Climate Change, Habitat Degradation Have An Effect On Non-Waterfowl Migrating Birds In Louisiana Too
story by Trey Iles, LDWF Public Information
photos by Michael Seymour, LDWF Ornithologist
It’s a term that will send you to the dictionary but once you understand the meaning, it sheds light on how climate change can alter the life cycle of species throughout the world. Phenology is the study of cyclic and seasonal natural phenomena primarily in relation to climate and animal and plant life.
The term phenological mismatch is often used by wildlife biologists to describe the interaction between the timing of resource availability and the life cycle of animals. That is, if the availability of food resources does not align with an animal’s need for those resources, negative consequences on reproduction and survival could result.
Because many of the alterations occur at different levels of the food chain, some animal species will be negatively impacted more than others while some will likely benefit.
One easy way to consider this is how azaleas bloom in Louisiana. If the state experiences a rather mild winter, azaleas begin budding as early as the middle of February. These early blooming azaleas could be out-of-bloom by the time many families are taking their annual Easter photos, if Easter is, say, in April. The effect in this example, or course, pales in comparison to impacts felt by the natural world.
For animals, the impacts can be far greater than a missed photo op. A warmer winter could mean the early flowering and fruiting of plants upon which many insects and other pollinators rely to survive.
If the warmer weather affects the plants at a different magnitude, or rate, than the insects that pollinate them there could be detrimental impacts to both the plants and the insects. This would likely lead to declines in both the plants and their associated pollinators.
If, however, insects emerge, equivalent to budding out in plants, early from winter inactivity animals that feed on those insects will likely experience a disruption in their life cycles. Alterations in timing of resource availability can be particularly detrimental to nesting and migrating animals.
Michael Seymour, an LDWF biologist supervisor and an ornithologist, shares similar concerns with other biologists.
“During nesting season, many of our birds, even ones we would think of as seedeaters like northern cardinals, require insects to feed their developing chicks,’’ Seymour said. “In fact, according to University of Delaware entomologist Doug Tallamy, Carolina chickadees feed more than 5,000 insects to each clutch of young. A shift in insect emergence could lead to the loss of some of our most common and beloved birds.”
But insects are seemingly omnipresent in Louisiana, a truth well known to duck hunters fending off mosquitos during their winter hunts.
Could the birds simply eat other species of insect? Unfortunately, not all insects are created equal. For example, several species of insects produce toxins. And even if palatable, other species may not provide similar levels of nutrients, leading to increased energy usage for less return on the investment.
The prevalence of invasive exotic insects and other organisms typically makes matters worse as invasive species often can spread unchecked and can outnumber native species. Exotic invaders may replace native organisms but may be far less suitable as a food resource.
When considering the effects of climate change on the spread of many invasive exotic species and their impacts to ecosystems, the disparity can become compounded and even more troubling.
Like migratory waterfowl, migratory nongame birds have changed their migratory timing and patterns, too.
Neotropical migratory land birds migrate from breeding grounds in North American to wintering grounds in Central and South America. This varied suite includes diverse birds from cuckoos to warblers, which have shifted arrival and departure times due to temperature change with earlier arrival to nesting grounds in spring and later departures in fall.
Although this would indicate a longer breeding season for such birds it could also indicate that mismatched phenology of food resources is causing the birds to stay longer than needed, decreasing the birds’ chances of finding suitable wintering territories.
Seymour said that because so many migratory bird species and individuals use Louisiana as a stopover and refueling point, our state is particularly well positioned to boost resilience of birds as they attempt to adapt to climate change. Conservation and restoration of coastal forests would be one such benefit to birds as well as people.
As you might expect, migration is a challenging process for birds. In fact, Seymour said it can be the most dangerous time in the life cycle of a bird. One of the keys for successful migration is getting enough energy for the trip. High quality habitat and its distribution on the landscape play important roles in ensuring proper provisioning.
“If the distribution of habitat changes due to climate change, for example, there could be an increased distance between suitable breeding and nonbreeding areas which means an increase in energy need,’’ Seymour said. “That energy need may be difficult to fulfill if there are significant changes in food availability due to climate change and the resulting mismatched phenology.”
And those non-waterfowl birds are oftentimes guided by internal wiring that alerts them when it’s time to head south and what routes to take.
“With longer lived birds like waterfowl and cranes, the adults teach the young their migratory routes,’’ Seymour said. “When it comes to species such as songbirds like warblers, it’s ingrained into their genetics where to go. They have an internal map that guides them. They’re wired to do that.’’
So if climate and habitat change have altered the landscape, how quickly can those birds adapt? It’s something ornithologists are observing closely.
“Some of them likely will be able to adapt even if habitat shifts significantly,’’ Seymour said. “Others may not be able to adapt as quickly.’’
Mitigating adaptation is likely linked to the distance of travel between seasonal locations and to whether or not migratory routes are learned or genetic.
Something else impacting neotropical migratory birds is the severity and frequency of storms over the Gulf of Mexico whether they be tropical or temperate in origin. Birds migrating over the Gulf can end up in the crosshairs of a hurricane or a strong spring cold front.
“It’s fairly safe to say we’re seeing more violent tropical storms and there is evidence that we could be seeing an increase in their frequency,’’ Seymour said. “Storms occurring over the Gulf during peak migration can be catastrophic for birds.
“In spring, many neotropical migratory birds leave the tip of the Yucatan Peninsula at sunset. They leave at 6 or 7 at night and fly, for example, to Grand Isle, where they show up at 1 or 2 p.m., about 19 hours of flight time. But if they’re flying over the Gulf and a spring storm comes through, you’re talking significant mortality, potentially hundreds of thousands of birds.’’
In fall, tropical cyclones, particularly in the Caribbean, can result in substantial losses of birds, too. Many of North America’s birds migrate south off the tip of Florida in fall and several species winter on Caribbean islands.
With their vast resources, states bordering the Gulf of Mexico, including Louisiana, remain a critical destination and stopover point for many migratory bird species. One study by Mehlman and colleagues broke migratory bird stopover sites into three categories that the casual observer could readily understand; convenience stores, full-service hotels and fire escapes.
A convenience store was compared to New York’s Central Park, a small area of forested habitat surround by inhospitable habitat. The idea is that birds facing otherwise adverse conditions can stop in, get some food, rest briefly then be on their way.
A full-service hotel provides plenty of food and ample rest opportunities. The Atchafalaya Basin in Louisiana is one of the few places in the southeast United States that acts as a full-service hotel.
The final type, the fire escape, is just what it sounds like, a place used in emergency conditions. A fire escape isn’t used continuously but its presence on the landscape is absolutely crucial to survival.
In fire escapes, birds can hunker down should conditions warrant it such as in strong spring storms over the Gulf. Louisiana’s coastal forests, its cheniers and barrier island forests, supply these fire escapes.
But Louisiana’s coastal habitats have shrunk significantly through the years. And as buffering coastal marsh is lost to sea level rise, subsidence and more violent storms, so too is the state’s coastal forest. Present-day acreage of coastal forest is only 1-5 percent of what occurred pre-settlement in Louisiana according to the Louisiana Wildlife Action Plan.
“It’s very simple,’’ Seymour said. “If we lose our coastal woodlots we will lose our birds. It’s a sobering thought. But in addition to active habitat management, bird scientists are directing their collective focus on understanding these critical needs while filling data gaps that would otherwise hinder conservation.’’
Technology to track migratory birds has vastly improved since the 1960s when VHF transmitters were first placed on animals. The transmitters, or tags, have become more powerful, more versatile and much smaller, allowing biologists to study the migration of birds that would have been unable to carry a tag just a few years ago.
The data are providing them with previously unknown, sometimes surprising, information. But there is still much to learn.
With the state’s Coastal Protection and Restoration Authority and LDWF leading the way, the state is working to improve habitat.
The state is using in excess of $4 billion in National Resource Damage Assessment, or NRDA, funds to restore coastal and nearshore habitat. About $148 million of these funds are earmarked for bird habitat. The money is all from the 2010 Deepwater Horizon oil spill settlement and will be distributed over 15 years.
“The bird funding will focus several species of birds that were heavily impacted by the BP oil spill,” said Todd Baker, LDWF’s Coastal Resource Scientist Manager. “An initial focus will be on colonial nesting waterbirds such as brown pelicans, egrets and herons.”
Other projects will focus on building habitat for several species of secretive marsh birds and mottled ducks. These projects will benefit Louisiana’s year-round resident birds such as rail, gallinule and seaside sparrows as well as a multitude of migrant birds of the same species plus many additional ones.
Habitats that are a primary focus for restoration include many habitats that are identified in Louisiana’s Coastal Master Plan and provide tremendous benefits for wildlife including barrier islands, coastal-forested ridges, colonial nesting islands and marsh.
One recently completed project, utilizing early restoration funding from the BP oil spill, is the restoration of Whiskey Island, the Caillou Lake Barrier Headland Restoration Project. This island is part of the Isle Dernieres Refuge located in Terrebonne Parish.
It’s designed to provide defense from tropical storms but an added benefit is the habitat it provides birds year round.
“The beach built there has already benefitted a lot of black skimmers and least terns which nest there,’’ Baker said. “Additionally many migratory birds, such as sand pipers, plovers and a host of other shore birds and wading birds were utilizing the new restoration project this past winter.’’
Two additional projects are also in the works. The restoration of Queen Bess Island near Grand Isle in Jefferson Parish is set to begin construction. Rabbit Island, located in Calcasieu Parish, is in the design phase and may be under construction in 2020. The star of the show in these projects is the brown pelican, a species that has recovered since its disappearance from Louisiana in the 1960s because of the pesticide DDT.
While brown pelicans will benefit from these two projects, the designs include features that will benefit more than one single species. These islands will provide critical nesting habitat for a number of bird species that are in decline across the Louisiana coast.
“Loss of our coastal wetlands equates to habitat loss for many species of wildlife and fisheries,’’ Baker said. “Species that live in the coastal zone and migrate there have suffered. The state is making a serious push to restore, preserve and improve those habitats so that our children and grandchildren can enjoy the wildlife, fisheries and wetlands that we have today.’’
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