What Happened to North America's Birds?

The United States and Canada have lost over 3 billion birds in the last 50 years. What is causing the emptying of our skies?

A gaggle of Canadian geese marches across a bike path in Chicago, Illinois.

Over 50 years ago, environmental author Rachel Carson helped launch the environmental movement with her landmark book, Silent Spring. Concerned with the increasing use of pesticides in our everyday life, Carson predicted the negative environmental impacts from the spraying of potentially toxic chemicals. One of her key predictions was eradication of the bird population, resulting in eerily silent springs. Unfortunately, her premonitions were spot on.

This week, a study in the journal Science reported that bird abundance in North America has decreased 29 percent since 1970. To add some context, three billion less birds soar through our skies today than fifty years ago. According to the study, the amount of birds migrating through North America has similarly dropped in only the last 10 years. The disturbing disappearance of birds appears to be a canary in a coal mine for future ecological disaster if things do not drastically change.

A lone black-crowned night heron in Wilmette, Illinois.

So what caused this severe decrease in birds? The driving cause is habitat loss. The study estimates that forests alone have lost nearly one billion birds as they are cut down in the name of progress. Birds of the plains, like the greater sage grouse, have seen their populations cut in half. The use of pesticides is also a major factor, as it was in Carson’s day. Many birds act as natural pest controls and often eat consume the poison in their food. Certain pesticides, such as neonicotinoids, also decrease a bird’s ability to put on weight, something that is vital before long migrations.

A red-winged blackbird looks for food in Chicago. Keep a look out for these guys when on a run or a bike ride in a forested area—they are very aggressive during nesting season and will swoop down to scare people that venture too close.

The deeper you dig into the results of the study, the more dire the situation seems. The study analyzed the populations of 529 bird species through the use of radar images and the largest collection of long-term-monitoring surveys ever used for one wildlife study. Surprisingly, the birds we see at our bird feeders everyday, like sparrows, warblers, blackbirds and finches, were hit the hardest. The population of white-throated sparrows declined by 90 million while the population of red-winged blackbirds declined by 92 million. Two out of every five Baltimore oriole has disappeared since 1970.

A hummingbird feeds at a feeder in Los Angeles, California.

Interestingly, some groups of birds have increased their populations in the last 50 years. Hawks and other raptors have tripled their populations, thanks to the ban of harmful pesticide DDT that would often work its way into the raptors body from their prey. The pesticide contributed to incredibly thin egg shells and almost resulted in the extinction of raptors last century. The other big winners over the last 50 years are waterfowl who have experienced a 50 percent increase over the period studied. The biggest reason why their populations have grown are initiatives for the preservation of wetlands, highlighted by a federal no-net-loss wetlands policy.

Ducks and other waterfowls are one of the only groups of birds that have experienced an increase in population size thanks to renewed efforts to preserve wetlands. Picture taken in Easton, Maryland.

But the overall results of this study are incredibly negative, especially when combined with the dramatic drop in the United State’s amphibian population. A similar study, published in 2013, found that the country’s populations of frogs, toads and salamanders was decreasing 3.7 percent each year on average. Alarmingly they could be erased from half of their habitats in as little as 20 years. The combination of the loss of amphibians and birds point to an ecological crisis that is taking place across our continent right now.

But there is still time to act as 70 percent of the continent’s birds are still around, but measures must be taken immediately to protect them. Habitat will need to be protected as greater care is taken in building design to prevent the 100 million birds that die from flying into windows each year. Simply using patterned glass and turning off the lights at night go a long way in making a building less dangerous to migrating birds. Carson was also extremely prophetic in predicting that pesticides could one day silence the world’s springs. Banning the use of harmful chemicals will go a long way to preventing further eradication of majestic bird populations who soar through our skies.

A Cooper’s hawk perched on shingles in Wilmette, Illinois. Cooper’s hawks kill other birds by grabbing them with their sharp talons and repeatedly squeezing its feet.

All photographs by Jack Tamisiea

Sources:

https://science.sciencemag.org/content/early/2019/09/18/science.aaw1313

https://www.nytimes.com/2019/09/19/science/bird-populations-america-canada.html

http://news.cornell.edu/stories/2019/09/nearly-30-birds-us-canada-have-vanished-1970

https://www.rachelcarson.org/SilentSpring.aspx

https://blogs.scientificamerican.com/extinction-countdown/amphibians-declining-alarming/

https://www.theguardian.com/environment/2019/apr/07/how-many-birds-killed-by-skyscrapers-american-cities-report

Alien Invasion

Examining the rapid takeover of Australia by the cane toad and its invasive brethren.

A cane toad poses next to a vanquished foe — a species of goanna with a mouthful of poison.

Cane toads were introduced onto the continent of Australia for one simple reason in 1935 --- to control the cane beetle population. It was easy to see why farmers clamored for a natural solution to the cane beetle predicament as cane beetles were destructive pests to sugarcane crops. Adult cane beetles ate the leaves of the crops while cane beetle larvae ate the roots, potentially killing the entire plant. At the time cane toads seemed like a logical, and less destructive, alternative to harmful chemical pesticides. But those who decided on the introduction of the large, toxic toads failed to take into account two glaring problems which thwart their ability to effectively serve as pest control agents against cane beetles --- The stocky toads do not climb (making it difficult to feed on the arboreal cane beetles) and cane toads are nocturnal, while cane beetles are diurnal. Now Australia is stuck with more than 200 million introduced toads and cane beetles.

Cane toads (Rhinella marina) are native from South America up to the southern U.S. In their native ranges, the toads populations are kept in check by an assortment of predators capable of tolerating the toad’s poison that is produced in two large large parotoid glands behind the toad’s ears. This poison is spread throughout their bodies and can be secreted from the parotoid glands as a milky, white substance. The deadly cocktail of toxins produced by the cane toad targets the functioning of the heart. When these toads were introduced to Australia, this new poison knocked every Australian predator, from venomous snakes to large goanna lizards and even beloved pet dogs and cats, back on their heels.

In addition to being a hopping toxin-producing machine, cane toads possess several other tools that make them a particularly destructive invasive species. The toads are voracious eaters, and will eat anything they can get their wide mouths around (except cane beetles, of course) and have outcompeted several insectivores, such as native skinks, in addition to depleting populations of native insects. They breed quickly and in almost any source of water. Even their tadpoles and eggs are poisonous to most animals.

Around 3,000 cane toads were released in northern Queensland in 1935 and they have spread like wildfire throughout the eastern and northern coasts of Australia. Moreover, their range is continuing to expand as they order their populations forth. Cane toads have even been found on the far-flung southwest corner of the continent. And they are not content with just Australia, either. They have been found in New Guinea and up into the Philippines. With their destructive traits, cane toads may circumvent the globe and arrive back in South America in a matter of decades.

The spread of the durable and leathery toad is not an isolated incident for Australia. The continent has been ripe for the spread of invasive species since Europeans arrived in the late 1700s. Australia’s isolation from most of the world, since its break from Antarctica about 35 million years ago, has produced a variety of incredible endemic species and allowed marsupials to dominate while being outcompeted by placental mammals (more advanced group of mammals including humans) everywhere else on earth. But this isolation has left the continent susceptible to outside invaders completely alien to native wildlife.

The most destructive invasive species have been nondescript species such as feral cats and foxes. Over the two centuries these European animals have been on Australian soil, at least 34 mammal species have gone extinct, giving Australia the dubious distinction as the world’s leader in mammal extinction. Most of these species are smaller-sized marsupials, like the lesser bilby or the beautiful toolache wallaby (who only survived 85 years of European colonization), that are the perfect size for cats and foxes to prey upon. Cane toads are extremely destructive and difficult to eliminate, but feral cats are a whole different story. The cuddly felines are one of the only animals known to kill for sport, creating depressingly steep kill totals of Australia’s small mammalian fauna.

Although these invaders may seem too staggering in numbers and destruction, there are several measures being undertaken by the Australian government to attempt to rid the continent of these dangerous aliens. Large-scale cat culls are underway throughout Western Australia, including an initiative to drop crate-fulls of poisoned sausages to the two to six million cats that live there.*

Intensive fox eradication programs have been undertaken on many islands, whose contained settings offer the only real chance of eliminating the elusive predators. On Phillip Island, off of Victoria, foxes have been successfully removed from the island in recent years. The bridge between the mainland and the island, the only way on and off the island for anything that does not want to get wet, is under constant surveillance to make sure no fox is able to sneak back on the island. Their eradication on Phillip Island has led to the reintroduction of the Eastern barred bandicoot, which has gone extinct in the wild because of foxes. In 2017, 44 captive bred bandicoots were released on the Summerland Peninsula, itself a symbol for effective conservation implementation. Hopefully the bandicoots can recoup their population on the island away from the threat of foxes.

The management of cane toads will take a concerted team effort by people all over Australia. In southern Australia, quarantine checks for the deadly amphibian, as well as education programs, have helped to curb its spread into the region. If a suspected cane toad is seen, the best outcome would be to capture the toad and report it to the nearest Parks office, as 2/3 of suspected cane toads end up being native frog species. Oftentimes these native frog species are harmless and themselves cane toad victims due to diseases the South American toad spreads.

Cane toads, foxes and cats, along with many invasive species of plants, are incredibly well-equipped and destructive invaders. It will take decades to wipe them out and save Australia’s unique wildlife, and even that may not be enough as these animals become more engrained in the Australian ecosystem. But progress is possible and needs to start right now in order to help Australia lose the title of being the global extinction capital and chart a new path towards saving the vulnerable local wildlife under siege by these ruthless invaders.

*Because cats, beloved pets to some and brooding houseguests to others, are the target of this mass culling, many public figures decried the decision. More than 160,000 people signed online petitions to prevent the killings of the cats, even as they wipe out species after species. Educated public outcry can be beneficial, but there clearly was a lack of understanding about the cats’ destructive capabilities. Thankfully, the Australian government persevered and proceeded with the plan, which killed 211,560 cats during the first year of the program and aims to shrink the population by 2 million cats by 2020.

Sources:

https://www.nationalgeographic.com/animals/amphibians/c/cane-toad/

https://australianmuseum.net.au/learn/animals/frogs/cane-toad/

https://phys.org/news/2018-04-australia-mammal-extinction-worsen-scientists.html

https://www.nytimes.com/2019/04/25/magazine/australia-cat-killing.html

https://www.penguins.org.au/conservation/research/eastern-barred-bandicoots/