Beavers’ dams good for songbirds


This is a video about beavers in Canada.

From Animal Science Blog in the USA:

Beavers: Dam good for songbirds

The songbird has a friend in the beaver. As per a research study by the Wildlife Conservation Society (WCS), the busy beaver’s signature dams provide critical habitat for a variety of migratory songbirds, especially in the semi-arid interior of the West.

The study, which appears in the October 2008 issue of the journal Western North American Naturalist, says that through dam building, beavers create ponds and stimulate growth of diverse streamside vegetation critical for birds, including a number of migratory songbirds in decline. The study observed that the more dams beavers build, the more abundant and diverse local songbirds become.

“We observed that increasing density of beaver dams was linked to a diverse and abundant bird community and the wetland and streamside habitat these species depend on,” said Hilary Cooke, the study’s lead author who is now finishing her dissertation at the University of Alberta in Edmonton. “This habitat is critical to birds in semi-arid regions yet has been severely degraded or lost through much of the West. Our results suggest that management of beavers may be an important tool for restoring habitat and reversing bird declines.”

Beaver populations once numbered in the millions in the American West but dramatically collapsed due to the fur trade in the 1800s. Currently, beaver are often considered a pest species when they take down trees and flood property. Their influence is still missing on most watersheds in the West, yet this and other studies suggest that beaver are very important to wildlife and to reviving the natural function of streams.

“Beaver are an essential ecosystem engineer,” said co-author Steve Zack of the Wildlife Conservation Society. “Beavers help repair degraded stream habitats and their dams and associated ponds recharge local water tables and create wetlands. With our changing climate likely to mean increasing droughts in the West, managing ways to allow watersheds to act more like sponges will be a challenge. Beaver are a powerful tool to be considered for that, and the associated benefits to other wildlife add to their value”.

This study was part of a larger effort by WCS to identify how to restore wildlife to streamside habitats in the western U.S. This study occurred in Wyoming where beaver reintroductions have been done on both private and public lands with owner consent and interest.

In 2007, WCS made history with other beaver news when an active beaver lodge was discovered in the Bronx River on the grounds of the Bronx Zoo the first one spotted in New York City in at least two centuries.

See also here. And here.

Pictured: first wild beavers born in Britain for over 500 years: here.

5 thoughts on “Beavers’ dams good for songbirds

  1. Snakes, salamanders and other creatures thrive in areas with higher deer populations
    Ohio State doctoral student Katherine Greenwald, seen here with the hellbender salamander, is studying how human disturbance to the environment affect different types of salamanders. Hellbenders are the third largest…
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    COLUMBUS, Ohio – Reducing the number of deer in forests and parks may unexpectedly reduce the number of reptiles, amphibians and insects in that area, new research suggests.

    A recent study by researchers at Ohio State University and National Park Service found that higher deer activity is modifying forest ecosystems in unexpected ways. Out of several species of snakes, salamanders, and invertebrates studied, a greater diversity of animals were found in areas with deer populations than were in areas with no deer activity.

    The study, which comes at a time when many states have begun to selectively control deer populations, challenges previous research that has suggested deer populations can negatively impact forest ecosystems through eating plants that many smaller animals may depend on.

    Instead, researchers found that high numbers of deer may in fact be attracting a greater number of species. This may be because their waste creates a more nutrient-rich soil and as a result, areas with deer draw higher numbers of insects and other invertebrates. These insects then attract larger predators which thrive on insect lava such as salamanders, and the salamanders in turn attract even larger predators such as snakes.

    The results, which were published recently in The Journal of Wildlife Management, highlight how recent attempts to control deer populations in and around forests may indirectly affect other animals in the forest.
    After catching creatures in the traps, Ohio State doctoral student Katherine Greenwald will take measurements of the animals caught to analyze the health of forest and riverbed ecosystems.
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    “By just reducing the number of deer in the forest, we’re actually indirectly impacting forest ecosystems without even knowing the possible effects,” said Katherine Greenwald, co-author of the study and doctoral student in evolution, ecology, and organismal biology at Ohio State.

    “Smaller creatures like salamanders and insects are all part of the base of a larger food web that can be affected by small changes.”

    Research was conducted in Cuyahoga Valley National Park, a 51-square-mile park in northeastern Ohio with an estimated deer population of 2,300 to 4,600. The park’s large population of deer and varying landscape made it an ideal place to test for the effects of these animals, she said.

    Researchers studied the forest by pairing 12 unfenced sites with 12 fenced sites, called exclosures, based on similar habitat type, forest cover, soil type, and slope. The exclosures, which are used frequently to test for differences in plant growth between grazed and untouched areas, prevent deer from grazing in certain areas. Both unfenced and fenced areas measured 10 meters by 10 meters (approximately 33 feet by 33 feet).

    Five square wood boards measuring almost one square foot (30 centimeters square) were placed in random spots in each fenced and unfenced site. These boards are placed on top of the soil and act as rocks or other ground cover for salamanders, slugs and other animals to hide under for protection.

    The researchers then counted the number of invertebrates and vertebrates under each board every three to four weeks from May through December in 2004 and monthly from May through September the following year.

    They identified a variety of species during the study including snakes, salamanders, earthworms, slugs, spiders, ants, beetles, and many more invertebrates. Species diversity was determined by comparing the variety of insect groups and invertebrates found in each area.

    The results, Greenwald said, were completely unexpected.

    “We thought the salamanders especially would be very sensitive to areas with deer because in those areas the whole undergrowth is basically gone. So we thought these creatures were going to be much more abundant in the fenced exclosures because it is just bursting with plants and other studies have shown that amphibians prefer damp, covered areas,” she said.

    Instead, they found that many of the species studied favored the unfenced areas where deer grazed frequently. Pill bugs, centipedes, millipedes, and beetles were found equally in grazed and fenced areas, but many other creatures were found in greater numbers in grazed areas.

    Researchers found nearly three times as many red-backed salamanders and five-and-a-half times more snakes in sites with deer than those without deer. Among invertebrates, snails were 11 percent more abundant in grazed areas than in exclosures and the diversity of arthropods was also 14 percent greater in these areas.

    Greenwald speculates that the areas with higher deer populations may appear to lack the high variety of low-lying plants found in exclosures, but the deer may be creating a richer soil mixture through their droppings. This rich soil may be benefiting some plants in the area, which in turn is attracting a larger diversity of insects and invertebrates.

    Salamanders and snakes may then be following these creatures, creating a more diverse animal population overall in areas with deer.

    “Another possibility is that we are observing a ‘refuge effect,’ where animals in the grazed areas are more likely to use the cover objects than animals in the ungrazed areas. If the ground in the exclosures really is more favorable, as we originally thought, maybe the animals there just have no need for our artificial cover boards,” Greenwald said.

    But no matter what the reason, she cautions that the take-home message of the study is that officials need to understand the forest ecosystem before making decisions about wildlife management.

    “We need to be aware of what’s happening in these forest ecosystems. Culling deer may cascade into affecting plants, salamanders, and other creatures in ways we can’t even imagine. So before we start removing deer we should study what’s really happening in these areas because there are a whole host of other issues that go along with culling,” she said.

    ###

    Greenwald conducted the study with Thomas Waite, former associate professor of evolution, ecology and organismal biology at Ohio State, and Lisa Petit of the Cuyahoga Valley National Park.

    Contact: Katherine Greenwald, (614) 578-3207; Greenwald.35@osu.edu

    Written by Jenna McGuire, (614) 247-8362; Mcguire.165@osu.edu

    http://www.eurekalert.org/pub_releases/2008-10/osu-ssa102008.php

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