Tag Archives: Foresters for the Birds

Studying Forest Structure At Elm Hill

Our bird conservation staff spent the past week collecting data at Elm Hill Wildlife Sanctuary, our demonstration site for Foresters for the Birds. Since we’re using this site to show how responsible forest management can enrich bird habitat, we need before-and-after data to compare changes in vegetation and bird diversity.

Birds See Forests For The Trees

The physical structure of a forest directly affects which birds are found there. The amount of vegetation near the forest floor (or “understory”) changes whether or not the forest can host a whole suite species that nest near the ground, like Ovenbirds and Black-throated Blue Warblers. Forests with open midstories (the layer of vegetation between 5–50 feet off the ground) attract flycatching birds like Eastern Wood-Pewees, but dense midstories appeal to Wood Thrushes and Canada Warblers.

The goal of our work at Elm Hill is to demonstrate how every forest species has its own habitat preferences, and how thoughtful land management can create habitat for declining species. Since three quarters of Massachusetts’ forests are in private hands, it’s critical to make these lands as hospitable as possible to wildlife.

Collecting Vegetation Data

A data sheet we use for recording information about trees and forest structure at Elm Hill.

Before we alter any habitat at Elm Hill, we’re recording these factors at sites where we’ve previously done bird surveys:

  • Total woody biomass (i.e., the average size and number of trees in a given area)
  • Tree species makeup (i.e., which trees are there, and how many of each)
  • Canopy density (i.e., the amount of cover provided by leaves in the treetops)
  • Sapling density (i.e., the number of young trees from around 1–6 feet tall)
  • Coarse woody debris (i.e., the number of logs and slash piles on the ground)

We outline a 400-square-meter plot with ropes at every site to make sure we collect data from the same area of land each time. This works pretty well until somebody tangles the ropes:

Jeff tangled the ropes. It definitely was not me.

While measuring trees, logs, and saplings is straightforward, you might wonder how researchers measure canopy density— and the instrument for this is quite cool. A spherical densiometer (pictured below) condenses a wide view of the canopy into a small image (much like a fisheye camera lens) with a grid over it. By estimating the percentage of each grid square occupied by leaves or trunks (and adding them up, and taking readings in each cardinal direction), we have a standardized and simple way of measuring canopy density. This also works as a proxy for determining how much light reaches the forest floor.

A spherical densiometer, used for measuring the amount of leaves in the treetops.

Long-term Goals

After foresters have cleared the woods of invasive species and created a variety of spatial habitat types, we’ll be able to show what changes this brings to Elm Hill’s bird species.

Elm Hill contains mostly 70–90-year-old forest, like much of Massachusetts. We’ll manage parts of the sanctuary for birds that prefer young forest, which are in trouble statewide, and in other part’s we’ll try to mimic old-growth forest conditions, which would take over a century to emerge naturally. Hopefully, we can then use this site as a physical example of how foresters and landowners can improve bird habitat on the properties they manage.

 

 

Surveying Wildlife at Elm Hill

In order to characterize the bird community at Elm Hill, point count surveys were performed at 24 locations within forested areas of the sanctuary.  During a ten minute period, the species of each individual bird is recorded, as detected by sight or sound, within 50 meters.  This gives us information on the abundance of each species and the overall species richness (number of species).  As is typical, each location was surveyed 3 times, and this yielded 789 detections of birds representing 51 species!

As discussed in previous blog posts about the development of a Foresters for the Birds demonstration site at Elm Hill, these surveys were done to establish a pre-management baseline, which will then be compared with conditions after management.  Wait a minute… 51 species!?!  Is management really necessary?

51 species may sound like a lot, leading to the conclusion that the forests are already providing good habitat.  That may be true, but for what species?  Upon closer examination of the data, we can see that many of the species we recorded (e.g., nuthatches, titmice, and catbirds) are quite common, thriving in our woodlands and backyards alike.  Others, such as Barred Owls, naturally occur at low densities, so we wouldn’t expect to find many of them.

It’s those species that we conspicuously did not detect, or recorded very few of, that we are managing for.  For example Black-throated Blue Warbler and Ruffed Grouse were not recorded.  These species rely on some degree of disturbance to the canopy, creating vegetative growth in the understory and a mix of tree ages in the forest.  These are conditions that can be created through sustainable forestry, and it would not be unreasonable to expect these, and other species of conservation concern, to show up at Elm Hill after appropriate habitat management.  Time will tell.

Please consider supporting our bird conservation work by making a donation today. Thank you!

Tree cavities: home to many creatures

When we think about a bird’s nest, we usually conjure up the image of a cup-shaped tangle of twigs and dried grass, with perhaps some moss or strips of bark, cleverly placed in a bush or the limb of a tree.  Maybe that’s because these are the most visible types of nests, whose remnants are easily seen when the leaves drop each fall.  Nests of other birds a quite difficult to see, even in plain sight.  For example, the Piping Plover creates a just slight depression in the sand, and the Eastern Whip-poor-will nests directly on the forest floor, each with highly camouflaged eggs.

Yet another type of nest are those placed in the cavity of a tree.  Many common bird species are actually cavity nesters, including nuthatches, chickadees, titmice, bluebirds, woodpeckers and some owls.  Cavity nests provide protection from predators, shelter from weather events, and can be chosen with respect to the regional climate.  For example, in northern latitudes woodpeckers are known to orient their cavities south towards the sun, so that their young will stay nice and toasty in the nest.

Pileated Woodpecker family; adult male on left, female on right. © Kim Nagy

Woodpeckers are particularly important in the world of cavity nesters.  While cavities can occur naturally in trees, most species are poorly suited to excavate their own cavities, and often rely on holes created by woodpeckers.

Cavities usually begin with a fungal infection, which creates a soft inner wood that is easy to excavate.  This condition is most common in older dying trees, which eventually become dead standing trees (called snags) and continue to be a good resource for cavity nesters.  Unfortunately, dying trees and snags present inefficiencies to timber production, and a history of land clearing and forestry practices have limited snag numbers.  Meanwhile, populations of woodpeckers and other cavity nesters can suffer if there are too few cavity trees available.

The good news is that forestry can also help to increase the number of cavity trees.  For example, the maintenance of large dying trees and snags is promoted by Mass Audubon’s Foresters for the Birds program.  This program, a partnership between Mass Audubon, MassWoodlands Institute, and the Mass Department of Conservation and Recreation, provides assistance to landowners who wish to manage their woods for bird habitat with sustainable forestry practices.

Empowering private landowners is critical because they own the majority (75%) of forests in Massachusetts.

— Jeff Ritterson, Forest Bird Conservation Fellow, Mass Audubon

Northern Flicker (yellow-shafted) adult female with young in cavity nest © Cynthia Rand

Please consider supporting our bird conservation work by making a donation today. Thank you!

Bird-friendly Forestry at Elm Hill

These 17 birds were chosen to represent different forest habitats and management options in the Massachusetts Foresters for the Birds program.

Mass Audubon’s Foresters for the Birds program provides assistance for private landowners to manage their forests for bird habitat. Empowering private landowners is important because about 75% of Massachusetts’ forests are privately owned, and management on these lands will be necessary to address conservation needs on a landscape scale.

To promote the program, and to engage and educate the public, we are creating a long-term demonstration site at our Elm Hill wildlife sanctuary in Brookfield and North Brookfield. The first step: develop a 100-year forest management plan for Elm Hill. To do this we are working with a forester who was trained in our Foresters for the Birds program.

In addition to mapping different forest resources, and describing the amount and value of the standing timber, this plan also includes an assessment of the current bird habitat and recommendations for improvement. For example, the structure of the forest understory and midstory, where many birds place their nests, are described in each area of the forest.

The plan also includes strategic locations for the placement of early successional habitat. We are currently reviewing initial drafts of the plan, and working with our forester to iron out the nitty gritty details.

Once the plan is complete, we will then undergo active forest management on the property (probably next year), which will include things like removing invasive plants, and selectively removing trees to improve the composition, health, and resiliency of the forest.

We are also designing a bird monitoring study which will investigate how effective our forestry practices will be.  Because on-the-ground management will not happen until well after this year’s breeding season for birds we have the opportunity this year to characterize how birds are currently using the forest. Comparing that data to similar data collected post management will help us adapt our future efforts to maximize the benefits to our birds.

Beginning as soon as this summer, we will invite foresters, landowners, land trusts, and other conservation entities to visit the property and see how they can manage their woodlands for birds and other wildlife.

Keep checking back for more updates as we nail down our plans and begin the bird monitoring. For more information about the project, see our previous blog post.


Photo credits From top left: American Woodcock © David Larson; Black-and-white Warbler © David Larson; Black-throated Blue Warbler © John Harrison; Black-throated Green Warbler © John Harrison; Brown Thrasher © Patricia Pierce; Canada Warbler © David Larson; Chestnut-sided Warbler © David Larson; Eastern Wood-Pewee © Fyn Kynd; Eastern Towhee © John Harrison; Mourning Warbler © Gerard Dewaghe; Northern Bobwhite © Paul McCarthy; Northern Flicker © Richard Campbell; Ruffed Grouse © Richard Johnson; Veery © Mark Thorne; White-throated Sparrow © David Larson; Wood Thrush © Sheila Carroll; Yellow-bellied Sapsucker © John Harrison