PRBO Conservation Science
Quarterly Journal of PRBO Conservation Science, Number 131, Winter 2003: Human Disturbance


Reducing research's impacts

Responsible Science

PRBO Biologists

Human Disturbance
Executive Director's Column
Vulnerable Coastal Habitats
Invasive Plants
Responsible Science
Birding Ethics
Focus on Feeders
Planned Giving to PRBO
Spain Oil Spill

Scientific knowledge, necessary for wildlife protection and habitat conservation, must sometimes be obtained at a cost-interference in the lives of wild animals. PRBO places a high priority on reducing impacts on our study species, as discussed in these four examples.--Editor


Russ Bradley

A Cassin's Auklet chick near its nest box on Southeast Farallon Island. PRBO photo.

I vividly remember the first time I crushed the entrance to a Cassin's Auklet burrow on the Farallons. My mind was filled with all the field work I needed to do that day when I accidentally demolished the well-dug nest site of one of these amazing planktivorous seabirds. Cursing myself, I carefully excavated the burrow to find a startled chick inside, very annoyed with the recent renovations to its home. I rebuilt the burrow the best I could, using a piece of wood and a rock to form a secure new roof, and returned the uninjured chick. A few weeks later when I peeked into the reconstructed burrow, I was thrilled to see the small chick fully feathered and nearly ready to fledge to the open sea.

Most seabird colonies are extremely sensitive to human disturbance. Many species that have evolved to breed in these isolated locations have few defenses against non-avian predators, because they have rarely been exposed to them. This is definitely the case on the Farallon Islands. As stewards of the Farallon National Wildlife Refuge, PRBO biologists monitor disturbance by passing boats and aircraft and ensure that unauthorized personnel are not permitted on the island. But how do we ensure that our own research activities do not negatively affect wildlife?

* Much of Southeast Farallon Island, where our research is conducted, is closed to all human activity--including researchers! And during seabird season (March 15-August 15), to protect nesting seabirds from disturbance, many areas that researchers visit during the fall and winter are off limits.

* Boardwalks prevent damage to auklet burrows, and artificial nest burrows (boxes) are used in studies of breeding behavior of burrowing birds to prevent disturbance to natural sites.

* Although some of our studies involve direct handling of birds for marking and measuring, we strive to reduce handling times and keep stress to an absolute minimum. Once birds are confirmed as breeders, they are left alone throughout the incubation period. We limit handling of animals during sensitive periods like chick brooding when the young are covered in the nest by their parents.

In 1999, PRBO's Karen Carney and Marine Program Director Bill Sydeman published a comprehensive review of human disturbance effects on nesting colonial waterbirds in the peer-reviewed journal Waterbirds. The article highlighted less intrusive research methods and emphasized the need for biologists to be ever vigilant in their interactions with seabirds.

PRBO's research on the breeding seabirds of the Farallons has just celebrated its 33rd anniversary. This is the longest data set on breeding seabirds in the Northern Hemisphere and has enabled us to examine important questions about long-term changes in the marine environment (see Observers 127, Winter 2002; and 130, Fall 2002). To gather these data, we must intrude into the world of breeding seabirds-an isolated world where humans really don't belong. Despite our occasional accidents, we strive to collect valuable data in ways that minimize disturbance to this sensitive environment and protect and sustain populations for the long haul.


Tom Gardali

Using a "nest stick" to locate and observe a songbird nest causes minimal disturbance. PRBO photo.

PRBO's field biologists locate and monitor over 2,000 songbird nests each spring, enabling us to estimate nesting success and investigate the factors influencing it (e.g., rainfall and nest location). Unbiased estimates of nest success are vital to our research. While the scientific literature contains several studies indicating that observer impacts on birds' nesting success are minimal or nonexistent, PRBO takes several precautionary measures to reduce any potential impacts associated with locating and monitoring nests.

Finding a nest is difficult, and pinpointing its location can cause some disturbance as the biologist carefully searches the vegetation (while the songbirds vocally scold the observer). In this situation and in subsequent nest checks, the biologist is perceived as a nest predator! Songbirds go to great lengths to minimize drawing attention to their nests, and we are obliged to do the same. PRBO field biologists use the following techniques and guidelines to reduce disturbance:

* Never approach a nest when avian nest predators are nearby. Jays and other corvids are smart and likely get behavioral cues, from the biologist and the songbirds, which they use to locate nests to rob.

* Conduct false "nest checks." Even if the biologist cannot see an avian predator in the vicinity, she/he should assume one is watching and pretend to check several false "nests" by peering into bushes before and after checking the real nest.

* Minimize physical disturbance to the area around the nest. Any trampling of vegetation may reduce nest cover and draw unnecessary attention to the location of the nest.

* Never create a dead-end trail that leads to the nest, and for each visit always try to approach a nest from a different direction. The idea is to not create trails, but if that is impossible, make sure that any trail does not lead predators such as raccoons directly to the nest.

* Use a "nest stick" to part vegetation, an indispensable tool for the nest searcher. One of the nest stick's many uses is to move any vegetation near the nest in order to check the contents without leaving a human scent.

* Be quick and accurate when checking nests. More time spent at a nest increases the amount of attention drawn to the area.

Each year, new field biologists are humbled by the privilege to intimately observe the home life of songbirds. The drama unfolds before them as they watch a pair of songbirds work tirelessly to construct nests, incubate eggs, and, if everything goes well, feed nestlings until they are old enough to depart the nest. Realization of this privilege makes training field biologists to be aware of and reduce research impacts a simple endeavor: the last thing they want is to negatively influence the outcome of a nesting attempt.


Nils Warnock, PhD

As researchers who study and handle birds, a question we have to ask is: Are we affecting the birds we study? We know that when a migrating Western Sandpiper has been captured and had a radio-transmitter glued to it (see Observer 126, Autumn 2001), its migration at its site of capture is delayed, but that afterward it behaves normally. For instance, Westerns radiomarked at San Francisco and subsequently seen at Grays Harbor, Washington, stayed an average of 1.9 days at Grays Harbor; during the same period when the San Francisco birds were migrating through, Westerns captured and radiomarked at Grays Harbor stayed for more than 7 days; this suggests a capture effect.

Why do we see these effects? Birds that experience stress undergo physiological responses, including elevated stress-related hormones in their bodies. These hormones send messages to the birds to stop worrying about certain activities (like eating) and instead deal with the stressful situation. A common pattern we see after banding birds is that they tend to lose body mass for a few days before beginning to regain mass. In trying to minimize this effect, we found that the quicker we handle the birds and let them go, the smaller the capture effect seems to be.

Are these effects of banding temporary or permanent? Using radiomarked shorebirds, we have gained some information. Our Western Sandpiper studies show that radiomarked birds have high survivorship during northward passage from wintering grounds in California to breeding grounds in Alaska. We typically detect over 80% of the Westerns that we radiomark in California at the Copper River Delta in Alaska, over 3,000 km (2,400 miles) away. Given that we miss some birds, and that some have their radios fall off or fail, survivorship of birds is apparently high during this period.

Does handling cause longer-term effects? Here, we look to data for Pacific Golden-Plovers radiomarked in Hawaii and tracked to breeding grounds in Alaska (a study in which I participated with lead researcher Dr. Wally Johnson of Montana State University). Since these plovers were also color-banded, we could see how many previously radiotagged individuals came back to their wintering sites in Hawaii the following fall. Of the 20 birds marked, only one bird failed to return, suggesting that there was no long-term effect on these birds.

We need to be aware that we can and do impact our study species--and be ever creative in evaluating and negating any such effects. However, results such as the above help assure us that we are not unintentionally harming the very species that we are trying to protect.


Peter Pyle

Just 20 years ago a fisherman killed four large sharks at Southeast Farallon Island (SEFI) in a single day and was glorified as a hero by the local media. Following this event we began a long campaign to change the image of the white shark in the human eye, using PRBO's shark research project at SEFI as a platform to help people understand and respect, rather than fear and castigate, this important keystone predator in the marine ecosystem. Through documentaries we conveyed our message to the public, and through petitioning we instigated a successful effort to legally protect the white shark in California waters. We were thus delighted when, recently, we were asked to review the effects of our own research on the behavior and well-being of the sharks--surely a sign that our campaign has succeeded, and beyond our wildest dreams at that.

We have always taken a "hands-off" (literally and otherwise!) approach with white sharks--refusing to use bait and attempting to alter their behavior as little as possible by our presence. When we have affected them--e.g., through the restricted (less than one hour per day) use of decoys to lure them to the surface, to identify individuals; by our proximity to feeding events to obtain video identifications; or through deployment of satellite transmitters (the equivalent of a mosquito bite in the turbulent life of a white shark)--we have constantly asked the question: Does what we learn from and about these animals justify our disturbance to them? Due to our very cautious observational approach and the increased public compassion and legal protection that have resulted from our research on this previously maligned animal, we feel strongly that the answer is "yes."

Nonetheless, we always welcome outside review of our own research behavior and want what is best for the sharks. Indeed, we have recently submitted recommendations for a complete ban on the use of chum (bait) and decoys, and a 50-meter limit for the approach of boats to feeding sharks; we want these regulations to apply to all vessels, commercial and research alike. Although this may reduce our ability to collect certain data, we are more than willing to make the sacrifice to benefit the sharks.

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