Yet another survey is being added to the continuing series of our “Griffith Park Natural History Survey” portfolio. Three local biologists and over 30 “citizen science” volunteers are surveying hawk and owl nests in Griffith Park and surrounds. Training sessions were conducted by the biologists beginning in early February just prior to raptors building new nests or improving their nests made of large sticks from previous years. Raptor pairs, often mating for life, sometimes return to the same nests for as long as a decade.

This survey marks the first of its kind in Griffith Park and in Los Angeles. It’s modeled after a successful nesting raptor survey at Irvine Ranch Conservancy, and fortunately biologist Courtney Aiken now brings her Irvine Ranch hands-on experience to our survey area.

During the two training sessions, there was an emphasis on professional monitoring practices in order to avoid flushing birds from nests or disturbing them in any way. Maintaining a safe distance is the most important factor, but other criteria include the length of the visit, and sounds to which the nesting birds may not be accustomed. Photography is not recommended when monitoring nests, unless at a far-away, safe distance. Often common sense dictates, and an observer can tell if a nesting parent bird seems threatened or perturbed.

Trained observers were initially tasked with locating nests, with quite a few nests already spotted or known even before February. Each nest was given an ID number and assigned to volunteers for regular visits throughout the nesting season. At the training sessions, volunteers learned all about nesting stages, including nest building, incubating, brooding, branching, and fledging. Volunteers took notes regarding nesting stages and periodically reported to the biologists who logged the information into a central database.

At the end of the nesting season, the survey will provide insights into the level of reproductive success, through metrics such as survival rates from one stage to the next, all the way to fledging. Each species will have its own results. Other interesting facts will be learned, for example, which species are more likely to nest in residential versus natural habitat areas.

Over 20 active raptor nests are currently being monitored in Griffith Park, and some already have fledged birds. Residential areas surrounding the park are also strongholds for raptors, and with a surplus of willing volunteers the survey has incorporated another 20 nests outside the park! The most common nesting species is the Red-tailed hawk, followed by Cooper’s hawk and Great Horned owl. Red-shouldered hawk nests have proven low in numbers and no kestrel (a falcon) nests were ever located.

On Thursday, June 15th, the three biologists, Friends’ scientific director Dan Cooper, Courtney Aiken and Andy Spyrka gave a panel discussion about the ongoing project at the first of Friends’ Summer Lecture Series. A more formal presentation of the Raptor Nesting Survey will be presented this fall, at the end of the survey.

Raptors grace the skies of Griffith Park and many residential portions of Los Angeles. Just as important, we value them as nature’s best way for balancing pests, such as rodents. Our citizen science volunteers should be proud of their contribution to science. And for all of them, taking part in this survey has been an amazing and rewarding educational experience.

~Gerry Hans