By Jon Friedman
Yellow-billed Cuckoo- a Threatened Species *
Photo by Dan Pancamo
Over the years, I have used the phrase “conservation status” in numerous conversations and written articles. While this phrase may sound steeped in scientific vocabulary, it simply and basically means understanding and gauging the population dynamics of any given species. What are the factors that determine whether the species population is shrinking, remaining the same or becoming enlarged? Understanding the “why” and “what” these factors represent help us measure our appreciation of the larger nature of the issues involved in conservation and determining conservation status.
Wikipedia defines “conservation status” generally as whether any species continues to exist and how likely that species is to become extinct in the near future. “Many factors are taken into account when assessing conservation status: not simply the number of individuals remaining, but the overall increase or decrease in the population over time, breeding success rates and known threats. Various systems of conservation status exist and are in use at international, multi-country, national and local levels as well as for consumer use.”
Red List Categories of Classification
Several categories of conservation status are used to quickly define the status of any species being examined. In short order, they are: Extinct, Threatened and Lower Risk. Within the extinct category, there are two classifications - Extinct (EX) and Extinct in the Wild (EW). In the Threatened category, there are three classifications – Critically Endangered (CR), Endangered (EN) and Vulnerable (VU). In the Lower Risk category, there are also three classifications – Near Threatened (NT), Conservation Dependent (CD) and Least Concern (LC). Two other categories exist, although they are rarely noted, for obvious reasons. They are Data Deficient (DD) and Not Evaluated (NE).
Through the scientific methods of data gathering and analysis, research, and field projects; as well as through advocacy and education, the International Union for Conservation of Nature (established in 1948 as the International Union for the Protection of Nature) strives to “influence, encourage and assist societies throughout the world to conserve nature and to ensure that any use of natural resources is equitable and ecologically sustainable”.
Red List Overview and Maintenance
The IUCN has evolved and developed the world’s most comprehensive inventory of the global conservation status of biological species. Its well-regarded “Red List” is recognized as the most authoritative guide to the status of biological diversity in the world today. Lists for all regions, countries and locales worldwide, and the above-mentioned categories of classification serve to describe any given species in relation to becoming extinct, or not. IUCN re-evaluates all species in question every 5 to 10 years. This is done in a peer-reviewed manner through their Species Survival Commission (SSC) Specialist Groups, which are the Red List Authorities, responsible for assigning classifications and recommending action when and where needed, for all threatened or endangered species concerned.
Most of the conservation threats that birds specifically, and wildlife in general, must deal with are caused, either directly or indirectly, by the decisions, actions and consequences of humans interfering with the natural order of the wild world. Persecution by humans, such as hunting, pose far less of a problem nowadays than in the past. For example, the extinction of the billions of passenger pigeons, thought to be 40% of the world’s living animals in the late 19th century, was a direct result of hunting, human encroachment and expansion into what were wilderness areas that encompassed their habitat and range. In addition, as humans have altered habitats, they have changed the distribution and abundance of many species, allowing predators, brood parasites and introduced invasive species to adversely affect the lives of native birds.
Southwestern Willow Flycatcher- a Federally-endangered subspecies of the Willow Flycatcher *. Endangered due to habitat loss.
Photo by John Hoffman
Total habitat loss is one of the most devastating problems for birds, and all wildlife. This problem can be found worldwide, not just limited to North America. As human populations grow and continue to expand, the increasing numbers of people range further to settle into wild areas. Moreover, as wild areas themselves are fast disappearing, humans are taking over and converting what’s left of the wild country (e.g., prairies, wetlands, coastal areas, forests, grassy hill country and mountain foothills, etc.) into human-designed habitat, while forcing the native birds and wildlife to seek suitable living conditions elsewhere – if any exist!
In mid-America, 99% of the tallgrass prairie has been lost to factory farming and mono-agricul-tural pursuits. Across the continent, wetlands have disappeared due to water diversion for use by cities and towns as well as large-scale agriculture. Wetlands also are drained and filled in to provide new developments for human residences and businesses. More than half of America’s wet-lands have disappeared within the last 200 years; less than 10% of California’s wetlands remain intact today. The loss of natural forests and the introduction of tree farming (Christmas trees and lumber for building materials) further degrade the natural higher diversity of the lost habitat. The loss of sand dunes, beaches and barrier islands to human development and expansion along the coasts is another example of our human shortsightedness when it comes to habitat loss. There are too many other examples to outline here, but I am sure everyone can think of other examples they have personally experienced.
Habitat Fragmentation – Patches and Edges
When humans extend their cities and towns into adjacent habitat due to growth and development, the avian and wildlife communities are impacted as well, unfortunately, all too often, for the worse. The expansion into what was previously natural or wild habitat now creates smaller patches of habitat and more “edges” between old and new habitat. This type of habitat fragmentation creates serious problems for birds and wildlife in general. Natural courses of travel are interrupted or disappear altogether. This affects courtship, nesting and breeding negatively. Patches of habitat isolate some members of particular species, preventing growth in numbers. Increased patches also means increased edges between habitats, further eliminating needed conditions that enable birds to flourish in numbers.
When habitat is fragmented, the locations where the old and new habitats meet are referred to as newly created “edges.” While some species may benefit from this type of occurrence, it is likely that more species are negatively impacted. Abiotic conditions may be created where they did not exist before. Increased predation usually results as predators now have increased access to the more interior parts of the patches from the newly created edges. Brood parasitism also increases for similar reasons.
Research has proven that changes in abiotic conditions, like noticeable temperature or wind increases/decreases near edges, affect the availability of food and nest site suitability for birds of the forest interiors. The density of insects in the leaf litter near forest edges becomes reduced causing food shortages for birds that depend on leaf litter-dwelling insects. This type of abiotic effect can extend hundreds of yards into fragmented habitat. As a result, small patches of habitat may become entirely subject to edge effects.
Habitat changes have benefited some species, particularly the brood parasites such as the cowbird and cuckoo families. While the human-caused changes in habitat may help those species, those changes in habitat may be particularly devastating to the species that invade songbird nests. For example, Brown-headed Cowbirds tend to parasitize all the nests of certain species within fragmented habitat. Some host species can recognize and destroy the cowbird eggs they discover in their nests, but others, such as the endangered Kirtland’s Warbler, do not. Ornithologists, for years now, have been trying to stabilize the Kirtland Warbler numbers by trapping, shooting or otherwise removing cowbirds form the critical and sensitive nesting areas.
In modern times and recent years, there has been an increase of many mid-sized bird predators as the larger predators, wolves and bears, for example, have seen their populations significantly reduced. As a result, there are many more coyotes, raccoons, skunks, crows, snakes; and feral dogs and cats have seen their populations explode, especially near human developments where crops and garbage enable them to thrive year round. These predators stalk not only adult birds but also chicks and eggs still in the nest.
Introduced and Invasive Species
Today, Florida in general, and the Everglades more specifically, provide an excellent example of how invasive and introduced species wreak havoc on the natural habitat. Although the Everglades have been negatively affected by the expansion of sugar cane plantations; the draining and filling in of large areas for human development; and the crisscrossing of hundreds of miles of canals; one of the most dangerous and immediate threats to the ecology of the area comes from the introduced invasive species that have now established themselves firmly in that specialized environment. Escaped or abandoned pet snakes, like boa constrictors and a variety of pythons, have proliferated greatly and are now threatening many native species of birds, reptiles and mammals with extinction.
Invasive species such as Zebra Mussels, Asian Carp, exotic grasses and plants all have negatively impacted native species and altered the natural harmony of the affected environments. Introduced exotic birds, such as the Mute Swan, have been displacing native water birds from both breeding and foraging sites. All across the Sunbelt regions, from southern California to southern Florida, native birds and wildlife are being displaced. I wrote an article last year about the large mixed flocks of parrots that now inhabit quite a few towns and cities in Southern California. We were staying in El Cajon for a few days, and while I did enjoy seeing many hundreds of parrots, I noticed a dearth of local native birds that I would have otherwise expected to see. This experience, this phenomenon is quickly becoming more commonplace in locations like Tucson, Phoenix, Las Vegas, Los Angeles, San Diego, El Paso and numerous other sites.
Even exotic grasses, plants and seeds, transported on the soles of our shoes, can replace native plants and grasses on which the native birds and wildlife depend. When food sources disappear, the animals that depend on those food sources may also disappear. Introduced exotic insects, like pine and bark beetles, threaten forests with devastating wildfires; introduced grasses, such as buffle grass, threaten even desert habitats with uncontrollable brushfires; introduced parasites and diseases continue to threaten whole bird populations; white-nose disease, imported from Europe, has been spreading westward across the continent’s bat caves and colonies, killing up to 99% of the infected bats; the list goes on and on. As human travel and world trade create a “smaller world,” more and more exotic and introduced species will create new threats to our en-vironments.
A wide range of pollutants threaten and damage bird populations around the globe. Oil spills, whether accidental like the Deepwater Horizon in the Gulf of Mexico or the Exxon Valdez incident in pristine Alaskan waters and coastline, or intentional, like the flushing of oil tanks on tanker ships, certainly take their toll on a daily basis.
Rachel Carson’s publication of Silent Spring, 50 years ago, foretold of the dangers of pesticide poisoning that nearly caused the mass extinction of many of our prized raptor species, in particular. Our national symbol, the Bald Eagle, suffered tremendously. So did Golden Eagles, falcons, Ospreys, and numerous other species.
Many industrial chemicals have found their way into our sensitive natural habitats and may go unnoticed for years before being recognized for the serious health threats that they actually are. Wherever people tend to congregate, pollutants are abundant. Sewage plants, landfills, large livestock farming operations, paper and lumber mills, mines, factories, and vehicular traffic only represent a fraction of the pollution daily. Most living things, like birds and people, that are ex-posed to these pollutants, find there are not positive gains that result.
Chemical pollution can damage and kill in many ways. Chemical pollution can lead to too-thin eggshells, travel up the food chain, affecting all living things along the way, and disrupt reproductive hormones, causing breeding failure. Heavy metal contamination and lead poisoning claim the lives of many water birds and the predators of those birds.
Even light pollution causes serious problems for night-migrating land birds and nocturnal seabirds. These birds collide with lit-up structures, such as buildings, bridges, and lighthouses. Even electric billboards will summon birds to their deaths.
In modern times hunting is no longer a serious issue as it affects bird populations. Hunting was responsible for steep declines of many populations of birds and was a major cause of the extinction of the Passenger Pigeon. ( See Demise of the Passenger Pigeon #1, Demise of the Passenger Pigeon #2, Demise of the Passenger Pigeon #3 by Jon Friedman)
The plume trade in the world fashion centers caused the extinction of several species and nearly several others. Several duck species were nearly wiped out, but the sale of duck stamps and hunting licenses help to save those species. (See Feathers #2 The Plume Trade)
We are now just beginning to understand the effects climate change will have on the planet and all its inhabitants as we move forward in time. Birds have dealt with climate change in the past, but we are experiencing it now on an accelerated pace as a result of human burning of fossil fuels. Its effects are wholesale and non-reversible. As the planet warms, plants and animals will have to migrate in order to be able to continue to exist. Hummingbirds in the Andes, for example, will have to adapt to higher elevations in order to survive. (See: https://www.ny-times.com/2018/09/21/climate/andes-saving-hummingbirds.html)
Polar birds and animals may cease to exist in the wild. With each passing year, we will be learning the devastating effects of climate change. I think, this is the biggest problem facing all living things on the only planet we can occupy. In a sense, we are all like the canary in the coalmine.
*More information on Threatened and Endangered species status: