Fall migration: Telltale takes on environment

November 25, 2019

 

Many birds across North America, including some migrating through Michigan, are struggling to survive in the face of manmade and natural threats, according to research based on radar data and new technology for tracking birds, and the overall migration data is serving as a forecast on the health of the environment.

Fall migration in Michigan tends to start in the third week of September and goes through the warmer part of November. During that time, birders not only see dozens of species leaving Michigan for the south, but other species passing through the state, with some northern birds coming into Michigan. For those tracking migration patterns and trends, the presence or absence of some species of birds, as well as changes in the timing of their comings and goings, serve as a sentinel of sorts, with changes in avian wildlife indicating larger environmental issues.

"Bird populations are declining, and over half of the birds in North American migrate. It's hard for scientists to pinpoint exactly where declines are happening... but habitat loss is probably the number one factor. That's true for any decline in species," said associate professor Jen Owen with Michigan State University's Department of Fisheries and Wildlife, who specializes in the behavioral ecology of migratory birds. "There are other disturbances. Invasive species have a substantial impact. Pollution, including light pollution particularly for migrating birds, is a problem. Cats also are a massive killer of birds."

Other factors, such as climate change, are having a notable effect on the timing and movement of birds.

"We’re seeing changes in phenology, or the movement and earlier arrival of birds," Owen said. "There is a mismatch when birds arrive and when food is present. In the spring they want to get here when there is a huge flush of insects, but if they arrive too late, whether because of events on the wintering grounds not matching breeding grounds, they may get here too early."

Overall, ornithologists and others studying birds have determined that nearly three billion birds, or about 29 percent of North America's bird population, have died off over the past 50 years, including many migrating birds. Those figures are part of the study, "Decline of North American Avifauna," published in September in the journal "Science," in which leading researchers said we are now in the midst of an ongoing biodiversity crisis.

"This loss of bird abundance signals an urgent need to address threats to avert future avifaunal collapse and associated loss of ecosystem integrity, function and services," according to the study's authors, who said that slowing the loss of biodiversity "is the defining challenge of the 21st century."

Contributing to the decline of bird populations is loss of habitat, climate change, unregulated harvest and other forms of human-caused mortality. Together, those changes have led to a "thousand-fold increase in global extinctions," which researchers say has been underestimated.

"Extinction of the Passenger Pigeon, once likely the most numerous bird on the planet, provides a poignant reminder that even abundant species can go extinct rapidly," the study noted. "Today, monitoring data suggest that avian declines will likely continue without targeted conservation action, triggering additional endangered species listings at tremendous financial and social cost.

"Moreover, because birds provide numerous benefits to ecosystems (e.g., seed dispersal, pollination, pest control) and economies (47 million people spend $9.3 billion U.S. dollars per year through bird-related activities in the U.S.), their population reductions and possible extinctions will have severe direct and indirect consequences."

However, the paper offers a silver lining: Population declines can be reversed through adaptive harvest management, wetland protection and restoration and other conservation efforts.

Researchers evaluated population changes for 529 species of birds in the continental United States and Canada, finding declines in 303 species, or about 57 percent of all that were surveyed over the past half-century. Of those, grassland birds showed the largest population loss, with 74 percent of grassland birds in decline. Still, the study found 419 native migratory species, which include many grassland birds, in North America experienced a net loss of 2.5 billion birds, with those overwintering in temperate regions having the largest loss.

"More than 90 percent of the total cumulative loss can be attributed to 12 bird familes, including sparrows, warblers, blackbirds and finches," the study noted. "Of 67 bird families surveyed, 38 showed a net loss in total abundance."

In Michigan, where seasonal variations can bring unexpected shifts in weather and temperatures, an early or late winter can have a range of impacts on birds in both fall and spring migration. While much of fall migration typically peaks in late September, early birds begin leaving the area as soon as August with late migration extending into November.

"Some weird temperatures are affecting migration and some birds are migrating later. And precipitation is changing the areas that birds use," said Ava Landgraf, a research associate with the Detroit Audubon Society. "Drier areas have become more flooded. And in the spring, when birds are arriving, they may not have access to insects or seeds and berries if they arrive too early and we get late winter weather."

In October of 2019, the Audubon Society published "Survival by Degrees: 389 Bird Species on the Brink," a new report regarding the impact of climate change on bird species. The report noted about two-thirds of the nation's birds are threatened with extinction from climate change. However, if global temperatures drop, it will help up to 76 percent of those species.

"We're already seeing the impacts of climate change in the Great Lakes region on birds and people," said Nathaniel Miller, acting executive director for Audubon Great Lakes, based in Chicago. "Storms and rapid fluctuations of lake levels impact birds at the same time that they impact people That is multiplied in coastal and urban areas. Slowing global warming and investing in green infrastructure – like coastal wetlands – is a win-win solution that can reduce impact for birds and people. This can make all the difference for birds like the Piping Plover, which is already on the brink and has just started to make a recovery."

The study includes an interactive web tool that allows users to search their county for vulnerable species. The tool includes seasonal projections based on increases in average temperature increases of 1.5 degrees, increases of two degrees by 2050; and three degrees by 2080. Like early or late frosts, rising temperatures and shifting weather patterns impact the ability for birds to find food and reproduce.

In Oakland County, a projected 1.5-degree increase in summer temperature could raise vulnerability to Trumpeter swans and Henslow's Sparrows. However, doubling that temperature by 2080 could result in a dozen species being considered "high vulnerability species." Those species include the Eastern Whip-poor-will; Red-headed woodpecker; Wood thrush; Brown thrasher; field Sparrow; Savannah Sparrow; Henslow's Sparrow; Eastern Towhee; Bobolink; Ceulean Warbler; Pine Warbler and Scarlet Tanager.

The projections present even more challenges to several of the species that are already considered Species of Greatest Concern under Michigan's Wildlife Action Plan, which is created by the Michigan Department of Natural Resources (DNR) and provides a framework for conservation in the state between 2015 and 2025. That number of species on the greatest concern list has been reduced from 99 in 2005 to 45 in 2015.

Species currently on the list of greatest concern include: American bittern; Bald eagle; Barn owl; Black tern; Black-backed woodpecker; Black-crowned night-heron; Caspian tern; Cerulean warbler; Common loon; Common moorhen; Common Nighthawk; Common tern; Dickcissel; Eastern Red Knot; Forster’s tern; Golden-winged Warbler; Grasshopper sparrow; Henslow’s sparrow; Hooded warbler; King rail; Kirtland’s warbler; Least bittern; Long-eared owl; Louisiana waterthrush; Merlin; Migrant loggerhead shrike; Northern goshawk; Northern harrier; Osprey; Peregrine falcon; Piping plover; Prairie warbler; Prothonotary warbler; Red-headed woodpecker; Red-shouldered hawk; Sharp-tailed grouse; Short-eared owl; Spruce grouse; Trumpeter swan; Western meadowlark; Whip-poor-will; Wilson’s phalarope; Yellow rail; Yellow-headed blackbird; Yellow-throated warbler.

Species in Oakland County considered to have high vulnerability to climate change that are already included as species of concern by the Michigan Department of Natural Resources (DNR), include:

• The Cerlean warbler, which according to the Michigan Breeding Bird Survey is in significant decline. From 1966 to 2010, the survey shows an annual decline of 2.98 percent, with an estimated population in 2011 of 5,000 in Michigan. The core range of the species is in the Appalachian Mountains.

• The Henslow's sparrow, which is listed as Endangered, with an estimated population of 5,000 in the state. The Breeding Bird Survey data indicate an alarming decline of 9.39 percent annually between 1966 and 2012 in Michigan.

• The Red-headed woodpecker, which is listed as a special species of concern. Population estimates of the species in Michigan is about 7,000. While considered common, the birds are in steep decline across the range, according to the DNR.

• The Trumpeter swan, which is one of few species expected to be downgraded by both the Audubon Society and the DNR. The state's Wildlife Action Plan Technical Advisory Comittee recommended the Trupeter swan be down-listed from Threatened to Special Concern because their restoration goal has been exceeded and breeding distribution and numbers are slowly expanding statewide.

• The Whip-poor-will, which currently has population estimates of more than 100,000, but is undergoing a long-term declining trend, according to the DNR. Specifically, the species is losing parts of its range in the southern Lower Peninsula of the state, which includes Oakland County.

In the early fall, many of the more colorful birds seen during the summer months leave and head south, as far as  Central America and South America. Those include a wide range of small warblers, hummingbirds and others.

Landgraf said species like the Indigo Bunting, Baltimore orioles and others colorful species of hummingbirds are ones that birders particularly enjoy.

"It starts as a slow trickle and slowly all the birds leave in the fall, where spring is more of a big boom," she said. "Fall is a slower, longer process that ends about the end of October or a week or so into November."

It should be pointed out that while some species may be present year-round at local bird feeders, it's normal for those spending warmer months in Michigan to fly south for the winter with other northern birds of the same species heading to the state for the winter. For instance, blue jays may be seen throughout the year because some of those that leave may be replaced by those coming in from farther north.

"There aren't too many that actually overwinter in Michigan," Owen, with Michigan State University, said. "There are some that breed in the winter from the Boreal region, which is also being hit pretty hard with dramatic weather issues, so we see a huge fluctuation in food."

Shorebirds looking for wetlands and muddy areas tend to migrate through in the early part of the season or late summer, followed by raptors, such as Broad-winged hawks and Sharp-shinned hawks flying through the state. Dabbling duck species, like mallards, Blue-winged teal and American widgeon also head south in September, along with gulls and songbirds, like blue jays, warblers, thrushes and ruby-throated hummingbirds.

By October, diving duck species from the north start arriving in Michigan, such as the common goldeneye, long-tailed ducks, and canvasback. Other species, like northern finches and sparrows, like dark-eyed juncos, white-throated sparrows, white-crowned sparrows, pine siskins, with the potential for pine grosbeaks, evening grosbeaks, common redpolls and crossbills, according to the Audubon Society. Northern breeding birds, like ruby-crowned and golden-crowned kinglets, brown creepers, American pipits and horned larks also move south in October, with some warblers still on the move, including blackpoll warblers, black-throated blue warblers, Nashville warblers, orange-crowned warblers and yellow-rumped warblers. At the same time, hawk species increase in diversity.

Blanche Wicke, with the EL Johnson Nature Center in Bloomfield Township, said in early November that the 40-acre site serves as a stopover for migrating birds, making it a great spot for local birders during both fall and spring migration.

"Any little pocket of greenery among the pockets of highways are a stopover for birds, and we have a bird banding program in May," she said. "We get the common species during migration, and get almost all of the warblers."

Two of the more unusual species of warblers that have been observed at the nature center are the Golden-winged and Blue-winged species that pass through during migration.

"It does seem like things are starting a little later, but warbler migration is over," Wicke said. "Ducks are still migrating. Occasionally we have a Bald Eagle fly over, and see Sandhill Cranes a little more often. We did see an osprey, and have the occassional Peregrene falcon – not that they nest here, but they fly through."

By November, some sparrows are still moving, while northern diving duck and sea duck species are on the move, including Eiders and Long-tailed ducks, and rare gulls, such as the Iceland gull, Sabine's gull, while Franklin's gull are looking for open water. Audubon says Lapland Longspurs and Snow Buntings travel in peak numbers in November, while owls are making their way to the Upper Penninsula, including Northern owls, great gray owls, snowy owls, Northern hawk-owls and boreal owls, while rough-legged hawks and golden eagles are moving through the state in good numbers.

"Coming in are deep-water duck species," Landgraf, with the Detroit Audubon Society said. "They spend their breeding season farther north, in Canada and Alaska, and then for winter they come here. We are their warm area. You can see them along the Detroit River."

In terms of birding in the metro Detroit area, Landgraf said the majority of metro parks are good for viewing during the migration season.

"Anywhere with trees that have more native plants, which attract more bugs and berries that birds like to eat, such as Kensington Metropark, Lake St. Clair Metropark, which is nice and near the water where birds like to follow the coastline," Landgraf said. "For viewing ducks, you can go to Belle Isle or Grosse Isle when the ice starts forming. The ducks like when the ice corrals them together and they end up in big groups."

Barbara Avers, waterfowl and wetlands specialist with the Michigan DNR, said the department focuses migration tracking and conservation primarily on game birds. However, the department's Wildlife Action Plan includes species of concern. Further, the department monitors status of specific species of concern that have conservation plans associated with them.

"The biggest place migration comes into play is with waterfowl, and the waterfowl hunting season. We have interest there in what those migration movements are like, and that tells us best how to set the hunting season," she said. "It also informs hunters on when and where they want to go to harvest ducks and geese, so that information is pretty important."

The state's MI Birds Program is a public outreach and education program created by a partnership by Audubon Great Lakes and the Michigan DNR. With the majority of conservation funds in the state coming from hunting licenses, the program aims to bridge the divide between hunters and birders.

"The Wildlife Action Plan is the framework for conservation in public lands through the DNR, and it's dependent on hunters' money," said Erin Rowan, Program Associate with MI Birds. "Nearly half of the state's managed areas are managed by the DNR, or 54 of 103, so they are contributing to non-game species. They often act as an umbrella."

The MI Birds program conducts public talks and engages residents in stewardship activities and community science projects

With much of the waterfowl hunting season extending into late December, the DNR does weekly counts of the state's seven waterfowl hunting areas, as well as refuge areas that are closed to hunting.

"There is some good research and data showing migration is occuring later for some duck species, like mallards, with delays from anywhere from one week to two weeks," Avers said. "A lot of that is tied back to climate change and more mild conditions. We are seeing some evidence of that, especially in southwest Michigan, where we are seeing mallards peaking later in December instead of later in the fall. Duck hunters are seeing that and it's part of the conversation of whether duck hunting dates should be later."

Additionally, Avers said the department is seeing more long tailed ducks in Lake Michigan in recent years than in the past.

"We think they are responding to zebra mussels as a source of food in the Great Lakes. Something is shifting their distribution toward the Great Lakes."

Avers said other diving duck species are also shifting ranges over time, which is most likely related to zebra mussels. She said weather patterns also play a part in migration in the Great Lakes, as waterfowl typically look for open water and food availability when flying south. Likewise, hunting pressure can play a part on where waterfowl species stop for the winter

"If there's open water and food availability, they won't go any farther," she said. "All of that plays a role."

While zebra mussels are an invasive species that has helped the state's waterfowl populations, other non-native plant species can crowd out wetlands and nesting habitat, such as phragmites and non-native cattail species.

"Particularly for fall migration, we are interested in the role of invasive plants," Owen from MSU said. "They are easier to obtain than insects and it doesn't take as much energy to obtain, and it’s packed with nutrients and antioxidants. But not all food is the same. Invasives like honeysuckle, autumn olive and others are not good nutritional value for migratory birds, and they out-compete dogwood, elderberry and other plants with high energy potential, which make birds get fat faster. Birds want to get fat for migration. They have to put on a lot of fat to make those flights."

Likewise, agricultural changes play a role in migration and breeding patterns.

"How much corn is being grown in the Great Plains and prairies may be a factor. That's where the majority of dabbling ducks breed. That prairie area is like a duck factory, and we have seen changes where those are being tilled up and being planted with corn," Avers said. "The biggest threat to waterfowl habitat is climate change, invasive species and development, both industrial, commercial and agricultural. Oil and gas exploration can be a problem where some waterfowl are nesting."

Agricultural shifts also are one of the greatest threats to grassland birds species. As such, the Audubon Society focuses much of its conservation efforts on those areas.

"It's kind of a tricky. People see flat areas without a lot of trees and think we have to build or turn it into something, but that's just as important as forest or wetland. It's still a habitat," Landgraf said. "We have destroyed so much of it because it's easy to build or farm, but there are many birds that depend on it."

Landgraf said species such as the Eastern bluebird, Bobolink, Dickcissel and Eastern meadowlark have been in decline in Michigan for quite some time. She said conservation efforts, such as Detroit Bird City, which partners with MI Birds and Detroit Audobon and others, is working to restore some of those habitats.

"They are working to take underused parks in Detroit and make them into green spaces that are nice for people to use and are very beautiful. They also provide habitat for birds," she said. "Those areas take care of themselves and don't need much upkeep, so the city saves time and money, and it acts as a meeting space and habitat for birds."

The declining trend of grasslands is evident across the state, and is in line with national and global trends, said Linnea Rowse, conservation program coordinator with the Michigan Audubon Society.

"Grassland birds aren't doing very well as a whole, and that includes a handful of birds," she said. "A lot need well-maintained grassland habitat that isn't broken up by woodlots or shrub areas. Those birds have developed for thousands of years with open grasslands, so the smaller parcels don't have the contiguous habitat they need."

While declines in bird populations have been apparent to amateur and professional birders for decades, advances in machine learning technology coupled with weather radar data is helping to put hard data numbers behind various local, state and national bird counts done by the eye.

Andrew Farnsworth is a research associate with the Cornell Lab of Ornithology and helps to run BirdCast, a forecasting system able to predict where and when birds will be thanks to the use of weather radar. The project also is able to utilize archived weather data to track long-term changes.

"The radar technology has been around for some time. It's almost 100 years old. The thing that took it to the next level and allowed you to think about it from what's happening from a biological aspect is machine learning and cloud data to track bird movement in real time. The United States has a unique situation in that the government has been archiving this data for 25 years, so it's been around a long time, but only really recently has there been an, 'oh wow moment,' where we can really do something with this data and track some meaningful patterns.

"People have envisioned it for the past 20 years, but the realization has been in the past 24 to 36 months."

The technology played a significant role in the "Decline of North American Avifauna" study, which was headed in part by the Cornell lab. Farnsworth said the data corroborates the patterns of deep decline in bird populations, particularly those in the western United States. The data shows conclusively that what has been "known" by hobby birders by quantifying the data for the first time.

"It's really a treasure trove of biology, and that's the big part of the next couple years of digging into that data and producing as much science as we can," he said. "By looking at the detail of radar data with citizen data, and acoustic data about movement at night, then integrating them, it tells you about biomass, and acoustics can tell you what species are up there."

By coupling longtime observations with quantifiable data, Farnsworth said scientists hope to produce compelling data that will result in stronger conservation efforts on the national level.

Stephanie Beilke, conservation science manager for Audubon Great Lakes, said the chapter and national Audubon Society is pushing for renewal of the Recovering America's Wildlife Act, which could provide dedicated wildlife conservation funding at a national level. In total, the bill, which was introduced by Michigan Congresswoman Debbie Dingell, would direct an annual $1.3 billion to states to help stem population declines in some 12,000 species of fish and wildlife, including 800 birds.

"A lot of local policies have gone into protecting game species, and there's a reason for that because we make money off of selling hunting and fishing licenses," Beilke said. "Unfortunately, we have less money to protect other species that aren't funded. Others can benefit from conservation of game species, but some of the species of concern on the state plans don't recognize that. A federal plan wouldn't be just for game species."

Turning to Michigan and the northern part of the country, Farnsworth said a soon-to-be released peer-reviewed paper is expected to  utilize the data to show quantifiable shifts in the timing of migration, and how the timing has changed over the past two decades.

"What is very clear is that timing should advance as warming temperatures happen, and not at an even distribution across the landscape," he said.

Farnsworth said researchers are learning that climate change won't be evenly distributed, and that changes in Michigan and other northern latitudes and advances of spring migration timing occurring earlier is one of the things we can say and point to the data.

"You hope the science is enough to shape policy because you can't argue what the truth is. You have these methodologies and the scientific method. When you can produce a peer-reviewed study, it's science that you should base some policy on," he said. "The U.S. had been making progress toward environmental regulations on a large scale, and the hope is that in light of these kind of studies, it would reinforce that. But, I'm just here to provide the information, where it goes from there – we hope it goes to that end.

"It's a fascinating time. It's almost a golden observation age that hasn't happened since the advent of binoculars."

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