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Moving On

Most of those flights were made with a sense of distinct unease in either very remote country or less than ideal flying conditions. Normally, pilots keep constant track of the location of and distance to the nearest airport in case of emergency. In remote areas, the answer is often “too far”. By comparison, today's flight over coastal Monterey Bay promised to be more pleasurable and I relaxed as Ed Allen's Cessna 172 gained speed on the runway.

We were soon airborne with the coastal mountains and sparkling Pacific spreading out below. I checked out the window to verify that my duct tape attachment of a radio telemetry antenna to the wing strut was secure and slipped on the receiver's headphones. I was searching for a great horned owl with a tiny backpack transmitter that would signal the owl's location if we happened to fly near enough to it.

Radio-telemetry has been a boon to wildlife researchers because it reveals so much about a creature's life history in a relatively non-invasive way. Researchers can monitor a subject's movements and selection of habitat over time without constantly following it about and disturbing the animal. With some animals following is impossible.

The great-horned owl was of interest to the Predatory Bird Research Group because it had been captured and moved away from a California least tern colony where it was suspected of preying on young terns. The least tern is endangered in California. It nests on open beaches where it is vulnerable to disturbance from development, human recreational interests, and wild and domestic predators. Under appropriate permits and a contract with the federal agency that managed the land where the colony was located, the owl was trapped and fitted with a transmitter by our associate Pete Bloom. By monitoring the owl's movements it was confirmed that the owl was using the vicinity of the tern colony as foraging habitat. While predation is of course a normal part of nature, in rare cases involving endangered species reduced to small numbers, in particular colonial ones like the least tern, an entire year’s production of youngsters can be wiped out at a given colony by a diligent predator.

The owl was again trapped and then transported from southern California to our offices at the UC Santa Cruz Long Marine Lab. After confirming the owl's well being and transmitter function, we released it in appropriate habitat where meadows merged with woodlands.

The owl remained in the vicinity of the release site for about one week and then the transmitter signal vanished. After driving here and there with an omni-directional antenna on the roof of my car and receiving no further signal, I contacted an old friend of the Predatory Bird Research Group who happily agreed to take time off work and provide us with a higher vantage point from which to receive a signal. It is in part because of friends like pilot Ed Allen that we have been able to accomplish so much over the years.

Heading north out of Watsonville Airport we began to receive a weak signal. By zeroing in on it, we discovered that the bird had moved out of the coastal basin near Santa Cruz and moved up the coast about fifteen miles. From the air I guessed that it was in one of the wooded arroyos that lead upslope from the coastline. Later that day, researcher Janet Linthicum was able to visually locate the owl alive and well in a copse of willows not far from Coast Route 1.

We all feel a little better knowing that the least terns were able to finish their breeding season without further molestation, and that the predator is doing well in a new location.

- Glenn R. Stewart