Introduction

As you are enjoying your time at the Arcata Marsh, do you ever wonder if your activities are affecting the birds?  Meeting public desires for recreational opportunities while avoiding negative impacts on wildlife is a constant challenge for wildlife managers.  Of the more than 200,000 people that visit the Arcata Marsh every year, many participate in various activities at Klopp Lake such as dog walking, bird watching, bicycle riding, and jogging.  Klopp Lake is also heavily used by migratory birds, therefore it is important to understand the effects of human activity in this valuable wildlife habitat. In this study, we measured abundance and distribution of waterfowl (e.g., Bufflehead) and shorebirds (e.g., Marbled Godwits) in response to human activity.

Methods

Our study included both passive observations and direct experimentation.  For our observations, we recorded the distribution and abundance of birds in response to the natural variation in human activity that occurs at Klopp Lake.  For our experiment, we temporarily closed the lake to the public and observed the abundance and distribution of birds in the absence of human activity.  We placed temporary orange buoys in the lake to help us record the distribution of birds in various regions of the lake, such as near-shore and far-shore waters (see map).  Then we “created” human activity by having 2 people each walk 2 dogs along the south shore of the lake for 15 minutes.  We recorded how bird abundance and distribution changed during this experimental human activity.  We repeated this experiment 9 times in March 2001, during the birds’ non-breeding season. A previous class project documented that bird abundance at Klopp Lake is highest at high tide when shorebirds roost on the islands.  Therefore, we collected all of our data at high tide to avoid confounding effects of tide (rather than human activity) influencing bird abundance and distribution.

 
 

Results

1.  Human activity was concentrated on the south and west shores

The number of people and dogs we recorded at Klopp Lake at any one time varied from 4 to 17, with an average of 12 people walking 1-2 dogs.  Most of this recreational activity occurred on the south and west shores of the lake.  Thus, the northern and eastern areas of the lake may provide a refuge for birds during periods of peak human activity. (See figure below).

 

2.  Human activity affected waterfowl distribution

Before the experiment, when the lake was closed to human activity, about 10% of the waterfowl were found within 25 m of shore.  During the experiment, the number of waterfowl near shore significantly decreased, as most left for a region farther from shore.  In some wetlands, areas nearer the shore are more rich in plant material and aquatic life than areas of deeper water.  Thus, the avoidance of near-shore waters during human activity could adversely affect foraging opportunities for birds.  Future research should focus on the foraging behavior of waterfowl in near- and far-shore waters at Klopp Lake. (See figure below).

 
 

3.  Human activity did not affect waterfowl abundance

Even though waterfowl distribution shifted as a result of human activity, the total number of waterfowl at the lake was not affected.  During both our observations and the experiment, waterfowl abundance stayed relatively constant regardless of the level of human activity.  (See figure below)

 
 

4. Human activity did not adversely affect shorebirds

Shorebirds were distributed similarly before and during human activity, with nearly all of the birds roosting on the islands (especially the eastern-most). All of the islands are at least 60 m from shore, which appears to be beyond the distance shorebirds flush from human activity.  Although human activity did not affect the distribution of shorebirds, a surprising result of our study was that the total number of shorebirds at Klopp Lake increased with increasing numbers of people and dogs.  This result is difficult to interpret.  People don’t feed shorebirds (they eat tiny invertebrates), so it is unlikely the birds are attracted to the lake by human activity.  Perhaps shorebirds and people both prefer to visit the lake during similar weather conditions.  Regardless, we can be confident that human recreational activities did not negatively affect shorebird numbers at Klopp Lake.  (See figure below)

Conclusions

Our results suggest that human activity does not negatively affect bird abundance at Klopp Lake. This finding is encouraging because it suggests that continued human enjoyment of the Arcata Marsh will not displace waterfowl and shorebirds from their habitats. Our results also suggest that human activity affects waterfowl distribution by causing birds to shift from near- to far-shore waters.  However, no immediate management is needed because these effects are probably relatively minor, and the species affected are not of immediate conservation concern.  To better evaluate the significance of this shift, future researchers should compare the quality of near- and far-shore waters for foraging waterfowl.  Additionally, these findings may be useful in managing human activity and its effects on any endangered waterfowl species that may use Klopp Lake in the future. It is important to note that our study did not examine excessively disruptive human activities, nor did it examine breeding birds.  Keeping dogs leashed and practicing respectful use of the Arcata Marsh should help minimize negative impacts of human activity, and disruption of active nesting areas should be avoided whenever possible.

 
 
 

This study was conducted by the HSU Wildlife Techniques class, spring 2001.  Poster committee (l to r): Hanna Mounce, Ellen Sherrill, Jessica Harned, Dr. Matt Johnson, and Jeff Goldberg.  Special thanks to teaching assistant Sean Matthews and the rest of the class.                                   an HSU Wildlife publication