Thursday, December 30, 2010
Rusty Blackbird populations have been declining precipitously throughout their range, and the causes of these disturbing trends are not yet entirely understood. Rusties feed singly or in mixed flocks during the winter in the southern U.S., often occurring with other species that are considered pests. The Migratory Bird Act allows take of blackbirds, cowbirds, grackles, crows, and magpies when individuals are “found committing or about to commit depredations upon ornamental or shade trees, agricultural crops, livestock, or wildlife, or when concentrated in such numbers and manner as to constitute a health hazard or other nuisance.” Although Rusty Blackbirds do not appear to have an impact on crops, they can become victims of control efforts aimed at other species, particularly at night roosts. The impact of control efforts on Rusty Blackbird populations are unknown.
In response to Rusty population declines, the U.S. Fish and Wildlife Service recently removed Rusty Blackbirds from the list of species for which take is allowed "because of long-term evidence of population declines throughout much of their range." A depredation permit is now required to conduct control actions affecting the species. Also, nontoxic shot or bullets must be used in most cases when a firearm is used to control the species. Finally, any control actions must be reported.
The Mexican (Tamaulipas) Crow was also removed form the list due to declining populations.
Click here for all the details, including comments and USFWS responses
Tuesday, December 28, 2010
Tattered Wings: Bats Grounded by White-Nose Syndrome’s Lethal Effects on Life-Support Functions of Wings
Damage to bat wings from the fungus associated with white-nose syndrome (WNS) may cause catastrophic imbalance in life-support processes, according to newly published research.
This imbalance may be to blame for the more than 1 million deaths of bats due to WNS thus far, proposes Carol Meteyer, a pathologist with the U.S. Geological Survey’s National Wildlife Health Center and a lead author of the research published in BMC Biology.
Physiological problems caused by the novel fungus, may, in fact, represent a completely new disease paradigm for mammals, Meteyer and her colleagues wrote. Other skin infections in mammals due to fungi (ringworm, athlete’s foot) remain superficial and do not invade living tissue—typically they only affect the surface of skin, hair and nails.
Not so for the aptly named Geomyces destructans. “This fungus is amazingly destructive — it digests, erodes, and invades the skin — particularly the wings — of hibernating bats,” said Meteyer. “The ability of this fungus to invade bats’ wing skin is unlike that of any known skin fungal pathogen in land mammals.”
The authors examined nearly 200 bats that had died from WNS, and also reviewed the critical function and physiology of bat wings during hibernation. As a result, they propose that G. destructans may cause unsustainable dehydration in hibernating bats, triggering thirst-associated arousals. In addition to the direct damage to the wings that would alter flight control, the erosion and invasion of skin may also cause significant changes in circulation, body-temperature regulation and respiratory function.
Since signs of the disease were first observed in New York during the winter of 2006-07, the fungus has spread through 11 states and 2 Canadian provinces, resulting in the first sustained high-mortality disease affecting bats in recorded history. Biologists assume that as the disease spreads to new areas, cave-hibernating bats in those areas will also be at risk, including some that are endangered.
“The high number of bat deaths and range of species being affected far exceeds the rate and magnitude of any previously known natural or human-caused mortality event in bats, and possibly in any other mammals,” said Paul Cryan, a lead author of the paper and a USGS bat ecologist at the Fort Collins Science Center.
Although the powdery white muzzles of affected bats gave the disease its name, the authors believe that the skin of bat wings is the most significant, though often less obvious, target of the fungus.
The order of bats is called Chiroptera, Greek for “hand-wing,” appropriately named since bat wings are essentially modified arms. Imagine, for a moment, your human hand with its fingers spread apart. Then imagine your fingers are 6 feet long, and the whole skeletal affair is covered with two layers of thin, somewhat transparent membranes attached to the sides of your torso and legs. Sandwiched between the membranes are blood and lymphatic vessels, delicate nerves, muscles and special connective tissues that help you fly and help keep you physiologically healthy.
“The disproportionately large areas of exposed skin that make up bat wings play critical roles in maintaining safe internal body conditions during hibernation,” noted Cryan. “Healthy wings are essential for day-to-day survival, even during winter when bats are mostly just hanging around. Wings damaged by the fungus may not always look so bad to the naked eye, but under the microscope things get ugly fast.”
When Meteyer examined wings of diseased bats microscopically, she discovered wing damage was often so severe that it led her and her colleagues to suggest multiple life-threatening effects on hibernating bats.
“A bat’s wings,” said Meteyer, “are obviously critical for flying, but they also play a vital part in essential functions such as body temperature, blood pressure, water balance and blood and gas circulation and exchange.”
Healthy bats occasionally rouse themselves from hibernation, probably to change roosts, drink, mate and even overcome sleep deprivation, biologists think. But bats afflicted with WNS arouse much more often. In fact, a characteristic of hibernation sites with WNS is daytime flights of affected bats outside caves.
“The prevailing hypothesis is that daytime winter flight is a last-ditch effort for starving bats to find insect prey,” Cryan said. “What we propose is that thirst, and maybe not always hunger, is driving these arousals. Unusual thirst during hibernation may result from water essentially leaking out of wings damaged by the fungus.”
Anecdotally, bats at hibernacula affected by WNS are sometimes seen flying over and drinking from water surfaces or eating snow, highlighting the plausibility of this hypothesis, the authors noted.
Hibernation itself is one reason this emerging disease is so successful. During hibernation, a bat’s immune function and metabolism are dramatically reduced, and body temperature drops significantly. Also, some of the worst-affected bat species roost in humid areas in dense clusters to conserve energy and decrease moisture loss.
“These ideal environmental conditions, combined with the hibernating bat’s suppressed immune system, likely allow the fungus to invade body tissues for nutrients without resistance, making the hibernating bat a most accommodating host for this new disease,” Meteyer said.
The researchers compare the ability of this novel bat fungus to destabilize internal functions with the electrolyte imbalance that occurs in frogs infected by chytrid fungus, which, like G. destructans, is a novel disease of vertebrates. Chytrid infection impairs the ability of frog skin to regulate hydration and internal equilibrium, causing electrolyte imbalance and ultimately cardiac arrest.
“The skin plays a critical role in the physiology of both amphibians and bats,” Meteyer said. “We suggest that a similar, but less subtle, disturbance could be occurring in the wing membranes of bats with WNS.”
The journal article can be accessed online.
Back-lit photographs of wings of White-nose Syndrome (WNS)-positive little brown bats, one with subtle circular and irregular pale areas (arrows) indicating areas of fungal infection (A) and another bat (B) with areas of relatively normal tone and elasticity (black arrow), compared to a WNS affected area that looks like crumpled tissue paper with loss of elasticity, surface sheen and areas of irregular pigmentation (white arrow). (C) Microscopic section of wing membrane from a little brown bat showing extensive infection with the fungus (magenta structures), G. destructans.Photographer: Carol Uphoff Meteyer, USGS
This multi-institutional study provides new insights into viral infections in native pollinators, suggesting that viral diseases may be key factors impacting pollinator populations.
According to Diana Cox-Foster, co-author and professor of entomology at Penn State, pollinator populations have declined for various reasons, including ribonucleic acid (RNA) viruses, which are emerging as a serious threat. "RNA viruses are suspected as major contributors to Colony Collapse Disorder (CCD ), where honey bee colonies die with few or no bees left in the hives. Recent detection of these viral species in bumble bees and other native pollinators indicates a possible wider environmental spread of these viruses with potential broader impact," explains Cox-Foster.
The researchers studied viral distributions from pollen pellets of honey bees and other pollinators collected from flowering plants in Pennsylvania, New York, and Illinois in the United States. "For the first time, RNA viruses such as deformed wing virus, sacbrood virus and black queen cell virus were detected in pollen pellets collected directly from forager bees," said Cox-Foster. "Pollen pellets from several uninfected forager bees were detected with virus, indicating that pollen itself may harbor viruses. The viruses in the pollen and honey stored in the hive were demonstrated to be infective, with the queen becoming infected and laying infected eggs after these virus-contaminated foods were given to virus-free colonies."
The detection of RNA viruses in other pollinators, including bumble bees, solitary bees and wasps, suggests that viruses might have a deeper impact on ecosystem health , given that these pollinators are essential to most plants for seed set and production of fruits, nuts, berries, and vegetables. The findings are important to the public and scientific community worldwide, given pollinators' role in agriculture and the environment and recent declines in native pollinators. The findings also raise biosecurity issues because pollen is currently being imported into many countries to feed honey bees used in agricultural pollination.
Tuesday, December 07, 2010
Based on the best available information, the Service recommends maintaining the status for the species classified as endangered in the North Atlantic and threatened in the Caribbean. The Caribbean roseate tern still meets the definition of a threatened species because disease or predation, and other natural or manmade factors continue to threaten its continued existence throughout the Caribbean.
The Caribbean roseate tern or “palometa” is a medium-sized tern, primarily white, slender-winged and long-tailed. It has a black crown, pale grey upper surface and immaculate white underparts. The three or four outer primaries (wing feathers) of roseate terns are frosted with silver-grey and edged with black. The species owes its name to the rose color of the chest and belly early in the breeding season. Three-quarters of the bill in Caribbean roseate terns gradually become reddish orange during the breeding season. The species breeds in large, dense single or mixed species colonies. It remains gregarious throughout the year, roosting in large groups.
The number of nesting pairs during the period 1990-2000 fluctuated from a low of 217 to a high of 731 nesting pairs in 1994 and 2000, respectively. Significant fluctuations were observed between 2001 and 2009, although an increasing trend is apparent. In Puerto Rico, roseate terns nest on off-shore cays near the coasts of Lajas, Manatí, Barceloneta, Culebra, Guayanilla, and Vieques.
U.S. Virgin Islands
The total number of nests varied among years from 500 to 2,300 pairs. Variability in the number of nests from year to year is high because roseate terns shift colony sites between the USVI and other areas outside the U.S. jurisdiction. In recent years, roseate terns nested at 17 different cays around the U.S. Virgin Islands.
Call to action:
The public can help in the recovery of this species because recreational activities in proximity to roseate tern colonies and visitation to breeding colonies are a significant source of disturbance to breeding terns. Egg collection continues to be a major source of egg loss and colony desertion in many Caribbean roseate tern colonies. Stay away from areas where roseate terns are nesting, usually between May to late July. To report sightings of dead or alive roseate terns and colony locations call 787-851-7297. You can learn to identify the species, its threats and ways to help by visiting us at http://www.fws.gov/caribbean/PDF/CaribbeanRoseateTern_Presentation.pdf .
The principal basis for this review is the scientific literature published since the respective recovery plans were completed including data collected by Service biologists and species experts during the past 20 years in PR and the USVI. In the USVI, personnel from the Department of Planning and Natural Resources have conducted monitoring efforts. As a result of these efforts, knowledge on the biology, feeding ecology, and habitat use of the Caribbean roseate tern has expanded, particularly for populations in Puerto Rico, and the U.S. Virgin Islands.
Service biologists have conducted population assessments of the Puerto Rico and Virgin Island roseate tern populations since 1990. Service personnel assisted by volunteers do boat and aerial surveys as well as complete nest counts at the roseate tern breeding colonies. At the beginning of each nesting season, the teams survey nesting pairs and latter in the season they count the number of chicks and fledglings. While surveying the beaches, the teams also document threats which include parasites and predation from fire ants, gulls, ruddy turnstones, peregrine falcon, rats and other unidentified mammals. Some years, they trap adults and older chicks to place identification bands on their legs to study the birds’ movement and distribution. These bands have allowed scientists to find out the areas where Caribbean roseate terns migrate to after breeding, and what threats they may be exposed to in those areas.
View/download copies of the 5 year reviews
Theoretical ecologists like to contemplate the differences between a species’ fundamental niche (a theoretical ideal) and its realized niche (actual, real-world conditions). In any given habitat, a species that is free from interference from other species is capable of occupying the full range of environmental conditions for which it is adapted – its fundamental niche. Imagine if the downy woodpecker was the only bird in a given forest stand. It could forage and nest wherever it wanted without worrying about competition for space and food. Nature is complex, however, and rarely, if ever, are competitors completely absent from natural communities. In New England, downy woodpeckers commonly share their territories with 3 or 4 (and sometimes as many as 5 or 6) other woodpecker species. In addition, they may compete with several other less closely related species for both food and breeding space. Just how these competitors allocate space and resources within an area (niche partitioning) determines what portion of the habitat each species actually occupies – its realized niche. For example, the diminutive downy woodpecker reduces competition with its larger and more aggressive relative, the hairy woodpecker, by focusing its foraging efforts on smaller branches and weed stems where hairys, with their larger bills and feet, cannot forage efficiently.
Species that have broad ecological niches are considered generalists, while those that have extremely narrow niches are specialists. Often, species with broad niches are widely distributed geographically while specialists have limited ranges. Consider two different hawks – the red-tailed hawk, a generalist that eats a wide variety of readily available food found in a wide variety of habitats stretching from Mexico to Alaska – and the snail kite, a specialist that feeds only on apple snails and whose range in the United States is limited to a few places in southern Florida. Narrow or broad, species seem to instinctively recognize their particular niche. In an experiment during the 1940s, two ornithologists removed 542 birds of 42 species from a 40-acre, spruce-fir forest. By the next morning, a bird of the same species as the original occupant had set up housekeeping in every territory that had been vacated the night before.
Remarkably, birds of closely related species may occupy separate niches within a single tree. In an elegant experiment conducted in the 1950s, R. H. MacArthur found that four species of warbler he studied in Maine spruce forests always had distinct niches even though the physical space they occupied for feeding and nesting often overlapped. MacArthur found that magnolia warblers foraged for insects on the lower trunk and nested within 15 feet of the ground; black-throated green warblers preyed on foliage-eating insects close to the trunk and nested in crotches of lower branches; blackburnian warblers foraged high in the treetops, caught insects on the wing, and nested on a high branch well out from the trunk; while Cape May warblers ate sap or insects gleaned from the bark and nested near the top of a tree.
Niche partitioning, as this is called, may even occur within the same species, and may be based upon gender. Male red-eyed vireos, for instance, glean insects from the upper canopy of deciduous forests, while females forage in the lower canopy closer to the ground. Although they eat similar food, primarily caterpillars, each sex utilizes different areas of the same forest tract.
Ecological relationships and processes are often difficult to tease apart due to the infinite number of variables that need to be considered. Whenever ecologists examine a species carefully, differences in niches are discovered, suggesting that any given niche is occupied by only one species. Or, said another way, each species helps define its own niche. How’s that for job security?