to Swainson’s hawks returning, it may be helpful to survey the project site to determine potential nest locations. Most nests are easily observed from relatively long distances, giving the surveyor the opportunity to identify potential nest sites, as well as becoming familiar with the project area. It also gives the surveyor the opportunity to locate and map competing species nest sites such as great homed owls from February on, and red-tailed hawks from March on. After March 1, surveyors are likely to observe Swainson’s hawks staging in traditional nest territories.

II. March 20 to April 5 Sunrise to 1000 3 1600 to sunset

Most Central Valley Swainson’s hawks return by April 1, and immediately begin occupying their traditional nest territories. For those few that do not return by April 1, there are often hawks (“floaters”) that act as place-holders in traditional nest sites; they are birds that do not have mates, but temporarily attach themselves to traditional territories and/or one of the site’s “owners.”

Floaters are usually displaced by the territories’ owner(s) if the owner returns.

Most trees are leafless and are relatively transparent; it is easy to observe old nests, staging birds, and competing species. The hawks are usually in their territories during the survey hours, but typically soaring and foraging in the mid-day hours. Swainson’s hawks may often be observed involved in territorial and courtship displays, and circling the nest territory. Potential nest sites identified by the observation of staging Swainson’s hawks will usually be active territories during that season, although the pair may not successfully nest/reproduce that year.

III. April 5 to April 20 Sunrise to 1200 1630 to Sunset

Although trees are much less transparent at this time, ‘activity at the nest site increases significantly. Both males and females are actively nest building, visiting their selected site frequently. Territorial and courtship displays are increased, as is copulation. The birds tend to vocalize often, and nest locations are most easily identified. This period may require a great deal of “sit and watch” surveying.

IV. April 21 to June 10 Monitoring known nest sites only Initiating Surveys is not recommended

Nests are extremely difficult to locate this time of year, and even the most experienced surveyor will miss them, especially if the previous surveys have not been done. During this phase of nesting, the female Swainson’s hawk is in brood position, very low in the nest, laying eggs, incubating, or protecting the newly hatched and vulnerable chicks; her head may or may not be visible. Nests are often well-hidden, built into heavily vegetated sections of trees or in clumps of mistletoe, making them all but invisible. Trees are usually not viewable from all angles, which may make nest observation impossible.

Following the male to the nest may be the only method to locate it, and the male will spend hours away from the nest foraging, soaring, and will generally avoid drawing attention to the nest site.

Even if the observer is fortunate enough to see a male returning with food for the female, if the female determines it is not safe she will not call the male in, and he will not approach the nest; this may happen if the observer, or others, are too close to the nest or if other threats, such as rival hawks, are apparent to the female or male.

V. June 10 to JuIy 30 (post-fledging) Sunrise to 1200 3 1600 to sunset

Young are active and visible, and relatively safe without parental protection. Both adults make numerous trips to the nest and are often soaring above, or perched near or on the nest tree. The location and construction of the nest may still limit visibility of the nest, young, ‘and adults.

DETERMINING A PROJECT’S POTENTIAL

FOR IMPACTING SWAINSON'S HAWKS

LEVEL

OF

RISK

HIGH

REPRODUCTIVE SUCCESS

(Individuals)

Direct physical contact with the nest tree while the birds are on eggs or protecting young.

(Helicopters in close proximity)

Loss of nest tree after nest building is begun prior to laying eggs.

evaluation.

Personnel within 50 yards of nest tree (out of vehicles) for extended periods while birds are on eggs or protecting young that are < 10 days old.

Initiating construction activities (machinery and personnel) within 200 yards of the nest after eggs are laid and before young are > 10 days old.

Heavy machinery only working within 50 yards of nest.

Initiating construction activities within 200 yards of nest before nest building begins or after young > 10 days old.

All project activities (personnel and machinery) greater than 200 yards from nest.

LONGTERM

SURVIVABlLlTY

(Population)

Loss of available foraging area.

Loss of nest trees.

Loss of potential nest trees.

Cumulative:

Multi-year, multi-site projects with substantial noise/personnel disturbance.

Cumulative:

Single-season projects with substantial noise/personnel disturbance that is greater than or significantly different from the daily norm.

Cumulative:

Single-season projects with activities that “blend” well with site’s “normal’ activities.

NORMAL SITE

CHARACTERISTICS

(Daily Average)

Little human-created noise, little human use:

nest is well away from dwellings, equipment yards, human access areas, etc.

Do not include general cultivation practices in

Substantial human-created noise and occurrence: nest is near roadways, well-used waterways, active airstrips, areas that have high human use.

Do not include general cultivation practices in evaluation.

NEST

MONI-

TORING

LESS