Many gardeners have an appreciation for backyard songbirds. It’s a natural fit. As gardeners, we do a lot to invite them into our landscapes with food and shelter. All the more reason it’s concerning to know that many bird species are rapidly falling in their numbers, some at alarming rates. It’s time we all learn more about bird population decline and what gardeners can do to help.
Our guest for this podcast is the perfect person to explain what’s happening, and how we can help create sustainable habitats. John Marzluff, Ph.D. is a Professor of Wildlife Science at the University of Washington and author of several books based on his study of birds.
His most recent book, Welcome to Subirdia, addresses tangible ways that we can successfully share our neighborhoods with wrens, robins, woodpeckers and other wildlife.
Ironically, the very day before this conversation, a study on bird population decline was released in Science Magazine, a highly-respected publication. Over the 50-year study, the rate of decline was staggering even to ornithologists. Nearly 30% of North America’s total bird population (3 billion) has been lost. It’s also considered a very conservative estimate.
The ripple effect of such a dramatic decline is far-reaching in its potential impact on food webs and other ecosystems. Just imagine – about 90% of a bird’s diet consists of insects. That’s a lot of bugs and a very effective method for keeping their populations in check. Take away 30% of the birds and we’ve got real problems. Birds are also critical in the dispersal of seeds and even help with pollination.
It’s a clear sign the system is not in good health and a vivid call to action that we all need to take action by doing whatever we can to halt the decline and turn it around to the extent that we can.
Reasons cited for this massive decline include changing agricultural practices and intensification of agriculture across the world. Endless acres of mono-crops such as industrial corn and soybeans are a major contributor. Add to that the increased use of pesticides and the conversion of remaining grass and pasture land and native prairie to cropland.
Along with the gloomy outlook, there are a few kernels of good news. Overall, wetland bird species have increased their populations significantly over the same time. Why? Efforts by conservationists, special interest groups such as duck hunters with an interest in promoting habitats, and environmental laws have all played a role.
Raptors were another group of birds making a comeback – at least in part. But not surprising when you think about the fact that a lot of that has to do with the decline of certain pesticides such as DDT. What we’re seeing is really just a rebound of their populations. Only time will tell to see if those numbers hold.
That said, in the midwest, some of the raptors like Northern Harriers, (a grassland raptor) and Swainson’s Hawks, are declining for the same reason that some of the other grassland birds are.
The Inspiration for Subirdia
According to John, writing Subirdia stemmed from a facet of urban ecology that for far too long, was mostly ignored by ecologists. Urban and suburban areas were mostly written off as not being of much use to conservation. But John says that’s changed in the last several decades. The results of his observations of many bird species adaptation to subdivision sprawl led to his book and title.
John and his colleagues at the university which included urban planners, geographers, and ecologists started looking at our urban system in more detail, trying to understand how it affected a variety of human and natural systems and the connections they shared. John’s part of that study was to observe the birds that live around the Seattle area and how they were being impacted by changing habitats.
The areas of study included large, high stature forests that were being cut down and planted with the things we like around our homes. One of the biggest surprises was in how the bird communities changed in the face of declining forests and expanding subdivisions.
The natural expectation was for an overall decline in the bird population. To be sure, some birds definitely did decline. Notable losses included the true forest dwellers as well as prairie birds. So when forest and grasslands go away, so do the birds that depend on those environments.
The birds impacted by declines in their primary habitat are referred to as avoiders of human activity, in this case, suburbanization. That said, studies in Seattle and elsewhere show that the total diversity of species increases when in the midst of suburban sprawl.
The belief is that when you bring a lot of different habitats in close proximity including golf courses, yards, and landscapes while keeping some forest or prairie remnants, you have this diverse mixture of habitats, each supporting different groups of birds. When you total all those little pieces up, you get a higher number of species.
But this is not equal across the board. We really have a complete shift in the community of many bird species that live around us versus those that live in more natural areas. Some birds exploit the opportunity by coming into our yards and using our feeders and the edges we create. In may cases, the net effect is an increase in the number of bird habitats and a higher diversity of bird species created in developed areas. John refers to this group of bird species as adapters.
Birds that exploit their human influence (think pigeons and crows) really do well around us. They actually have their best success being close to human habitation.
In other instances, the changes were too much and led to dramatic reductions. Imagine going from expansive forests to endless lawns in a couple of years. That’s very detrimental to some species. Winter wrens were an example of such birds that do not adapt well to sudden changes like this.
Actionable Steps We Can Take
If you’re concerned with bird population decline and want to know what you as a gardener can do to help, start by creating a more inviting and sustainable habitat for birds. Here are a few steps you can take that will make a difference.
Increase the habitat quality in your yard. The diversity of plants is key to better habitats. Focus on native plants, not just ornamentals, or at least choose ornamentals that are producing food berries or nectar.
Reduce the lawn. Grass doesn’t provide any fulltime benefit for birds. Consider replacing grass with plants and trees that provide more ecological function for the birds that provide food, shelter and nesting sites.
For the lawn you have, consider making part of it a “freedom lawn”. The term originated from a Yale study that included information related to letting your lawn assume a more natural, less mowed appearance. When you can get away with it (as John has done in part of his backyard), the results are amazing for what is attracted to this naturalized environment. For John, he’s noticed a remarkable increase in the bees, birds, and insect activity. Even salamanders have increased their numbers now that the non-disturbed area stays moist.
We discussed this concept in an episode of Growing a Greener World®. Garden writer and author Margaret Roach showcased a beautiful and lively example of this in her 2.3 acre upstate New York garden landscape.
Focus on structure and layers. Birds favor certain layers of your landscape, from the highest canopy trees, understory trees beneath, shrubs, perennials, and groundcovers. By including all layers in your landscape, you provide the greatest diversity of habitat for a wide variety of bird species.
Growing a Greener World also has a good example of this layering concept in this episode featuring Rick Darke and Doug Tallamy in our episode on Bringing Nature Home.
Focus on attracting native birds. It’s important to know what birds are there, and what effect they have on the ecosystem. If you’re just feeding non-native birds like starlings and house sparrows, then it really isn’t doing any good. While it’s maintaining those species, they might be using resources that native species could use better. And so again, if your first strategy is to diversify your plantings, you’re going to be helping native birds.
Provide food and nest boxes. In most cases, especially here in the United States, providing nesting boxes and supplemental food sources is beneficial. It increases the health of the birds that are eating those foods and it increases their survivorship during the winter and even during the breeding season. That’s very important because it translates into larger populations of those species that can live with us and that do utilize the food we provide.
Don’t light the night sky. A lot of our migratory birds do so at night. If the sky is lit, they may be attracted or disoriented by those lights and oftentimes that cause them to crash into structures nearby. Mortality is increased by the lights that we put out at night, especially during the spring and autumn migration periods.
Even small ornamental and house lights that are increasingly popular now cast a broad swath of light. The problem is that many birds that hunt at night rely on that darkness as their cover. With outdoor lighting, that’s taken away from them and species decline because of that.
Avoid the use of pesticides and herbicides. If we’re killing insects with non-selective pesticides, we’re taking out a vital food source that birds depend on. Even though we might provide feeders with seeds or even mealworms and other bugs, that’s no substitute for the blooms of insects that most of our birds have come to rely upon.
Birds have evolved to time their breeding when insects are abundant to feed their young that high protein, high-fat diet that that a young growing bird needs. The more pesticides we apply to reduce those insects is directly detrimental to bird populations.
Herbicides that kill weeds also eliminate their seed production. Think of thistle and dandelions. Goldfinches and many birds rely upon these and other seeds as a primary food source.
Keep cats inside. It is estimated that three to four billion birds die each year by cats. It’s the number one cause of bird mortality. Keeping cats inside is the number one thing we can all do to increase the sustainability of birds in our yards. Another effective but under-utilized option is to use a leash when giving cats some time outdoors.
Take precautions to avoid birds flying into windows. Window strikes are the second most common cause of bird mortality. According to Margaret Roach from this episode of Growing a Greener World on Gardening for Birds, feeders should be within three feet or more than 30-feet from windows to minimize the risk of bird strikes.
Other options to reduce strike risks include stretching bird netting tightly across the exterior side of the window to serve as a cushion when birds fly towards the window. Another option is to use ultraviolet reflective stickers and tape. These products are nearly invisible to humans yet birds see them as a solid, non-transparent area and fly clear of the glass.
Hopefully, by now you’ve had a chance to listen to this fascinating conversation. If not, you can simply head back up to the top of this post and click the arrow in the green play bar to listen now. You can also subscribe to The joe gardener Show Podcast wherever you consume podcasts. We’re a weekly show with new episodes posting every Thursday.
Links & Resources
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