http://www.usgs.gov/public/press/public_affairs/press_releases/pr1524m.html
News Release
U.S. Department of the Interior
Release November 7, 2001
U.S. Geological Survey
There's Room for Shorebirds Too
Think of southern California, and images of beach, sun and surf come to
mind, coupled with boundless recreation opportunities for beach-goers.
What's missing from these images? It could be the shorebirds that cavort
at the edge of the sea and sand.
According to a USGS study, disturbance by people and their pets is
causing shorebirds like the threatened western snowy plover to wing it
to more remote locations where less human disturbance occurs. Protection
of small areas of special habitat can provide important sanctuaries for
these birds, however, with relatively little impact to the beach-going
public, said Dr. Kevin Lafferty, a marine ecologist with the USGS
Western Ecological Research Center in Santa Barbara, Calif.
'Research points to humans and pets as a frequent source of disturbance
for shorebirds,' said Lafferty. 'For beach-nesting birds like the snowy
plover, such disturbance has made the majority of former breeding sites
unsuitable.'
Lafferty measured rates of disturbance on beaches, providing managers
information that they in turn could use to reduce disturbance at Coal
Oil Point Reserve, a public beach in Santa Barbara, Calif. Lafferty then
evaluated the success of resulting management actions. This research is
the subject of Lafferty's recent articles in the journals Biological
Conservation and Biodiversity and Conservation, and a presentation he
will make at the Western Society of Naturalists meeting in Ventura,
Calif., Nov. 12.
Lafferty found that human activity often displaced shorebirds approached
within 20 yards. He discovered that 10 percent of humans and 40 percent
of dogs disturbed birds, and more than 70 percent of birds flew away
when disturbed. Birdspecies varied in their frequency of disturbance,
partially because a few bird species foraged on the upper beach where
contact with people was less frequent.
'Most disturbances occurred near the water, but people used so much of
the beach that birds were unable to find predictable places without
people to rest and feed,' said Lafferty.
Western snowy plovers chose to hide from people up on the dry sand
instead of moving, said Lafferty. Even with this strategy, each snowy
plover was disturbed about 115 times per week, 16 times more than at
remote or protected areas where these birds still breed. Despite
disturbance, Lafferty found that snowy plovers stayed faithful to their
preferred habitat around a lagoon mouth, though they were less abundant
near beach-access points.
Lafferty noted the types of disturbance snowy plovers were most
sensitive to, measured the distance at which they reacted to disturbance
and determined the preferred habitat of plovers within a three-kilometer
area of critical habitat for the population. He then developed a
mathematical model that predicted the smallest portion of the beach that
could be closed to maximize protection of plovers with minimal
inconvenience to beach users.
A preliminary trial began at the Reserve this summer to help buffer a
snowy plover chick and its father from disturbance. A rope fence denoted
the boundaries of the sensitive area. People could walk along the
water's edge for a 300-yard stretch, but were asked not to enter the
adjoining dry sand or the area around the lagoon. Volunteers staffed the
area to encourage people to respect the closed area and to comply with
the local dog-leash ordinance.
The result: disturbance to snowy plovers and other birds decreased
dramatically, helping the plover chick successfully fledge. By comparing
the distribution of birds before and after placement of the rope fence,
Lafferty found that snowy plover densities doubled inside the fenced
area. In addition, the number of least terns, an endangered species,
increased six-fold. In total, the abundance of birds in the protected
area increased four-fold. Counts of birds outside the fence remained
largely unchanged, indicating that additional birds were entering the
protected area.
'Two things appear to be operating,' said Lafferty. 'Birds can now sit
in one spot without being forced away within a few minutes. In addition,
other birds flying along the coast notice a lot of birds sitting on the
beach, realize the area must be a safe place to rest for a spell and fly
in.'
Since most beach users walked along the wet sand, the closure meant that
less than 5 percent of the people using the beach had to choose a
different patch of sand to sit on. Interviews with beach-goers revealed
that many people valued the increased opportunity to view wildlife, and
even more said they were glad that the minor inconvenience was an
alternative to beach closures used elsewhere to protect endangered
birds.
Lafferty will speak about the preliminary beach trial at the Western
Society of Naturalists 82nd Annual Meeting at the Clarion Ventura Beach
Hotel, 2055 Harbor Blvd., Ventura, Calif. His talk, 'Numerical Responses
of Shorebirds to Protection from Human Disturbance,' is scheduled for
Nov. 12 at 2:20 p.m., room 1. Note: Additional information about
this meeting can be found at http://www.wsn-online.org.
Lafferty?s recent journal articles are:
Kevin D. Lafferty, 'Disturbance to wintering western snowy plovers,'
Biological Conservation vol. 101, no. 3 (2001), pages 315-325.
Kevin D. Lafferty, 'Birds at a Southern California beach: seasonality,
habitat use and disturbance by human activity,' Biodiversity and
Conservation vol. 10, no. 11 (Nov. 2001), pages 1947-1960.
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